GlueX Start Counter Meeting, September 8, 2011

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Location, Time

Thursday, September 8, 2011
10 am EDT
JLab: CEBAF Center, Room F326/7


  1. Announcements
  2. Review minutes from previous meeting: all
  3. Prototype Report
  4. MOU status
  5. Meeting time, communication methods: Mark

Communication Information


To connect by telephone:

  1. dial:
  2. enter access code followed by the # sign: 3421244#

Video Conferencing


Talks can be deposited in the directory /group/halld/www/halldweb/html/talks/2011-3Q on the JLab CUE. This directory is accessible from the web at . You have to be a member of the "halld" Unix group to do this.



  • FIU: Werner Boeglin, Lei Guo, Puneet Khetarpal, Eric Pooser
  • JLab: Chuck Hutton, Mark Ito (chair), Tim Whitlatch, Beni Zihlmann

Review of Drawings

We reviewed drawings that Tim posted:

We discussed mechanical considerations for SiPM read-out:

  • The big difference between the 2009 drawing and the current concept (though not shown in Werner's drawings) is we want to use a very short-light guide, mounting the SiPM's as close to the scintillator as possible. There is very little space in for doing this.
  • Werner prefers a 30-counter design (versus the original 40). Fitting the SiPM's close to the counters almost forces us to this.
  • It is unlikely that we can provide for cooling other than air circulation given the space constraints.
  • Werner pointed out that we could use the support tube need not be made of Rohacell all they back to the supporting flange. A thinner, stronger material could be used for the cantilever up to the SiPM mounting.
  • Tim et al. will generate a new drawing based on Werner's dimensions. He will aim for the next meeting (in two weeks).


Werner reported that the University wants some changes to the MOU, though none of them are major. He has some paper work left to do finish generating a revised document.

Plastic Craft Scintillator

Lei has been in contact with the company. They claim they can do a better job on the scintillator surfaces. He will send some of the current samples back to them for re-polishing.


  • The new meeting time is OK with everyone.
  • We don't need the phone connection anymore. If needed it can be requested.

Action Items

  • Produce new drawings of the start counter.
  • Send some samples back to Plastic Craft for re-polishing.
  • Further timing tests with the SiPM.
  • Get MOU changes back to JLab for review.