Run Coordinator report: Spring 2020 w4
Run Coordinator Report for January 22 - 29, 2020
The second phase of the GlueX experiment (E12-12-002) in Hall D was scheduled to run for 164 hours this week, but received only 92.0 hours of CW beam on target (56%). The experiment was able to use 78.7 hours of acceptable beam (48%). Even though the solenoid tripped twice this week (see below), it did not cause a significant down time on our side, as it coincided almost exactly with a period when the accelerator operation was impeded by issues with the chopper. Detector calibration, radiator configuration changes and DAQ issues caused the remaining down time. So far, the experiment ran for 15.9% of the scheduled Spring 2020 beam time and collected 15.1% of the total data expected for this period. During this week, we started running with 350nA, which is the nominal beam current for GlueX Phase 2.
After a significant accelerator down time in the previous week, we decided to continue running with 250nA until Monday, January 27. After checking a firmware update of tagger and pair spectrometer and a shift of the ADC base time offset of SC and TagH, data taking was very stable over the weekend. As a special task, we recorded empty target runs with 2 different beam currents: 71533 with 250nA and 71532 with 350nA. In addition, the CompCal anode current was tested with 2 different beam currents on Sunday evening.
On Monday morning, we switched off the TagH counters below the Tagger Microscope and increased the beam current to 350nA, starting with run 71592. In this condition, the trigger rate increased to 75kHz with an acceptable dead time of 91%. The PS timing window was reduced from 100 to 80 samples. At around 11:30pm, a compressor in the cryogenic system went off, which caused the solenoid to trip. After a reset of this compressor, the magnet could be ramped up again. At about 4pm, the magnet tripped again while the current was stationary at 800A, this time caused by an instability in the power supply. This issue provoked a lengthy investigation into the cause, which was found to be an offset in the PXI quench detector output. After implementing a temporary fix, the solenoid magnet could be ramped up and it reached nominal current shortly after midnight. Beam came back around this time as well, so we could happily resume production running. New discriminator thresholds for the tagger microscope were also implemented during the down time, which significantly improved the shape of the coherent Bremsstrahlung enhancement in the goniometer GUI.
