LASER INTERFEROMETER GRAVITATIONAL WAVE OBSERVATORY 12 LIGO Laboratory / LIGO Scientific Collaboration LIGO-T00xxxx-xx-D ADVANCED LIGO mm/dd/yy AOS System Design Requirements Document Michael Smith, Michael Zucker, Ken Mason, Author No. 3, … Distribution of this document: LIGO Science Collaboration This is an internal working note of the LIGO Project. California Institute of Technology LIGO Project – MS 18-34 1200 E. California Blvd. Pasadena, CA 91125 Phone (626) 395-2129 Fax (626) 304-9834 E-mail: [email protected]Massachusetts Institute of Technology LIGO Project – NW17-161 175 Albany St Cambridge, MA 02139 Phone (617) 253-4824 Fax (617) 253-7014 E-mail: [email protected]LIGO Hanford Observatory P.O. Box 1970 LIGO Livingston Observatory P.O. Box 940
Mail Stop S9-02Richland, WA 99352Phone 509-372-8106Fax 509-372-8137
LIGO Livingston ObservatoryP.O. Box 940
Livingston, LA 70754Phone 225-686-3100Fax 225-686-7189
http://www.ligo.caltech.edu/
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Table of Contents1 INTRODUCTION...................................................................................................................................................11
1.2.1 Stray Light Control....................................................................................................................................111.2.2 Active Optics Compensation (AOC)..........................................................................................................121.2.3 Active Optics Compensation Controls.......................................................................................................121.2.4 Output Mode Cleaner................................................................................................................................121.2.5 PO Mirror Assembly and Telescope..........................................................................................................121.2.6 Initial Alignment System (IAS)..................................................................................................................121.2.7 Optical Lever System (OptLev).................................................................................................................121.2.8 Photon Drive.............................................................................................................................................121.2.9 Photon Drive Controls..............................................................................................................................12
2 GENERAL DESCRIPTION.................................................................................................................................16
2.2.1 Stray Light Control Perspective................................................................................................................162.2.1.1 Wedge Angles.........................................................................................................................................................162.2.1.2 Beam Dumps and Baffles.......................................................................................................................................162.2.1.3 Attenuators..............................................................................................................................................................172.2.1.4 Layout.....................................................................................................................................................................17
2.2.2 Active Optics Compensation Perspective..................................................................................................172.2.3 Active Optics Compensation Controls Perspective...................................................................................172.2.4 Output Mode Cleaner Perspective............................................................................................................172.2.5 PO Mirror Assembly and Telescope Perspective......................................................................................172.2.6 Initial Alignment System Perspective........................................................................................................182.2.7 Optical Lever System Perspective.............................................................................................................182.2.8 Photon Drive Perspective..........................................................................................................................182.2.9 Photon Drive Controls Perspective...........................................................................................................18
2.3 PRODUCT FUNCTIONS..........................................................................................................................................182.3.1 Stray Light Control Functions...................................................................................................................182.3.2 Active Optics Compensation Functions.....................................................................................................192.3.3 Active Optics Compensation Controls Functions......................................................................................192.3.4 Output Mode Cleaner Functions...............................................................................................................192.3.5 PO Mirror Assembly and Telescope Functions.........................................................................................192.3.6 Initial Alignment System Functions...........................................................................................................192.3.7 Optical Lever System Functions................................................................................................................192.3.8 Photon Drive Functions............................................................................................................................192.3.9 Photon Drive Controls Functions.............................................................................................................19
2.4 GENERAL CONSTRAINTS......................................................................................................................................192.4.1 Stray Light Control Constraints................................................................................................................202.4.2 Active Optics Compensation Constraints..................................................................................................202.4.3 Active Optics Compensation Controls Constraints...................................................................................202.4.4 Output Mode Cleaner Constraints............................................................................................................202.4.5 PO Mirror Assembly and Telescope Constraints......................................................................................202.4.6 Initial Alignment System Constraints........................................................................................................202.4.7 Optical Lever System Constraints.............................................................................................................202.4.8 Photon Drive Constraints..........................................................................................................................20
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2.4.9 Photon Drive Controls Constraints...........................................................................................................202.5 ASSUMPTIONS AND DEPENDENCIES.....................................................................................................................20
3.1 STRAY LIGHT CONTROL REQUIREMENTS............................................................................................................233.1.1 Introduction...............................................................................................................................................233.1.2 Stray Light Control Characteristics..........................................................................................................24
3.1.2.1 Stray Light Control Performance Characteristics...................................................................................................243.1.2.2 Stray Light Control Physical Characteristics..........................................................................................................273.1.2.3 Stray Light Control Interface Definitions...............................................................................................................283.1.2.4 Stray Light Control Reliability...............................................................................................................................283.1.2.5 Stray Light Control Maintainability.......................................................................................................................283.1.2.6 Stray Light Control Environmental Conditions......................................................................................................283.1.2.7 Stray Light Control Transportability......................................................................................................................29
3.1.3 Stray Light Control Design and Construction...........................................................................................293.1.3.1 Materials and Processes..........................................................................................................................................293.1.3.2 Stray Light Control Workmanship.........................................................................................................................303.1.3.3 Stray Light Control Interchangeability...................................................................................................................303.1.3.4 Stray Light Control Safety......................................................................................................................................303.1.3.5 Stray Light Control Human Engineering................................................................................................................30
3.1.4 Stray Light Control Assembly and Maintenance.......................................................................................303.1.5 Stray Light Control Documentation..........................................................................................................30
3.1.5.1 Stray Light Control Specifications.........................................................................................................................303.1.5.2 Stray Light Control Design Documents..................................................................................................................303.1.5.3 Stray Light Control Engineering Drawings and Associated Lists..........................................................................313.1.5.4 Stray Light Control Technical Manuals and Procedures........................................................................................313.1.5.5 Stray Light Control Documentation Numbering....................................................................................................313.1.5.6 Stray Light Control Test Plans and Procedures......................................................................................................31
3.1.6 Stray Light Control Logistics....................................................................................................................313.1.7 Stray Light Control Precedence................................................................................................................313.1.8 Stray Light Control Qualification.............................................................................................................31
3.2 ACTIVE OPTICS COMPENSATION REQUIREMENTS...............................................................................................313.2.1 Introduction...............................................................................................................................................313.2.2 Active Optics Compensation Characteristics............................................................................................32
3.2.2.1 Active Optics Compensation Performance Characteristics....................................................................................323.2.2.2 Active Optics Compensation Physical Characteristics...........................................................................................323.2.2.3 Active Optics Compensation Interface Definitions................................................................................................323.2.2.4 Active Optics Compensation Reliability................................................................................................................323.2.2.5 Active Optics Compensation Maintainability.........................................................................................................323.2.2.6 Active Optics Compensation Environmental Conditions.......................................................................................323.2.2.7 Active Optics Compensation Transportability.......................................................................................................34
3.2.3 Active Optics Compensation Design and Construction............................................................................343.2.3.1 Materials and Processes..........................................................................................................................................343.2.3.2 Active Optics Compensation Workmanship...........................................................................................................363.2.3.3 Active Optics Compensation Interchangeability....................................................................................................363.2.3.4 Active Optics Compensation Safety.......................................................................................................................363.2.3.5 Active Optics Compensation Human Engineering.................................................................................................36
3.2.4 Active Optics Compensation Assembly and Maintenance.........................................................................363.2.5 Active Optics Compensation Documentation............................................................................................36
3.2.5.1 Active Optics Compensation Specifications...........................................................................................................373.2.5.2 Active Optics Compensation Design Documents...................................................................................................373.2.5.3 Active Optics Compensation Engineering Drawings and Associated Lists...........................................................373.2.5.4 Active Optics Compensation Technical Manuals and Procedures.........................................................................373.2.5.5 Active Optics Compensation Documentation Numbering.....................................................................................37
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3.2.5.6 Active Optics Compensation Test Plans and Procedures.......................................................................................383.2.6 Active Optics Compensation Logistics......................................................................................................383.2.7 Active Optics Compensation Precedence..................................................................................................383.2.8 Active Optics Compensation Qualification...............................................................................................38
3.3 ACTIVE OPTICS COMPENSATION CONTROLS REQUIREMENTS.............................................................................383.3.1 Introduction...............................................................................................................................................383.3.2 Active Optics Compensation Controls Characteristics.............................................................................38
3.3.2.1 Active Optics Compensation Controls Performance Characteristics.....................................................................383.3.2.2 Active Optics Compensation Controls Physical Characteristics............................................................................383.3.2.3 Active Optics Compensation Controls Interface Definitions.................................................................................383.3.2.4 Active Optics Compensation Controls Reliability..................................................................................................393.3.2.5 Active Optics Compensation Controls Maintainability..........................................................................................393.3.2.6 Active Optics Compensation Controls Environmental Conditions........................................................................393.3.2.7 Active Optics Compensation Controls Transportability.........................................................................................40
3.3.3 Active Optics Compensation Controls Design and Construction.............................................................413.3.3.1 Materials and Processes..........................................................................................................................................413.3.3.2 Active Optics Compensation Controls Workmanship............................................................................................423.3.3.3 Active Optics Compensation Controls Interchangeability.....................................................................................423.3.3.4 Active Optics Compensation Controls Safety........................................................................................................423.3.3.5 Active Optics Compensation Controls Human Engineering..................................................................................42
3.3.4 Active Optics Compensation Controls Assembly and Maintenance..........................................................433.3.5 Active Optics Compensation Controls Documentation.............................................................................43
3.3.5.1 Active Optics Compensation Controls Specifications............................................................................................433.3.5.2 Active Optics Compensation Controls Design Documents....................................................................................433.3.5.3 Active Optics Compensation Controls Engineering Drawings and Associated Lists............................................433.3.5.4 Active Optics Compensation Controls Technical Manuals and Procedures..........................................................443.3.5.5 Active Optics Compensation Controls Documentation Numbering.......................................................................443.3.5.6 Active Optics Compensation Controls Test Plans and Procedures........................................................................44
3.3.6 Active Optics Compensation Controls Logistics.......................................................................................443.3.7 Active Optics Compensation Controls Precedence...................................................................................443.3.8 Active Optics Compensation Controls Qualification................................................................................44
3.5 PO MIRROR AND TELESCOPE REQUIREMENTS....................................................................................................51
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3.5.1 Introduction...............................................................................................................................................513.5.2 PO Mirror and Telescope Characteristics................................................................................................51
3.5.2.1 PO Mirror and Telescope Performance Characteristics.........................................................................................513.5.2.2 PO Mirror and Telescope Physical Characteristics................................................................................................523.5.2.3 PO Mirror and Telescope Interface Definitions.....................................................................................................533.5.2.4 PO Mirror and Telescope Reliability......................................................................................................................543.5.2.5 PO Mirror and Telescope Maintainability..............................................................................................................543.5.2.6 PO Mirror and Telescope Environmental Conditions............................................................................................543.5.2.7 PO Mirror and Telescope Transportability.............................................................................................................54
3.5.3 PO Mirror and Telescope Design and Construction................................................................................543.5.3.1 Materials and Processes..........................................................................................................................................543.5.3.2 PO Mirror and Telescope Workmanship................................................................................................................553.5.3.3 PO Mirror and Telescope Interchangeability..........................................................................................................553.5.3.4 PO Mirror and Telescope Safety............................................................................................................................553.5.3.5 PO Mirror and Telescope Human Engineering......................................................................................................56
3.5.4 PO Mirror and Telescope Assembly and Maintenance.............................................................................563.5.5 PO Mirror and Telescope Documentation................................................................................................56
3.5.5.1 PO Mirror and Telescope Specifications................................................................................................................563.5.5.2 PO Mirror and Telescope Design Documents........................................................................................................563.5.5.3 PO Mirror and Telescope Engineering Drawings and Associated Lists................................................................563.5.5.4 PO Mirror and Telescope Technical Manuals and Procedures...............................................................................563.5.5.5 PO Mirror and Telescope Documentation Numbering...........................................................................................573.5.5.6 PO Mirror and Telescope Test Plans and Procedures.............................................................................................57
3.5.6 PO Mirror and Telescope Logistics..........................................................................................................573.5.7 PO Mirror and Telescope Precedence......................................................................................................573.5.8 PO Mirror and Telescope Qualification...................................................................................................57
3.6 INITIAL ALIGNMENT SYSTEM REQUIREMENTS....................................................................................................573.6.1 Introduction...............................................................................................................................................573.6.2 Initial Alignment System Characteristics..................................................................................................57
3.6.2.1 PO Mirror and Telescope Performance Characteristics.........................................................................................573.6.2.2 Initial Alignment System Physical Characteristics.................................................................................................583.6.2.3 Initial Alignment System Interface Definitions......................................................................................................603.6.2.4 Initial Alignment System Reliability......................................................................................................................603.6.2.5 Initial Alignment System Maintainability..............................................................................................................603.6.2.6 Initial Alignment System Environmental Conditions.............................................................................................613.6.2.7 Initial Alignment System Transportability.............................................................................................................62
3.6.3 Initial Alignment System Design and Construction...................................................................................623.6.3.1 Materials and Processes..........................................................................................................................................623.6.3.2 Initial Alignment System Workmanship................................................................................................................633.6.3.3 Initial Alignment System Interchangeability..........................................................................................................633.6.3.4 Initial Alignment System Safety.............................................................................................................................633.6.3.5 Initial Alignment System Human Engineering.......................................................................................................64
3.6.4 Initial Alignment System Assembly and Maintenance...............................................................................643.6.5 Initial Alignment System Documentation..................................................................................................64
3.6.5.1 Initial Alignment System Specifications................................................................................................................643.6.5.2 Initial Alignment System Design Documents........................................................................................................643.6.5.3 Initial Alignment System Engineering Drawings and Associated Lists.................................................................643.6.5.4 Initial Alignment System Technical Manuals and Procedures...............................................................................653.6.5.5 Initial Alignment System Documentation Numbering...........................................................................................653.6.5.6 Initial Alignment System Test Plans and Procedures.............................................................................................65
3.6.6 Initial Alignment System Logistics............................................................................................................653.6.7 Initial Alignment System Precedence........................................................................................................653.6.8 Initial Alignment System Qualification.....................................................................................................65
3.7 OPTICAL LEVER SYSTEM REQUIREMENTS...........................................................................................................663.7.1 Introduction...............................................................................................................................................663.7.2 Optical Lever System Characteristics.......................................................................................................66
3.7.2.1 Optical Lever System Performance Characteristics...............................................................................................663.7.2.2 Optical Lever System Physical Characteristics......................................................................................................663.7.2.3 Optical Lever System Interface Definitions...........................................................................................................663.7.2.4 Optical Lever System Reliability............................................................................................................................66
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3.7.2.5 Optical Lever System Maintainability....................................................................................................................673.7.2.6 Optical Lever System Environmental Conditions..................................................................................................673.7.2.7 Optical Lever System Transportability...................................................................................................................68
3.7.3 Optical Lever System Design and Construction........................................................................................683.7.3.1 Materials and Processes..........................................................................................................................................683.7.3.2 Optical Lever System Workmanship......................................................................................................................703.7.3.3 Optical Lever System Interchangeability...............................................................................................................703.7.3.4 Optical Lever System Safety..................................................................................................................................703.7.3.5 Optical Lever System Human Engineering............................................................................................................70
3.7.4 Optical Lever System Assembly and Maintenance....................................................................................703.7.5 Optical Lever System Documentation.......................................................................................................71
3.7.5.1 Optical Lever System Specifications......................................................................................................................713.7.5.2 Optical Lever System Design Documents..............................................................................................................713.7.5.3 Optical Lever System Engineering Drawings and Associated Lists......................................................................713.7.5.4 Optical Lever System Technical Manuals and Procedures....................................................................................713.7.5.5 Optical Lever System Documentation Numbering.................................................................................................723.7.5.6 Optical Lever System Test Plans and Procedures..................................................................................................72
3.7.6 Optical Lever System Logistics.................................................................................................................723.7.7 Optical Lever System Precedence.............................................................................................................723.7.8 Optical Lever System Qualification...........................................................................................................72
4.1 GENERAL.............................................................................................................................................................864.1.1 Responsibility for Tests..............................................................................................................................864.1.2 Special Tests..............................................................................................................................................86
Table of FiguresFigure 1 Block Diagram....................................................................................................................17Figure 2: RM, ITM, and ETM ghost beam naming convention........................................................24Figure 3: BS ghost beam naming convention....................................................................................25Figure 4: Glint Reflection of GBAR3 Back Into the IFO..................................................................93
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Abstract
This technical note is being generated to provide a general outline to be followed for developing a Design Requirements Document (DRD) for the LIGO Detector Group. The following pages provide the outline, including section/paragraph numbering and headings, along with a brief explanation (and some examples) of what is to go into each paragraph.
The basis for the following outline is a combination of the IEEE guide for software requirement documentation and the MIL-STD-490A guide to requirement specification. Sections 1 and 2 particularly follow the IEEE standard. The remaining sections are more in line with the MIL-STD format, with some extras or variations that I’ve found useful in the past.
This document is a MicroSoft Word template. All instructions (guidelines and examples) in this document are in normal text, and should be deleted when an individual DRD is written. This document also shows “boilerplate” text, which should appear in every LIGO detector DRD. This boilerplate appears in this document as italic text and should not be removed from individual DRDs.
This section (Abstract) was purposely titled without using the LIGO tech document template ‘Header’ paragraph format, such that the Table of Contents of this document directly reflects the outline for a DRD.
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1 Introduction
1.1 Purpose
The purpose of this document is to describe the design requirements for the Auxiliary Optics Support (AOS). Primary requirements are derived (“flowed-down”) from the LIGO principal science requirements. Secondary requirements, which govern Detector performance through interactions between AOS and other Detector subsystems, have been allocated by Detector Systems Engineering (see Figure 1.)
1.2 Scope
Identify the item to be produced by name, such as Alignment Sensing and Control.
Explain what the item will and, if necessary, will not do. An example of the latter, from the CDS document is: CDS specifically does not provide: 1) Personnel safety system 2) Facilities Control System 3) etc. The point is to emphasize to reviewers what the system will not do where there may be some doubt or uncertainty.
Describe the objectives, goals of the item development.
