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CSC Gas Discussion
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Europe/Zurich
4 (CERN)
4
CERN
We conclude from the two presentations that the impurities encountered in most of the CSC's at P5 are of the same order of magnitude as measured in the GIF tests some years ago, i.e. ~ 300-400 ppm of O2 and 1'000 to 2'000 ppm of N2 measured at the chamber outlet with one gas volume exchange in 12h.
Here below I normalize the various impurity measurements to standard Flows (1 volume exchange in 12h)
Results from P5:
Me+1/1: N2 = 600 ppm
ME+1/2: N2 = 4'000 ppm (factor 2 higher than in GIF test)
ME+1/3: N2 ~2'500 ppm
ME+2: N2 = 900ppm ( average over full wheel)
ME+3: N2 = 1'100 ppm ( average over full wheel)
Results from ISR:
ME+1/2: N2 = 4'160 ppm (factor 2 higher than in GIF test)
ME+2/2: N2 = 1'100 ppm
ME+4/1: N2 = 3'000 ppm (factor 1.5 higher than in GIF test)
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Purifier Parameter for O2 removal:
Total Circulation Flow: 5-7 m3/h
Expected O2 concentration at chamber outlet 400 ppm
Desired O2 concentration at chamber inlet 50-100 ppm
Need to remove:
325*10-6 * 6*10+3 = 2.0 ltr. of O2 / h => 48ltr/d
Absorbers:
a) the present purifier capacity (filled with 18 kG Cu) => 72 ltr. oxygen => cartridge lifetime ~1.5d for the full detector.
b) if filled with 20 kG Leuna Ni 6503 or 6510
Capacity will increase to 280 ltr. => => cartridge lifetime 5-6d for the full detector.
After the Technical Run next week DT1/GS can re-fill the purifiers.
Only 70-80% of the circulation flow should be passed through the purifiers.
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Flow adjustements:
One should optimize the flow settings of the detector in such a way that channels with high impurity see a higher flow, e.g. Me1/2 could be increased to ~80l/h/channel other channels with less impurities could be reduced.
In order to optimize the flow settings -in particular on the Minus-Side- we need more gas analysis measurements. As the effect seems to be rather systematic, one could measure a few channels per wheel (-Valeri ?)
The total flow should be set between 5-7m3/h (with 10% refreshment in closed loop). If we manage to keep the N2 concentrations after one passage between 1000 or 2000 ppm, we will get N2 concentrations between 1-2% when running in closed loop, which would be approx. the expectations from 2001.
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