[Halld-pid] Time-of-Flight Meeting Minutes, October 7, 2020

[Mark Ito]

Collaborators,

Please find the minutes here 
<https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_October_7,_2020#Minutes> 
and below.

   -- Mark

_____________________________________________________


    GlueX TOF Meeting, October 7, 2020, Minutes

Present: Mark Ito (chair), Sasha Ostrovidov, Susan Schadmand, Simon 
Taylor, Tim Whitlatch, Beni Zihlmann

There is a recording of this meeting 
<https://bluejeans.com/s/XShAv015Zfb/> on the BlueJeans site. Login with 
your JLab credentials starting from https://jlab.bluejeans.com 
<https://jlab.bluejeans.com> to gain access.


      Review of minutes from the last meeting

We went over the minutes from September 23 
<https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_September_23,_2020#Minutes>. 


  * Tim reported that there were not issues with Hot-Check Out at the
    end of the Summer run.
  * We reminded ourselves that the PrimEx group needs to be aware of the
    need for tracking if they would like to calibrate the TOF.


      Hardware Assessment

Beni led us through two of his recent entries in the TOF log.

 1. TOF PMT signal checks <https://logbooks.jlab.org/entry/3853854>
      * Beni noted that in the table, the next-to-next-to-last column is
        the set HV, the next-to-last column is the position of the MIP
        peak in the ADC integral in beam data, and the last column is
        the peak voltage he saw with a scope in the Hall after the run.
        Vertical 25 BOT 23B is the channel that shows up as weak in the
        beam data but it looks fine on the scope.
 2. Follow-up Re: TOF PMT signal checks
    <https://logbooks.jlab.org/entry/3854094>
      * Here the PMT current is plotted versus electron beam current
        during the run. The PMT currents do not change much from beam on
        to beam off as expected, including the "weak" channel, shown in
        the top line in the plot in blue. So no huge rate sensitivity
        for that PMT.

The problem with the weak channel remains a mystery.

Beni's next step is to look at beam data taken in raw mode to see if 
that gives insight into the ratio of peak voltage and integrated pulse 
area.

He also noted that any channel with a high set voltage and low ADC 
response is a candidate for replacement in situ. But given what we know 
now, there is not a compelling reason to dismount the TOF from the 
forward carriage.

And by the way, the large scope he normally uses in the Hall is broken. 
He had to borrow one to do this work.


      Calibration

Beni has redone the calibration for the summer run, including the runs 
taken at the end, with the fixes to the program that he described in the 
last meeting. After consulting with Sean Dobbs, all new constants have 
been entered into the CCDB.


      TOF NIM paper

Nothing new.


      Action Item Recap

 1. Decide on when to ship PMTs to JLab from FSU (Mark, Paul Eugenio)
 2. Prepare a complete draft of the TOF NIM paper. (all)
 3. Make a plan for TOF repair during the SAD, including Paul in the
    discussion. (all)
 4. Send TOF calibration skim email discussion to Beni. (Mark)
 5. Remind PrimEx folks that they need tracking if they want to
    calibrate the TOF. (Mark)


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