Introduction to DECam(This document is in Doc-db 6311)

• Dark Energy Camera is a complex instrument with 21 subsystems

• The purpose of this training is – to present an integrated picture of

DECam and – to familiarize you with these

subsystems

• This training will not make you an expert on any of them 1

Draft V1.01 Sept. 10, 2012

Introduction to DECam

• For each subsystem, this training will describe the subsystem– Functionality (Purpose) – Requirements (the relation to other

sub-systems in DECam & CTIO)– Risks– How errors and/or alarms are

reported &– Describe detailed training

(documented procedures) that is available

2

21 DECam Subsystems

• Cage, Barrel, and Optical Corrector

• Hexapod• Filter-Changer• Shutter• ICS2 (Slow Controls)• Imager Vacuum System• LN2 Recirculation System• CCDs• CCD Readout & Heater

Electronics• PFC Power Distribution

• SISPI/Computers

• DoNut Focus

• BCams

• Guiding

• Databases

• DECal(s)

• RASICam

• ATMCam

• GPSMon

• Imager Handling System

• F/8 Handling3

KEYCompleteMostly DoneNot DoneCan’t be done yet

P.F. Cage & Barrel

• The Barrel & Cage supports DECam at the Prime Focus– A baffle (not shown) is installed in front of the

corrector in the cage. Covers (not shown) surround the sides and top.

– Trim weights are supported at the top end & the F/8 or equivalent counterweight on the other (also not shown)

– Cage houses temperature & humidity sensors

• Requirements– Provides electrical isolation of the Cage from the

telescope using G-10 washers at the joints between the spider and cage.

– Top cover and black styro-foam covers prevent thermal plumes from getting out (heat exchangers on the H-frame at the top) 4

Soon, maybe, a photo from NW station

C1

C2 - C3

C5, vacuum window

Filters &Shutter

Focal plane

BipodsAttachment ring

Barrel & Optical Corrector

• The optical corrector makes a focal plane.

• The lenses “C1-C5” are made from fused silica and held in INVAR cells.

• C1 is closest to the Primary Mirror

• C5 is the Imager vacuum window.

0.98m175 kg lens

P.F. Cage & Barrel

• More Requirements– Compressed, clean dry air purges the barrel at the front of the C5 lens

(to keep it from frosting up) and to keep the corrector at slightly positive pressure (against dust)

– A G-10 flange electrically isolates the imager from the barrel.– Baffle against external stray light

• Risks– Dust on lenses/Frost on C5 if not dry– Mishandling components => damage to the fused silica– Improper isolation => More R.O. noise

• Alarms: none, not directly• Procedures

– Cage covers installation/removal– H-frame installation/removal

6

Hexapod

• Function: 6 actuator arms provide 6 degree-of-freedom motion– To counteract relative motion of the

DECam optics with respect to the primary mirror.

– To allow focus corrections

– Connects the barrel to the cage

• Requirements:– Six 230V 11A AC power and six

multi-wire control lines run from the Hexapod Rack in the Coude Room up to the hexapod

– Network Connection, SISPI or standalone program 7

Acceptable Range of Motion• |Z|<21 mm• sqrt(X2 + Y2) < 11.3 mm for |Z|<5 mm• Allowable sqrt(X2+Y2) decreases linearly to 0 at |Z|=21 mm• Tip/Tilt < 500 arcsec• Rotation not allowed

Hexapod

• Risks– Exceeding the range of motion

could damage the flex joints. Protected by software and by hardware limit switches.

– This is a moving part so we need to take care that nothing on the barrel can be made to impact the cage

• Errors and/or alarms are reported – From the Hexapod Controller to

SISPI+

• Procedures– some maintenance 8

Above: One of the flex joints

+ Note: if SISPI is not running we may not know if an error has occurred.

