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This is an internal CERN publication and does not necessarily reflect the views of the CERN management.

sLHC Project Note 0026

2011-01-24

janic.kevin.chambrillon@cern.ch

Cleanroom refurbishment in SM18 within the SPL project frame, feasibility

study.

Janic Chambrillon / BE-RF

Keywords: SPL, cleanroom, cleanroom upgrade, SRF cavity, high gradient cavity, cavity rinsing,

cavity assembling, ultra pure water, UPW, high pressure rinsing, HPR, optical inspection, SM18.

Summary

Manufacturing of SRF cavities with high gradient (>25 MV/m) requires a good control of the

cleaning and assembling procedure. To do so, it has been recommended to update the CERN

cleanroom facility in SM18. Improvement of the existing cleanroom class, construction of a new

clean space and acquisition of a new high pressure rinsing system are the essential parts of the

upgrade. New control procedures and new instrumentations will help to monitor each step of the

cleaning and assembling procedure.

1. Introduction

Cleanrooms are an essential part of the manufacturing process for a superconducting accelerator.

CERN cleanroom facilities are now 15 years old, and even if they are sufficient for the LHC cavity

gradient (5 MV/m), they are not sufficient to reach the 25 MV/m gradient needed by proton drivers

as the SPL. In fact, with high gradient resonators cleanliness becomes a key parameter and

additional controls of the manufacturing and assembling process should be established to obtain

good performance. Therefore, improvements of the facilities have to be done.

2. SM18 area current infrastructure

With the approval by the management of the SPL study, CERN decided to refurbish the existing

SM18 test facility to comply with the required gradients of 25 MV/m. In March 2010, a visit at

CERN of power coupler experts from different institutes confirmed that the actual facilities had to

be refurbished. The SM18 cleanroom facility is composed of three parts, each measuring 15 meters

long; an outside working place, a Class 10’000/ISO7 cleanroom and a Class 10/ISO4 cleanroom,

used as an assembly area for LHC cavities (Figure 1). However, because of the door opening the

actual useful space is around 13 meters long by 2.10 meters high. The useful height can be extended

to 2.60 meters thanks to a small door on top of the main door. It was designed to let LHC power

coupler pass the doors after the final assembling. Finally, an additional Class 100/ISO5 softwall

cleanroom (baldaquin) is located outside of the main facility. According to the coupler experts’

recommendations, the SM18 cleanroom has a good potential for the SPL coupler work1. The Class

2

10/ISO4 area provided by the facility is the best place to reach gradients greater than 25 MV/m. The

final coupler assembling should be done in such room as well as niobium cavity rinsing2.

3. SM18 cleanroom facility upgrade

To achieve the manufacturing of such high voltage gradient components, carrying operations

between different cleanroom facilities should be avoided. They are time consuming and they

introduce additional risks in terms of particle contamination (ripping of plastic bag when moving

the equipment, possible contamination at unpacking). The philosophy should be to control as much

as possible the manufacturing process, and therefore remove any hazardous operations. Thus, the

SM18 facility needs an upgrade of its cleanliness class.

Within this scope, experts recommended to provide additional Class 100 and Class 1’000 clean

rooms1 (Figure 2). A new Class 1’000 room should be built for the personnel dressing and be

ideally equipped with an air shower to access to the working area. The actual Class 10’000 rooms

can be upgraded to provide the new Class 100 area, used as a preparation area before entering into

the class 10 cleanroom. In addition, other projects with lower cleanliness needs could use this new

class 100 space as an assembling area. The actual air shower should be replaced by an ionized air

shower to access to the Class 10 area. Finally, an additional baldaquin (n°2 on Figure 2) could be

installed for long term storage of components.

Nevertheless, the cleaning processes must be done in dedicated rooms, to avoid contamination of

the assembling areas. Thus a new Class 100 cleanroom, dedicated to power coupler elements

rinsing and degreasing, should be built in direct connection with the future class 100 one. Moreover,

an additional Class 10 cabinet is needed for installing the high pressure rinsing (HPR) system to

clean the cavities. This cabinet will be connected from outside (for maintenance reason) to the

rinsing room and will constitute a local class 10 space. Likewise, an Ultra Pure Water (UPW)

supply system must be installed next to the cleanroom to limit the size of the UPW circulation

circuit. An additional water tank may be considered, if needed, to buffer the ultra pure water

consumption during the rinsing operations.

