CSC gas studies

Valery Andreev (UCLA)

Roberto Guida (CERN)

April 28, 2008

April 28, 2008 V. Andreev, R. Guida 2

CSC gas system: faced problems• Mixer

– Calibration - fixed • Purifier:

– Fast saturation – Changing working mixture

• Pump– Membranes - replaced by better version

• Distribution racks – Flowcells performance - tolerable for the moment– Broken bubblers - protection covers installed

• Backup system– Can change mixture ratios - use Ar(40%)-CO2(60%) instead

of CO2(100%): done

• Huge air intake

Ruptured membrane

To be fixed

To be understood / fixed

April 28, 2008 V. Andreev, R. Guida 3

• Saturates in 1-2 days

– Could be due to high level of air intake discovered recently

• Multiple HV trips after switching ON the purifier

– Absorbs/eats CO2 component of the mixture

– Safe operation mode to adopt

CSC gas operations: Purifier

April 28, 2008 V. Andreev, R. Guida 4

• System has been running in closed loop for YE+ since November 2007

• Analysis rack (Water/Oxigen and InfraRed) at SGX5 is running since March 2008– Oxygen : 4000 ppm (to compare with old (wrong) measurement of 180 ppm)– Water: 330 ppm ( old device measurement -> 50 ppm)

• Chromatograph measures ~20000 ppm (2%) Nitrogen – in rough agreement with Oxygen measurement by analysis rack sensor

• Big air intake, source is not identified yet

• Stop of HV on March 26

• Running in open loop mode since March 27, till things understood / fixed– Costly operation

CSC gas operations Issue: Air intake level

CSC

Status:All positive end under gas Fill modePurifier under test

Gas analysis:Before Purifier O2 ~ 600-700 ppmVol N2 ~ 0,284 %Vol (~2840 ppmVol) H2O ~ 200 ppm

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First test for CSC purifier (it was already used)Regenerated with Ar H2 3%, flow 300 l/h

April 28, 2008 V. Andreev, R. Guida 7

Second test for CSC purifier (it was already used)Regenerated with Ar H2 3%, flow 300 l/h

April 28, 2008 V. Andreev, R. Guida 8

28-mar     11-apr     24-apr    

flow N2 (%) check flow N2 (%)   flow N2 (%)  

after pump   0,14 0,14        

66 ME+1/1 150 0,03   150 0,031   139 0,034  

67 ME+1/2,3 700 0,23   450 0,475   306 0,614  

68 ME+2 700 0,09   450 0,177   321 0,244  

69 ME+3 700 0,11   435 0,199   312 0,276  

70 ME+4             123 0,319  

Measurements at the pre-distribution

Return from chambers

April 28, 2008 V. Andreev, R. Guida 9

chn flow (l/h) N2 (%)

1 30 0,436

2 17 0,402

3 30 0,469

4 18 0,394

5 30 0,519

6 17 0,364

7 29  

8 17  

9 22  

10 18  

11 29  

12 19  

13 30  

14 17 0,427

15 32 0,500

16 18 0,408

17 32 0,524

18 18 0,409

ME+1 (unit67)

Return from individual channel red ME+1/2 back ME+1/3

Hypothesis for the different concentration:1. Different flow2. Different leak rate

N2 concentration in the supply line:0,03-0,04 %

ME+1/3 27-30 Bypass on disk ME+1/3 27

Bypass test

Last week

April 28, 2008 V. Andreev, R. Guida 11

Nitrogen value vs chamber overpessure

0.5 mbar 1.5 mbar

Rack # 67 0.45 % 0.475 %

Rack # 68 0.18 % 0.215 %

Air intake Independent of overpressure !- to check at 3 mbar yet

Leak test for channel 15 (ME+1/2) 16 (ME+1/3)

Leak rate very similar: <= 1 ml/min (0,06 l/h)

Do not explain the different in N2

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chn flow (l/h) N2 (%)   flow (l/h) N2 (%)

15 ME+1/2 30 0,505   30 0,528

16 ME+1/3 16 0,387   29 0,229

17 ME+1/2 30 0,503   29 0,540

18 ME+1/3 16 0,397   30 0,225

Increasing the flow, decrease the N2 levelSomething it is really different in the chamber

April 28, 2008 V. Andreev, R. Guida 15

Results from ISR

ME1/2 N2 (%) N2 (%) H2O (a.u.) H2O (a.u.)

after 4 0,416 0,056 51,86 11,21

after 3 0,36 0,05 40,65 11,8

after 2 0,31 0,159 28,85 13,41

after 1 0,151 0,14 15,44 10,62

supply 0,011   4,82  

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Results from ISR

ME2/2 N2 (%) N2 (%) H2O (a.u.) H2O (a.u.)

after 3 0,22 0,089 52,51 15,11

after 2 0,131 0,05 37,4 17,75

after 1 0,081 0,069 19,65 15

supply 0,012   4,65  

Gas channel

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Results from ISR

ME2/1 N2 (%) N2 (%) H2O (a.u.) H2O (a.u.)

after 1 0,102 0,089 14,47 9,77

supply 0,013   4,7