The AOS system is comprised of nine distinct subsystems: Stray Light Control (SLC), Active Optics Compensation (AOC), Active Optics Compensation Controls, Output Mode Cleaner, PO Mirror Assembly and Telescope, Initial Alignment System (IAS), Optical Lever System (OptLev), Photon Drive, and Photon Drive Controls.
1.2.1 Stray Light Control
The Stray Light Control subsystem will control and reduce to acceptable levels the intensities of all principal ghost beams (reflections from anti-reflection (AR) coatings and optic wedges) produced by COC and reflections from viewport windows. The Stray Light Control subsystem also will provide optical baffling around the COC elements and any other optical elements within the vacuum housing in order to reduce glare within the IFO to acceptable levels.
The Stray Light Control subsystem will provide baffling around the Input Mode Cleaner and between the output of the IO Mode Matching telescope and the input to the recycling cavity. It will not provide baffling for other parts of the IO optical train, nor for the PSL optical train.
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1.2.2 Active Optics Compensation (AOC)
1.2.3 Active Optics Compensation Controls
1.2.4 Output Mode Cleaner
1.2.5 PO Mirror Assembly and Telescope
The PO Mirror Assembly and Telescope subsystem will generate optical pick-off (PO) beams from core optical elements and deliver those beams with a specified beam waist and location outside the vacuum housing for use by the LSC/ASC in the feedback control of the interferometer (IFO) alignment and length, and for monitoring purposes. These PO beams include the following: BS PO, ITMx PO, ITMy PO, ETMx transmitted beams, ETMy transmitted beams, and APS beam.
The PO Mirror Assembly and Telescope subsystem will provide viewport windows for the following beams: input PSL beam, SPS beam, Input Modecleaner ASC beam, and the PSL Intensity stabilization beam; it does not include other optical pick-off beams within the IO or PSL systems.
1.2.6 Initial Alignment System (IAS)
The Initial Alignment subsystem will provide a means of positioning the LIGO-2 suspended core optics in global coordinates and provide angular alignment to within 10% of the core optics adjustment range. This will allow the operator to use the CDS control system to position the beam back upon itself and to switch to the ASC Alignment Sensing and Control system.
Initial Alignment will be similar to the LIGO-1 system with revisions to accommodate changes to suspensions, core optic materials, and the active seismic isolation system.
1.2.7 Optical Lever System (OptLev)
The Optical Lever subsystem will provide an external means of monitoring the LIGO-2 core optic orientation. The optical levers will be used for long term monitoring and maintenance. They are not intended as feedback devices to the ASC Alignment Sensing and Control subsystem.
The optical lever system will be similar to the LIGO-1 system with revisions to accommodate changes to core optic positioning , materials, and other AOS system changes.
1.2.8 Photon Drive
1.2.9 Photon Drive Controls.
1.3 Definitions
Define all terms used in the document as necessary to interpret its contents. For example, a CDS specification may make use of terminology, such as “real-time software”, which is subject to
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interpretation. This section should specifically define what “real-time software” means in the context of this document.
NOTE: This should include all standard names used in interface discussions/drawings.
1.4 Acronyms
List all acronyms and abbreviations used in the document.
ASC Optical Lever Design Requirement Document, LIGO-T950106-01-D
Core Optics Components, DRD LIGO-E950099-03-D
End Test Mass Substrate, Dwg. D960791-A-D
LIGO Vacuum Compatibility, Cleaning Methods and Procedures, LIGO-E960022-00-D
Vacuum Equipment Specification, LIGO-E940002-02-V
HAM Assembly, LIGO Vacuum Equipment Dwg. V049-4-002
BSC, LIGO Vacuum Equipment Dwg. V0494-001
Seismic Isolation DRD, LIGO-T960065-02-D
Effect of PO Telescope Aberrations on Wavefront Sensor Performance, LIGO-T980007-00-D
Core Optics Support Design Requirements Document, LIGO-T970071-02-D
Core Optics Support Conceptual Design, LIGO-T970072-00-D
Core Optics Support Preliminary Design, LIGO-T970071-02-D
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Baffling Requirements for the 4K and 2K IFO, LIGO-T980027-00-D
Up-Conversion of Scattered Light Phase Noise from Large Amplitude Motions, LIGO-T980101-00
ETM PO Beam Optical Relay System, LIGO-T980071-00-D
Initial Alignment Procedures, LIGO-T970151-C-D
Optical Lever Calibration Procedures, T990026-00-D
COS Beam-dump & Stray Light Baffle Revised Requirements and Concepts, LIGO-T980103-00
1.5.2 Non-LIGO Documents
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2 General descriptionThis section (Section 2) should describe the general factors that affect the product and its requirements. This section does not state specific requirements; it only makes those requirements easier to understand.
2.1 Specification Tree
This document is part of an overall LIGO detector requirement specification tree. This particular document is highlighted in the following figure.
2.2 Product Perspective
This section should show how this specified item relates to the rest of a larger system. For instance, a general block diagram would go here which shows the item to be developed and its relationship to the larger system.
2.2.1 Stray Light Control Perspective
2.2.1.1 Wedge Angles
The Stray Light Control subsystem will set minimum wedge angle requirements for the substrates of the recycling mirror (RM), the beam splitter (BS), the signal recycling mirror (SM), the input test mass mirrors (ITMx and ITMy), and the end test mass mirrors (ETMx and ETMy). The minimum wedge angles guarantee that the ghost beams will separate sufficiently from the main beam to enable the placement of beam dumps and PO mirrors.
2.2.1.2 Beam Dumps and Baffles
The Stray Light Control subsystem will provide beam dumps that are mounted to the walls of the BSC chambers for reducing the energy of the scattered ghost beams from the COC to acceptable levels. Baffles will be mounted inside the arm cavity to reduce the energy of the diffuse scattered light from the COC into the arm cavity that re-enters the interferometer main beam. Baffles will be placed inside the HAM chambers to restrict the passage of scattered light from the Input Optics system into the recycling cavity. Baffles will be placed inside the cryopump to obscure the cryopump surface from the test masses.
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2.2.1.3 Attenuators
Attenuators and Faraday isolators, will be mounted on the BSC and HAM optical tables in the PO and APS optical paths to reduce the scattered light from the ISC LSC and ASC photodetectors that re-enters the interferometer main beam.
2.2.1.4 Layout
A schematic layout of the detector assembly is shown in the figure following, indicating the physical relationship of the Stray Light Control subsystem elements to the rest of the detector system.
Figure 1 Block Diagram
2.2.2 Active Optics Compensation Perspective
2.2.3 Active Optics Compensation Controls Perspective
2.2.4 Output Mode Cleaner Perspective
2.2.5 PO Mirror Assembly and Telescope Perspective
The PO Mirror Assembly and Telescope subsystem contains pick-off (PO) mirrors mounted to a BSC optical table for directing PO beams to the PO telescopes that are mounted on a HAM optical
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table. An APS telescope, also mounted on the HAM optical table, will receive the APS beam from the anti-symmetric port. Beam steering periscopes and steering mirrors will direct the output beams from the telescopes through the AOS viewports in the HAM chamber to the ISC system outside the vacuum.
2.2.6 Initial Alignment System Perspective
The Initial Alignment system interfaces with Suspension design, Core Optic design, and all other AOS subsystems. The core optic provides reflectivity at 670 nm for the laser autocollimator to sense the return beam. The Suspensions system provides a means of measuring its position and the ability to make rough and fine linear and angular adjustments.
Initial Alignment is performed on each core optic individually. An AOS autocollimator operating at 980 nm is then used to verify the optical path thru a group of core optics.
2.2.7 Optical Lever System Perspective
The optical levers will be positioned on the face of the suspended optic prior to removal of the IAS Initial Alignment subsystem. It will then monitor the angular orientation to assure no movement occurs during the period from alignment to operation.
2.2.8 Photon Drive Perspective
2.2.9 Photon Drive Controls Perspective
2.3 Product Functions
This section should provide a summary of the functions that the specified item will perform. This should just be general statements, not the detail that will go into the requirements section (Section 3).
2.3.1 Stray Light Control Functions
Beam dumps will reduce the scattered light phase noise from the following sources: ghost beams that originate from the wedged AR surfaces of the core optics mirrors and the reflection of pick-off beams from the surfaces of AOS viewports. Arm Cavity Baffles will reduce the scattered light phase noise caused by the small-angle diffuse scattering from the test mass mirrors in the arm cavity. Elliptical Baffles will control the excess light that spills around the BS. Conical Baffles will obscure the reflecting surfaces of the cryopumps within the arm cavity near the input test mass mirror. Input Mode Cleaner Baffles will control the scattered light from the Input Mode Cleaner mirrors. An IO Baffle will reduce the passage of scattered light from the input (IOO) optics region into the recycling cavity region. Attenuators will reduce the scattered light phase noise from the PO beam photodetectors. Faraday isolators will reduce the scattered light phase noise from the APS photodetectors.
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2.3.2 Active Optics Compensation Functions
2.3.3 Active Optics Compensation Controls Functions
2.3.4 Output Mode Cleaner Functions
2.3.5 PO Mirror Assembly and Telescope Functions
Ghost beams from the ITMx, ITMy, and BS mirrors will be used as PO beams for sensing and control (ISC) of the COC mirrors. The PO beams will be directed by PO mirror assemblies into beam reducing telescopes and will be subsequently directed with steering mirrors through vacuum viewports to the ISC photodetectors.
The PO beams and APS beam will exit through the vacuum chamber to a specified location with a specified beam waist and a specified wavefront distortion.
2.3.6 Initial Alignment System Functions
The Initial Alignment system will provide the monuments, instrumentation, and procedures to position and align the final Input Optic and all LIGO-2 core optics to within the positioning and angular alignment requirements.
2.3.7 Optical Lever System Functions
The Optical Lever system provides two primary functions. They provide a means of monitoring the optic orientation for long-term drift due to the suspensions or seismic isolation system. They also provide maintenance and setup functions such as diagonalization of the core optic, core optic replacement, and realignment caused by catastrophic events (i.e. Earthquakes).
2.3.8 Photon Drive Functions
2.3.9 Photon Drive Controls Functions
2.4 General Constraints
This section should give a general description of any other items that will limit the designer’s options, such as general policies, design standards, interfaces, etc. This subsection should not be used to impose specific requirements or specific design constraints on the solution. This subsection should provide the reasons why certain specific requirements or design constraints are later specified as part of Section 3. A CDS example for the CDS PSL document might be:
The overall CDS system is being developed using VME based systems as the standard interface. Therefore, all I/O modules being developed for the PSL will be constrained to this format.
Another general example might be:
LIGO must operate continuously, therefore this subsystem must be designed with high reliability and low mean time to repair. (Note that this is a general statement, and the MTBF and MTTR will be exactly specified in Section 3).
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2.4.1 Stray Light Control Constraints
2.4.2 Active Optics Compensation Constraints
2.4.3 Active Optics Compensation Controls Constraints
2.4.4 Output Mode Cleaner Constraints
2.4.5 PO Mirror Assembly and Telescope Constraints
The input beam diameter shall include the 100 ppm diameter of the main interferometer beam. The output beam diameter shall be the same as LIGO 1.
2.4.6 Initial Alignment System Constraints
Initial Alignment is constrained by existing internal vacuum and external equipment, which requires setting up from an offset centerline and the use of various optical techniques, and auxiliary equipment to meet positioning and orientation requirements.
2.4.7 Optical Lever System Constraints
In order for the optical levers to provide stable monitoring of the optic orientation it must not be influenced by thermal or load induced movements of the seismic isolation or vacuum chambers. This requires that the laser source and photo detector be kinematically mounted and secured to the concrete foundation.
2.4.8 Photon Drive Constraints
2.4.9 Photon Drive Controls Constraints
2.5 Assumptions and Dependencies
This section should list factors that affect the requirements i.e. certain assumptions have been made in the writing of the requirements, and, if these change, then the requirements will have to be changed. For example, it is assumed that green light wavelengths will be used as the basis for optics requirements. If this is changed to infrared, then the requirements that follow will need to change.
2.5.1 Core Optics Parameters
See Core Optics Components DRD: LIGO-Exxx
Physical Quantity RM BS ITMx ITMy ETM
AR coating @ 1060 nm <0.0005 <0.0005 <0.0005 <0.0005 <0.0005
refractive index @ 1064 nm 1.77 1.77 1.77 1.77 1.77
100ppm power contour radius, mm 116 116 116 116 116
1ppm power contour radius, mm 142 142 142 142 142
beam radius parameter w, mm 54 54 54 54 54
Mirror diameter, mm 280 280 280 280 280
Mirror thickness, mm 120 120 120 120 120
2.5.2 Interferometer Design Parameters
Laser input power 125 watts
SPS power 2.5 watts
APS power 1.0 Watt
IFO Gaussian beam radius, w 54 mm
Recycling cavity gain 16.8
Arm cavity gain 789
2.5.3 ISC Interface Characteristics
2.5.3.1 ISC Sensor Beam Parameters
The COS PO beam characteristics will be compatible with the ISC design. ISC Conceptual Design:________? The beam characteristics at the exit of the HAM viewport are as follows:
Physical Quantity Characteristic
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Output PO beam aperture: APS, BS, ITM
20 mm
Output PO beam aperture: ETM
20 mm
wavefront distortion < 0.7 wave p-v
beam waist position TBD
Gaussian beam radius parameter
w = 4.2 mm
beam height Centered on the viewport
beam orientation nominally horizontal
beam polarization horizontal (TBD)
2.5.4 Seismic Environment
The scattered light noise calculations in this document are based on the assumption that the rms velocity of scattering surfaces is sufficiently low so that up-conversion of large amplitude low fre-quency motion does not produce in-band phase noise. This is true for the vacuum housing and is also true of the SEI platforms for stack Q’s less than 1000. See Seismic Isolation DRD, LIGO-T960065-02-D, and Locally Damped Test Mass Motion, LIGO-T970092-00-D.
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3 RequirementsThis section contains the specific requirements of the product to be developed. This is the most important part of the document. It must be:
Unambiguous: every requirement listed has only one interpretation
Complete: Inclusion of all significant requirements
Verifiable: A requirement is verifiable if and only if there exists some finite cost-effective process whereby the final product can be checked/tested to meet the requirement. If no method can be devised to determine if the product meets a particular requirement, either (1) the requirement should be removed, or (2) a point in the development cycle should be identified at which the requirement can be put into a verifiable form.
Consistent: No two requirements should conflict with each other.
Modifiable: The structure and style should be such that any necessary changes can be made easily, completely, and consistently.
Traceable: Backward (references to source of requirements, such as a higher level specification, design, or standards) and Forward (unique numbering of requirements such that they can be identified/referenced in design and test documentation).
Usable during operations and maintenance: often items are modified during commissioning and maintenance periods. The requirements should specifically call out critical areas (such as failure of this component to meet this requirement can cause severe injury), and other such items, such that this fact s not lost to maintenance personnel.
3.1 Stray Light Control Requirements
3.1.1 Introduction
Requirements flow down tree from Detector DRD should be included in this section.
The scattered light phase noise shall not exceed 1/10 the advanced LIGO sensitivity as given in the LIGO Science Requirements Document: LIGO-Exxx.
Light scattered from baffles and other optical elements whose rays lie within the Rayleigh solid angle of the interferometer cavity will cause phase noise on the output signal. The amplitude of the phase noise is proportional to the rms amplitude of the horizontal motion of the scattering surface and to the rms electric field amplitude of the scattered light injected into the IFO. This assumes surface motions small compared to a wavelength of the light, which is a valid assumption for resonant surfaces with Qs less than 1000.
Three categories of scattered light, in decreasing order of amplitude, are considered: 1) scattering from windows, beam-dumps, and baffles mounted on the vacuum housing, 2) scattering from beam-dumps and baffles mounted on SEI optical platforms, and 3) scattering from SUS COCs.
The most significant scattered light noise sources are the following: 1) the APS beam, that is back-scattered from the surface of the photodetector in the ISC system, 2) the BS PO beam and the two
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ITM PO beams that back-scatter from the surface of the photodetector in the ISC system, 3) The SPS beam, that is back-scattered from the surface of the photodetector in the ISC system, 4) the two ETM PO beams that back-scatter from the surface of the photodetector in the ISC system, 5) the diffuse light scattered by the test mass mirrors toward the opposite ends of the arm cavity, and 6) the first-order ghost beams from the COC mirrors that are captured with beam dumps. These scattered light noise sources account for over 98% of the scattered light noise.
Light scattered from the SEI mounted surfaces and from SUS suspended surfaces can be neglected.
In general, the light back-scattered from an external surface into the solid angle of the IFO is proportional to the following factors: 1) the light power incident on the scattering surface, 2) a transmission factor that accounts for the return-trip transmissivity through the COC element which produced the incident beam, 3) the cosine of the incident angle at the scattering surface, 4) the BRDF of the surface, 5) the solid angle of the IFO beam, 6) the added attenuation factor (if any) of the return path, and (7) the square of the de-magnification factor.
The de-magnification factor must be included whenever scattering occurs from an incident beam whose diameter has been de-magnified from the original IFO diameter by the AOS telescope or by other focusing elements in the ISC detection system. An increase in acceptance solid angle results from a decrease in beam diameter because the product of solid angle and beam area is proportional to the total radiant flux, which is an optical invariant; therefore, as the beam area decreases the solid angle increases proportionally. The acceptance solid angle for the scattered light is inversely proportional to the square of the de-magnification factor.
3.1.2 Stray Light Control Characteristics
3.1.2.1 Stray Light Control Performance Characteristics
3.1.2.1.1 Baffles and Beam Dumps
Descriptions of the ghost beam naming conventions for the COC mirrors and the beam splitter are shown in the following figures.
Figure 2: RM, ITM, and ETM ghost beam naming convention
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Figure 3: BS ghost beam naming convention
The light scattered into the interferometer from each source was calculated from the following equation:
Where Pi is the incident power, T is the transmissivity into the IFO from the scattering source, M is the beam de-magnification ratio, Ai is an additional attenuation factor of the scattered light as it re-enters the IFO.
The scattered light requirements were calculated from the following equation:
Where Po is the laser power into the recycling cavity, Fi is the noise allocation factor, Ki is the amplitude noise strength parameter, and Ni is the number of identical sources.
