Run Coordinator report: Spring 2018 r3
This was a productive week devoted mostly to collecting physics data. We were scheduled to receive 168 hours of beam (i.e., 24x7), and we had beam available for 106 hours. Out of them, we have used 90 hours (or 85% of available beam) for actual data taking. During this week, we collected close to 12.8 billion events bringing the total to about 26 billion events so far for the Spring'18 run.
For the most part, the beam from the accelerator was acceptable. It has developed frequent trips late on Sunday necessitating a maintenance day for RF recovery on Monday (and, correspondingly, canceling the planned Beam Studies day on Tuesday). There were a couple of relatively long (2-3 hours) unplanned downtimes. On Thursday, beam was off for 8 hours to bring Hall A up. It went off for 2 hours for Hall B pass change on Friday, and for 4 hours for Hall C pass change on Tuesday. Apart from these downtimes, the frequency of beam trips was kind of average. While beam position was stable, its convergence on the collimator was varying from good to marginal to acceptable without any obvious reason.
On Tuesday, CEBAF achieved a major milestone when CW was sent to all 4 halls at once at the highest energies (i.e., at 5 and 5.5 passes). The only thing left for CEBAF to reach the design goals is to double the maximum current delivered to Hall C.
Below is a brief summary of what was going on day by day.
Wed Jan 24 and Thu Jan 25: We were taking production data almost all the time.
Friday Jan 26: In addition to production, 2 hours of 300nA AMO high-luminosity run to study L1 trigger and DAQ response. 65kHz rate with 96% live-time was achieved. Also, drift chambers performed well under these conditions. Later in the day, Hall went into Controlled access for 4 hours. During this access, TPOL persistent noise problem was fixed. TPOL exhibits now the same clean signals it had a year ago. Baselines of TPOL fADC were re-calibrated. Also, a dead TAGM channel was fixed.
Saturday Jan 27 and Sunday Jan 28: These were quiet production data taking days until the machine developed frequent trips toward the end of the weekend.
Monday Jan 29: Accelerator maintenance day. A few tasks were performed during this time. A few dead TAGM channels were brought back to live and HV scan was done. A dozen of FCAL HV bases were replaced. TRD detector was rearranged. Suspicious TPOL channel was looked at. After the beam came back in the evening, we returned to production runs.
Tuesday Jan 30: Once again, mostly production data taking.
Wednesday Jan 31: Started empty target runs at 6am, including a raw-mode run. For a short time, studied chamber currents without a radiator and with/without a collimator. At 9am, started TAC run which is still ongoing.
As of now, our hardware seems to be in the top shape not counting a dead channel here or there. There are a few issues requiring further attention: improving beam convergence, measuring polarization, understanding variations of the trigger rates for apparently the same beam flux. But nothing prevents us from continuing to collect good physics data.
