How_to_run_BCMcalib

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

There are two types of BCM calibrations. The first is ``calibrating the Hall A bcms with the OLO2'', the second is ``Cross Calibrating the OL02 BCM with Faraday cup (fcup)''. Both of these procedures are invasive. We do both of them at the same time. The Run Coordinator must coordinate this with MCC and Hall B, at the 8am meeting that morning (if not earlier). During the shift the calibration will take place, the Hall B shift workers should know we are going to do this and they are expecting us to inform them before starting, so they can stop their data taking.

Make sure Hall B agrees to have no beam while you are doing this. (The run coordinate shoud have informed Hall B already, so they should be expecting us doing this during a particular shift. Just walk over to Hall B counting house and let them know you are starting.)
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 and the radiator are 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 for about 3 minutes each: 10uA, 20uA, 30uA, 40uA, 50uA, 60uA, 70uA, 80uA, 90uA, 100uA.

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.

For each current, Faraday cup (located at the end of the injector) should be removed for 90 seconds and then inserted for 90 seconds.
If a beam trip occurs, the corresponding setting should be extended until a full 90 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 B
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. From here the procedure is invasive (no other halls can get beam). MCC will make sure about this.
When they call, start both HRSs CODA runs, start logging the current monitor DVM data (from the Hall A Tools menu).

start from current = 10 uA. MCC does the following two steps.

Beam delivery to Hall A for 90 seconds (Faraday cup is not inserted during this time). Hall A will see beam during this time;
The Faraday cup is then inserted at the end of the injector region to measure the absolute current for about 90 seconds. Hall A will not see beam during this time.

Repeat the above steps for the remaining beam currents: 20, 30, 40, 50, 60, 70, 80, 90, 100 uA.
During the whole process, check Lumi data to see if counts scale with beam current.
Reminder: beam trips should be minimize during the calibration process. If a trip occurs, MCC should extend the corresponding current setting (fcup inserted or removed) for 90 seconds, until a full 90 second 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 involves a 2 hours of downtime for all Halls though the official time for this procedure is about 1 hour.
After offline analysis, update BCM conversion factors in Hall A Tools (coordinate this with the Run Coordinator, do not do before the Run Coordinator allows you to implement these calibration constants).