The noise allocation factors Fi were assigned by modeling all of the anticipated scattering sources and paths (See Core Optics Support Conceptual Design, LIGO-T970072-00-D), and by allocating the total noise budget in proportion to the scattered light of the principal sources. The noise allocation factors are discussed in the appendix. See “Noise Allocation Factor” on page ? . The noise strength parameters Ki are discussed in the appendix. See “Ki Values” on page ?.
The following parameters were assumed.
Input laser power, Po = 125 w
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recycling cavity gain, Grc = 16.83
M = 0.00846
BRDF of photodetector surface = 0.0008
Solid angle of interferometer beam = 1.24E-10 sr-1.
Attenuation factor for PO path = 0.2
Attenuation factor for APS path = 2.0E-6
Attenuation factor for ETM path = 0.005
Attenuation factor for SPS path = 0.3
Attenuation of Arm Cavity Baffle = 3.3E-3
AR reflectivity of COC = 0.0005
Transmissivity of SM = 0.05
ratio of anti-symmetric port signal (APS) to input laser power = 0.00833
ratio of symmetric port signal (SPS) to input laser power = 0.02
The scattered light requirements for each principal scattering source, at the gravity wave frequencies of interest, are shown in the table below, together with the calculated power scattered into the IFO by that source. Approximately 98% of the scattered light budget is allocated to the principal scattering paths proportionally to the relative magnitudes of the particular paths, and 2% is allocated to all other scattering paths.
The criteria for deciding which of the ghost beams should be dumped is that the glint power into the IFO from any spurious ghost beam reflected from the wall of the chamber shall not exceed the scattered light requirement for that beam. If it does, then that ghost beam must be captured in a beam dump. Beam dumps are required for the following ghost beams:
Appropriate attenuators shall be provided in the PO optical path to reduce the scattered light power to acceptable levels in the following PO beams: SPS, ITMx, ITMy, BS, ETMx and ETMy. Appropriate Faraday isolators shall be placed in the APS optical path to reduce the scattered light power to acceptable levels.
The attenuators shall not cause excessive wavefront distortion of the PO beams. Acceptable wavefront distortion will maintain the WFS signal contrast ratio >5:1
3.1.2.2 Stray Light Control Physical Characteristics
3.1.2.2.1 Vacuum compatibility of COS elements
3.1.2.2.1.1 Outgassing of COS elements
The COS elements shall be fabricated from materials whose outgassing properties are compatible with the vacuum requirements of the LIGO. See LIGO Vacuum Compatibility, Cleaning Methods and Procedures, LIGO-E960022-00-D
3.1.2.2.2 Access for Optical lever beams and TV Camera Viewing of COCs
The beam-dump/baffle assemblies shall allow access to the optical lever beams and TV camera viewing of the COC elements. See ASC Optical Lever Design Requirement Document, LIGO-T950106-01-D
3.1.2.3 Stray Light Control Interface Definitions
3.1.2.3.1 Interfaces to other LIGO detector subsystems
3.1.2.3.1.1 Mechanical Interfaces
The beam dumps will bolt to the chamber walls and to the SEI platforms, in the BSC and HAM chambers, without interfering with the COC mirror structures.
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The elliptical baffles will mount to the COC suspension structures by means of external clamps.
The arm cavity baffles and the cryopump baffles will be self-supporting and will be held in position inside the vacuum manifold and inside the cryopump by means of mechanical forces.
3.1.2.3.1.2 Electrical Interfaces
There are no electrical interfaces.
3.1.2.3.1.3 Optical Interfaces
The beam dumps shall intercept the 100ppm diameter of the ghost beams.
3.1.2.3.1.4 Stay Clear Zone
The beam dumps shall maintain a stay clear zone of >34 mm from the 1ppm margin of the main interferometer beam.
The arm cavity baffles, the elliptical baffles, and the cryopump baffles shall maintain a stay clear zone of >10 mm from the 1ppm margin of the main interferometer beam.
3.1.2.3.2 Interfaces external to LIGO detector subsystems
There are no interfaces external to the LIGO detector.
3.1.2.4 Stray Light Control Reliability
All Stray Light Control elements are passive and are expected to have a 100% availability. The MTBF is expected to be equal to the life of the detector.
3.1.2.5 Stray Light Control Maintainability
Spare components will be stocked for the replacement during installation of long lead-time items such as telescope mirrors and lenses.
3.1.2.6 Stray Light Control Environmental Conditions
The Stray Light Control elements will operate in a temperature and humidity controlled laboratory environment. Prior to assembly, the components of the Stray Light Control subsystem can be subjected to normal commercial shipping and handling environments.
The Stray Light Control subsystem shall be compatible with the environment of the SEI system.
3.1.2.7 Stray Light Control Transportability
All items shall be transportable by commercial carrier without degradation in performance. As necessary, provisions shall be made for measuring and controlling environmental conditions (temperature and accelerations) during transport and handling. Special shipping containers, shipping and handling mechanical restraints, and shock isolation shall be utilized to prevent damage. All containers shall be movable for forklift. All items over 100 lbs. that must be moved into place within LIGO buildings shall have appropriate lifting eyes and mechanical strength to be lifted by cranes.
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3.1.3 Stray Light Control Design and Construction
The design and construction of the Stray Light Control subsystem allow adequate cleaning, either on site or at an appropriate outside vendor, and shall fit inside the vacuum baking ovens on site.
3.1.3.1 Materials and Processes
The materials and processes used in the fabrication of the Stray Light Control subsystem shall be compatible with the LIGO approved materials list.
Metal components shall have quality finishes on all surfaces, suitable for vacuum finishes. Aluminum components used in the vacuum shall not have anodized surfaces.
3.1.3.1.1 Materials
A list of currently approved materials for use inside the LIGO vacuum envelope can be found in LIGO Vacuum Compatible Materials List (LIGO-E960022). All fabricated metal components exposed to vacuum shall be made from stainless steel, copper, or aluminum. Other metals are subject to LIGO approval. Pre-baked viton (or fluorel) may be used subject to LIGO approval. All materials used inside the vacuum chamber must comply with LIGO Vacuum Compatibility, Cleaning Methods and Procedures (LIGO-E960022-00-D).
The only lubricating films permitted within the vacuum are dry plating of vacuum compatible materials such as silver and gold.
3.1.3.1.2 Processes
3.1.3.1.2.1 Cleaning
All materials used inside the vacuum chambers must be cleaned in accordance LIGO-E960022-00-D, or LIGO-E000007-00.
Materials shall be joined in such a way as to facilitate cleaning and vacuum preparation procedures; i. e. internal volumes shall be provided with adequate openings to allow for wetting, agitation and draining of cleaning fluids and for subsequent drying.
3.1.3.1.3 Component Naming
All components shall be identified using the LIGO Naming Convention (LIGO-E950111-A-E). This shall include identification (part or drawing number, revision number, serial number) physically stamped on all components, in all drawings and in all related documentation.
3.1.3.2 Stray Light Control Workmanship
All components shall be manufactured according to good commercial practice.
3.1.3.3 Stray Light Control Interchangeability
Common elements, with ordinary dimensional tolerances, will be interchangeable. Certain telescope elements with unusually tight dimensional tolerances, such as the ETM telescope focus barrel, will be manufactured as matched sets and will not be interchangeable.
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3.1.3.4 Stray Light Control Safety
This item shall meet all applicable NSF and other Federal safety regulations, plus those applicable State, Local and LIGO safety requirements. A hazard/risk analysis shall be conducted in accordance with guidelines set forth in the LIGO Project System Safety Management Plan LIGO-M950046-F, section 3.3.2.
3.1.3.5 Stray Light Control Human Engineering
NA
3.1.4 Stray Light Control Assembly and Maintenance
Assembly fixtures and installation procedures shall be developed in conjunction with the Stray Light Control hardware design. These shall include (but not be limited to) fixtures and procedures for:
• installation and assembly of beam dumps and baffles into the vacuum
• assembly of the in vacuum components in a clean room (class 100) environment
3.1.5 Stray Light Control Documentation
The documentation shall consist of working drawings, assembly drawings, and alignment procedures
3.1.5.1 Stray Light Control Specifications
Specifications for the purchase of specialized components and assemblies such as Faraday isolator, optical mirrors, windows, and lenses shall be developed.
3.1.5.2 Stray Light Control Design Documents
The following documents will be produced:
• LIGO Stray Light Control Preliminary Design Document (including supporting technical design and analysis documentation)
• LIGO Stray Light Control Final Design Document (including supporting technical design and analysis documentation)
• LIGO Stray Light Control Installation Procedures
3.1.5.3 Stray Light Control Engineering Drawings and Associated Lists
A complete set of drawings suitable for fabrication will be provided along with Bill of Material (BOM) and drawing tree lists. The drawings shall comply with LIGO standard formats and will be provided in electronic format. All documents shall use the LIGO drawing numbering system, be drawn using LIGO Drawing Preparation Standards, etc.
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3.1.5.4 Stray Light Control Technical Manuals and Procedures
3.1.5.4.1 Procedures
Procedures shall be provided for the installation, and final alignment of the Stray Light Control elements.
3.1.5.5 Stray Light Control Documentation Numbering
All documents shall be numbered and identified in accordance with the LIGO documentation control numbering system LIGO document TBD
3.1.5.6 Stray Light Control Test Plans and Procedures
All test plans and procedures shall be developed in accordance with the LIGO Test Plan Guidelines, LIGO document TBD.
3.1.6 Stray Light Control Logistics
The design shall include a list of all recommended spare parts and special test equipment required.
3.1.7 Stray Light Control Precedence
The relative importance of the positioning of the beam dumps and baffles shall be as follows:
1) satisfy the stay clear requirements
2) align the baffles and beam dumps with the centers of the ghost beams
3.1.8 Stray Light Control Qualification
N/A
3.2 Active Optics Compensation Requirements
3.2.1 Introduction
Requirements flow down tree from Detector DRD should be included in this section.
3.2.2 Active Optics Compensation Characteristics
3.2.2.1 Active Optics Compensation Performance Characteristics
This section should contain all functional and performance characteristics that the product must fulfill i.e. what is expected of the product.
3.2.2.2 Active Optics Compensation Physical Characteristics
This area contains any physical requirements or constraints on the product: dimensional and weight limitations, acceptable materials or properties of the materials, durability factors, transportation and storage requirements, etc.
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3.2.2.3 Active Optics Compensation Interface Definitions
Specify all interfaces to other systems/subsystems/components and the characteristics (electrical/mechanical/optical) of those interfaces. Note that these are all requirements placed on the item specified, NOT requirements this item places on other systems.
3.2.2.3.1 Interfaces to other LIGO detector subsystems
3.2.2.3.1.1 Mechanical Interfaces
3.2.2.3.1.2 Electrical Interfaces
3.2.2.3.1.3 Optical Interfaces
3.2.2.3.1.4 Stay Clear Zones
3.2.2.3.2 Interfaces external to LIGO detector subsystems
3.2.2.3.2.1 Mechanical Interfaces
3.2.2.3.2.2 Electrical Interfaces
3.2.2.3.2.3 Stay Clear Zones
3.2.2.4 Active Optics Compensation Reliability
Mean Time Between Failures (MTBF), Availability
3.2.2.5 Active Optics Compensation Maintainability
Mean Time To Repair (MTTR); Qualitative requirements for accessibility, modular construction, test points, etc.
3.2.2.6 Active Optics Compensation Environmental Conditions
Environments that the equipment is expected to experience in shipment, storage, service or use. Subparagraphs should include, as necessary, climate, shock, vibration, noise, etc.
3.2.2.6.1 Natural Environment
3.2.2.6.1.1 Temperature and Humidity
Example:
Table 1 Environmental Performance Characteristics
Operating Non-operating (storage) Transport
+0 C to +50 C, 0–90 % RH 40 C to +70 C, 0–90 % RH 40 C to +70 C, 0–90 % RH
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3.2.2.6.1.2 Atmospheric Pressure
3.2.2.6.1.3 Seismic Disturbance
The following example for the SEI subsystem is illustrative:
Restraint against seismically induced large motion is required.
The system shall be designed to resist the static equivalent lateral forces defined in the Uniform Building Code (UBC), 1994 edition, for a seismic zone factor Z = 0.15 (i.e. zone 2B, Hanford) and a structure importance factor I = 1. The support structure shall resist the seismic loads without damage. The seismic stack shall sustain the base shear motion of the support structure without collapse or release of any of the stack layers. At a minimum, failure of the actuators under these loads should not cause failure of the bellows or cause the seismic stack to “drop”; ideally the actuators would survive these loads with no damage.
As an alternative to this static equivalent load, an acceleration design spectrum for use in dynamic analysis could be used.
Interpretation of the requirement: If there is no damping or plastic deformation to absorb the seismic loading (Rw = 1), and the SEI first frequency is between 2.5 Hz and 10 Hz (i.e. at the peak), then the base shear,
Vb = (Z I C/Rw) W = (0.15 (1) 2.75/1) W = 0.4 W
or the SEI must sustain a 0.4 g lateral load. If, as in the case of the Corner Station building, Rw = 6, then, then SEI must sustain a 0.1 g lateral load.
3.2.2.6.2 Induced Environment
These are environmental conditions induced by equipment. The following subparagraphs list some possible categories. Remember to list the requirements both in terms of:
What the item to be designed must accept from its surroundings
What environment the item to be designed is allowed to generate
3.2.2.6.2.1 Electromagnetic Radiation
Electrical equipment associated with the subsystem shall meet the EMI and EMC requirements of VDE 0871 Class A or equivalent. The subsystem shall also comply with the LIGO EMI Control Plan and Procedures (LIGO-E960036).
3.2.2.6.2.2 Acoustic
Equipment shall be designed to produce the lowest levels of acoustic noise as possible and practical. As a minimum, equipment shall not produce acoustic noise levels greater than specified in Derivation of CDS Rack Acoustic Noise Specifications, LIGO-T960083.
3.2.2.6.2.3 Mechanical Vibration
Mechanical vibration from the subsystem shall not increase the vibration amplitude of the facility floor within 1 m of any other vacuum chambers and equipment tables by more than 1 dB at any
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frequency between 0.1 Hz and 10 kHz. Limited narrowband exemptions may be permitted subject to LIGO review and approval.
3.2.2.7 Active Optics Compensation Transportability
All items shall be transportable by commercial carrier without degradation in performance. As necessary, provisions shall be made for measuring and controlling environmental conditions (temperature and accelerations) during transport and handling. Special shipping containers, shipping and handling mechanical restraints, and shock isolation shall be utilized to prevent damage. All containers shall be movable for forklift. All items over 100 lbs. which must be moved into place within LIGO buildings shall have appropriate lifting eyes and mechanical strength to be lifted by cranes.
3.2.3 Active Optics Compensation Design and Construction
Minimum or essential requirements that are not controlled by performance characteristics, interfaces, or referenced documents. This can include design standards, requirements governing the use or selection of materials, parts and processes, interchangeability requirements, safety requirements, etc.
3.2.3.1 Materials and Processes
Such items as units of measure to be used (English, Metric) should be listed and any other general items, such as standard polishing procedures and processes.
3.2.3.1.1 Finishes
Examples:
Ambient Environment: Surface-to-surface contact between dissimilar metals shall be controlled in accordance with the best available practices for corrosion prevention and control.
External surfaces: External surfaces requiring protection shall be painted purple or otherwise protected in a manner to be approved.
• Metal components shall have quality finishes on all surfaces, suitable for vacuum finishes. All corners shall be rounded to TBD radius.
• All materials shall have non-shedding surfaces.
• Aluminum components used in the vacuum shall not have anodized surfaces.
• Optical table surface roughness shall be within 32 micro-inch.
3.2.3.1.2 Materials
A list of currently approved materials for use inside the LIGO vacuum envelope can be found in LIGO Vacuum Compatible Materials List (LIGO-E960022). All fabricated metal components exposed to vacuum shall be made from stainless steel, copper, or aluminum. Other metals are subject to LIGO approval. Pre-baked viton (or fluorel) may be used subject to LIGO approval. All materials used inside the vacuum chamber must comply with LIGO Vacuum Compatibility, Cleaning Methods and Procedures (LIGO-E960022-00-D).
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The only lubricating films permitted within the vacuum are dry plating of vacuum compatible materials such as silver and gold.
3.2.3.1.3 Processes
3.2.3.1.3.1 Welding
Before welding, the surfaces should be cleaned (but baking is not necessary at this stage) according to the UHV cleaning procedure(s). All welding exposed to vacuum shall be done by the tungsten-arc-inert-gas (TIG) process. Welding techniques for components operated in vacuum shall deviate from the ASME Code in accordance with the best ultra high vacuum practice to eliminate any “virtual leaks” in welds; i. e. all vacuum welds shall be continuous wherever possible to eliminate trapped volumes. All weld procedures for components operated in vacuum shall include steps to avoid contamination of the heat affected zone with air, hydrogen or water, by use of an inert purge gas that floods all sides of heated portions.
The welds should not be subsequently ground (in order to avoid embedding particles from the grinding wheel).
3.2.3.1.3.2 Cleaning
All materials used inside the vacuum chambers must be cleaned in accordance with Specification Guidance for Seismic Component Cleaning, Baking, and Shipping Preparation (LIGO-L970061-00-D). To facilitate final cleaning procedures, parts should be cleaned after any processes that result in visible contamination from dust, sand or hydrocarbon films.
Materials shall be joined in such a way as to facilitate cleaning and vacuum preparation procedures; i. e. internal volumes shall be provided with adequate openings to allow for wetting, agitation and draining of cleaning fluids and for subsequent drying.
3.2.3.1.4 Component Naming
All components shall be identified using the LIGO Naming Convention (LIGO-E950111-A-E). This shall include identification (part or drawing number, revision number, serial number) physically stamped on all components, in all drawings and in all related documentation.
3.2.3.2 Active Optics Compensation Workmanship
Standard of workmanship desired, uniformity, freedom from defects and general appearance of the finished product.
3.2.3.3 Active Optics Compensation Interchangeability
Specify the level at which components shall be interchangeable or replaceable.
3.2.3.4 Active Optics Compensation Safety
This item shall meet all applicable NSF and other Federal safety regulations, plus those applicable State, Local and LIGO safety requirements. A hazard/risk analysis shall be conducted in accordance with guidelines set forth in the LIGO Project System Safety Management Plan LIGO-M950046-F, section 3.3.2.
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3.2.3.5 Active Optics Compensation Human Engineering
Note: For many detector subsystems, this section is not applicable.