4. Quality control

To guarantee a good control of the manufacturing and assembling process, the monitoring of

critical parameters has to be done as much as possible. Thanks to CERN and DESY’s

experience3,4,5,6

we are able to define a list of control procedures and therefore a list of the

equipment to be obtained (Table 1, Table 2, Table 3).

Ultra Pure Water quality

Controls are mainly done on the Ultra Pure Water quality; particle counting, bacteria analysis,

water resistivity measurement and Total Organic Carbon (TOC) test (Table 1, Table 2). Such

controls must be done at the inlet and if possible at the outlet of the rinsing systems to check the

rinsing efficiency. In fact, the rinsing water contains many bubbles that lead to unstable and non

relevant measurements of the particle content. An alternative solution used at DESY3 consists of

filtering a relevant sample of the rinsing water with a mechanical filter. This filter is then analysed

under a light microscope to determine the numbers and the size of the particles. However this

counting operation has to be done manually and can take up two hours. For that reason it should be

3

considered as an optional method to check the outlet water. Water resistivity measurements at the

outlet were used at CERN to minimize the time needed for conditioning of the LEP SC cavity6.

This method is still used at CERN to validate the rinsing with the HPR system. Measurements at

inlet, outlet and filter analysis will then be reported in a database which will be used to detect

failures in the process and thus improve it.

Cleanroom class 10 / ISO4:

Name - Description: Comment:

High pressure cavity rinsing system Nozzle moving through a rotating cavity

Online liquid particle counter At inlet of the cavity rinsing system

Online Ohm-meters Check water resistivity at inlet

Bacteria analysis system Check water quality at rinsing system inlet

Mechanical filter Validate the rinsing at rinsing system outlet

Optical microscope Analysis of the mechanical filter

Online TOC analyser Check carbon presence in UPW

Drying system Accelerate cavities' drying

Air monitoring system / Particle counter Control air quality

Leak detection system He test

Online O2 monitoring system Survey of the O2 level

Air tight boxes & cabinet Storage of clean component, have to be in stainless

steel

Fog generator Study and check air flow movement

Optical cavity inspection system Study cavity surface defects

Spray gun Removal of dust

Ultrasound cleaning bath Removal of dust

Table 1: equipment needed for the class 10 areas, in blue are the UPW related equipment

4

Air quality

Monitoring of the air quality is necessary. Temperature and humidity are easy to monitor and are

already in place in the current cleanroom facility. To guarantee the laminar flow conditions, air flow

velocity measurement should be done on each filter regularly along the year. Once assembling,

rinsing and carrying procedures will be defined, a first verification with handheld particle counter

must be done to validate them. A global operation pattern will appear, and lead to the definition of

specific measurement point for an online particle density monitoring. Moreover, specific checking

should be considered before any critical operation3. Within the same scope, cleanliness of a

component could be validated by blowing with filtered and dry gas7. Particle measurement is done

in the blowing direction.

Optical inspection of cavities

Finally, the control process could be completed by the acquisition of an optical inspection system

for SRF cavities. It is composed of a cylinder fitting the iris of the cavity, on which an illumination

system and a CCD camera are installed. It allows the characterization of surface defects. A

correlation between data from T-map or quench location measurements, obtained during RF test,

and surface aspect is done to locate defects produced when manufacturing the cavities. This system,

originally developed at KEK/Kyoto University, has proven its efficiency8 and has been delivered to

other institutes such as DESY9, where it is still in development.

Cleanroom class 100 / ISO5:

Name - Description: Comment:

Power Coupler & HOM rinsing system Low pressure rinsing

Online liquid particle counter At inlet & outlet of the cavity rinsing system

Online Ohm-meters Check water resistivity at inlet & at outlet

Bacteria analysis system Check water quality at rinsing system inlet

Mechanical filter Validate the rinsing at rinsing system outlet

Optical microscope Analysis of the mechanical filter

Online TOC analyser Check carbon presence in UPW

Air monitoring system / Particle counter Control air quality

Leak detection system He test

Online O2 monitoring system Survey of the O2 level

Air tight boxes & cabinet For storage of clean component, have to be in stainless

steal

Table 2: equipment needed for class 100 areas, in blue are the UPW related equipment

5

5. Upgrade priority

To spread over time the total cost of the refurbishment, the project can be divided into steps with

different priority levels (Appendix I, Appendix II Appendix III). However the first step represents

itself 90% (Appendix IVAppendix III) of the total amount of the refurbishment. In fact, it includes

the upgrade of the cleanroom facility, the installation of a new HPR associated to a new UPW

production unit and its monitoring instrumentation. A way to reduce the cost of the first step could

be achieved if the HPR system from CERN gives good result on SPL cavity. A first rinsing on a

one cell SPL prototype cavity is planned by the end of December 2010. In case of good

performances when rinsing the cavities with CERN’s HPR, the installation of a new HPR can be

postponed. In that case, the cost of the first step drops to 58% of the total refurbishment cost.

