DCH Conditions for turning HV on

Two simple conditions must be met before the Drift chamber is ready to turn on the high voltage.

• The gas system must have Isobutane in it at greater than 19.5% and less than 20.5%. These are the yellow alarm limits in the corrected Isobutane value in the DCH Epics gas shifters panel (ajshifters.dl). Outside of these tolerances the operations manager should ensure that the HV is ramped to off and the terminators are removed from the CAEN HV cards.


• The gas system should have a certain level of water in the gas mix. For no field (magnet off) running the water should be between 3000 to 3800 ppm as measured in the water display on ajshifters.dl. This is the same as for normal running. For magnet on Cosmic running we can turn the HV on at a water level between 2000 ppm and 3800 ppm.