GlueX TOF Meeting, May 8, 2019

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GlueX Time-of-Flight Meeting
Wednesday, May 8, 2019
10:00 am
JLab: CEBAF Center, Room F226
BlueJeans: 350 531 998


  1. Announcements
  2. Review of minutes from the last meeting
  3. Upgrade Plan
  4. Action Item Recap


Talks can be deposited in the directory /group/halld/www/halldweb/html/talks/2019 on the JLab CUE. This directory is accessible from the web at .



  • FSU: Paul Eugenio, Sasha Ostrovidov
  • JLab: Thomas Britton, Ashley Ernst, Mark Ito (chair), Simon Taylor, Tim Whitlatch, Beni Zihlmann

There is a recording of this meeting on the BlueJeans site. Use your JLab credentials to access it.

Review of minutes from the last meeting

We looked at the minutes from the meeting on April 24. Mark did end up buying the mill bit and the scintillator modules as per Paul's specs.

Upgrade Reports

  • Paul reported that the scintillator order was received by Eljen. Delivery to FSU is expected May 31.
  • More light guide material will be needed. There is another run planned at the factory this month. Paul is reluctant to try a different manufacturer since the material from this one has been problem-free.
  • Beni has had a second look at the electronics situation. We seem to be OK. Fernando Barbosa is aware of what we will need.
  • Tim reported that the technical staff is all ready to go on the job of unmounting the TOF and laying it horizontal in the Hall. Work can start as soon as the current tasks on the DIRC have been completed.
  • Paul will send photos of the arrays during the initial installation. He would like it if the orientation could be the same as it was last time.

Air Light Guides

Sasha has been testing joining the half-length counters optically across the beam hole region with an air channel; essentially extending the ESR/Tedlar wrapping across the gap. He has been using the half-length counters from the mini-TOF at FSU. Looking at scaled coincidence rates of cosmics using an end-to-end coincidence of a full-length counter as trigger, he sees the following probabilities of seeing a signal in one half-length counter when the other one fires:

HV (V) Hit Probability (%)
1200 3
1300 18
1400 60

However if an additional scintillator is added to the coincidence to insure a cosmic hit near the air light guide (within 6 cm), the other-counter-hit-probability increases to 90% at 1400 V.

Sasha is repeating the study with a full data acquisition system.

Beni suggested some stiffening material for the walls of the light guide (low mass, e. g., cardboard).

There was some discussion of support for the ends of the counters around the beam hole. This would be complicated by the presence of air light guides.


Ashley pointed out that we will need to modify the geometry of the TOF for the upgraded configuration. She will look into how much work is involved in that.

Collaboration Meeting

Paul will give a report at next week's collaboration meeting on the status of the upgrade.


Beni has started calibrating the Spring 2019 data. Results are hard to check because of the absence of tracking. Simon pointed out that the FDC was on for a few runs; perhaps those runs can be examined.