Specify any special or unique requirements, e.g., constraints on allocation of functions to personnel, and communications and personnel/equipment interactions. Also include any specified areas, stations, or equipment that require concentrated human engineering attention due to the sensitivity of the operation, i.e. those areas where the effects of human error would be particularly serious.
Example: Seismically isolated platforms or points must accommodate addition, removal and adjustment of equipment with a minimum of force or torque applied to the platforms. This requires that adequate space be provided surrounding the optics platform for an individual to move into proper position for the work intended. Equipment mounted to the optics platform should be provided with fasteners that can accommodate these force/torque requirements.
3.2.4 Active Optics Compensation Assembly and Maintenance
Assembly fixtures and installation/replacement procedures shall be developed in conjunction with the AOS hardware design. These shall include (but not be limited to) fixtures and procedures for:
• AOS component insertion and assembly into the vacuum chambers without load support from the chambers
• assembly of the in vacuum components in a clean room (class 100) environment
• initial alignment of the AOS components
3.2.5 Active Optics Compensation Documentation
Requirements for documentation of the design, including types of documents, such as operator manuals, etc.
3.2.5.1 Active Optics Compensation Specifications
List any additional specifications to be provided during the course of design and development, such as Interface Control Documents (ICD) and any lower level specifications to be developed.
3.2.5.2 Active Optics Compensation Design Documents
List all design documents to be produced, including installation and commissioning plans, standards documents, etc.
Example:
• LIGO SEI System Preliminary Design Document (including supporting technical design and analysis documentation)
• LIGO SEI System Final Design Document (including supporting technical design and analysis documentation)
• LIGO SEI Prototype/Test Plans
• LIGO SEI Installation and Commissioning Plans and Procedures
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3.2.5.3 Active Optics Compensation Engineering Drawings and Associated Lists
A complete set of drawings suitable for fabrication must be provided along with Bill of Material (BOM) and drawing tree lists. The drawings must comply with LIGO standard formats and must be provided in electronic format. All documents shall use the LIGO drawing numbering system, be drawn using LIGO Drawing Preparation Standards, etc.
3.2.5.4 Active Optics Compensation Technical Manuals and Procedures
3.2.5.4.1 Procedures
Procedures shall be provided for, at minimum,
• Initial installation and setup of equipment
• Normal operation of equipment
• Normal and/or preventative maintenance
• Installation of new equipment
• Troubleshooting guide for any anticipated potential malfunctions
3.2.5.4.2 Manuals
Any manuals to be provided, such as operator’s manual, etc.
3.2.5.5 Active Optics Compensation Documentation Numbering
All documents shall be numbered and identified in accordance with the LIGO documentation control numbering system LIGO document TBD
3.2.5.6 Active Optics Compensation Test Plans and Procedures
All test plans and procedures shall be developed in accordance with the LIGO Test Plan Guidelines, LIGO document TBD.
3.2.6 Active Optics Compensation Logistics
The design shall include a list of all recommended spare parts and special test equipment required.
3.2.7 Active Optics Compensation Precedence
This section should list the relative importance of requirements (or goals) to be achieved by the design.
3.2.8 Active Optics Compensation Qualification
Test and acceptance criteria.
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3.3 Active Optics Compensation Controls Requirements
3.3.1 Introduction
Requirements flow down tree from Detector DRD should be included in this section.
3.3.2 Active Optics Compensation Controls Characteristics
3.3.2.1 Active Optics Compensation Controls Performance Characteristics
This section should contain all functional and performance characteristics that the product must fulfill i.e. what is expected of the product.
3.3.2.2 Active Optics Compensation Controls Physical Characteristics
This area contains any physical requirements or constraints on the product: dimensional and weight limitations, acceptable materials or properties of the materials, durability factors, transportation and storage requirements, etc.
3.3.2.3 Active Optics Compensation Controls Interface Definitions
Specify all interfaces to other systems/subsystems/components and the characteristics (electrical/mechanical/optical) of those interfaces. Note that these are all requirements placed on the item specified, NOT requirements this item places on other systems.
3.3.2.3.1 Interfaces to other LIGO detector subsystems
3.3.2.3.1.1 Mechanical Interfaces
3.3.2.3.1.2 Electrical Interfaces
3.3.2.3.1.3 Optical Interfaces
3.3.2.3.1.4 Stay Clear Zones
3.3.2.3.2 Interfaces external to LIGO detector subsystems
3.3.2.3.2.1 Mechanical Interfaces
3.3.2.3.2.2 Electrical Interfaces
3.3.2.3.2.3 Stay Clear Zones
3.3.2.4 Active Optics Compensation Controls Reliability
Mean Time Between Failures (MTBF), Availability
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3.3.2.5 Active Optics Compensation Controls Maintainability
Mean Time To Repair (MTTR); Qualitative requirements for accessibility, modular construction, test points, etc.
3.3.2.6 Active Optics Compensation Controls Environmental Conditions
Environments that the equipment is expected to experience in shipment, storage, service or use. Subparagraphs should include, as necessary, climate, shock, vibration, noise, etc.
3.3.2.6.1 Natural Environment
3.3.2.6.1.1 Temperature and Humidity
Example:
Table 2 Environmental Performance Characteristics
Operating Non-operating (storage) Transport
+0 C to +50 C, 0–90 % RH 40 C to +70 C, 0–90 % RH 40 C to +70 C, 0–90 % RH
3.3.2.6.1.2 Atmospheric Pressure
3.3.2.6.1.3 Seismic Disturbance
The following example for the SEI subsystem is illustrative:
Restraint against seismically induced large motion is required.
The system shall be designed to resist the static equivalent lateral forces defined in the Uniform Building Code (UBC), 1994 edition, for a seismic zone factor Z = 0.15 (i.e. zone 2B, Hanford) and a structure importance factor I = 1. The support structure shall resist the seismic loads without damage. The seismic stack shall sustain the base shear motion of the support structure without collapse or release of any of the stack layers. At a minimum, failure of the actuators under these loads should not cause failure of the bellows or cause the seismic stack to “drop”; ideally the actuators would survive these loads with no damage.
As an alternative to this static equivalent load, an acceleration design spectrum for use in dynamic analysis could be used.
Interpretation of the requirement: If there is no damping or plastic deformation to absorb the seismic loading (Rw = 1), and the SEI first frequency is between 2.5 Hz and 10 Hz (i.e. at the peak), then the base shear,
Vb = (Z I C/Rw) W = (0.15 (1) 2.75/1) W = 0.4 W
or the SEI must sustain a 0.4 g lateral load. If, as in the case of the Corner Station building, Rw = 6, then, then SEI must sustain a 0.1 g lateral load.
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3.3.2.6.2 Induced Environment
These are environmental conditions induced by equipment. The following subparagraphs list some possible categories. Remember to list the requirements both in terms of:
What the item to be designed must accept from its surroundings
What environment the item to be designed is allowed to generate
3.3.2.6.2.1 Electromagnetic Radiation
Electrical equipment associated with the subsystem shall meet the EMI and EMC requirements of VDE 0871 Class A or equivalent. The subsystem shall also comply with the LIGO EMI Control Plan and Procedures (LIGO-E960036).
3.3.2.6.2.2 Acoustic
Equipment shall be designed to produce the lowest levels of acoustic noise as possible and practical. As a minimum, equipment shall not produce acoustic noise levels greater than specified in Derivation of CDS Rack Acoustic Noise Specifications, LIGO-T960083.
3.3.2.6.2.3 Mechanical Vibration
Mechanical vibration from the subsystem shall not increase the vibration amplitude of the facility floor within 1 m of any other vacuum chambers and equipment tables by more than 1 dB at any frequency between 0.1 Hz and 10 kHz. Limited narrowband exemptions may be permitted subject to LIGO review and approval.
3.3.2.7 Active Optics Compensation Controls Transportability
All items shall be transportable by commercial carrier without degradation in performance. As necessary, provisions shall be made for measuring and controlling environmental conditions (temperature and accelerations) during transport and handling. Special shipping containers, shipping and handling mechanical restraints, and shock isolation shall be utilized to prevent damage. All containers shall be movable for forklift. All items over 100 lbs. which must be moved into place within LIGO buildings shall have appropriate lifting eyes and mechanical strength to be lifted by cranes.
3.3.3 Active Optics Compensation Controls Design and Construction
Minimum or essential requirements that are not controlled by performance characteristics, interfaces, or referenced documents. This can include design standards, requirements governing the use or selection of materials, parts and processes, interchangeability requirements, safety requirements, etc.
3.3.3.1 Materials and Processes
Such items as units of measure to be used (English, Metric) should be listed and any other general items, such as standard polishing procedures and processes.
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3.3.3.1.1 Finishes
Examples:
Ambient Environment: Surface-to-surface contact between dissimilar metals shall be controlled in accordance with the best available practices for corrosion prevention and control.
External surfaces: External surfaces requiring protection shall be painted purple or otherwise protected in a manner to be approved.
• Metal components shall have quality finishes on all surfaces, suitable for vacuum finishes. All corners shall be rounded to TBD radius.
• All materials shall have non-shedding surfaces.
• Aluminum components used in the vacuum shall not have anodized surfaces.
• Optical table surface roughness shall be within 32 micro-inch.
3.3.3.1.2 Materials
A list of currently approved materials for use inside the LIGO vacuum envelope can be found in LIGO Vacuum Compatible Materials List (LIGO-E960022). All fabricated metal components exposed to vacuum shall be made from stainless steel, copper, or aluminum. Other metals are subject to LIGO approval. Pre-baked viton (or fluorel) may be used subject to LIGO approval. All materials used inside the vacuum chamber must comply with LIGO Vacuum Compatibility, Cleaning Methods and Procedures (LIGO-E960022-00-D).
The only lubricating films permitted within the vacuum are dry plating of vacuum compatible materials such as silver and gold.
3.3.3.1.3 Processes
3.3.3.1.3.1 Welding
Before welding, the surfaces should be cleaned (but baking is not necessary at this stage) according to the UHV cleaning procedure(s). All welding exposed to vacuum shall be done by the tungsten-arc-inert-gas (TIG) process. Welding techniques for components operated in vacuum shall deviate from the ASME Code in accordance with the best ultra high vacuum practice to eliminate any “virtual leaks” in welds; i. e. all vacuum welds shall be continuous wherever possible to eliminate trapped volumes. All weld procedures for components operated in vacuum shall include steps to avoid contamination of the heat affected zone with air, hydrogen or water, by use of an inert purge gas that floods all sides of heated portions.
The welds should not be subsequently ground (in order to avoid embedding particles from the grinding wheel).
3.3.3.1.3.2 Cleaning
All materials used inside the vacuum chambers must be cleaned in accordance with Specification Guidance for Seismic Component Cleaning, Baking, and Shipping Preparation (LIGO-L970061-00-D). To facilitate final cleaning procedures, parts should be cleaned after any processes that result in visible contamination from dust, sand or hydrocarbon films.
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Materials shall be joined in such a way as to facilitate cleaning and vacuum preparation procedures; i. e. internal volumes shall be provided with adequate openings to allow for wetting, agitation and draining of cleaning fluids and for subsequent drying.
3.3.3.1.4 Component Naming
All components shall be identified using the LIGO Naming Convention (LIGO-E950111-A-E). This shall include identification (part or drawing number, revision number, serial number) physically stamped on all components, in all drawings and in all related documentation.
3.3.3.2 Active Optics Compensation Controls Workmanship
Standard of workmanship desired, uniformity, freedom from defects and general appearance of the finished product.
3.3.3.3 Active Optics Compensation Controls Interchangeability
Specify the level at which components shall be interchangeable or replaceable.
3.3.3.4 Active Optics Compensation Controls Safety
This item shall meet all applicable NSF and other Federal safety regulations, plus those applicable State, Local and LIGO safety requirements. A hazard/risk analysis shall be conducted in accordance with guidelines set forth in the LIGO Project System Safety Management Plan LIGO-M950046-F, section 3.3.2.
3.3.3.5 Active Optics Compensation Controls Human Engineering
Note: For many detector subsystems, this section is not applicable.
Specify any special or unique requirements, e.g., constraints on allocation of functions to personnel, and communications and personnel/equipment interactions. Also include any specified areas, stations, or equipment that require concentrated human engineering attention due to the sensitivity of the operation, i.e. those areas where the effects of human error would be particularly serious.
Example: Seismically isolated platforms or points must accommodate addition, removal and adjustment of equipment with a minimum of force or torque applied to the platforms. This requires that adequate space be provided surrounding the optics platform for an individual to move into proper position for the work intended. Equipment mounted to the optics platform should be provided with fasteners that can accommodate these force/torque requirements.
3.3.4 Active Optics Compensation Controls Assembly and Maintenance
Assembly fixtures and installation/replacement procedures shall be developed in conjunction with the AOS hardware design. These shall include (but not be limited to) fixtures and procedures for:
• AOS component insertion and assembly into the vacuum chambers without load support from the chambers
• assembly of the in vacuum components in a clean room (class 100) environment
• initial alignment of the AOS components
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3.3.5 Active Optics Compensation Controls Documentation
Requirements for documentation of the design, including types of documents, such as operator manuals, etc.
3.3.5.1 Active Optics Compensation Controls Specifications
List any additional specifications to be provided during the course of design and development, such as Interface Control Documents (ICD) and any lower level specifications to be developed.
3.3.5.2 Active Optics Compensation Controls Design Documents
List all design documents to be produced, including installation and commissioning plans, standards documents, etc.
Example:
• LIGO SEI System Preliminary Design Document (including supporting technical design and analysis documentation)
• LIGO SEI System Final Design Document (including supporting technical design and analysis documentation)
• LIGO SEI Prototype/Test Plans
• LIGO SEI Installation and Commissioning Plans and Procedures
3.3.5.3 Active Optics Compensation Controls Engineering Drawings and Associated Lists
A complete set of drawings suitable for fabrication must be provided along with Bill of Material (BOM) and drawing tree lists. The drawings must comply with LIGO standard formats and must be provided in electronic format. All documents shall use the LIGO drawing numbering system, be drawn using LIGO Drawing Preparation Standards, etc.
3.3.5.4 Active Optics Compensation Controls Technical Manuals and Procedures
3.3.5.4.1 Procedures
Procedures shall be provided for, at minimum,
• Initial installation and setup of equipment
• Normal operation of equipment
• Normal and/or preventative maintenance
• Installation of new equipment
• Troubleshooting guide for any anticipated potential malfunctions
3.3.5.4.2 Manuals
Any manuals to be provided, such as operator’s manual, etc.
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3.3.5.5 Active Optics Compensation Controls Documentation Numbering
All documents shall be numbered and identified in accordance with the LIGO documentation control numbering system LIGO document TBD
3.3.5.6 Active Optics Compensation Controls Test Plans and Procedures
All test plans and procedures shall be developed in accordance with the LIGO Test Plan Guidelines, LIGO document TBD.
3.3.6 Active Optics Compensation Controls Logistics
The design shall include a list of all recommended spare parts and special test equipment required.
3.3.7 Active Optics Compensation Controls Precedence
This section should list the relative importance of requirements (or goals) to be achieved by the design.
3.3.8 Active Optics Compensation Controls Qualification
Test and acceptance criteria.
3.4 Output Modecleaner Requirements
3.4.1 Introduction
Requirements flow down tree from Detector DRD should be included in this section.
3.4.2 Output Modecleaner Characteristics
3.4.2.1 Active Optics Compensation Performance Characteristics
This section should contain all functional and performance characteristics that the product must fulfill i.e. what is expected of the product.
This area contains any physical requirements or constraints on the product: dimensional and weight limitations, acceptable materials or properties of the materials, durability factors, transportation and storage requirements, etc.
3.4.2.3 Output Modecleaner Interface Definitions
Specify all interfaces to other systems/subsystems/components and the characteristics (electrical/mechanical/optical) of those interfaces. Note that these are all requirements placed on the item specified, NOT requirements this item places on other systems.
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3.4.2.3.1 Interfaces to other LIGO detector subsystems
3.4.2.3.1.1 Mechanical Interfaces
3.4.2.3.1.2 Electrical Interfaces
3.4.2.3.1.3 Optical Interfaces
3.4.2.3.1.4 Stay Clear Zones
3.4.2.3.2 Interfaces external to LIGO detector subsystems
3.4.2.3.2.1 Mechanical Interfaces
3.4.2.3.2.2 Electrical Interfaces
3.4.2.3.2.3 Stay Clear Zones
3.4.2.4 Output Modecleaner Reliability
Mean Time Between Failures (MTBF), Availability
3.4.2.5 Output Modecleaner Maintainability
Mean Time To Repair (MTTR); Qualitative requirements for accessibility, modular construction, test points, etc.
Environments that the equipment is expected to experience in shipment, storage, service or use. Subparagraphs should include, as necessary, climate, shock, vibration, noise, etc.
3.4.2.6.1 Natural Environment
3.4.2.6.1.1 Temperature and Humidity
Example:
Table 3 Environmental Performance Characteristics
Operating Non-operating (storage) Transport
+0 C to +50 C, 0–90 % RH 40 C to +70 C, 0–90 % RH 40 C to +70 C, 0–90 % RH
3.4.2.6.1.2 Atmospheric Pressure
3.4.2.6.1.3 Seismic Disturbance
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The following example for the SEI subsystem is illustrative:
Restraint against seismically induced large motion is required.
The system shall be designed to resist the static equivalent lateral forces defined in the Uniform Building Code (UBC), 1994 edition, for a seismic zone factor Z = 0.15 (i.e. zone 2B, Hanford) and a structure importance factor I = 1. The support structure shall resist the seismic loads without damage. The seismic stack shall sustain the base shear motion of the support structure without collapse or release of any of the stack layers. At a minimum, failure of the actuators under these loads should not cause failure of the bellows or cause the seismic stack to “drop”; ideally the actuators would survive these loads with no damage.
As an alternative to this static equivalent load, an acceleration design spectrum for use in dynamic analysis could be used.
Interpretation of the requirement: If there is no damping or plastic deformation to absorb the seismic loading (Rw = 1), and the SEI first frequency is between 2.5 Hz and 10 Hz (i.e. at the peak), then the base shear,
Vb = (Z I C/Rw) W = (0.15 (1) 2.75/1) W = 0.4 W
or the SEI must sustain a 0.4 g lateral load. If, as in the case of the Corner Station building, Rw = 6, then, then SEI must sustain a 0.1 g lateral load.
