Summary of the Spring 2018 Run

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Spring 2018 summary:

The main goal of the run was physics running. CEBAF ran successfully with 4-hall operations, mostly 5-pass for all Halls, some at high current. Beside the main goal of production data taking, we planned to commission 1) the Active Collimator fast raster beam characterization; 2) the fastfeedback B, 3) the nA BPM and stripline BPM at low current, 4) the new Beam Energy Monitoring; 5) the Rapid-access system. Other tests were A) High intensity DAQ/L1 tests; B) Low intensity GlueX production runs; C) TAC V-wire radiator commissioning and TAC run test; and D) TPol study with thick and thin converters. Finally, a number of non-standard detectors were tested/used: a) Muon chamber, b) TRD, c) the CompCal prototype.

The run was done with an electron beam energy of 11.62 GeV (similar to Fall 2016 and Spring 2017) with repetition rate 250 MHz (as for Spring 2017. Fall 2016 was 500 MHz) and slit shared with Hall A. We mainly used the 58 μm diamond (JD70-100. It gave about 37% polarization) with the 5mm collimator hole. The Solenoid was at 1350A. It ramped down twice during the run, due to PXI communication losses. The time loss due to the first event was mitigated by taking the straight-track data initially planned for the end of the run, and by testing the 17 μm diamond (JD70-104).

Beam restoration happened very quickly and smoothly, in part thanks to the preparation work Accelerator Operation did during the December 2017 Fall run. Beam came back ahead of schedule and we had to man the counting house starting on Jan. 10th, ahead of time (start of the beam was scheduled for Jan. 12th). We quickly proceeded to data production, thanks to our own preparation in December. The beam quality was suited for good data production. A 3 weeks (March 5th-28th) unexpected down occurred due to a CHL transformer failure and replacement A total of 150B triggers were gathered. The DAQ/Trigger tests was successful, yielding a 65 kHz rate for 96% lifetime. The V-wire test were also successful, allowing for TAC runs at 30 nA. Furthermore, the low current BPM tests were successful as well, which allows for standard TAC run (baring large bleedthrough from other halls).

Overall, we ran 13 weeks (Jan. 10th-May. 6th), including the CHL event. We had 2014h (84 days) scheduled, of which we ran 1111.8h (46 days). This yields an ABU of 55%.

A more detailed summary can be found here and from the RC weekly summaries.

A. Deur