[Halld-pid] Time-of-Flight Meeting Minutes, November 3, 2021

[Mark Ito]

Folks,

Please find the minutes here 
<https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_November_3,_2021#Minutes> 
and below.

   -- Mark

      _________________________________


    GlueX TOF Meeting, November 3, 2021, Minutes

Present: Edmundo Barriga, Eugene Chudakov, Mark Ito (chair), Sasha 
Ostrovidov, Simon Taylor, Beni Zihlmann

There is a recording of this meeting 
<https://bluejeans.com/s/jWw4CuOUZxl/>. Log into the BlueJeans site 
<https://jlab.bluejeans.com> first to gain access (use your JLab 
credentials).


      Review of minutes from the last meeting

We went over the minutes from the meeting on October 6th 
<https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_October_6,_2021#Minutes>. 



        Occupancy Plots

Beni remarked on the changes in the monitoring plots for the current run 
after the magnetic field was turned on.

*Before: run 81347*

TOF occupancy before.png 
<https://halldweb.jlab.org/wiki/index.php/File:TOF_occupancy_before.png>

*After: run 81696*

TOF occupancy after.png 
<https://halldweb.jlab.org/wiki/index.php/File:TOF_occupancy_after.png>

The "before" plots are much more symmetric, left-right, up-down, and 
front-layer-back-layer. Beni remember that this effect is also seen in 
the distribution of charged tracks around the beam line.

We could not recall exactly when the acrylic shield for the inner TOF 
was removed; that may have had an effect. Eugene mentioned that high TOF 
rate near the beamline may have an effect on the current η 
reconstruction efficiency since the TOF is used as a veto for photons. 
Here the acrylic shield may help. Beni also noted that there is a big 
rate difference in the TOF depending on whether the target is full or 
empty.

Beni is planning a study of the observed asymmetries using scalar 
records from the EPICS Archiver.


        Calibration

Beni reported that the TOF gains have dropped a bit during the course of 
the current run.

He is going to get back in touch with Jackson Pybus. The TOF calibration 
has been streamlined to make it easier to hand off.


      TOF II Trigger

Mark and Beni reported on the discussion at the CPP Meeting earlier 
today. Ilya has a plan for the test, but we have run out of time to 
execute it during the PrimEx run. The CPP group will try to get a short 
period of time for a test during SRC. Beni pointed out that since there 
is a lot of set-up to do, trigger-wise, for SRC, that the new TOF 
firmware might be made part of the plan, at least for very high-level 
tests (basic operation, i.e., no crashes).


      Beam Angle Measurement during SRC

Beni suggested that during the period where SRC is running with a series 
of thin carbon targets (8 of them, 2 mm thick each, equally spaced in z, 
spanning 21 cm in z) we might be able to reconstruct vertices and 
measure the beam angle, using a series of x-y measurements at several 
z-positions.
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