Filter Changer

• Function: Position filters on command prior to exposures– Controlled by SISPI through Ethernet– Possibility to provide a “shutter-like” “dark” blocker instead of a filter

• Requirements:– 60-100 psi compressed air – 24V DC power from H-frame – note: 720+ lbs weight– Network Connection, SISPI or

standalone program

• Risks– Possibility to be stuck– Possibility for damage to filters– Filters may slide (gravity) if

pressure is lost 9

Filter Changer, in transport frame

Filter Changer

• Errors/Alarms– Reported through SISPI+

• Procedures– Maintenance– Filter Installation to cells– Filter Changer Installation to Barrel– Filter + Cell Installation to the Filter

Changer

10

Filter to Filter Cell Installation

+ Note: if SISPI is not running we may not know if an error has occurred.

Shutter

• Function: Open and close on command to make exposures– Attached to the Filter Changer on the C4 side– Controlled by SISPI over the network or through ICS2

• Requirements:– 24V DC from the H-Frame

• Risks– Possibility to be stuck Open

• Errors/Alarms– Reported through ICS2

• Procedures– Some maintenance– See FCM for Installation 11

Shutter interior

ICS2 (Slow Controls)

• Function of the Windows PC– Monitor/Control Imager Vacuum, focal plate

temperature, photo diodes, LN2 cooling system, FEE crate, ICS2 Alarms, shutter controls

– Communication to cRIO & cFP on Imager – Create Telemetry Information

• Requires – AC Power and a small UPS to accommodate

short power interruptions – Ethernet

• Risks (part 1)– Damage to the CCDs by overheating

(mitigated by thermal protection)12

ICS2 Computer on old Console Floor

ICS2 (Slow Controls)

• Risks (part 2)– Mechanical Damage to the CCDs by cooling to LN2 temperature– Damage to the electronics– Damage to the ion pump, turbo pump, or imager vacuum gauge– Failure of ICS2 Computer (no spare)

• Alarms are distributed by– Autodialer makes phone calls for urgent responses– Email when values out of normal range– See alarm list and response sheet– Marco Bonati is the expert!

• Procedures– Start-up or Shut-down of ICS2– Operation of ICS2

13

ICS2 Computer on old Console Floor

Imager Vacuum System

• Function of the Imager Vacuum System– Keep the imager under vacuum, especially

when the CCDs are cold

• Requires – AC Power is on UPS to accommodate short

power interruptions– Ion pump is on the Imager Back Flange on

UPS, imager vacuum gauge has its own small flange

– Roughing pump and Turbo Pump (emergency back-up) available on UPS, connected at the gate valve

– Some of this is Controlled from ICS2 or (manual mode) directly at the hardware controllers 14

Imager Back Flange

Imager Vacuum System

• Risks– Contamination of the CCD surface

through loss of vacuum when cold– Damage to the ion pump, turbo pump, or

imager vacuum gauge

• Alarms are distributed by ICS2• Procedures

– Installation/removal of C5 and Rear flange

– Operation/maintainance/replacement of the turbo pump, ion pump, vacuum gauge

– Operation of the roughing pump– Operation of ICS2 controls

15

Ion Pump Controller

Turbo Pump Controller

LN2 Circulation System

• Function– Provides cooling to the CCDs– LN2 is pumped from the tank to

the imager where it is coupled to the focal plate

• Risks– Disturbing the cooling system

takes a long time to return to stable cold CCDS

– Cold Hazards to CCDs (LN2 is 77K)

– Oxygen Deficiency Hazards in the Coude Room

• Alarms– Distributed from ICS2

16

Console room area,LN2 process tank, valveboxSlow controls computer

LN2 Circulation System

• Procedures– Operations checklist performed

each shift– Tank fill/top-up/drain– Make or unmake the

connections at the Imager

• Maintenance– Check vacuum jackets on

transfer lines for good vacuum periodically

– LN2 Circulation pump replacement

– O2 Monitor replacement

17

Console room area: LN2 fill/drainPanel, ICS2 computer console

CCDs: Focal plane

18

74 Detectors:

62 imaging CCDs 2k x 4k8 focusing CCDs 2k x 2k4 guiding CCDs 2k x 2k

Each detector has 2 amplifiers and the readout takes 17 sec. Focus and imaging detectors readout at the same time. Guiding CCDs are read during the exposure.