3.4.2.6.2 Induced Environment
These are environmental conditions induced by equipment. The following subparagraphs list some possible categories. Remember to list the requirements both in terms of:
What the item to be designed must accept from its surroundings
What environment the item to be designed is allowed to generate
3.4.2.6.2.1 Electromagnetic Radiation
Electrical equipment associated with the subsystem shall meet the EMI and EMC requirements of VDE 0871 Class A or equivalent. The subsystem shall also comply with the LIGO EMI Control Plan and Procedures (LIGO-E960036).
3.4.2.6.2.2 Acoustic
Equipment shall be designed to produce the lowest levels of acoustic noise as possible and practical. As a minimum, equipment shall not produce acoustic noise levels greater than specified in Derivation of CDS Rack Acoustic Noise Specifications, LIGO-T960083.
3.4.2.6.2.3 Mechanical Vibration
Mechanical vibration from the subsystem shall not increase the vibration amplitude of the facility floor within 1 m of any other vacuum chambers and equipment tables by more than 1 dB at any frequency between 0.1 Hz and 10 kHz. Limited narrowband exemptions may be permitted subject to LIGO review and approval.
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3.4.2.7 Output Modecleaner Transportability
All items shall be transportable by commercial carrier without degradation in performance. As necessary, provisions shall be made for measuring and controlling environmental conditions (temperature and accelerations) during transport and handling. Special shipping containers, shipping and handling mechanical restraints, and shock isolation shall be utilized to prevent damage. All containers shall be movable for forklift. All items over 100 lbs. which must be moved into place within LIGO buildings shall have appropriate lifting eyes and mechanical strength to be lifted by cranes.
3.4.3 Output Modecleaner Design and Construction
Minimum or essential requirements that are not controlled by performance characteristics, interfaces, or referenced documents. This can include design standards, requirements governing the use or selection of materials, parts and processes, interchangeability requirements, safety requirements, etc.
3.4.3.1 Materials and Processes
Such items as units of measure to be used (English, Metric) should be listed and any other general items, such as standard polishing procedures and processes.
3.4.3.1.1 Finishes
Examples:
Ambient Environment: Surface-to-surface contact between dissimilar metals shall be controlled in accordance with the best available practices for corrosion prevention and control.
External surfaces: External surfaces requiring protection shall be painted purple or otherwise protected in a manner to be approved.
• Metal components shall have quality finishes on all surfaces, suitable for vacuum finishes. All corners shall be rounded to TBD radius.
• All materials shall have non-shedding surfaces.
• Aluminum components used in the vacuum shall not have anodized surfaces.
• Optical table surface roughness shall be within 32 micro-inch.
3.4.3.1.2 Materials
A list of currently approved materials for use inside the LIGO vacuum envelope can be found in LIGO Vacuum Compatible Materials List (LIGO-E960022). All fabricated metal components exposed to vacuum shall be made from stainless steel, copper, or aluminum. Other metals are subject to LIGO approval. Pre-baked viton (or fluorel) may be used subject to LIGO approval. All materials used inside the vacuum chamber must comply with LIGO Vacuum Compatibility, Cleaning Methods and Procedures (LIGO-E960022-00-D).
The only lubricating films permitted within the vacuum are dry plating of vacuum compatible materials such as silver and gold.
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3.4.3.1.3 Processes
3.4.3.1.3.1 Welding
Before welding, the surfaces should be cleaned (but baking is not necessary at this stage) according to the UHV cleaning procedure(s). All welding exposed to vacuum shall be done by the tungsten-arc-inert-gas (TIG) process. Welding techniques for components operated in vacuum shall deviate from the ASME Code in accordance with the best ultra high vacuum practice to eliminate any “virtual leaks” in welds; i. e. all vacuum welds shall be continuous wherever possible to eliminate trapped volumes. All weld procedures for components operated in vacuum shall include steps to avoid contamination of the heat affected zone with air, hydrogen or water, by use of an inert purge gas that floods all sides of heated portions.
The welds should not be subsequently ground (in order to avoid embedding particles from the grinding wheel).
3.4.3.1.3.2 Cleaning
All materials used inside the vacuum chambers must be cleaned in accordance with Specification Guidance for Seismic Component Cleaning, Baking, and Shipping Preparation (LIGO-L970061-00-D). To facilitate final cleaning procedures, parts should be cleaned after any processes that result in visible contamination from dust, sand or hydrocarbon films.
Materials shall be joined in such a way as to facilitate cleaning and vacuum preparation procedures; i. e. internal volumes shall be provided with adequate openings to allow for wetting, agitation and draining of cleaning fluids and for subsequent drying.
3.4.3.1.4 Component Naming
All components shall be identified using the LIGO Naming Convention (LIGO-E950111-A-E). This shall include identification (part or drawing number, revision number, serial number) physically stamped on all components, in all drawings and in all related documentation.
3.4.3.2 Output Modecleaner Workmanship
Standard of workmanship desired, uniformity, freedom from defects and general appearance of the finished product.
3.4.3.3 Output Modecleaner Interchangeability
Specify the level at which components shall be interchangeable or replaceable.
3.4.3.4 Output Modecleaner Safety
This item shall meet all applicable NSF and other Federal safety regulations, plus those applicable State, Local and LIGO safety requirements. A hazard/risk analysis shall be conducted in accordance with guidelines set forth in the LIGO Project System Safety Management Plan LIGO-M950046-F, section 3.3.2.
3.4.3.5 Output Modecleaner Human Engineering
Note: For many detector subsystems, this section is not applicable.
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Specify any special or unique requirements, e.g., constraints on allocation of functions to personnel, and communications and personnel/equipment interactions. Also include any specified areas, stations, or equipment that require concentrated human engineering attention due to the sensitivity of the operation, i.e. those areas where the effects of human error would be particularly serious.
Example: Seismically isolated platforms or points must accommodate addition, removal and adjustment of equipment with a minimum of force or torque applied to the platforms. This requires that adequate space be provided surrounding the optics platform for an individual to move into proper position for the work intended. Equipment mounted to the optics platform should be provided with fasteners that can accommodate these force/torque requirements.
3.4.4 Output Modecleaner Assembly and Maintenance
Assembly fixtures and installation/replacement procedures shall be developed in conjunction with the AOS hardware design. These shall include (but not be limited to) fixtures and procedures for:
• AOS component insertion and assembly into the vacuum chambers without load support from the chambers
• assembly of the in vacuum components in a clean room (class 100) environment
• initial alignment of the AOS components
3.4.5 Output Modecleaner Documentation
Requirements for documentation of the design, including types of documents, such as operator manuals, etc.
3.4.5.1 Output Modecleaner Specifications
List any additional specifications to be provided during the course of design and development, such as Interface Control Documents (ICD) and any lower level specifications to be developed.
3.4.5.2 Output Modecleaner Design Documents
List all design documents to be produced, including installation and commissioning plans, standards documents, etc.
Example:
• LIGO SEI System Preliminary Design Document (including supporting technical design and analysis documentation)
• LIGO SEI System Final Design Document (including supporting technical design and analysis documentation)
• LIGO SEI Prototype/Test Plans
• LIGO SEI Installation and Commissioning Plans and Procedures
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3.4.5.3 Output Modecleaner Engineering Drawings and Associated Lists
A complete set of drawings suitable for fabrication must be provided along with Bill of Material (BOM) and drawing tree lists. The drawings must comply with LIGO standard formats and must be provided in electronic format. All documents shall use the LIGO drawing numbering system, be drawn using LIGO Drawing Preparation Standards, etc.
3.4.5.4 Output Modecleaner Technical Manuals and Procedures
3.4.5.4.1 Procedures
Procedures shall be provided for, at minimum,
• Initial installation and setup of equipment
• Normal operation of equipment
• Normal and/or preventative maintenance
• Installation of new equipment
• Troubleshooting guide for any anticipated potential malfunctions
3.4.5.4.2 Manuals
Any manuals to be provided, such as operator’s manual, etc.
All documents shall be numbered and identified in accordance with the LIGO documentation control numbering system LIGO document TBD
3.4.5.6 Output Modecleaner Test Plans and Procedures
All test plans and procedures shall be developed in accordance with the LIGO Test Plan Guidelines, LIGO document TBD.
3.4.6 Output Modecleaner Logistics
The design shall include a list of all recommended spare parts and special test equipment required.
3.4.7 Output Modecleaner Precedence
This section should list the relative importance of requirements (or goals) to be achieved by the design.
3.4.8 Output Modecleaner Qualification
Test and acceptance criteria.
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3.5 PO Mirror and Telescope Requirements
3.5.1 Introduction
Requirements flow down tree from Detector DRD should be included in this section.
3.5.2 PO Mirror and Telescope Characteristics
3.5.2.1 PO Mirror and Telescope Performance Characteristics
3.5.2.1.1 APS, ITM, and BS PO Beams
3.5.2.1.1.1 Wavefront Distortion
The PO Mirror, APS Telescope, PO Telescope, Steering Mirrors, and output viewports shall not cause excessive wavefront distortion of the PO beams. Acceptable wavefront distortion will maintain the WFS signal contrast ratio >5:1.
3.5.2.1.1.2 Clear Input Aperture, PO and APS Beams
232mm diameter, which is equal to the 100 ppm diameter of the main beam.
3.5.2.1.1.3 Telescope De-magnification Ratio, PO and APS Telescopes
12:1
3.5.2.1.1.4 Clear Output Aperture, PO and APS Beams
> 19mm diameter, which is equal to the 100 ppm diameter of the output beam
3.5.2.1.1.5 Optical Train Transmissivity
>96% for APS optical train
>88% for PO optical train
3.5.2.1.1.6 Field-of-View
The PO and APS telescopes shall function satisfactorily with an angular field-of-view of +/- 0.0004 rad.
3.5.2.1.2 ETM Monitor Beam
3.5.2.1.2.1 Wavefront Distortion
N/A
3.5.2.1.2.2 Clear Input Aperture, ETM Beams
> 160mm diameter
3.5.2.1.2.3 Telescope De-magnification Ratio, PO and APS Telescopes
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8:1
3.5.2.1.2.4 Optical Train Transmissivity
>96% for ETM monitor optical train
3.5.2.1.2.5 Field-of-View
N/A
3.5.2.2 PO Mirror and Telescope Physical Characteristics
3.5.2.2.1 Vacuum compatibility of COS elements
3.5.2.2.1.1 Outgassing of COS elements
The COS elements shall be fabricated from materials whose outgassing properties are compatible with the vacuum requirements of the LIGO. See LIGO Vacuum Compatibility, Cleaning Methods and Procedures, LIGO-E960022-00-D
3.5.2.2.2 Access for Optical lever beams and TV Camera Viewing of COCs
The beam-dump/baffle assemblies shall allow access to the optical lever beams and TV camera viewing of the COC elements. See ASC Optical Lever Design Requirement Document, LIGO-T950106-01-D
3.5.2.2.3 Optical Alignment of COS
The AOS telescopes shall be pre-aligned before assembly into the IFO vacuum housing.
The AOS telescopes and optical beam-dump/baffles shall be final aligned to the IFO optical cen-terline and ghost beam centerlines during the initial IFO optical alignment.
3.5.2.2.4 Resonant Frequency of AOS Elements Mounted on the Optics Platform
The resonant frequencies and Q’s of the PO mirrors and Telescopes and accessory optics which are mounted to the optics platforms shall not cause excessive induced thermal-noise of the test mass.
The advanced LIGO requirement for thermally induced noise amplitude impressed on the test mass shall not exceed
in the frequency band 10-1000Hz. See LIGO-Exxx.
The maximum thermal noise amplitude occurs at resonance, and the minimum resonant frequency which meets the requirement is given by
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The thermal motion induced in the SEI platform is attenuated by the test mass suspension system,
With a 58 kg mass telescope having a Q of 10 and with the test mass suspended by a three-stage pendula seismic isolation system, the minimum resonant frequency of the telescope body which meets the requirement is
3.5.2.3 PO Mirror and Telescope Interface Definitions
3.5.2.3.1 Interfaces to other LIGO detector subsystems
3.5.2.3.1.1 Mechanical Interfaces
The PO Mirrors shall mount to the SEI platforms, in the BSC chambers, without interfering with the COC mirror structures.
The Telescopes and associated optical train elements shall mount to the SEI platform in the BSC and HAM chambers, without interfering with the COC mirror structures.
The viewport windows shall mount to the existing ports in the HAM chamber and BSC chamber doors.
3.5.2.3.1.2 Electrical Interfaces
There are no electrical interfaces.
3.5.2.3.1.3 Optical Interfaces
The Telescopes shall provide a large enough field of view so that the PO beams and APS beams will be properly acquired before and after pump-down of the vacuum chambers.
The output beams from the Telescopes will be steered through the centers of the viewports in the appropriate HAM and BSC chambers and shall be accessible to the ISC system.
3.5.2.3.1.4 Stay Clear Zones
The PO mirrors and Telescopes shall maintain a stay clear zone of >34 mm from the 1ppm margin of the main interferometer beam.
3.5.2.4 PO Mirror and Telescope Reliability
All PO Mirror and Telescope elements are passive and are expected to have a 100% availability. The MTBF is expected to be equal to the life of the detector.
3.5.2.5 PO Mirror and Telescope Maintainability
Spare components will be stocked for the replacement during installation of long lead time items such as telescope mirrors and lenses.
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3.5.2.6 PO Mirror and Telescope Environmental Conditions
The PO Mirror and Telescope elements will operate in a temperature and humidity controlled laboratory environment. Prior to assembly, the components of the PO Mirror and Telescope subsystem can be subjected to normal commercial shipping and handling environments.
3.5.2.7 PO Mirror and Telescope Transportability
All items shall be transportable by commercial carrier without degradation in performance. As necessary, provisions shall be made for measuring and controlling environmental conditions (temperature and accelerations) during transport and handling. Special shipping containers, shipping and handling mechanical restraints, and shock isolation shall be utilized to prevent damage. All containers shall be movable for forklift. All items over 100 lbs. which must be moved into place within LIGO buildings shall have appropriate lifting eyes and mechanical strength to be lifted by cranes.
3.5.3 PO Mirror and Telescope Design and Construction
The design and construction of the PO Mirror and Telescope subsystem allow adequate cleaning, either on site or at an appropriate outside vendor, and shall fit inside the vacuum baking ovens on site.
3.5.3.1 Materials and Processes
The materials and processes used in the fabrication of the PO Mirror and Telescope subsystem shall be compatible with the LIGO approved materials list.
3.5.3.1.1 Finishes
• Metal components shall have quality finishes on all surfaces, suitable for vacuum finishes. All corners shall be rounded to TBD radius.
• All materials shall have non-shedding surfaces.
• Aluminum components used in the vacuum shall not have anodized surfaces.
3.5.3.1.2 Materials
A list of currently approved materials for use inside the LIGO vacuum envelope can be found in LIGO Vacuum Compatible Materials List (LIGO-E960022). All fabricated metal components exposed to vacuum shall be made from stainless steel, copper, or aluminum. Other metals are subject to LIGO approval. Pre-baked viton (or fluorel) may be used subject to LIGO approval. All materials used inside the vacuum chamber must comply with LIGO Vacuum Compatibility, Cleaning Methods and Procedures (LIGO-E960022-00-D).
The only lubricating films permitted within the vacuum are dry plating of vacuum compatible materials such as silver and gold.
3.5.3.1.3 Processes
3.5.3.1.3.1 Cleaning
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All materials used inside the vacuum chambers must be cleaned in accordance LIGO-E960022-00-D, or LIGO-E000007-00.
Materials shall be joined in such a way as to facilitate cleaning and vacuum preparation procedures; i. e. internal volumes shall be provided with adequate openings to allow for wetting, agitation and draining of cleaning fluids and for subsequent drying.
3.5.3.1.4 Component Naming
All components shall be identified using the LIGO Naming Convention (LIGO-E950111-A-E). This shall include identification (part or drawing number, revision number, serial number) physically stamped on all components, in all drawings and in all related documentation.
3.5.3.2 PO Mirror and Telescope Workmanship
All components shall be manufactured according to good commercial practice.
3.5.3.3 PO Mirror and Telescope Interchangeability
Common elements, with ordinary dimensional tolerances, will be interchangeable. Certain telescope elements with unusually tight dimensional tolerances, such as the ETM telescope focus barrel, will be manufactured as matched sets and will not be interchangeable.
3.5.3.4 PO Mirror and Telescope Safety
This item shall meet all applicable NSF and other Federal safety regulations, plus those applicable State, Local and LIGO safety requirements. A hazard/risk analysis shall be conducted in accordance with guidelines set forth in the LIGO Project System Safety Management Plan LIGO-M950046-F, section 3.3.2.
3.5.3.5 PO Mirror and Telescope Human Engineering
NA
3.5.4 PO Mirror and Telescope Assembly and Maintenance
Assembly fixtures and installation procedures shall be developed in conjunction with the Stray Light Control hardware design. These shall include (but not be limited to) fixtures and procedures for:
• installation and assembly of beam dumps and baffles into the vacuum
• assembly of the in vacuum components in a clean room (class 100) environment
3.5.5 PO Mirror and Telescope Documentation
The documentation shall consist of working drawings, assembly drawings, and alignment procedures.
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3.5.5.1 PO Mirror and Telescope Specifications
Specifications for the purchase of specialized components and assemblies such as Faraday isolator, optical mirrors, windows, and lenses shall be developed.
3.5.5.2 PO Mirror and Telescope Design Documents
The following documents will be produced:
• LIGO Stray Light Control Preliminary Design Document (including supporting technical design and analysis documentation)
• LIGO Stray Light Control Final Design Document (including supporting technical design and analysis documentation)
• LIGO Stray Light Control Installation Procedures
3.5.5.3 PO Mirror and Telescope Engineering Drawings and Associated Lists
A complete set of drawings suitable for fabrication must be provided along with Bill of Material (BOM) and drawing tree lists. The drawings must comply with LIGO standard formats and must be provided in electronic format. All documents shall use the LIGO drawing numbering system, be drawn using LIGO Drawing Preparation Standards, etc.
