Run Coordinator report: spring 2019 w7
RC summary, Mar. 6th - Mar. 13th 2019
I started my duty as run coordinator when the energy of the accelerator was reduced from 11.6 to 11.2 GeV for stability reasons. During this down time, Chris Keith and Chris Carlin finalized the settings for the liquid He target operation and left the operation to the shift crew. Beam restoration was expected during owl shift on Friday, we therefore staffed the counting house from midnight on and started filling the lHe target. The entire day was dedicated to beam restoration, including ion chamber calibration, radiation level checks and several iterations of harp scans. We had to abandon the plans to perform an active collimator scan on Friday evening after the beam position was very unstable and the beam was finally taken away to perform a spin dance. In parallel, the CDC HV was ramped to nominal values. It was confirmed that the currents in the inner rings of the CDC did not reach critical values for nominal beam conditions. Around 8pm, we started to take production data on the lHe target, 200 nA beam current, 5 mm collimator and a 10^-4 Al radiator. During the whole weekend, we saw the y position of the beam on both 5C11B and the active collimator drift by several hundred mum, even though it was locked on the AC. During the swing shift on Saturday, Sasha performed trigger studies and included the CDC into the read-out. Unfortunately, a bug in the reconstruction algorithm for straight tracks stopped the monitoring system, so the group decided to exclude the CDC for the rest of the weekend. On Monday morning, this problem was fixed and the CDC could be included into the data stream. After a rapid access to reset the communication to the ComCal HV main frame, the beam position was stable enough to perform a scan of the active collimator, which resulted in a about 10% higher transmission at the new nominal position (-0.1, 0.0). For the rest of my tenure, the conditions for production data taking were extremely stable. Out of the 91.5h of CW beam on target, we could use 87.2h (95%) and recorded almost 8 billion triggers.
Alexander Austregesilo