CCDs: Bias Voltage

19

Very thick CCDs !! 250 microns to increase QE in the red. The substrate is biased at 40V. We keep this voltage OFF when we are not using the detector (during the day). This voltage is controlled with the main observed GUI. This will be the only voltage to which the observer has easy control.

No electrostatic discharge (ESD) safety built into the CCDs. This means that the detectors are extremely sensitive to ESD. Need full ESD training and equipment to touch the imager vessel!

40V

CCDs: light level control

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The CCDs are protected to high light levels. Damage can occurs if the shutter with day light and the CCDs are ON. Three photodiodes installed on the focal plane will shutdown the electronics if the system gets close to risky light levels. The alarm system will generate an alarm if this happens.

CCDs Summary

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Function: Scientific Imaging : 62 CCDs 2k x 4kFocus control : 8 CCDs 2k x 2kGuiding: 4 CCDs 2k x 2k

Risks to data quality:Temperature instability/non-uniformity

Risks to instrument:Cold focal plane in poor vacuums risks contamination in the detectorsPoor vacuum outside the cleanroom risks contamination of detectorsExtremely sensitive to ESDDamage could be produced with excessive light levels

Alarms:All risks (expect ESD) are mitigated by the alarms/interlock system

controlled by ICS

Procedures and Training:SISPI training needed to operate imagerCCD Installation/RemovalESD training needed to touch imager vessel

CCD Readout Electronics

• Function: Readout of the CCDs– 3 Monsoon Electronics Crates

• 6 backplanes

• 6 Master Control Boards

• 10 Clock Boards (Main/Rear)

• 14 12CH Acquisition Boards (Main/Rear)

• Requirements:– AC Power enabled through

Instrument Controls System (ICS2) and PFC Power Dist. Box

– Glycol cooling for crates– (Dry air for crates)

22

CCD Readout Electronics

• Risks– If electronics card(s) have an error, CCD(s) will not be readout properly– Internal Glycol leak from cooling system will cause significant damage– System may not turn on is an error condition is detected

• Crate over-temperature OR Overvoltage condition on DC power supplies• CCD over-temperature OR CCD photodiode protection

• Errors and alarms are reported via ICS2• Training and Procedures

– Introduction to FE Electronics (docdb 6065)– Crate Installation/Removal Procedure– FE Electronics Main/Rear Module Handling Procedures (docdb 6281)– Imager ESD Handling Procedures (docdb 6267)– Installation of FE Electronics crate heat shield (docdb 5108)

23

VIBs & Crate Covers

• Function:– The Vacuum Interface Boards (VIBs) penetrate the imager

wall and carry the clocks, biases and video signals – The Covers Protect the electronics & VIBs from the

environment and contain the heat generated within.

• Requirements– Physical protection & thermal isolation

• Risks– The two VIB’s (and their cables) are protected but they are delicate electronics susceptible to damage.

• Alarms: N/A• Procedures:

– Installation/Removal 24

VIB and Cables(VIB Covers Removed)

CCD Heater Crate

• Function: Provide heat to the 10 focal plane copper heater braids

• Requirements:– ICS2 Control (by cRIO) of heater crate and

heaters. AC power from PFC Power Dist. Box

– Glycol cooling for crates, dry air

• Risks– CCD over-temperature prevented by thermal

shut-off resistors

– CCD over-cold through heater crate failure

• Errors: reported through ICS2• Procedures

– Installation and Hook-up (docdb 6066) 25

Connections at front of the heater patch panel board.

4 RTD’s on the focal plate provide temperature to theLabview Controls.

PFC Power Distribution

• Function: Provides AC and DC power to dedicated equipment within the Prime Focus Cage (PFC).– Receives 208 VAC, 3-phase

UPS power from the Coude’ room.

– Supplies 9 dedicated 120 VAC and 6 dedicated DC circuits.

– Provides ability to remotely power-cycle the circuits individually (PDCC)

– Smoke detector interlock and shutdown capability on inner panel chassis

26

Power Distribution Chassis showing the inner

panel controls

PFC Power Distribution

• Major Components:– Power Distribution Chassis

(PDC) mounted on the PFC’s utility H-frame (previous slide).