As a second step of the upgrade, we should focus equipments which will lead to the improvement of

the working procedure and reinforce the quality control: fog generator, cavity optical inspection

system, bacteria analysis in UPW and O2 survey system if needed.

Finally, the two last steps will focus on dedicated equipment for the cleanroom like pumping

equipment, cleanroom monitoring equipment, and storage equipment for clean components.

6. Conclusion

The aim of this upgrade is not only to provide a cleaner environment for high gradient component,

but also, thanks to new control procedure, to provide a real follow-up of the manufacturing process

for each element needing a high degree of cleanliness. Moreover, the upgrade will benefit other

projects such as LHC spare cavities, by upgrading their manufacturing and assembling process.

Additional external equipment:

Name - Description: Comment:

UPW production unit Production of UPW

UPW tank Buffer UPW use

High pressure pump 100 bars needed

Primary vacuum pump Oil free

Secondary vacuum pump Oil free

Table 3: cleanroom upgrade, additional equipment, in blue are the UPW related equipment

6

Figure 1: Cleanroom at SM18, present configuration

7

Figure 2: Cleanroom at SM18, configuration proposal.

8

Appendix I: Equipment table 1 (Priority A1). Light blue rows are elements of the equipment described in the dark blue row on top of them.

Name - Description: Qty: Cleanliness

class:

Price/unit chf

(ExW):

Total prices

chf (Exw): Providers: Manufacturers: Comments: Priority:

Low Pressure Rinsing

Equipment 1 Class 100

Nan CERN CERN

A1

SM18 clean room upgrade 1 Class 100

to 10 640 000,00 640 000,00 Company 1 Company 1

1st estimate. On site

works should not

exceed 6 weeks

A1

New Personnel Access

Class 1000

Company 1 Company 1

A1

New Cleaning Area

Class 100

Company 1 Company 1

A1

Upgrade of the Class 10 000

Area Class 100

Company 1 Company 1

A1

Ionised aire shower

(upgrade) Class 10

Company 1 Company 1

A1

Upgrade of the Class 10 Area

Class 10

Company 1 Company 1

A1

Ultra Pure Water

Production Unit 1 Type 1+ 230 000,00 230 000,00 Company 2 Company 2

A1

Pre-treatment unit 1 grey 80 000,00 80 000,00 Company 2 Company 2 water softener A1

Main system 1 grey 150 000,00 150 000,00 Company 2 Company 2

deionisation + tank +

pump + UV light +

monitoring at 1400 L/h

available in 900 L/h for

130 000,00 CHF

A1

Liquid Particle Counter 1 Class 10 30 650,00 30 650,00 Company 3 Company 4 remote LPC A1

Spray Gun 2 Class 10 250,00 500,00

A1

Total Organic Carbon TOC

& Ohm meter 1

Type1+ &

Class 10 47 000,00 47 000,00 Company 5 Company 5

A1

Ultrasound Cleaning bath 1 Class 100 1 000,00 1 000,00 CERN

magasin CERN

A1

9

Appendix II: Equipment table 2 (Priority A2 to C). Light blue rows are elements of the equipment described in the dark blue row on top of them.

Name - Description: Qty: Cleanliness

class:

Prices / unit

chf (ExW):

Total prices

chf (Exw): Providers: Manufacturers: Comments: Priority:

High Pressure Rinsing

System 1 Class 10 522 000,00 522 000,00 To be defined To be defined

Based on DESY's new

HPR, some

modifications could be

necessary to adapt it

at CERN

A2

Stainless Steel Cabinet 1 Nan To be defined To be defined A2

Rinsing System 1 Nan To be defined To be defined A2

Touch Control Device 1 Nan To be defined To be defined Optional A2

High Pressure Pump 1 Grey 80 000,00 80 000,00 To be defined To be defined

Too big for the system,

a smaller compressor

will reduce the cost of

the system

A2

Bacteria Analysis Procedure 1 Class 100 Nan To be defined To be defined Should be done by an

