GlueX TOF Meeting, June 5, 2019

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GlueX Time-of-Flight Meeting
Wednesday, June 5, 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. New scintillator test
  5. 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
  • JLab: Thomas Britton, Mark Ito (chair), Simon Taylor

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 went over the minutes from the meeting on May 22.

  • Mark submitted the order for the last of the acrylic light guide material.
  • Mark has ordered RTV and primer for Paul.
  • The Hamamatsu PMT model we used in the original construction has been discontinued. Paul and Mark reviewed the suggested replacement model and it looks like it should work. The physical dimensions and performance specs are the same as the original.
  • The design of the racks for storage in the Hall has been settled.
  • Paul would like Mark to remind Tim to send the final drawings for the shield collars so FSU can get started on them.
  • After reading the minutes Sean Dobbs told us that he thinks that the software issues we discussed may not be so bad. He thinks he has structured things so that the changes will be relatively painless.
  • Thomas will talk to David Lawrence about monitoring histograms for the new TOF configuration.

Construction Update

Paul gave the report.

  • The scintillator bars from Eljen were unboxed and given a physical inspection. Dimensions were checked and surface quality assessed. They look good, save for a few very minor nicks here and there.
  • Scintillator attenuation length measurements:
    • The bars arrived wrapped in transparent plastic sheets.
    • Attenuation length measurements were performed on the wrapped and unwrapped bars by moving a UV LED along the surface. Sasha Ostrovidov posted some representative ADC data from the measurements. The unwrapped measurements look as good as those obtained during the original construction.
    • The measurements for the wrapped bars are a factor of two worse than unwrapped (the wrapping is in optical contact with the scintillator surface) and the factor seems consistent from bar to bar. The idea is to do the measurement with the wrapping on all of the bars, and only do spot checks without the wrapping. This is greatly reduce the amount of handling the bars experience, while still catching any bars with very poor attenuation length.
  • Light guides
    • We are expecting the final order of acrylic to come in this week.
    • The final cutting of ends for the made light guides has been done.
    • Polishing has started.
  • First-article module
    • Paul plans to take the first pair of polished light guides and assemble a complete module.
    • Some of the procedures have changed since the original construction.
    • After assembly, the module will go to testing.
    • By going through the complete procedure, Paul hopes to iron out any glitches in the construction procedure.
    • The complete module should be done by the next meeting.
  • Paul may want JLab to purchase some extruded aluminum bars to construct fixtures including one for carrying the modules around the building safely.
  • The acrylic bars for the light guides were all manufactured by the same company as we used last time, although the purchase went through two different suppliers. There are no UV inhibitors in the acrylic. In the end, there was no need to identify a different manufacturer. Paul plans to measure transmission all of the light guides with an UV source and a photo-spectrometer.