GlueX Start Counter Meeting, March 20, 2014

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GlueX Start Counter Meeting
Thursday, March 20, 2014
10:00 am EDT
JLab: CEBAF Center F326


  1. Announcements
    • No-Cost Extension
  2. Review minutes from previous meeting
  3. Review of Bruce's Q/A Visit to Eljen (all)
  4. Counter construction status
  5. Support structure construction status
    • Geometry Decision

Communication Information

Video Conferencing

  • ESNet: 8542554, non-standard channel
  • SeeVogh
    • Direct meeting link
    • Phone Bridge ID: 100 2777


  1. Dial
  2. enter access code followed by the # sign: 1833622#

Desktop Sharing

  1. Go to
  2. In the "join a meeting" box enter the Hall D code: 1833622
  3. Fill in the participant registration form.


Talks can be deposited in the directory /group/halld/www/halldweb/html/talks/2014-1Q on the JLab CUE. This directory is accessible from the web at .



  • FIU: Werner Boeglin, Eric Pooser
  • JLab: Chuck Hutton, Mark Ito (chair)

Find a recording this meeting here.


Werner initiated a no-cost extension to the contract. It would have expired at the end of the month. The extension has been fully executed (both parties have signed).

Review Minutes from Previous Meeting

We looked over items from the March 6th meeting.

  • "y"-scan with the Test Stand: the time resolution was measured for different positions of the SiPMs with respect to the scintillator along the "radial" direction. The qualitatively, the results show less dependence on position than we might have feared; an offset of up to 0.5 mm is not serious. The measurements do need to be repeated; the translation stage was damaged and that has been holding things up.
  • Eric has been working on the calibration procedure. He has a prototype set of classes for doing the calibration. He is drafting a proposal for the set of calibration constants we will need. The parametrization for the time-walk correction is still being studied. He will give a talk on his work at the Calibration Meeting next week.

Review of Bruce's Q/A Visit to Eljen

We discussed Bruce Lenzer's visit and the notes from Mark on the conference call we had with folks at Eljen. Things look a lot better now. We thought that it really helped that Bruce was able to go out there. Thirty good scintillators have already been produced, twenty more (to complete the order) should be done in two weeks.

Eric will follow up with McNeal on taking shipment of these first thirty ASAP. Even if they prefer to have all fifty on hand before starting production, we would like to know if they like what they see with this batch.

Support Structure Construction Status

Eric gave us a very detailed report on measurements of the dimensions of one of the paddles, complete with pictures. The counter was wrapped in aluminum foil as we plan to do. This counter with wrapping turns out to be the same thickness as the nominal scintillator itself, without wrapping, thus this paddle is under spec.

Eric will go ahead and measure a few more of the paddles on hand at FIU.

We decided if these additional measurements indicate that the width being under spec is typical, we will fix on a gap between the scintillators of 100 microns when sizing dimensions of the the support structure.

Werner floated the idea of making two aluminum support rings and only drilling holes in one, keeping the other in stock in case there are surprises.

Eric suggested we try to get measurements from McNeal as well. We agreed that this should be pursued.