[Halld-pid] Time-of-Flight Meeting Minutes, February 9, 2022

[Mark Ito]

Folks,

Please find the minutes here 
<https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_February_9,_2022#Minutes> 
and below.

   -- Mark

      _______________________________


    GlueX TOF Meeting, February 9, 2022, Minutes

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

There is a recording of this meeting 
<https://jlab-org.zoomgov.com/rec/share/6qbL5I-czldjb683Py7RhgMF1YpHh18eJ4f0p6jaKzHlbDLpKvUKEOvHI8os1ao.lafz-tPwYNB34s1c> 
on the ZoomGov site. Use passcode: xut*x!b8 .


      Review of minutes from the last meeting

We went over the minutes from the meeting on January 26th 
<https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_January_26,_2022#Minutes>. 


Paul reported on a few points related to the *equipment loan*.

  * Edmundo Barriga is stationed in Newport News, but will be traveling
    to Tallahassee for the collaboration meeting. He will pick up some
    items covered by the loan agreement, including the VXS crate, and
    bring them back to the Lab.
  * The bulk of the remaining items are the spare PMTs.


      Long-Term Detector Health

Sasha presented work he has done to assess the lifetime of the TOF, in 
particular the degradation of PMT gain as a function of 
time/beam-exposure. See his slides 
<https://hadron.physics.fsu.edu/~ostrov/tof/2022-02-08/index.pdf> for 
the details.

Some items from the discussion:

  * Beni: specs on PMT gain as a function of integrated charge on the
    last dynode is provided by Hamamatsu. Integrated charge, in turn,
    can be estimated by the from the time integrated rate of minimizing
    particles.
  * Paul: we learned a lot from the PMT-relacement exercise last year. A
    strategy of identifying weak tubes and replacing them will help
    maintain uniform acceptance of the array.
  * Beni: he identified candidates for replacement last year in part by
    noting PMTs that did not respond with the expected amount of
    increased gain with increased voltage during gain balancing.
  * Eugene: in general, there are other sources of gain loss besides
    degradation of the last dynode, including damage to the
    scintillators (surface crazing, radiation damage) and damage to the
    voltage ladder in the PMT base.
  * Sasha could use a table of the correspondence between read-out
    channel and HV channel. Mark will query his database for this
    information.

Much of this material will be presented at the upcoming Collaboration 
Meeting.


      TOF II Trigger

Beni reported that this month has been reserved for Sascha Somov to do 
tests on the TOF II trigger.

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