Run Coordinator report: Spring 2020 w3
We had an eventful week met with successful production data collection, several tests completed, as well as a few challenges to overcome. Things for this period of running began relatively smoothly with production data collection at 150 nA from Jan 15-16. The afternoons of Jan 16 and 17 saw several planned tests: trigger studies, cDAQ tests, and a high current study probing systematics of accidentals. The trigger study showed good live time up to 450 nA of beam current, with 91% live time at this current. Electronics are our limiting factor, with TPOL accounting for 5% of dead time followed by the DIRC with 3.5% contribution (as a caveat, the TOF thresholds were changed --- its contribution is not reflected in the study). The accidental study overseen by Richard Jones on Jan 17 saw a maximum current of 2100 nA to Hall D. The accelerator was successfully able to deliver this current with acceptable beam quality, and RadCon monitored and found the increased current to be acceptable. An empty target run was taken immediately following as well.
Collection of production data continued through the long weekend, with Jan 18 and 19 being fairly smooth. We increased the current from 150 nA to 250 nA during the Jan 18 owl shift. Preliminary studies of the rate increase show physics events per trigger to be stable before and after the increased current.
The day of Jan 20 saw a few setbacks. First, the tagger PSS system unexpectedly dropped to restricted in the tagger hall. Overlapping with this, a vacuum pump failed in the Hall D beamline requiring expert work (Keith). A little later, firmware was updated to TAGH, TAGM, PS, and ST systems introducing timing offsets requiring timing window and other calibrations. We believe these effects have been calibrated, though this took some time and effort. A little later in the day, the solenoid unexpectedly tripped. The underlying cause is still unclear. Within a few hours we were able to recover and begin ramping the magnet again, though unfortunately beam did not return until the next RC’s term due to accelerator issues.
In all, we were able to collect 1.8 billion triggers running at 150 nA and 6.9 billion triggers at 250 nA during my RC term. I would like to acknowledge the work of Scott Spiegel and Eugene working late in the night to recover our solenoid (plus Tim and Beni for their work from afar), Keith Blackburn for weekend vacuum pump fixes, Sean for the many calibration fixes needed, Alexandre for his guidance, and to our adept shift crews for keeping our experiment running smoothly.