– Power Distribution Control Chassis (PDCC) mounted in the Coude’ room (in the Hexapod control rack).

– Main AC Power cable (shielded) from Coude Room safety switch center to PDC

– Power distribution control cable (connected between the PDC and the PDCC).

– Up to three smoke detectors mounted inside of the PFC.

27

Power Distribution Control Chassis shown mounted in the Hexapod

control rack.

PDCC to PDC cable

PFC Power Distribution

• Risks:– Improper connection of loads

(PFC equipment) to the PFC’s outputs.

– Improper or incomplete grounding connections

– Improper setting of the options switches that incorrectly engages the smoke detector interlocks.

– Connecting additional equipment/loads to dedicated outputs thus exceeding the power assigned to that output will trip a breaker 28

Power Distribution Chassis showing dedicated AC and DC power outputs.

AC

DC

PFC Power Distribution

• Risks (continued):– Improper operation of the safety

shut-off switches (SSW) that control the AC power to the PFC and Hexapod.

– Dust or clogged air filters that does not allow sufficient cooling air into the PDC unit when in operation.

• Risk Mitigation:– Following the assigned

procedures and connections.– Periodically replacing/cleaning

the air filters on the PDC. 29

SSWs for controlling the AC power to the Prime Focus Cage.

These switches ARE NOT to be operated unless specifically authorized to do so.

SSW used for powering the imager in the Coude’ room.

SSW used for AC power to the PFC.

PFC Power Distribution

• Error/Status Reporting:– There is no electronic readout of

status. Status is indicated by the LEDs on the Power Distribution Control Chassis (PDCC).

• Specific Procedures:– Power-up procedure.– Power-down procedure.– Interlocks trip reset procedure.– Grounding connections procedure

during installation or removal (not done yet).

– Periodic inspection/maintenance of air filters (not done yet). 30

Procedures taped to PDC inner panel.

SISPI/Computers

• Function: SISPI is the readout andcontrol system for DECam. – It orchestrates the exposure sequence,

provides the observer interface, andmonitors instrument operation providing quality assurance

– Communicates with TCS, DTS, DECam, RASICAM (see next slide)

31

• Requirements: – Electrical Power and cooling in the computer room. Network

availability.

• Risks: – Possible unauthorized access to low level functions could interrupt the

exposure sequence and potentially harm the instrument

SISPI Overview

Data

Flow

DTS

SISPI/Computers

• Errors and Alarms: – SISPI monitors the

alarm database and displays alarm messagesin the Alarm History GUI.

– Special actionssuch as emails, logbook entries, etc can be defined on a per alarm basis. Severe alarms can stop the exposure loop and break the configuration interlock.

• Procedures: – User login and usage information.

Observers are not expected to (re-)start SISPIMaintenance will be performed by the SISPI team.

– A SISPI User’s Guide is under development.

33

Active Optics System(part of SISPI)

Function: Provides focus and alignment information to Hexapod

Risks: If AOS is not functioning, focus will require manual adjustments (trim)

Procedures: AOS should be enabled by default in SISPI

Both DHSF donut trigger (Focus CCD is readout) and hexapod update enable required.

34

DONUT BCAM

AOS

Hexapod (if enabled)

Focus CCD Readout & DCHF Trigger

(Note: AOS query to BCAM shared variable depends on DONUT sending in results)

LookUp Table

DONUT Focus

• Determines wavefront “errors” and provides hexapod correction via AOS

• Requires Focus CCD Data & (DHSF trigger enable) in order to process data. Flow:1. Star locations sent at start of

new exposure.

2. Trigger from DHSF (new file)

3. “Stamp” out donuts

4. Process

5. Send results to AOS within 7 seconds of 2.

35

• Errors & Alarms – All (almost) DONUT

communications go through SISPI

• Procedures– Are within SISPI

– DONUT Focus runs automatically if enabled in the relevant SISPI GUI

BCams

• Function: Determine relative position of Barrel w.r.t. Primary Mirror using 4 pairs of laser alignment units.

