GlueX TOF Meeting, October 7, 2020

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GlueX Time-of-Flight Meeting
Wednesday, October 7, 2020
10:00 am EDT
BlueJeans: 350 531 998


  1. Announcements
  2. Review of minutes from the last meeting
  3. Hardware assessment
  4. Calibration
  5. TOF NIM paper
  6. Action Item Recap


Talks can be deposited in the directory /group/halld/www/halldweb/html/talks/2020 on the JLab CUE. This directory is accessible from the web at .


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

There is a recording of this meeting on the BlueJeans site. Login with your JLab credentials starting from to gain access.

Review of minutes from the last meeting

We went over the minutes from September 23.

  • 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
    • 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
    • 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.


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)