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User name Olivier
Log entry time 19:50:03 on December 5,2000
Entry number 52954
keyword=FPP chambers 3 and 4 gas flow read out
When the shift crew did the check list (proving it is actually usefull), they discover that gas flow in FPP ch 3 was 0, and ch 4 was fluctutating 0-positive values. We did not know what it was related to (there was no gas alarm whatsoever). We called Jack, and made an access to the left spectrometer. It turned out that the bubblers were bubbling OK, but that the digital readout on ch 3 was showing ~-160 (should not be negative !), and ch 4 was oscillating between positive and negative values.
Touching the connectors on these readouts made them go back to reasonnable values, and the value read in EPICS in the counting house was back to normal. There was actually no gas problem.
This problem might occur again during the experiment. If so (you notice a 0 value in the gas flow of one of those chambers), it is HIGHLY PROBABLE that it is the same readout problem. You don't need to call RC or Jack Segal.
Of course, if later you see that the HV of the entire chamber trips, or if the efficiency dropps, then you have a problem and call (or fix it ?).