Summer 2020 CDC HV scan procedure

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Aug 2020 CDC HV scan procedure

Collect 10M triggers with all CDC HV set to the following voltage:

2150 2125 2100 2075 2050 2025 2000 1975

This should be done with stable beam and normal weather (not when a storm is rolling in).

The most sensitive part of the scan is the first half, when the HV is highest and the CDC is on or close to its efficiency plateau. The atmospheric pressure can be monitored using the EPICS variable RESET:i:GasPanelBarPress1 Its units are kPa, the long-term mean is around 100kPa (due to a calibration offset).

Ideally, the average pressure during each of the first 4 runs should differ by no more than 0.1kPa. If that is exceeded, or if the pressure is changing by 0.3kPa/h or more, stop and reschedule the scan.

Contact CDC experts (Naomi or Beni) in case of problems or questions.