3.5.5.4 PO Mirror and Telescope Technical Manuals and Procedures
3.5.5.4.1 Procedures
Procedures shall be provided for the installation, and final alignment of the Stray Light Control elements.
3.5.5.5 PO Mirror and Telescope Documentation Numbering
All documents shall be numbered and identified in accordance with the LIGO documentation control numbering system LIGO document TBD
3.5.5.6 PO Mirror and Telescope Test Plans and Procedures
All test plans and procedures shall be developed in accordance with the LIGO Test Plan Guidelines, LIGO document TBD.
3.5.6 PO Mirror and Telescope Logistics
The design shall include a list of all recommended spare parts and special test equipment required.
3.5.7 PO Mirror and Telescope Precedence
The relative importance of the PO Mirror and Telescope subsystem requirements are as follows:
1) clear aperture through the APS and PO optical trains
2) optical transmissivity through the APS and PO optical trains
3) compatibility with COC elements
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3.5.8 PO Mirror and Telescope Qualification
N/A
3.6 Initial Alignment System Requirements
3.6.1 IntroductionInitial alignment must set the Nd Yag laser beam within the range of adjustment of the COS such that a transition to acquisition alignment can take place.
3.6.2 Initial Alignment System Characteristics
3.6.2.1 Initial Alignment System Performance Characteristics
Bearings: Ball type with a run out of 0.000025 of an inch or less
Approximate Weight: Instrument, 34 pounds; instrument and case, 54
pounds; shipping, 56 pounds
Laser Autocollimator
Source Visible laser diode modulated at 10 kHz
Wavelength 670 nm
Peak power 900 µW (Class II)
Beam diameter 31 mm
Beam divergence 100 µrad
Beam direction 500 µrad
Equivalent focal length 280 mm
Measurement field ±2000 µrad
Ocular field ±15 mrad (±1.1°)
Resolution 0.1 µrad
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Measurement distortion ±1 {±0.02 x measurement} µrad (i.e. 2%)
Reflector Min. 2% reflectivity
Noise 0.02 µrad/Hz (at 100% reflectivity)
Weight 1.1 kg
3.6.2.3 Initial Alignment System Interface Definitions
3.6.2.3.1 Interfaces to other LIGO detector subsystems
3.6.2.3.1.1 Mechanical Interfaces
The PLX retro reflector and the optical flat are auxiliary alignment equipment, which must lie within the vacuum tube spool pieces.
3.6.2.3.1.2 Electrical Interfaces
There are no electrical interfaces.
3.6.2.3.1.3 Optical Interfaces
There are no optical interfaces.
3.6.2.3.1.4 Stay Clear Zones
During critical alignments a roped off area of 48” minimum is required to prevent disturbance of the alignment equipment.
3.6.2.3.2 Interfaces external to LIGO detector subsystems
There are no interfaces external to the LIGO detector subsystem.
3.6.2.4 Initial Alignment System Reliability
There are no published system reliability for alignment instrumentation. Alignment equipment is supplied to each site. In the event of failure the equipment from the alternate site will be available as backup.
3.6.2.5 Initial Alignment System Maintainability
The following calibrations should be performed following shipment, storage or extended use:
Theodolite / 3-D Coordinate Measuring System
• Adjust tilt sensing error per appendix 2 of Field Manual.
• Check optical plummet accuracy per page 155 of Field Manual.
• Check double centering error per page 149 of Field Manual.
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Transit Square
• Check squareness per LIGO T970151-C appendix B.
• Check double centering error per Field Manual.
• Check horizontal axis with vertical wire per Field Manual.
Laser Autocollimator
• Check accuracy per auto calibration kit supplied.
3.6.2.6
3.6.2.7 Initial Alignment System Environmental Conditions
3.6.2.7.1 Natural Environment
3.6.2.7.1.1 Temperature and Humidity
Table 4 Environmental Performance Characteristics
Operating Non-operating (storage) Transport
17°C to +24°C (62°F to 75°F)
-10°C to +40°C (14°F to 104°F)
-10°C to +40°C (14°F to 104°F)
3.6.2.7.1.2 Atmospheric Pressure
3.6.2.7.1.3 Seismic Disturbance:
The Initial Alignment equipment requires a stable, rigid foundation for accurate angular alignment. The alignment instruments and optic should be on a common block. The first bending mode of the foundation block should be greater than 100 Hz.
3.6.2.7.2 Induced Environment
3.6.2.7.2.1 Electromagnetic Radiation
Electrical equipment associated with the subsystem shall meet the EMI and EMC requirements of VDE 0871 Class A or equivalent. The subsystem shall also comply with the LIGO EMI Control Plan and Procedures (LIGO-E960036).
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3.6.2.7.2.2 Acoustic
Equipment shall be designed to produce the lowest levels of acoustic noise as possible and practical. As a minimum, equipment shall not produce acoustic noise levels greater than specified in Derivation of CDS Rack Acoustic Noise Specifications, LIGO-T960083.
3.6.2.7.2.3 Mechanical Vibration
Mechanical vibration from the subsystem shall not increase the vibration amplitude of the facility floor within 1 m of any other vacuum chambers and equipment tables by more than 1 dB at any frequency between 0.1 Hz and 10 kHz. Limited narrowband exemptions may be permitted subject to LIGO review and approval.
3.6.2.8 Initial Alignment System Transportability
All items shall be transportable by commercial carrier without degradation in performance. As necessary, provisions shall be made for measuring and controlling environmental conditions (temperature and accelerations) during transport and handling. Special shipping containers, shipping and handling mechanical restraints, and shock isolation shall be utilized to prevent damage. All containers shall be movable for forklift. All items over 100 lbs. which must be moved into place within LIGO buildings shall have appropriate lifting eyes and mechanical strength to be lifted by cranes.
3.6.3 Initial Alignment System Design and Construction
The design and construction of the Initial Alignment equipment used in vacuum must allow for adequate cleaning, either on site or at an appropriate outside vendor, and shall fit inside the vacuum baking ovens on site.
3.6.3.1 Materials and Processes
The materials and processes used in the fabrication of the Initial Alignment subsystem shall be compatible with the LIGO approved materials list.
3.6.3.1.1 Finishes:
Ambient Environment: Surface-to-surface contact between dissimilar metals shall be controlled in accordance with the best available practices for corrosion prevention and control.
External surfaces: External surfaces requiring protection shall be painted purple or otherwise protected in a manner to be approved.
• Metal components shall have quality finishes on all surfaces, suitable for vacuum finishes. All corners shall be rounded to TBD radius.
• All materials shall have non-shedding surfaces.
• Aluminum components used in the vacuum shall not have anodized surfaces.
• Optical table surface roughness shall be within 32 micro-inch.
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3.6.3.1.2 Materials
A list of currently approved materials for use inside the LIGO vacuum envelope can be found in LIGO Vacuum Compatible Materials List (LIGO-E960022). All fabricated metal components exposed to vacuum shall be made from stainless steel, copper, or aluminum. Other metals are subject to LIGO approval. Pre-baked viton (or fluorel) may be used subject to LIGO approval. All materials used inside the vacuum chamber must comply with LIGO Vacuum Compatibility, Cleaning Methods and Procedures (LIGO-E960022-00-D).
The only lubricating films permitted within the vacuum are dry plating of vacuum compatible materials such as silver and gold.
3.6.3.1.3 Processes
3.6.3.1.3.1 Welding
Before welding, the surfaces should be cleaned (but baking is not necessary at this stage) according to the UHV cleaning procedure(s). All welding exposed to vacuum shall be done by the tungsten-arc-inert-gas (TIG) process. Welding techniques for components operated in vacuum shall deviate from the ASME Code in accordance with the best ultra high vacuum practice to eliminate any “virtual leaks” in welds; i. e. all vacuum welds shall be continuous wherever possible to eliminate trapped volumes. All weld procedures for components operated in vacuum shall include steps to avoid contamination of the heat affected zone with air, hydrogen or water, by use of an inert purge gas that floods all sides of heated portions.
The welds should not be subsequently ground (in order to avoid embedding particles from the grinding wheel).
3.6.3.1.3.2 Cleaning
All materials used inside the vacuum chambers must be cleaned in accordance with Specification Guidance for Seismic Component Cleaning, Baking, and Shipping Preparation (LIGO-L970061-00-D). To facilitate final cleaning procedures, parts should be cleaned after any processes that result in visible contamination from dust, sand or hydrocarbon films.
Materials shall be joined in such a way as to facilitate cleaning and vacuum preparation procedures; i. e. internal volumes shall be provided with adequate openings to allow for wetting, agitation and draining of cleaning fluids and for subsequent drying.
3.6.3.1.4 Component Naming
All components shall be identified using the LIGO Naming Convention (LIGO-E950111-A-E). This shall include identification (part or drawing number, revision number, serial number) physically stamped on all components, in all drawings and in all related documentation.
3.6.3.2 Initial Alignment System Workmanship
All components shall be manufactured according to good commercial practice.
3.6.3.3 Initial Alignment System Interchangeability
Common elements, with ordinary dimensional tolerances will be interchangeable.
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3.6.3.4 Initial Alignment System Safety
This item shall meet all applicable NSF and other Federal safety regulations, plus those applicable State, Local and LIGO safety requirements. A hazard/risk analysis shall be conducted in accordance with guidelines set forth in the LIGO Project System Safety Management Plan LIGO-M950046-F, section 3.3.2.
3.6.3.5 Initial Alignment System Human Engineering
Platforms that bridge over piping and conduit are to be designed to minimize eye and back strain.
3.6.4 Initial Alignment System Assembly and Maintenance
Assembly fixtures and installation/replacement procedures shall be developed in conjunction with the AOS hardware design. These shall include (but not be limited to) fixtures and procedures for:
• AOS component insertion and assembly into the vacuum chambers without load support from the chambers
• assembly of the in vacuum components in a clean room (class 100) environment
• Initial alignment of the AOS components
3.6.5 Initial Alignment System Documentation
The documentation shall consist of working drawings, assembly drawings, and alignment procedures.
3.6.5.1 Initial Alignment System Specifications
Specifications for the purchase of specialized components and assemblies such as optical mirrors, windows, and targets shall be developed.
3.6.5.2 Initial Alignment System Design Documents
The following documents will be produced:
• LIGO Initial Alignment Procedures Document.
• LIGO Initial Alignment Final Design Review Document
• LIGO Initial Alignment Installation and Commissioning Plans.
3.6.5.3 Initial Alignment System Engineering Drawings and Associated Lists
A complete set of drawings suitable for fabrication must be provided along with Bill of Material (BOM) and drawing tree lists. The drawings must comply with LIGO standard formats and must be provided in electronic format. All documents shall use the LIGO drawing numbering system, be drawn using LIGO Drawing Preparation Standards, etc.
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3.6.5.4 Initial Alignment System Technical Manuals and Procedures
3.6.5.4.1 Procedures
The following procedures shall be provided:
• Initial installation and setup of equipment
• Normal operation of equipment
• Normal and/or preventative maintenance
• Installation of new equipment
• Troubleshooting guide for any anticipated potential malfunctions
3.6.5.4.2 Manuals
Provided by manufacturer.
3.6.5.5 Initial Alignment System Documentation Numbering
All documents shall be numbered and identified in accordance with the LIGO documentation control numbering system LIGO document TBD
3.6.5.6 Initial Alignment System Test Plans and Procedures
All test plans and procedures shall be developed in accordance with the LIGO Test Plan Guidelines, LIGO document TBD.
3.6.6 Initial Alignment System Logistics
The design shall include a list of all recommended spare parts and special test equipment required.
3.6.7 Initial Alignment System Precedence
The relative importance of the Initial Alignment subsystem requirements is as follows:
1) Optic position and orientation requirements.
2) Reflectivity of core optics at 670 nm.
3) Minimizing disturbances to existing core optics, auxiliary optics, and operating equipment.
3.6.8 Initial Alignment System Qualification
During the setup of the PO Mirror and Telescope Subsystem a 980 nm laser autocollimator is introduced into the beam path. This beam is traced thru the corner station optics to verify the positions and orientations of the core optics.
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3.7 Optical Lever System Requirements
3.7.1 Introduction
Suspended Core optics and the final IO optic will be monitored during and after installation by an optical lever system. This system will provide an angular readout of the pitch and yaw angles of the optic with respect to the local facility foundation.
3.7.2 Optical Lever System Characteristics
3.7.2.1 Optical Lever System Performance Characteristics
The optical lever is intended as a reference for core optic alignment to maintain continuity between installation and operation. Its performance is limited by motions of the facility foundations; for example, pump down of a vacuum equipment component section is likely to induce floor tilts of order 100 micro radian, and changes due to cycling temperature gradients in the order of tens of micro radians. However these effects are in principal predictable. As a result the long-term stability of the optical lever performance will be +/- 50 micro radian peaks over extended time periods.
3.7.2.2 Optical Lever System Physical Characteristics
The optical levers must be isolated mechanically from the vacuum chambers and view ports in order to not be effected by pump down or thermal movements of the vacuum system. Flexible bellows will enclose the laser beam and provide isolation from for the optical lever systems.
3.7.2.3 Optical Lever System Interface Definitions
3.7.2.3.1 Interfaces to other LIGO detector subsystems
3.7.2.3.1.1 Mechanical Interfaces
Optical lever structures must be secured directly to the foundation. Examples of accepted structures include rigid stands and seismic piers. The laser source and photodiode assemblies are to be coupled to the vacuum viewports such that no thermal or vacuum induced movement is translated to the optical lever.
3.7.2.3.1.2 Electrical Interfaces
The laser source requires 5v electrical power and current sensing. The photodiode voltage output is fed to the DAQ system for monitoring.
3.7.2.3.1.3 Optical Interfaces
Clearance must be made for optical lever beams to pass through AOS baffles.
3.7.2.3.1.4 Stay Clear Zones
3.7.2.3.2 Interfaces external to LIGO detector subsystems
3.7.2.3.2.1 Mechanical Interfaces
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3.7.2.3.2.2 Electrical Interfaces
3.7.2.3.2.3 Stay Clear Zones
3.7.2.4 Optical Lever System Reliability
Optical lever laser sources are to have a MTBF of 10,000 hours.
3.7.2.5 Optical Lever System Maintainability
The following components are susceptible to failure:
1. Diode laser source assembly.
2. Motorized optic mount.
3. Photodiode assembly.
Each of these items is to have plug connections and are easily replaceable. Re-alignment of the laser source and photodiode calibration can be accomplished in less than 1 day.
3.7.2.6 Optical Lever System Environmental Conditions
3.7.2.6.1 Natural Environment
3.7.2.6.1.1 Temperature and Humidity
Example:
Table 5 Environmental Performance Characteristics
Operating Non-operating (storage) Transport
+15C to +45C, non- condensing
0C to +50C, non-condensing
0C to +50C, non- condensing
3.7.2.6.1.2 Atmospheric Pressure
3.7.2.6.1.3 Seismic Disturbance
The optical lever system requires a stable, rigid foundation for accurate monitoring of optic orientation. The optical lever source, receiver, and optic should be on a common block. The first bending mode of the foundation block should be greater than 100 Hz.
3.7.2.6.2 Induced Environment
3.7.2.6.2.1 Electromagnetic Radiation
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Electrical equipment associated with the subsystem shall meet the EMI and EMC requirements of VDE 0871 Class A or equivalent. The subsystem shall also comply with the LIGO EMI Control Plan and Procedures (LIGO-E960036).
3.7.2.6.2.2 Acoustic
Equipment shall be designed to produce the lowest levels of acoustic noise as possible and practical. As a minimum, equipment shall not produce acoustic noise levels greater than specified in Derivation of CDS Rack Acoustic Noise Specifications, LIGO-T960083.
3.7.2.6.2.3 Mechanical Vibration
Mechanical vibration from the subsystem shall not increase the vibration amplitude of the facility floor within 1 m of any other vacuum chambers and equipment tables by more than 1 dB at any frequency between 0.1 Hz and 10 kHz. Limited narrowband exemptions may be permitted subject to LIGO review and approval.
3.7.2.7 Optical Lever System Transportability
All items shall be transportable by commercial carrier without degradation in performance. As necessary, provisions shall be made for measuring and controlling environmental conditions (temperature and accelerations) during transport and handling. Special shipping containers, shipping and handling mechanical restraints, and shock isolation shall be utilized to prevent damage. All containers shall be movable for forklift. All items over 100 lbs. which must be moved into place within LIGO buildings shall have appropriate lifting eyes and mechanical strength to be lifted by cranes.
3.7.3 Optical Lever System Design and Construction
The optical lever system is designed and constructed with long-term stability in mind. The interface between materials of different coefficients of expansion is to be kinematically mounted in such a way that expansion will occur in the direction of the beam.
3.7.3.1 Materials and Processes
The materials and processes used in the fabrication of the Initial Alignment subsystem shall be compatible with the LIGO approved materials list.
3.7.3.1.1 Finishes
Ambient Environment: Surface-to-surface contact between dissimilar metals shall be controlled in accordance with the best available practices for corrosion prevention and control.
External surfaces: External surfaces requiring protection shall be painted purple or otherwise protected in a manner to be approved.
• Metal components shall have quality finishes on all surfaces, suitable for vacuum finishes. All corners shall be rounded to TBD radius.
• All materials shall have non-shedding surfaces.
• Aluminum components used in the vacuum shall not have anodized surfaces.
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• Optical table surface roughness shall be within 32 micro-inch.
3.7.3.1.2 Materials
A list of currently approved materials for use inside the LIGO vacuum envelope can be found in LIGO Vacuum Compatible Materials List (LIGO-E960022). All fabricated metal components exposed to vacuum shall be made from stainless steel, copper, or aluminum. Other metals are subject to LIGO approval. Pre-baked viton (or fluorel) may be used subject to LIGO approval. All materials used inside the vacuum chamber must comply with LIGO Vacuum Compatibility, Cleaning Methods and Procedures (LIGO-E960022-00-D).
The only lubricating films permitted within the vacuum are dry plating of vacuum compatible materials such as silver and gold.
3.7.3.1.3 Processes
3.7.3.1.3.1 Welding
Before welding, the surfaces should be cleaned (but baking is not necessary at this stage) according to the UHV cleaning procedure(s). All welding exposed to vacuum shall be done by the tungsten-arc-inert-gas (TIG) process. Welding techniques for components operated in vacuum shall deviate from the ASME Code in accordance with the best ultra high vacuum practice to eliminate any “virtual leaks” in welds; i. e. all vacuum welds shall be continuous wherever possible to eliminate trapped volumes. All weld procedures for components operated in vacuum shall include steps to avoid contamination of the heat affected zone with air, hydrogen or water, by use of an inert purge gas that floods all sides of heated portions.