• Requirements:– SISPI, Active Optics System (AOS), Cass. Cage Power,

Network, Analyzed BCam is in fits header

• Risks– Red laser pulses during

imaging prevented by

software sequencing.

• Errors/Alarms– Reported through SISPI

• Procedures– Operation. No maintenance expected. 36

Upper Mount and BCamScale ~6”

Guider

• Function: Correct the telescope tracking errors – Based on the information provided by the 4 2kx2k Guide CCDs with

a variety of options including using fast (~ 1 second) readout of a region-of-interest

• Requirements:– SISPI online and running

– Interfaces with GCS and OCS

• Risks– Could provide unstable corrections

to TCS

• Errors/Alarms– Reported through SISPI

• Procedures– Operation: see SISPI 37

Guider application

Databases

• Function: Provide information storage and access methods– Constants: Tracks constants required for operation of SISPI and

DECam– Telemetry: Maintain a permanent history of instrument parameters– Alarms: Stores alarms from ICS2 & SISPI– Exposures: Every exposure and much information– ELog: The info is actually stored in the DB– Quick Reduce: QA & History Plots (soon)

• Requirements:– SISPI Computers, ICS2 (cFP & cRIO),

Network

• Risks– Required for Control of the Imager– Write access must be controlled 38

Databases

• Errors/Alarms– Some DB errors and alarms are reported to SISPI

– Computer process checks “heartbeat” and sends an email to subsystem expert

– A live “mirror” database is constantly operating and can be made into the default

• URLs/GUIs– Constants:

http://system1.ctio.noao.edu:8080/ConstantsDB/ConstantsDBApp.py/Snapshots/index

– Telemetry: http://system1.ctio.noao.edu:8080/TV/TelemetryViewerApp.py/T/index

– Alarms: http://system1.ctio.noao.edu:8080/AV/AlarmsBrowserApp.py/index

– Exposures: http://system1.ctio.noao.edu:8080/EXPO/Expo.html

– Elog: http://system1.ctio.noao.edu:8080/ECL/decam/E/index

– QR: (soon)39

• Function: Flat field and spectrophotometric calibration system• Requirements:

– AC Power to 4 units on the Serrurier Truss, Ethernet– DECals is controlled by VNC-accessible computer – DECal (flat fields) controlled through SISPI

• Risks– Don’t stare at the LED source. It is bright-enough to damage your eyes

• Errors/Alarms– Flat Field errors are reported through SISPI

• Procedures– Operation (and be sure to use the correct (new) flat-field screen) User’s Manual

DECal(s)

40

Really is 2 separatesystems!

RASICAM

• Function: Full-sky cloud coverage info.– For each exposure: RASICAM is polled & it

returns cloud coverage information for current field. There is a viewable control console.

• Requirements:– RASICAM is a standalone system

• Risks– System is completely automated except for

“sleep” and “wake”. Close up in bad weather.

• Alarms: SISPI will issue an error if it cannot contact RASICAM through TCS within 100M s.

• Procedures– Operation & Maintenance– Cleaning the mirror

41

Imager Handling System

• Function: Attaching or removing the imager from the Prime Focus Cage or moving it in the Coude Room

• Requirements:– ESD Precautions– Proper Electrical Grounding

• Risks– ESD or Mechanical damage to

imager components

• Errors/Alarms– None

• Procedures– Installation/removal procedure– ESD-safe handling guidelines– Imager Grounding Requirements 42

Imager Handling System

f/8 Mirror Handler

• Function: Install and remove the f/8 mirror on the DECam cage or DECam counterweight (CWT)– Standalone system, no outside control or internet access.

– Push-button controls or computer controls are mounted on handler.

• Requirements:– 208V 3-phase

• Risks– Can collide with DECam cage

• Errors/Alarms– All errors/alarms are internal

– Interlock to prevent f/8 and

CWT moving at same time.

• Procedures– Some maintenance

– Operation 43

f/8 Mirror Handler

Summary

• Dark Energy Camera is a complex instrument with 21 subsystems

• The purpose of this training was – to present an integrated picture of DECam and – to familiarize you with these subsystems

• This training cannot not make you an expert on any of them

44