BCM calibration Procedure (i.e. BCM Linearity Test)

Non-invasive procedure

• Find the BCM Logging GUI beforehand and make sure it works. It should be at ``Hall A Main Menu -> BCM -> BCM Logging''.
• Make sure the target is in empty position;
• Make sure the radiator is out. (radiator should never be in for PVDIS anyway);
• Tell MCC:
• that you want to do a BCM calibration and you wnat to step through the following currents TWICE for about 1 minute each: 10uA, 20uA, 30uA, 40uA, 50uA, 60uA, 70uA, 80uA, 90uA, 100uA, 115uA; between each two currents MCC should stop the beam for 60-90 seconds.
• sometimes it will take a few minutes for MCC to find the numbers they need to get to all the currents. It speeds things up later because they will be able to jump to the right currents easily as they step through. It's a good time to make sure you can find the BCM Logging screen that you will need.
• It's important that the MCC finds the corresponding attenuator setpoint for each current before the procedure starts, to speed up the real process.
• Tell the MCC that you do not need the EXACT current if it is difficult to do. A tolerance of +/-2uA will make things much easier.
  
• In case someone asks, we do NOT need the Faraday cup to be inserted, (if it is, it would be invasive to all Halls).
• If a beam trip occurs, the corresponding setting should be extended until a full 60 seconds of data are accumulated without any trip for that setting.
• Beam delivery during this time should be to Hall A without loss:
• No beam to Hall C (Note: Hall C is off during PVDIS anyway)
• No loss (beam loss monitor) (MCC knows what this means)
• Note: the no-loss mode allows people to believe that all the current from the injector region makes to the BCMs in Hall A.
• Ask MCC to get ready and call you back before starting the procedure.
• When they call, start both HRSs CODA runs, as well as Parity CODA runs, start logging the current monitor DVM data (from the Hall A Tools menu).
1. start from current = 10 uA. MCC does the following two steps:
1. delivers beam to Hall A for 1 minute; (Note: Too much shorter, e.g.<30sec will not provide enough data and too much longer, e.g.>90sec will make our calibration vulnerable to possible baseline drift of Unser. Both should be avoided.)
2. stop beam delivery to Hall A for 1 minute.
2. Repeat the above steps for the remaining beam currents: 20, 30, 40, 50, 60, 70, 80, 90, 100, 115 uA.
3. Afterwards, repeat the procedure but in the opposite order: 115, 100, 90, 80, 70, 60, 50, 40, 30, 20, 10uA.
• note: the exact sequence is not important as long as we have stable data for each setpoint TWICE.
4. During the whole process, check Lumi data to see if counts scale with beam current.
5. Reminder: beam trips should be minimize during the calibration process. If a trip occurs, MCC should extend the corresponding current setting, a full 2-minute data are accumulated without any trip.
• When all this is done, stop the CODA runs and the BCM Logger. Halog the CODA run numbers and the BCM logging filename (which only updates after you hit stop, it should be like "/usr/opdata/bcm_hallA/BcmLog_xxxx"). The whole thing usually takes about 1 hour.
  
• Perform offline analysis.