The welds should not be subsequently ground (in order to avoid embedding particles from the grinding wheel).
3.7.3.1.3.2 Cleaning
All materials used inside the vacuum chambers must be cleaned in accordance with Specification Guidance for Seismic Component Cleaning, Baking, and Shipping Preparation (LIGO-L970061-00-D). To facilitate final cleaning procedures, parts should be cleaned after any processes that result in visible contamination from dust, sand or hydrocarbon films.
Materials shall be joined in such a way as to facilitate cleaning and vacuum preparation procedures; i. e. internal volumes shall be provided with adequate openings to allow for wetting, agitation and draining of cleaning fluids and for subsequent drying.
3.7.3.1.4 Component Naming
All components shall be identified using the LIGO Naming Convention (LIGO-E950111-A-E). This shall include identification (part or drawing number, revision number, serial number) physically stamped on all components, in all drawings and in all related documentation.
3.7.3.2 Optical Lever System Workmanship
All components shall be manufactured according to good commercial practice.
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3.7.3.3 Optical Lever System Interchangeability
Common elements, with ordinary dimensional tolerances will be interchangeable.
3.7.3.4 Optical Lever System Safety
This item shall meet all applicable NSF and other Federal safety regulations, plus those applicable State, Local and LIGO safety requirements. A hazard/risk analysis shall be conducted in accordance with guidelines set forth in the LIGO Project System Safety Management Plan LIGO-M950046-F, section 3.3.2.
3.7.3.5 Optical Lever System Human Engineering
Not applicable.
3.7.4 Optical Lever System Assembly and Maintenance
Assembly installation/calibration documentation shall be developed in conjunction with the optical lever hardware design.
3.7.5 Optical Lever System Documentation
The documentation shall consist of working drawings, assembly drawings, and alignment procedures.
3.7.5.1 Optical Lever System Specifications
Specifications for the purchase of specialized components and assemblies such as diode lasers optical mirrors, windows, and targets shall be developed.
3.7.5.2 Optical Lever System Design Documents
Revised drawings and calibration documents will be produced.
3.7.5.3 Optical Lever System Engineering Drawings and Associated Lists
A complete set of drawings suitable for fabrication will be provided along with Bill of Material (BOM) and drawing tree lists. The drawings will comply with LIGO standard formats and must be provided in electronic format. All documents shall use the LIGO drawing numbering system, be drawn using LIGO Drawing Preparation Standards, etc.
3.7.5.4 Optical Lever System Technical Manuals and Procedures
3.7.5.4.1 Procedures
Procedures shall be provided for, at minimum,
• Initial installation and setup of equipment
• Normal operation of equipment
• Normal and/or preventative maintenance
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• Installation of new equipment
• Troubleshooting guide for any anticipated potential malfunctions
3.7.5.4.2 Manuals
All manufacturer’s operating and installation manuals will be supplied and LIGO calibration procedures.
3.7.5.5 Optical Lever System Documentation Numbering
All documents shall be numbered and identified in accordance with the LIGO documentation control numbering system LIGO document TBD
3.7.5.6 Optical Lever System Test Plans and Procedures
All test plans and procedures shall be developed in accordance with the LIGO Test Plan Guidelines, LIGO document TBD.
3.7.6 Optical Lever System Logistics
The design shall include a list of all recommended spare parts and special test equipment required.
3.7.7 Optical Lever System Precedence
3.7.8 Initial Alignment System Precedence
The relative importance of the Initial Alignment subsystem requirements is as follows:
1. Long term stability of +/- 50 micro-radians.
2. MTBF of 5000 hours.
3. Visible wavelength for ease of alignment and troubleshooting.
3.7.9 Optical Lever System Qualification
Calibration of optical levers per LIGO documents T990026-00.
3.8 Photon Drive Requirements
3.8.1 Introduction
Requirements flow down tree from Detector DRD should be included in this section.
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3.8.2 Photon Drive Characteristics
3.8.2.1 Active Optics Compensation Performance Characteristics
This section should contain all functional and performance characteristics that the product must fulfill i.e. what is expected of the product.
3.8.2.2 Photon Drive Physical Characteristics
This area contains any physical requirements or constraints on the product: dimensional and weight limitations, acceptable materials or properties of the materials, durability factors, transportation and storage requirements, etc.
3.8.2.3 Photon Drive Interface Definitions
Specify all interfaces to other systems/subsystems/components and the characteristics (electrical/mechanical/optical) of those interfaces. Note that these are all requirements placed on the item specified, NOT requirements this item places on other systems.
3.8.2.3.1 Interfaces to other LIGO detector subsystems
3.8.2.3.1.1 Mechanical Interfaces
3.8.2.3.1.2 Electrical Interfaces
3.8.2.3.1.3 Optical Interfaces
3.8.2.3.1.4 Stay Clear Zones
3.8.2.3.2 Interfaces external to LIGO detector subsystems
3.8.2.3.2.1 Mechanical Interfaces
3.8.2.3.2.2 Electrical Interfaces
3.8.2.3.2.3 Stay Clear Zones
3.8.2.4 Photon Drive Reliability
Mean Time Between Failures (MTBF), Availability
3.8.2.5 Photon Drive Maintainability
Mean Time To Repair (MTTR); Qualitative requirements for accessibility, modular construction, test points, etc.
3.8.2.6 Photon Drive Environmental Conditions
Environments that the equipment is expected to experience in shipment, storage, service or use. Subparagraphs should include, as necessary, climate, shock, vibration, noise, etc.
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3.8.2.6.1 Natural Environment
3.8.2.6.1.1 Temperature and Humidity
Example:
Table 6 Environmental Performance Characteristics
Operating Non-operating (storage) Transport
+0 C to +50 C, 0–90 % RH 40 C to +70 C, 0–90 % RH 40 C to +70 C, 0–90 % RH
3.8.2.6.1.2 Atmospheric Pressure
3.8.2.6.1.3 Seismic Disturbance
The following example for the SEI subsystem is illustrative:
Restraint against seismically induced large motion is required.
The system shall be designed to resist the static equivalent lateral forces defined in the Uniform Building Code (UBC), 1994 edition, for a seismic zone factor Z = 0.15 (i.e. zone 2B, Hanford) and a structure importance factor I = 1. The support structure shall resist the seismic loads without damage. The seismic stack shall sustain the base shear motion of the support structure without collapse or release of any of the stack layers. At a minimum, failure of the actuators under these loads should not cause failure of the bellows or cause the seismic stack to “drop”; ideally the actuators would survive these loads with no damage.
As an alternative to this static equivalent load, an acceleration design spectrum for use in dynamic analysis could be used.
Interpretation of the requirement: If there is no damping or plastic deformation to absorb the seismic loading (Rw = 1), and the SEI first frequency is between 2.5 Hz and 10 Hz (i.e. at the peak), then the base shear,
Vb = (Z I C/Rw) W = (0.15 (1) 2.75/1) W = 0.4 W
or the SEI must sustain a 0.4 g lateral load. If, as in the case of the Corner Station building, Rw = 6, then, then SEI must sustain a 0.1 g lateral load.
3.8.2.6.2 Induced Environment
These are environmental conditions induced by equipment. The following subparagraphs list some possible categories. Remember to list the requirements both in terms of:
What the item to be designed must accept from its surroundings
What environment the item to be designed is allowed to generate
3.8.2.6.2.1 Electromagnetic Radiation
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Electrical equipment associated with the subsystem shall meet the EMI and EMC requirements of VDE 0871 Class A or equivalent. The subsystem shall also comply with the LIGO EMI Control Plan and Procedures (LIGO-E960036).
3.8.2.6.2.2 Acoustic
Equipment shall be designed to produce the lowest levels of acoustic noise as possible and practical. As a minimum, equipment shall not produce acoustic noise levels greater than specified in Derivation of CDS Rack Acoustic Noise Specifications, LIGO-T960083.
3.8.2.6.2.3 Mechanical Vibration
Mechanical vibration from the subsystem shall not increase the vibration amplitude of the facility floor within 1 m of any other vacuum chambers and equipment tables by more than 1 dB at any frequency between 0.1 Hz and 10 kHz. Limited narrowband exemptions may be permitted subject to LIGO review and approval.
3.8.2.7 Photon Drive Transportability
All items shall be transportable by commercial carrier without degradation in performance. As necessary, provisions shall be made for measuring and controlling environmental conditions (temperature and accelerations) during transport and handling. Special shipping containers, shipping and handling mechanical restraints, and shock isolation shall be utilized to prevent damage. All containers shall be movable for forklift. All items over 100 lbs. which must be moved into place within LIGO buildings shall have appropriate lifting eyes and mechanical strength to be lifted by cranes.
3.8.3 Photon Drive Design and Construction
Minimum or essential requirements that are not controlled by performance characteristics, interfaces, or referenced documents. This can include design standards, requirements governing the use or selection of materials, parts and processes, interchangeability requirements, safety requirements, etc.
3.8.3.1 Materials and Processes
Such items as units of measure to be used (English, Metric) should be listed and any other general items, such as standard polishing procedures and processes.
3.8.3.1.1 Finishes
Examples:
Ambient Environment: Surface-to-surface contact between dissimilar metals shall be controlled in accordance with the best available practices for corrosion prevention and control.
External surfaces: External surfaces requiring protection shall be painted purple or otherwise protected in a manner to be approved.
• Metal components shall have quality finishes on all surfaces, suitable for vacuum finishes. All corners shall be rounded to TBD radius.
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• All materials shall have non-shedding surfaces.
• Aluminum components used in the vacuum shall not have anodized surfaces.
• Optical table surface roughness shall be within 32 micro-inch.
3.8.3.1.2 Materials
A list of currently approved materials for use inside the LIGO vacuum envelope can be found in LIGO Vacuum Compatible Materials List (LIGO-E960022). All fabricated metal components exposed to vacuum shall be made from stainless steel, copper, or aluminum. Other metals are subject to LIGO approval. Pre-baked viton (or fluorel) may be used subject to LIGO approval. All materials used inside the vacuum chamber must comply with LIGO Vacuum Compatibility, Cleaning Methods and Procedures (LIGO-E960022-00-D).
The only lubricating films permitted within the vacuum are dry plating of vacuum compatible materials such as silver and gold.
3.8.3.1.3 Processes
3.8.3.1.3.1 Welding
Before welding, the surfaces should be cleaned (but baking is not necessary at this stage) according to the UHV cleaning procedure(s). All welding exposed to vacuum shall be done by the tungsten-arc-inert-gas (TIG) process. Welding techniques for components operated in vacuum shall deviate from the ASME Code in accordance with the best ultra high vacuum practice to eliminate any “virtual leaks” in welds; i. e. all vacuum welds shall be continuous wherever possible to eliminate trapped volumes. All weld procedures for components operated in vacuum shall include steps to avoid contamination of the heat affected zone with air, hydrogen or water, by use of an inert purge gas that floods all sides of heated portions.
The welds should not be subsequently ground (in order to avoid embedding particles from the grinding wheel).
3.8.3.1.3.2 Cleaning
All materials used inside the vacuum chambers must be cleaned in accordance with Specification Guidance for Seismic Component Cleaning, Baking, and Shipping Preparation (LIGO-L970061-00-D). To facilitate final cleaning procedures, parts should be cleaned after any processes that result in visible contamination from dust, sand or hydrocarbon films.
Materials shall be joined in such a way as to facilitate cleaning and vacuum preparation procedures; i. e. internal volumes shall be provided with adequate openings to allow for wetting, agitation and draining of cleaning fluids and for subsequent drying.
3.8.3.1.4 Component Naming
All components shall be identified using the LIGO Naming Convention (LIGO-E950111-A-E). This shall include identification (part or drawing number, revision number, serial number) physically stamped on all components, in all drawings and in all related documentation.
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3.8.3.2 Photon Drive Workmanship
Standard of workmanship desired, uniformity, freedom from defects and general appearance of the finished product.
3.8.3.3 Photon Drive Interchangeability
Specify the level at which components shall be interchangeable or replaceable.
3.8.3.4 Photon Drive Safety
This item shall meet all applicable NSF and other Federal safety regulations, plus those applicable State, Local and LIGO safety requirements. A hazard/risk analysis shall be conducted in accordance with guidelines set forth in the LIGO Project System Safety Management Plan LIGO-M950046-F, section 3.3.2.
3.8.3.5 Photon Drive Human Engineering
Note: For many detector subsystems, this section is not applicable.
Specify any special or unique requirements, e.g., constraints on allocation of functions to personnel, and communications and personnel/equipment interactions. Also include any specified areas, stations, or equipment that require concentrated human engineering attention due to the sensitivity of the operation, i.e. those areas where the effects of human error would be particularly serious.
Example: Seismically isolated platforms or points must accommodate addition, removal and adjustment of equipment with a minimum of force or torque applied to the platforms. This requires that adequate space be provided surrounding the optics platform for an individual to move into proper position for the work intended. Equipment mounted to the optics platform should be provided with fasteners that can accommodate these force/torque requirements.
3.8.4 Photon Drive Assembly and Maintenance
Assembly fixtures and installation/replacement procedures shall be developed in conjunction with the AOS hardware design. These shall include (but not be limited to) fixtures and procedures for:
• AOS component insertion and assembly into the vacuum chambers without load support from the chambers
• assembly of the in vacuum components in a clean room (class 100) environment
• initial alignment of the AOS components
3.8.5 Photon Drive Documentation
Requirements for documentation of the design, including types of documents, such as operator manuals, etc.
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3.8.5.1 Photon Drive Specifications
List any additional specifications to be provided during the course of design and development, such as Interface Control Documents (ICD) and any lower level specifications to be developed.
3.8.5.2 Photon Drive Design Documents
List all design documents to be produced, including installation and commissioning plans, standards documents, etc.
Example:
• LIGO SEI System Preliminary Design Document (including supporting technical design and analysis documentation)
• LIGO SEI System Final Design Document (including supporting technical design and analysis documentation)
• LIGO SEI Prototype/Test Plans
• LIGO SEI Installation and Commissioning Plans and Procedures
3.8.5.3 Photon Drive Engineering Drawings and Associated Lists
A complete set of drawings suitable for fabrication must be provided along with Bill of Material (BOM) and drawing tree lists. The drawings must comply with LIGO standard formats and must be provided in electronic format. All documents shall use the LIGO drawing numbering system, be drawn using LIGO Drawing Preparation Standards, etc.
3.8.5.4 Photon Drive Technical Manuals and Procedures
3.8.5.4.1 Procedures
Procedures shall be provided for, at minimum,
• Initial installation and setup of equipment
• Normal operation of equipment
• Normal and/or preventative maintenance
• Installation of new equipment
• Troubleshooting guide for any anticipated potential malfunctions
3.8.5.4.2 Manuals
Any manuals to be provided, such as operator’s manual, etc.
3.8.5.5 Photon Drive Documentation Numbering
All documents shall be numbered and identified in accordance with the LIGO documentation control numbering system LIGO document TBD
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3.8.5.6 Photon Drive Test Plans and Procedures
All test plans and procedures shall be developed in accordance with the LIGO Test Plan Guidelines, LIGO document TBD.
3.8.6 Photon Drive Logistics
The design shall include a list of all recommended spare parts and special test equipment required.
3.8.7 Photon Drive Precedence
This section should list the relative importance of requirements (or goals) to be achieved by the design.
3.8.8 Photon Drive Qualification
Test and acceptance criteria.
3.9 Photon Drive Controls Requirements
3.9.1 Introduction
Requirement flow down tree from Detector DRD should be included in this section.
This area contains any physical requirements or constraints on the product: dimensional and weight limitations, acceptable materials or properties of the materials, durability factors, transportation and storage requirements, etc.
Specify all interfaces to other systems/subsystems/components and the characteristics (electrical/mechanical/optical) of those interfaces. Note that these are all requirements placed on the item specified, NOT requirements this item places on other systems.
3.9.2.3.1 Interfaces to other LIGO detector subsystems
3.9.2.3.1.1 Mechanical Interfaces
3.9.2.3.1.2 Electrical Interfaces
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3.9.2.3.1.3 Optical Interfaces
3.9.2.3.1.4 Stay Clear Zones
3.9.2.3.2 Interfaces external to LIGO detector subsystems
3.9.2.3.2.1 Mechanical Interfaces
3.9.2.3.2.2 Electrical Interfaces
3.9.2.3.2.3 Stay Clear Zones
3.9.2.4 Photon Drive Controls Reliability
Mean Time Between Failures (MTBF), Availability
3.9.2.5 Photon Drive Controls Maintainability
Mean Time To Repair (MTTR); Qualitative requirements for accessibility, modular construction, test points, etc.
Environments that the equipment is expected to experience in shipment, storage, service or use. Subparagraphs should include, as necessary, climate, shock, vibration, noise, etc.
3.9.2.6.1 Natural Environment
3.9.2.6.1.1 Temperature and Humidity
Example:
Table 7 Environmental Performance Characteristics
Operating Non-operating (storage) Transport
+0 C to +50 C, 0–90 % RH 40 C to +70 C, 0–90 % RH 40 C to +70 C, 0–90 % RH
3.9.2.6.1.2 Atmospheric Pressure
3.9.2.6.1.3 Seismic Disturbance
The following example for the SEI subsystem is illustrative:
Restraint against seismically induced large motion is required.
The system shall be designed to resist the static equivalent lateral forces defined in the Uniform Building Code (UBC), 1994 edition, for a seismic zone factor Z = 0.15 (i.e. zone 2B, Hanford) and a structure importance factor I = 1. The support structure shall resist the seismic loads without
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damage. The seismic stack shall sustain the base shear motion of the support structure without collapse or release of any of the stack layers. At a minimum, failure of the actuators under these loads should not cause failure of the bellows or cause the seismic stack to “drop”; ideally the actuators would survive these loads with no damage.
As an alternative to this static equivalent load, an acceleration design spectrum for use in dynamic analysis could be used.