external company B

Fog Generator 1 Class 100 to

10 12 700,00 12 700,00 Company 3 Company 6 B

O2 survey system

Class 100 to

10 Nan To be defined To be defined

To be define when the

new cleanroom air

condition will be known

B

Optical inspection system for

Cavities 1 Class 100 68 000,00 68 000,00 Company 7 Company 7

Raw estimation from

DESY, their system

was loan by KEK

B

Air monitoring system 1 Class 100

to 10 22 990,00 Company 3 Company 4 C

Air Partcile Counter 3 Class 10 3 665,00 10 995,00 Company 3 Company 4 R2014 C

Air Partcile Counter 3 Class 100 3 665,00 10 995,00 Company 3 Company 4 R2014 C

Vacuum pump for Particle

counter 1 Grey 1 000,00 1 000,00 Company 3 Company 4 C

10

Appendix III : Equipment table 3 (Priority C to D). Light blue rows are elements of the equipment described in the dark blue row on top of them.

Name - Description: Qty: Cleanliness

class:

Prices / unit

chf (ExW):

Total prices

chf (Exw): Providers: Manufacturers: Comments: Priority:

Ionic Pumping system 1 Class 100

to 10 7 000,00 7 000,00 Company 8 Company 8 C

Ionic Pump 1 Class 100 Nan Company 8 Company 8 VacIon Plus 75 C

Power Supply 1 Grey Nan Company 8 Company 8 C

Controller 1 Class 100 Nan Company 8 Company 8 Dual unit single channel C

Leak Detection system 1 Class 100 30 262,50 30 262,50 Company 9 Company 9 SmartTest HLT 570 C

He leak detection system

(dry pump) 1 Class 100 27 795,00 27 795,00 Company 9 Company 9 C

Wireless remote 1 Class 100 2 467,50 2 467,50 Company 9 Company 9 C

Pumping Group 1 Grey 17 234,00 17 234,00 Company 9 Company 9 HiCube Turbo

pumping station C

Primary Pump 1 Grey

Nan Company 9 Company 9 C

Secondary Pump 1 Grey Nan Nan Company 9 Company 9 C

Air tight boxes & Cabinets Class 100 Nan To be defined To be defined D

Anemometer Probe 1 Class 100 to

10 720,00 720,00 Company 3 Company 4 D

Differential Pressure Probe 3 Class 100 to

10 480,00 1 440,00 Company 3 Company 4 D

11

Appendix IV: Prices for each steps and its percentage over the total cost.

Total: 1 631 496,50 CHF 100,00 %

A1 + A2 1 471 150,00 CHF 90,20 %

A1 949 150,00 CHF 58,20 %

A2 522 000,00 CHF 32,00 %

B 80 700,00 CHF 5,00 %

C 77 486,50 CHF 4.70 %

D 2 160,00 CHF 0,10 %

12

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2 O. Capatina, Fabrication of Nb and Cu SPL cavities and required tools CERN Satus, SPL Cavity Working Group

Meeting, February 8th, 2010.

3 N. Krupka, T. Ebeling, K. Escherich, A. Matheisen, Morales Zimmermann, B. Petersen, D. Reschke, N. Steinhau-

Kuehl, F. Zhu, Quality control at the TTF-Cleanroom infrastructure for cavity-processing.

4 N. Krupka, K. Escherich, M. Habermann, K. Harries, A. Matheisen, B. Petersen, Quality control update of the

cleanroom for superconducting multi cell cavities at DESY, contribution to the SRF2005, Ithaca, New-York, USA

5 K.Escherich, A.Matheisen, N.Krupka, B.Petersen, M.Schmökel, Clean-room facilities for high gradient resonator

preparation, contribution to the SRF2005, Ithaca, New-York, USA

6 C. Benvenuti, P. Bernard, D. Bloess, G. Cavallari, E. Chiaveri, E. Haebel, N. Hilleret, J. Tückmantel and W.

Weingarten, Superconducting niobium sputter-coated copper cavity modules for the LEP energy upgrade, CERN

7 A. Matheisen, Feng Zhu, Preparation of the RF power couplers for the tesla test facility, TESLA

collaboration 8 Y. Iwashita, H. Hayano, Y. Tajima, Development of a high resolution camera and observations of superconducting

cavities, Proceeding of EPAC08, Genoa, Italy

9S. Aderhold, Optical inspection of SRF cavities at Desy, Proceedings of IPAC’10, Kyoto, Japan