CDC HV scan instructions October 2021

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The HV scan needs stable beam conditions, and also relatively stable pressure.

Use the same beam current that will be used for the production runs with the CDC on. At present that is 200nA on the run plan doc.

You will need to monitor the atmospheric pressure using EPICS PV RESET:i:GasPanelBarPress1


Please collect 9M triggers at the following HV settings (in V) for the entire CDC, in this order:

2125 2150 2140 2130 2125 2120 2110 2100 2090 2080

Note the atmospheric pressure when you start the first run (it is listed in RCDB as cdc_gas_pressure). If the pressure changes by 0.1 kPa or more from that value, then stop the HV scan. You do not need to repeat the 2125V measurement if the pressure is within 0.02kPa of the starting pressure.


To set the HV: Find the main action bar (vertical menu), click CDC voltages.

In the middle of the circle on the left, click ALL HV, then select from the dropdown menu "CDC: Set CDC HV parameters" Change voltage to what you want in the left column, hit return.