Run Coordinator report: Fall 2021 w18

Tuesday December 21

1. Last 24h:
   • ~6h of production on ⁴He (150 nA, 0/90 perp only: para was too degraded.)
   • 3h35 (3:40am-7:15am) empty target data taking.
   • trigger tests in raw data mode and CPP trigger test.
2. Issues
   • Target OVC vacuum.
   • Target temperature increases
   • Transmission rate decreased by 5%
3. Summaries
   • Electron beam energy during the SRC-CT run.
   • Normalized rates for SCR-CT Fall 2021 run
4. Plans
   • End of Fall 2021 run. Hall shut down tasks:
     • Secure beam line:
       • All radiators retracted.
       • Collimator in blocking position.
       • PS and sweeping magnets off.
     • Solenoid ramp down.
     • Target will already be empty. Keep PTR on since the target group might do some investigation of the vacuum event.
     • High and low Voltages off.
     • Crates will be kept on.

Monday December 20

1. Last 24h:
   • ~4h of production on ⁴He (150 nA, 0/90 para and perp).
   • 2 long down times: ~5h between Sunday 9am-13:45 (multiple causes. Mains ones: Bulk power supply and 1L04 RF). Monday: 1am-ongoing (IL05 RF).
   • 2h on Amorphous radiator (runs 90631, 90632).
   • CPP trigger tests (~5h)
2. Issues
   • Target pressure event due to large vacuum spike in the Outer Vacuum Can (OVC). No incidence on data taking. (Most of the event unfolded during beam down time in any case.)
   • Target status and comments from Chris C. and Hovanes
   • Target status (7pm)
   • Diamond degradation
3. Plans
   • Production on ⁴He (150 nA, 0/90 para and perp) until Tuesday 7am.
   • 3h trigger tests in raw data mode.
   • 1h CPP trigger test.
   • Finish run period with ~3h Empty target run, from 3:30am (12/21/2021) to shutdown around 7am. (This will permit to check if the target event above has made ice to accumulate on the target cell).
   • No analysis meeting today

Sunday December 19

1. Last 24h:
   • Smooth data collection on ⁴He (150 nA, 0/90 para and perp).
2. Issues
   • Nothing special.
3. Plans
   • Production on ⁴He (150 nA, 0/90 para and perp).
   • Amorphous run Sunday morning.
   • CPP trigger tests (During A. Somov shift in the afternoon.)

RC summary, December 15-21 2021

This RC tenure is the last of the SRC-CT (E12-19-003) run period. It started with the target filled with LD₂. Wednesday 12/15/2021 saw smooth production on LD₂ at 140 nA, 0/90 para and perp. It was interrupted only by ~1h of RF-related beam down time and a search for better spot on diamond JD70-105 since it had degraded due to beam damage. H. Egiyan tried to find a new location that improved the 0/90 para and 45/135 para/perp coherent peaks, but to no avail. Untrouble data taking continued on Thursday, 12/16/2021, with about 6h of beam-related interruption. After the RC morning meeting, SRC-CT leadership decided that the experiment would benefit from changing the target from LD₂ to ⁴He the next day (Friday, 12/17/2021. This was a long discussion because none of the Target Group persons who knew how to do the change (C. Keith, J. Maxwell) were available. Eventually, C. Carlin agreed to do it with C. Keith, who was out of town, writing a detailed procedure and supporting by phone. On Friday, 12/17/2021, LD₂ (140 nA, 0/90 para and perp) data taking continued until 14:10, followed by a 1h empty target run since such data were needed and the target had to be first emptied. (This failed at first because the target cell boiler used to evacuate the cell would not respond. C. Carlin asked for Rapid Access and fixed the issue. This problem reduced the empty target run from the planned 2h to 1h). The target gas change went relatively smoothly and was done within the expected time. A planned Rapid Access was done for switching gas. A. Somov, L. Penchev, S. Botarinov and V. Berdnikov took advantage of that access to re-position the calorimeter prototype in the Pair Spectrometer test area. while the target ⁴He gas cooled down (a process taking about 3h), the Hall was closes and A. Somov requested the beam for opportunistic Pair Spectrometer background data taking. Around 23:00 (12/17/2021) the ⁴He reached its nominal temperature and SRC-CT was ready for production but the beam was unavailable. the beam was unavailable. It came back at about 1:50am (Saturday 12/18/2021) and we started production on ⁴He (150 nA, 0/90 para and perp).

For the whole SCR-CT run:

There were 41.3 days scheduled for SRC-CT (43.3 days on the ENP schedule, but 48h were spent in beam studies).

The ABU+BANU was 71.6% (708.5h) The ABU was 60.7% (601.2h)

If we want to assess the time for SRC-CT itself, we need to remove about 6h of dedicated to CPP trigger test. I think there was nothing else unrelated to SRC-CT (all overheads like target change etc. should be included the PAC request).

In that case, ABU+BANU=70.9% (702.5h) ABU=60.1% (595.2h) Assuming the usual 50% run efficiency and using the 21 pac days allocated to the experiment (not the 41.3 days actually scheduled), SRC-CT should have gathered 118% of the expected data.

As usual, this does not account for details, like data taking overhead higher than expected (e.g. due to radiator swaps, reducing the data taking efficiency), or the fact the SRC-CT run used a coherent enhancement that effectively favored better kinematics (increasing the data taking efficiency).

Noticeable events were

1. • On 12/17/2021: Target LD2 nominal temperature before reboot was 1.3K higher than nominal temperature after reboot.