Run Coordinator report: summer 2022 w1

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My RC period covered the beam restoration (June 1st-8th 2022) and first week of physics beam delivery (June 8th-15th) for the CPP/NPP E12-13-008 experiment. In summary, it was a relatively successful week given that it consisted of starting a new experiment, including commissioning several new detectors and set-ups, while accelerator operators were still trying to establish physics beam to Halls B, C and D. Beam became available nearly on time and at the end of my RC period, we were well along in commissioning, with the beam quality checkout mostly done, detector/beamline calibration/checkout done, the new detectors commissioning ongoing, the trigger set-up started and the diamond (JD70-103) aligned, with the diamond quality (from the coherent peak shape) appearing to be quite good, peaking at more than 70% according to the preliminary analysis. We also took a large amount of "pre-production" data (unpolarized photon beam, and trigger and detector set-ups not finalized) including empty target data. There was no critical problem on the Hall D side. The major tasks that remained before being ready for data production were understanding the new detectors, in particular the CToF, optimizing the photon flux/polarization, and setting up the level-1 trigger. A more detailed description of the week follows.

Physics beam delivery was scheduled for Wednesday June 8th 2022. The beam came nearly on time, with the Beam Operation Group (Ops) asking us to be ready by 11am/noon for physics beam. We required shifts to be staffed starting at noon but beam came only the next day (Thursday 9th) around 8am-9am mainly due to problems trying to tune beam to Hall C (Hall B was still open: it started a few days late due work on its polarized target). One significant item regarding our beam tuning was that one of the quadrupoles (MQP5C09) on Hall D line was not operable. CASA devised a tune for us that bypassed this quadrupole, so we had an unusual beam tuning for the beginning of the run (at least, it was still the case at the end of my RC period). Our program started after Ops did our ion chambers calibration. We started by checking our radiation levels, which were reasonably good. We then did the radiation levels scans with current (50nA, 75nA, 100nA) and radiator thickness (RL=0, 1E-4 and 3E-4). They show similar behaviors compared to those of the latest run (Fall 2021), which had some marked differences with those of previous run periods. Then, the beam envelope and convergence were checked and found to not be acceptable, even for commissioning. Beam transport was refined during Friday night. Although the beam was unavailable for about 10h during the rest of Friday, it was still a productive day: preliminary Level-1 trigger studies were conducted, part of the detector general calibration was done, the ToF and CToF high-voltage scans were done (although it was realized that CToF scans will need to be redone). This was followed by the CDC high-voltage scan, done early on Saturday. The beam was unavailable again Saturday morning for 4h. When it came back early afternoon, the detector general calibration was finalized, some more work was done on the level-1 trigger and an attempt was made at calibrating the active collimator and optimizing the photon flux. This failed however because the beam position locks at the collimator level did not keep the beam position stable enough. Sunday during the night, we took some first pre-production data using the 3E-4 radiation length aluminum foil, and the newly tuned (but still preliminary) L1 trigger. High rates (background) in the CTOF resulted in low DAQ livetime (~50%) even with beam current limited to 60 nA. Sunday morning, the beam was down again for 6 hours (half of it due to a severe thunderstorm) and we took the opportunity to access the Hall to switch the target from the Pb foil to no-foil target. We ran 2.5h in that condition and, as the beam was down again far an additional 3h, we accessed the Hall once more to switch back the target to Pb foil position. When the beam came back in the evening, we performed a few special runs to diagnose some issues seen in the FDC and CToF, redid the high-voltage scan (which again would need to be redone a third time as understanding this detector turned out to be difficult) and spent the night taking pre-production data on the Pb target. After a 2h beam down time Monday morning, the TAGM high-voltage scan was started but could not be completed because Ops took the decision to use the day for beam study in order to understand why they cannot deliver high current beam to Hall C. Consequently the beam was taken away for 14 hours and came back only shortly before midnight. The problem with Hall C beam delivery was not resolved and continued to puzzle Ops and CASA. A couple of accesses to the tagger hall were made to address issues with a TAGH board and the tagger magnet NMR but the later re-occurrence of the issues showed that the interventions did not fix these problems. Pre-production data were taken overnight with the CToF removed from the trigger, which allowed us to run at 100nA on aluminium radiator with high livetime (~98%, 12 kHz DAQ rate). Tuesday morning, the TAGM high voltage scan was finalized and a third CToF high voltage scan (more precisely, high voltage studies) was performed. About 1h of pre-production data were taken following that. After the 14 hours beam down time of the previous day (Monday), the Program Deputy decided to maximize beam delivery to Hall B and D for Tuesday, and not repeat the studies of the Hall C beam delivery problem. This was to give Ops and CASA time to study the Hall C issue, to ensure enough beam time to Hall B so that it could move to its 5-pass program on Wednesday and for Hall D to have stable enough beam to align its diamond. The latter was done (two directions, 45° and 135°, as specified in the runplan) and took slightly more than 8 hours, which is relatively fast for such task. Preliminary studies of the coherent peak shows a beam polarization peaking above 70%. Ops then did the ion chamber calibration on the diamond. In the evening, a Pb absorber (which is placed right upstream of FMWPC, the muon wire chambers) study was conducted until slightly after midnight and we spent the night on pre-production using the aluminum radiator and 60 nA (the current was reduced from 100nA because of low livetime). Several DAQ issues occurred during the night, with the symptoms being either very low livetime or widely fluctuating livetime. (It was decided to not run on diamond overnight because the collimator was not aligned yet, so we may not have had a good photon beam polarization.) The beam went down for more than an hour Wednesday morning and an opportunistic access was decided to install steel shielding to see if it would help reduce a large background seen in some of the FMWPC layers. Pre-production data taking was them resumed for 1h, which allowed us to see that the steel shielding was not successful. Then beam was shut down (7:40am) for a long period (eventually about 40h, with the beam coming back on Thursday at 11pm) to address a RF cavity issue and the Hall C beam delivery problem. In all, this first week of commissioning was successful despite low beam time (mostly due to Hall C high current delivery problem) and substandard Hall D beam quality. The main issues for us during that time was the large background seen in the new CToF detector. Beside understanding this, the other important items that remain to be done before being ready for production were to establish the Level-1 trigger (only a very preliminary trigger was set-up during the week) and align the collimator with the beam, which was prevented due to beam instability coming from either a lock problem or/and the fact that the beam is inherently instable because only Hall B and D are running (no high current beam in the machine to stabilise the orbits). The Scheduled Program for the week was 136 hours, we had about 60h of CW beam on target (43% of the scheduled time) among which 54 hours of acceptable beam in use (40% of the scheduled time), which is quite good for a commissioning/initial beam establishment period.