Run Coordinator report: Spring 2018 r1 2

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 -except for an early divergence issue- was suited for good data production, in contrast with the Hall D beam quality in December 2017.

The setup (accelerator or hall D) is the same as the few last run periods except that we are now sharing a chopper slit with Hall A. This seems a better situation than sharing with Hall B since it allows us more beam current flexibility. We checked the bleedthrough and found it at the expected level of a few nA when the other halls are operating.

After the usual start-of-run check-outs and verifications, standard data production started on the very end of Jan. 11th. In addition, the special tasks accomplished are:

• Alignment of the production diamond (JD70-100),
• Straight track runs (see below)
• FDC/HDC HV scans, threshold scan and timing checks,
• 6h of data taking at low luminosity (100nA, 10^-4 radiator),
• Photon-beam transmission study to see if it depends on the diamond orientation,
• High rate runs at 250 uA and 300 uA on the 3.5 10^-4 Al. radiator. These pushed the acquisition rate to 65kHz and 75kHz, respectively. Running at 65kHz was fine, with 96% livetime. Higher rate running crashed the DAQ frequently (every 10 min). These runs can be compared to the 150 uA and 180 uA amorphous runs that are taken daily for the data production (we started taking amorphous runs at 150 uA and increased the current to 180 uA after Jan. 19th).
• An empty target run was taken (at higher current than usual: 300nA),
• A few raw-mode runs were taken, and
• Harp scans were done daily.
• We also took data for the muon-chamber prototype. The chamber is currently out of the beam in anticipation of TAC runs.

In all, we did essentially all what we planned during these two weeks, see:

https://halldweb.jlab.org/wiki/index.php/File:Spring18_week1.jpg https://halldweb.jlab.org/wiki/index.php/File:Spring18_week2.jpg

At the end of my RC tenure (Wed. 24th), we had collected about 13.5 billion triggers (split in 4 polarization orientations and amorphous data). This is about 14% of our goal, while we have spent already 21% of the Spring 2018 run time. We should catch back to our goal, now that we are done with most of our special tasks and that the accelerator and the other halls are mostly settled.

We encountered a few significant issues during this start of run:

• Many timing shifts were seen, some jeopardizing the data (100 ns and 37 ns shifts), some making the calibration more difficult and lengthy (4 ns shifts). The problem with the large 37 ns and 100 ns shifts seems to have been fixed or worked around. The small 4ns shifts remain, probably for the duration of this run.
• The DAQ is very slow to start and sometime would not allow to start a run. Several workarounds have been found and the start-of-run crashes are now rarer, but starts-of-run remain slow and a significant overhead.
• Initially, the beam was converging too much in x and diverging in y. This was fixed by adjusting the last quadrupole on the hall D line. This procedure is rather fast: the MCC crew does it in less than 1h. They did it twice so far.
• The coherent peak was garbled. This was corrected by adjusting the TAGM signals.
• The beam polarization seemed low compared to (10% lower) last Spring run. We now believe it is similar to Spring 2017 and that the difference comes from a dilution uncorrected for in the current online analysis.
• The TPol is not working (noisy signals).
• Online monitoring tools were unreliable or crashing during the first few days. This is now mostly fixed.

In addition, we had a solenoid ramp down on Saturday Jan. 13th due to a loss of PXI communication. The downtime was mitigated by taking straight-track runs while the magnet was down. In all, we lost about 14h due to this event.

On the accelerator side, the operation was good, with good RF trip rates. There were a few CHL trips, that were quickly recovered, typically in 2-4h. The beam delivery was impaired for a few days (around the 17th, and 22nd-24th) because of path-length changes due to temperature changes, and unstable orbit, respectively.

There are some very notable successes on the accelerator side that concern us: CEBAF has been running for the first time in 4-hall operation, with good efficiency. Furthermore, the 5th RF separator has been operating continuously since early January. Before it had not been operated for more than a day.