Run Coordinator report: winter 2023 w2

Run Coordination report for the week from 01/18-01/25/2023 (Alexandre Deur).

The main task during this RC week was to align the diamond (JD70-103) and start production with linearly polarized photons. The diamond was aligned on Sunday (01/22/2023) and production started right after. The reason why alignment could not be done sooner is multiple issues with the accelerator. For the first day of the week, Wednesday Jan. 18th 2023, the beam was not available during the day due to beam and RF studies, and a long recovery from these studies: acceptable beam came back only Thursday at 1:10am. Hovanes, the expert aligning the diamond, waited until 1am and left since the beam was still unavailable and it was getting too late to start to do the long work of diamond alignment efficiently. We therefore took amorphous data in production configuration once the beam came back. Thursday, the beam was again taken way for RF study because the accelerator could not provide the high currents required concurrently by the Hall A and C experiments. The beam came back around 17:30. Hovanes checked if he could align the 0/90 directions of the diamond, which he hoped could be quick since they were already aligned for the CPP/NPP experiments. However, it happened to not be the case and that the alignment will need to be redone from scratch. Since it was getting too late for such task, diamond alignment was postponed again. Thus, during Thursday night, we ran again on amorphous radiator, choosing to do one production run (2h) on each of the 4 available Aluminum foils. This was to check the dependence of the rates with radiator thickness to try to understand why detector and PS rates counted 30% higher than expected for our nominal current. (This was ultimately traced back to a BCM calibration problem, see below in the list of issues). Friday, the beam was unavailable again starting around 7:30am due to a vacuum issue in South Linac. The beam came back Saturday at 2am. Hovanes was not available for Diamond alignment on Saturday, so the task was postponed to Sunday and we did production on the amorphous radiator of the goniometer until Sunday 9am. At that time, Hovanes started diamond alignment. It was relatively quick, finishing by Sunday 17:30. Then we started the GlueX-II data production, cycling over 0/90/45/135/amorphous and continued until the end of my RC tenure Wednesday, Jan. 25th. There was a pause on Tuesday due beam studies scheduled for the day (6h). The coherent peak spectrum displays a sharp edge and relatively high (~40%) maximum photon polarization.

Beside diamond alignement, the other special tasks done during the week were completing the detector check-out and calibrations (the detectors are working well) and, while waiting for the diamond to be aligned, to do a long empty target run (done during the Tuesday-Wednesday night). Its analysis shows the expected vertex distribution.

In all, the useful beam time (ABU) for the week was 47h, and we lost about 8h due to problems on our side (BANU), largely due to usual overheads (changing radiators/diamond orientations and DAQ stop/start).

Issues discovered or that arose during the week (beside the usual running woes such as DAQ or FADC troubles) were:

• The calibration of our BCMs differed by 30% compared to the run period of 2020. Discussions with Ops revealed that the BCM calibration (called BLA calibration) is not done systematically before each run period and the last calibration was done in 2021. We discussed with Ops to ensure that it should now be done at each start of a new run period. We did a BLA calibration on Thursday, 01/24/2023;
• The Start Counter is effectively (apparently not physically) rotated by about 96 degree. At the time this summary is being written (01/29/2023), the issue is not solved or fully understood;
• Loss of communication with the target: for a few days, the target could only be could monitored, but not controlled remotely (e.g., switch empty <=> full). This was not a problem since there was no need to empty the target during that period;
• Loss of communication with the TAGH high voltage crate;
• DIRC LED TDC missing and the DIRC disconnecting from the DAQ;
• NMR probe readout failures;
• Beam energy modulations of a few MeV at most, due to artifacts in BPMs;
• The pressure sensor for the CDC producing unphysical spikes and triggering alarms. The sensor information was temporarily removed from the alarm. When the sensor was inspected during an access, it was found hanging. After being put back and shielded from winds, the spikes disappeared. Nevertheless, a spare was bought and will replace the current sensor.