Interpretation of the requirement: If there is no damping or plastic deformation to absorb the seismic loading (Rw = 1), and the SEI first frequency is between 2.5 Hz and 10 Hz (i.e. at the peak), then the base shear,
Vb = (Z I C/Rw) W = (0.15 (1) 2.75/1) W = 0.4 W
I.e. the SEI must sustain a 0.4 g lateral load. If, as in the case of the Corner Station building, Rw = 6, then, then SEI must sustain a 0.1 g lateral load.
3.9.2.6.2 Induced Environment
These are environmental conditions induced by equipment. The following subparagraphs list some possible categories. Remember to list the requirements both in terms of:
What the item to be designed must accept from its surroundings
What environment the item to be designed is allowed to generate
3.9.2.6.2.1 Electromagnetic Radiation
Electrical equipment associated with the subsystem shall meet the EMI and EMC requirements of VDE 0871 Class A or equivalent. The subsystem shall also comply with the LIGO EMI Control Plan and Procedures (LIGO-E960036).
3.9.2.6.2.2 Acoustic
Equipment shall be designed to produce the lowest levels of acoustic noise as possible and practical. As a minimum, equipment shall not produce acoustic noise levels greater than specified in Derivation of CDS Rack Acoustic Noise Specifications, LIGO-T960083.
3.9.2.6.2.3 Mechanical Vibration
Mechanical vibration from the subsystem shall not increase the vibration amplitude of the facility floor within 1 m of any other vacuum chambers and equipment tables by more than 1 dB at any frequency between 0.1 Hz and 10 kHz. Limited narrowband exemptions may be permitted subject to LIGO review and approval.
3.9.2.7 Photon Drive Controls Transportability
All items shall be transportable by commercial carrier without degradation in performance. As necessary, provisions shall be made for measuring and controlling environmental conditions (temperature and accelerations) during transport and handling. Special shipping containers, shipping and handling mechanical constraints, and shock isolation shall be utilized to prevent damage. All containers shall be movable for forklift. All items over 100 lbs., that must be moved
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into place within LIGO buildings, shall have appropriate lifting eyes and mechanical strength to be lifted by cranes.
3.9.3 Photon Drive Controls Design and Construction
Minimum or essential requirements that are not controlled by performance characteristics, interfaces, or referenced documents. This can include design standards, requirements governing the use or selection of materials, parts and processes, interchangeability requirements, safety requirements, etc.
3.9.3.1 Materials and Processes
Such items as units of measure to be used (English, Metric) should be listed and any other general items, such as standard polishing procedures and processes.
3.9.3.1.1 Finishes
Examples:
Ambient Environment: Surface-to-surface contact between dissimilar metals shall be controlled in accordance with the best available practices for corrosion prevention and control.
External surfaces: External surfaces requiring protection shall be painted purple or otherwise protected in a manner to be approved.
• Metal components shall have quality finishes on all surfaces, suitable for vacuum finishes. All corners shall be rounded to TBD radius.
• All materials shall have non-shedding surfaces.
• Aluminum components used in the vacuum shall not have anodized surfaces.
• Optical table surface roughness shall be within 32 micro-inch.
3.9.3.1.2 Materials
A list of currently approved materials for use inside the LIGO vacuum envelope can be found in LIGO Vacuum Compatible Materials List (LIGO-E960022). All fabricated metal components exposed to vacuum shall be made from stainless steel, copper, or aluminum. Other metals are subject to LIGO approval. Pre-baked viton (or fluorel) may be used subject to LIGO approval. All materials used inside the vacuum chamber must comply with LIGO Vacuum Compatibility, Cleaning Methods and Procedures (LIGO-E960022-00-D).
The only lubricating films permitted within the vacuum are dry plating of vacuum compatible materials such as silver and gold.
3.9.3.1.3 Processes
3.9.3.1.3.1 Welding
Before welding, the surfaces should be cleaned (but baking is not necessary at this stage) according to the UHV cleaning procedure(s). All welding exposed to vacuum shall be done by the tungsten-arc-inert-gas (TIG) process. Welding techniques for components operated in vacuum shall deviate from the ASME Code in accordance with the best ultra high vacuum practice to eliminate any “virtual leaks” in welds; i. e. all vacuum welds shall be continuous wherever possible to eliminate
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trapped volumes. All weld procedures for components operated in vacuum shall include steps to avoid contamination of the heat affected zone with air, hydrogen or water, by use of an inert purge gas that floods all sides of heated portions.
The welds should not be subsequently ground (in order to avoid embedding particles from the grinding wheel).
3.9.3.1.3.2 Cleaning
All materials used inside the vacuum chambers must be cleaned in accordance with Specification Guidance for Seismic Component Cleaning, Baking, and Shipping Preparation (LIGO-L970061-00-D). To facilitate final cleaning procedures, parts should be cleaned after any processes that result in visible contamination from dust, sand or hydrocarbon films.
Materials shall be joined in such a way as to facilitate cleaning and vacuum preparation procedures; i. e. internal volumes shall be provided with adequate openings to allow for wetting, agitation and draining of cleaning fluids and for subsequent drying.
3.9.3.1.4 Component Naming
All components shall be identified using the LIGO Naming Convention (LIGO-E950111-A-E). This shall include identification (part or drawing number, revision number, serial number) physically stamped on all components, in all drawings and in all related documentation.
3.9.3.2 Photon Drive Controls Workmanship
Standard of workmanship desired, uniformity, freedom from defects and general appearance of the finished product.
3.9.3.3 Photon Drive Controls Interchangeability
Specify the level at which components shall be interchangeable or replaceable.
3.9.3.4 Photon Drive Controls Safety
This item shall meet all applicable NSF and other Federal safety regulations, plus those applicable State, Local and LIGO safety requirements. A hazard/risk analysis shall be conducted in accordance with guidelines set forth in the LIGO Project System Safety Management Plan LIGO-M950046-F, section 3.3.2.
3.9.3.5 Photon Drive Controls Human Engineering
Note: For many detector subsystems, this section is not applicable.
Specify any special or unique requirements, e.g., constraints on allocation of functions to personnel, and communications and personnel/equipment interactions. Also include any specified areas, stations, or equipment that require concentrated human engineering attention due to the sensitivity of the operation, i.e. those areas where the effects of human error would be particularly serious.
Example: Seismically isolated platforms or points must accommodate addition, removal and adjustment of equipment with a minimum of force or torque applied to the platforms. This requires
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that adequate space be provided surrounding the optics platform for an individual to move into proper position for the work intended. Equipment mounted to the optics platform should be provided with fasteners that can accommodate these force/torque requirements.
3.9.4 Photon Drive Controls Assembly and Maintenance
Assembly fixtures and installation/replacement procedures shall be developed in conjunction with the AOS hardware design. These shall include (but not be limited to) fixtures and procedures for:
• AOS component insertion and assembly into the vacuum chambers without load support from the chambers
• assembly of the in-vacuum components in a clean room (class 100) environment
• initial alignment of the AOS components
3.9.5 Photon Drive Controls Documentation
Requirements for documentation of the design, including types of documents, such as operator manuals, etc.
3.9.5.1 Photon Drive Controls Specifications
List any additional specifications to be provided during the course of design and development, such as Interface Control Documents (ICD) and any lower level specifications to be developed.
3.9.5.2 Photon Drive Controls Design Documents
List all design documents to be produced, including installation and commissioning plans, standards documents, etc.
Example:
• LIGO SEI System Preliminary Design Document (including supporting technical design and analysis documentation)
• LIGO SEI System Final Design Document (including supporting technical design and analysis documentation)
• LIGO SEI Prototype/Test Plans
• LIGO SEI Installation and Commissioning Plans and Procedures
3.9.5.3 Photon Drive Controls Engineering Drawings and Associated Lists
A complete set of drawings suitable for fabrication must be provided along with Bill of Material (BOM) and drawing tree lists. The drawings must comply with LIGO standard formats and must be provided in electronic format. All documents shall use the LIGO drawing numbering system, be drawn using LIGO Drawing Preparation Standards, etc.
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3.9.5.4 Photon Drive Controls Technical Manuals and Procedures
3.9.5.4.1 Procedures
Procedures shall be provided for, at minimum,
• Initial installation and setup of equipment
• Normal operation of equipment
• Normal and/or preventative maintenance
• Installation of new equipment
• Troubleshooting guide for any anticipated potential malfunctions
3.9.5.4.2 Manuals
Any manuals to be provided, such as operator’s manual, etc.
All documents shall be numbered and identified in accordance with the LIGO documentation control numbering system LIGO document TBD
3.9.5.6 Photon Drive Controls Test Plans and Procedures
All test plans and procedures shall be developed in accordance with the LIGO Test Plan Guidelines, LIGO document TBD.
3.9.6 Photon Drive Controls Logistics
The design shall include a list of all recommended spare parts and special test equipment required.
3.9.7 Photon Drive Controls Precedence
This section should list the relative importance of requirements (or goals) to be achieved by the design.
3.9.8 Photon Drive Controls Qualification
Test and acceptance criteria.
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4 Quality Assurance ProvisionsThis section includes all of the examinations and tests to be performed in order to ascertain the product, material or process to be developed or offered for acceptance conforms to the requirements in section 3.
4.1 General
This should outline the general test and inspection philosophy, including all phases of development.
4.1.1 Responsibility for Tests
Who is responsible for testing.
4.1.2 Special Tests
4.1.2.1 Engineering Tests
List any special engineering tests that are required to be performed. Engineering tests are those which are used primarily for the purpose of acquiring data to support the design and development.
4.1.2.2 Reliability Testing
Reliability evaluation/development tests shall be conducted on items with limited reliability history that will have a significant impact upon the operational availability of the system.
4.1.3 Configuration Management
Configuration control of specifications and designs shall be in accordance with the LIGO Detector Implementation Plan.
4.2 Quality conformance inspections
Design and performance requirements identified in this specification and referenced specifications shall be verified by inspection, analysis, demonstration, similarity, test or a combination thereof per the Verification Matrix, Appendix 1 (See example in Appendix). Verification method selection shall be specified by individual specifications, and documented by appropriate test and evaluation plans and procedures. Verification of compliance to the requirements of this and subsequent specifications may be accomplished by the following methods or combination of methods:
4.2.1 Inspections
Inspection shall be used to determine conformity with requirements that are neither functional nor qualitative; for example, identification marks.
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4.2.2 Analysis
Analysis may be used for determination of qualitative and quantitative properties and performance of an item by study, calculation and modeling.
4.2.3 Demonstration
Demonstration may be used for determination of qualitative properties and performance of an item and is accomplished by observation. Verification of an item by this method would be accomplished by using the item for the designated design purpose and would require no special test for final proof of performance.
4.2.4 Similarity
Similarity analysis may be used in lieu of tests when a determination can be made that an item is similar or identical in design to another item that has been previously certified to equivalent or more stringent criteria. Qualification by similarity is subject to Detector management approval.
4.2.5 Test
Test may be used for the determination of quantitative properties and performance of an item by technical means, such as, the use of external resources, such as voltmeters, recorders, and any test equipment necessary for measuring performance. Test equipment used shall be calibrated to the manufacture’s specifications and shall have a calibration sticker showing the current calibration status.
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5 Preparation for DeliveryPackaging and marking of equipment for delivery shall be in accordance with the Packaging and Marking procedures specified herein.
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6 Preparation for DeliveryPackaging and marking of equipment for delivery shall be in accordance with the Packaging and Marking procedures specified herein.
6.1 Preparation
• Vacuum preparation procedures as outlined in LIGO Vacuum Compatibility, Cleaning Methods and Procedures (LIGO-E960022-00-D) shall be followed for all components intended for use in vacuum. After wrapping vacuum parts as specified in this document, an additional, protective outer wrapping and provisions for lifting shall be provided.
• Electronic components shall be wrapped according to standard procedures for such parts.
6.2 Packaging
Procedures for packaging shall ensure cleaning, drying, and preservation methods adequate to prevent deterioration, appropriate protective wrapping, adequate package cushioning, and proper containers. Proper protection shall be provided for shipping loads and environmental stress during transportation, hauling and storage. The shipping crates used for large items should use for guidance military specification MIL-C-104B, Crates, Wood; Lumber and Plywood Sheathed, Nailed and Bolted. Passive shock witness gauges should accompany the crates during all transits.
For all components which are intended for exposure in the vacuum system, the shipping preparation shall include double bagging with Ameristat 1.5TM plastic film (heat sealed seams as practical, with the exception of the inner bag, or tied off, or taped with care taken to insure that the tape does not touch the cleaned part). Purge the bag with dry nitrogen before sealing.
6.3 Marking
Appropriate identification of the product, both on packages and shipping containers; all markings necessary for delivery and for storage, if applicable; all markings required by regulations, statutes, and common carriers; and all markings necessary for safety and safe delivery shall be provided.
Identification of the material shall be maintained through all manufacturing processes. Each component shall be uniquely identified. The identification shall enable the complete history of each component to be maintained (in association with Documentation “travelers”). A record for each component shall indicate all weld repairs and fabrication abnormalities.
For components and parts that are exposed to the vacuum environment, marking the finished materials with marking fluids, die stamps and/or electro-etching is not permitted. A vibratory tool with a minimum tip radius of 0.005" is acceptable for marking on surfaces that are not hidden from view. Engraving and stamping are also permitted.
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7 NotesThis section should contain information of a general or explanatory nature, and no requirements shall appear here. This could be such items as modeling data/results, R&D prototype information, etc.
7.1 Scattered Light Control
7.1.1 Noise Allocation Factor
The scattered light from each of the various paths contributes to the total scattered light phase noise. Some paths contribute more noise than other paths, so a systematic approach to allocating the noise budget will be developed in the following. The APS scattered light phase noise current will be calculated as an example, and the results will be generalized to include all the other noise sources.
The photodetector current at the antisymmetric port output resulting from the scattered light field combining with the carrier light field on the surface of the BS is proportional to the 1) phase mod-ulation of the light caused by the in-band horizontal displacement of the scattering surface, and to the 2) field amplitude of the scattered light reflecting from the ITM onto the BS.
PsAPS, is the light power back-scattered through the dark port into the IFO; R, is the reflectivity of the Fabry-Perot arm cavity; and xvh(f), is the horizontal displacement spectral density of the scattering surface.
The photodetector current which carries the gravity wave signal is proportional to the 1) phase modulation of the arm cavity light caused by the differential displacement of the IFO mirrors, which is increased by the storage time of the light in the arm cavity at the gravity wave frequency, and to the 2) field amplitude of the carrier light at the BS.
The carrier light power on the BS is greater than the input laser power at the RM by the recycling cavity gain factor,
X(f), is the gravity wave differential displacement spectral density; Grc, is the gain of recycling cavity; P0, is the laser power incident on the RM; and T, is the transmissivity of the ITM mirror.
The ratio of the scattered light noise current to the gravity wave signal current is given by
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Therefore, the noise/signal current ratio is proportional to the square root of the ratio of scattered light to input laser power, where the proportionality constant is defined by
The KAPS value was evaluated at 10 Hz using the corresponding seismic displacement spectral density, and the advanced LIGO displacement sensitivity spectral density, assuming a cavity resonance at 100 Hz:
KAPS = 1.02 x 107
The noise/signal power ratio for any other typical scattering path can be described by a similar K value. (See Secondary Light Noise Sources in LIGO, LIGO-T970074-00-D.)
The total noise/signal power is additive and must not exceed the requirement.
It can be seen that each noise path contributes a fraction of the noise power
.
The noise budget will be optimally utilized if each scattered light path is allocated part of the total noise budget in proportion to the noise allocation factor, Fi , for the particular scattering path.
This allocation procedure also ensures that the individual scattered light noise requirements add up to the required total.
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7.1.2 Scattered Light Power Ratio Requirement
The scattered light power ratio requirement for a particular scattering path is given by
Where Ni and Fi are estimated from the scattered light calculations presented in the Core Optics Support Conceptual Design, LIGO-T970072-00-D, and the Ki for the stated seismic spectral densities and Advanced LIGO sensitivity spectral densities are presented below.
7.1.3 K Values
Table 8 : K values
parameter value
10 Hz 30 Hz 100 Hz 300 Hz 1000 Hz
Seismic spectral density, m/Hz^0.5
1E-09 1E-10 1E-11 1E-12 1E-13
Advanced LIGO sensitivity, m/Hz^0.5
3.6E-19 5.2E-20 1.48E-20 5.2E-21 3.0E-20
K values, chamber-mounted surfacesK-ITM 1.02E+07 7.34E+06 3.49E+06 2.22E+06 1.24E+05
The criterion for determining which ghost beams must be dumped will be that an un-dumped ghost beam which reflects from the wall of the vacuum housing and causes a direct glint into the IFO shall not cause excessive phase noise. The worst case estimate would result from a cylindrical
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surface aligned exactly perpendicular to the ghost beam direction, as shown in the figure 13 (note: the surface can be either convex or concave). An example of such a glint surface might be the inner wall of the BSC housing.
The ghost beam glint from the reflecting surface will etro-reflect into the solid angle of the IFO provided the tilt of the curved surface is within the diffraction angle of the IFO beam.
Figure 4: Glint Reflection of GBAR3 Back Into the IFO
The maximum illuminated area of the glint surface that meets these conditions is
The tro-reflected light from the glint into the IFO is proportional to the incident power, to the ratio of glint area to ghost beam area, and to the return transmissivity through the COC.
The width of the glint surface is
and the geometric optics approximation is valid for
For the LIGO IFO parameters, the approximation is valid for R> 0.4 m.
We will estimate the glint power assuming a radius of R=1.5m, which corresponds to the inside walls of the BSC chamber, and the following parameters:
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The glint power was calculated for each GB4 beam, assuming that the GB4 beams were not dumped, and the result was that the following ghost beams may cause a glint into the IFO which exceeds the scattered light noise requirement, and therefore must be dumped: ITMxGBAR4, ITMyGBAR4, BSGBAR4x, BSGBHR4x, ITMxGBHR4, and ITMyGBHR4 beams.
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Appendix A Quality Conformance Inspections
Appendixes are used to append large data tables or any other items which would normally show up within the body of the specification, but, due to their bulk or content, tend to degrade the usefulness of the specification. Whenever an Appendix is used, it shall be referenced in the body of the specification.
Appendix 1 shall always contain a table that lists the requirements and the method of testing requirements. An example table follows. Additional appendixes can contain other information, as appropriate to the subsystem being specified.
