Difference between revisions of "Run Coordinator report: winter 2023 w2"

Revision as of 10:19, 29 January 2023

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

The main task during the RC week from 01/18-01/25/2023 was to align the diamond and start then 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 because of multiple issues with the accelerator. Wednesday, the beam was not available during the day for beam and RF study and a long recovery from these study: acceptable beam came back only Thursday at 1:10am. Hovanes, the expert aligning the diamond waited until 1am and left as the beam was still not there and it was getting too late to do the long work efficiently. We therefore took amorphous data in production configuration when the beam. Thursday, the beam was again taken way for RF study. The reason was that the accelerator could not reach the high currents required by the Hall A and C experiments. The beam came back around 17:30. Hovanes tried to see if he could align the 0/90 directions of the diamond, which he hoped would be quick to align since they were already aligned for the CPP/NPP experiments, but it turned out not the be the case and he realized he will have to redo the alignment from scratch. By the time, it was getting too late for such task. During Thursday night, we ran again on amorphous radiator, choosing to do one run on each of the 4 available Al. foils in order to check the dependence of the rates with radiator thickness. This was due to the rate appearing to be 30% larger than expected for our nominal current. (This was ultimately traced back to a BCM calibration problems, see below in the list of issues). Friday, the beam became unavailable again starting around 7:30am due to a vacuum issue in south linac. It came back Saturday at 2am. Hovanes was not available for Diamond alignment on Saturday, so it was postponed to Sunday and we did production on the amorphous radiator of the goniometer until Sunday 9am. Then Hovanes started diamond alignment. It was relatively quick, finishing by Sunday 17:30. Then we started production cycling over 0/90/45/135/amorphous and continued until the end of my RC tenure Wednesday, Jan. 25th, with a pause on Tuesday when beam study where 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 calibration (the detectors are working well) and, while waiting for the aligned diamond to become available, 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 ***, and we lost about *** due to problem on our side (BANU).

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

• The calibration of our BCM differed by 30% compared to the run in 2020. Discussions with Ops revealed that the BCM calibration (called BLA calibration) is not done systematically before each run period and the last one was done in 2021. We discussed with Ops to ensure that it should now be done at each start of new run period. We did the BLA calibration on Thursday, 01/24/2023;
• The Start Counter was effectively (but not physically) rotated by about 96 degree;
• Loss of communication with the target: for a few days, it could be only locally controlled: we could monitor the target, but not control it remotely (switch empty <=> full).This is not a crucial problem since there was no need to empty the target during that week;
• Loss of communication with the TAGH high voltage crate;
• DIRC issues (LED TDC missing, DIRC disconnecting from the DAQ);
• NMR probe readout failures;
• beam energy modulations of a few MeV 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 it was inspected during an access, found hanging. After being put back and shielded from winds, the spikes disappeared.