[Halld] Run Coordinator report for November 7-14, 2018

[Alexander Austregesilo]

Run Coordinator report for November 7-14, 2018

(from 
https://halldweb.jlab.org/wiki/index.php/Run_Coordinator_report:_Fall_2018_w12)

The GlueX experiment in Hall D was scheduled for 152 hours of beam this 
week, but received only 87.3 hours (57%). We could use about 80.8 hours 
(ABU) or 53% of the scheduled beam time. Major causes for down time on 
our side were a readout failure of the 5C11B beam position monitor 
(~2h), a period during which our slow control system (CSS/EPICS) was not 
responsive (~2h) and the scheduled installation of a new 10 inch beam 
pipe for the Compton Calorimeter (~8h, during beam studies). The 
remaining losses can be attributed to configuration changes. So far, the 
experiment ran for 86% of the scheduled fall 2018 beam time and 
collected 67% of the total data expected for this period.

This week was dedicated to a special measurement of cross sections at 
lower energies in order to overlap with previous measurements from CLAS 
and obtain a better understanding of systematic uncertainties. For this 
purpose, the current in the PS magnet was reduced from 910A to 400A 
which shifted the PS acceptance to the region between 3 and 5.5 GeV. The 
tagger hodoscope counters in this energy region were turned on, which 
limited the acceptable beam current to 40nA. We decided to take 40% of 
the data with an amorphous radiator (trigger rate ~9kHz) and 60% with 
the 47mum diamond radiator (trigger rate ~13kHz). For the latter, the 
coherent edge was shifted down to 7GeV, producing a peak polarization 
above 60%.

We started the low-energy program on Wednesday, when we recorded a TAC 
run to determine the PS acceptance. Around 11pm, we started our first 
low energy run and continued this program until Monday morning. Even 
though the accelerator was down for more than 20 hours due to a HV issue 
in RF cavity 1L23 over the weekend, we managed to collect 2.3B triggers 
for the special low-energy data set while cycling through the different 
radiator orientations 6 times. This corresponds to about 116% of the 
previously defined goal.

The scheduled system recovery period on Monday was used for preparations 
of the installation that was planned for Tuesday, for FCAL maintenance 
and for investigations on the liquid hydrogen target. In addition, an 
upgrade to Hall D current locks was performed. Unfortunately, the beam 
was not available during the night. On Tuesday, a new beam pipe was 
installed in preparation for the Compton Calorimeter for PrimEx. On 
Tuesday evening, all settings were restored and the standard production 
running was resumed.

Many thanks to the excellent shift crews and the commited experts on call!

Alex