GlueX Start Counter Meeting, December 15, 2011

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GlueX Start Counter Meeting
Thursday, December 15, 2011 10 am EST
JLab: CEBAF Center, Room L207


  1. Announcements
  2. Review minutes from previous meeting
  3. Prototype Report
  4. SiPM configuration
  5. Contract Status
  6. Simulation Status

Communication Information

Video Conferencing


Talks can be deposited in the directory /group/halld/www/halldweb/html/talks/2011-4Q on the JLab CUE. This directory is accessible from the web at . You have to be a member of the "halld" Unix group to put files in this directory.



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

Scintillator shaping and polishing

Werner was not happy with the scintillator shaped and polished and then re-polished by Plastic Craft. Two came back from re-polishing slightly better, two came back worse. He started looking for another vendor and has identified two candidates so far, McNeal Enterprises and E&F Plastics. He sent drawings to both, and both say that they can do the job. E&F proposes to mill all thirty counters out of a single solid piece of scintillator. (Plastic Craft presses the scintillator.) Responses from both companies have been prompt. The quotes come in at about $200 per piece. Subsequently, Werner sent a "good" and "bad" scintillator to each; the "good" for re-re-polishing, the "bad" any destructive studies they care to do.

Re-measurement of Plastic Craft samples

Eric re-measured the two "good" scintillators after re-polishing by Plastic craft. He sees about 500 ps resolution from the far end and about 300 ps from the near end, a slight improvement from what was measured before re-polishing. These are unwrapped pieces, using SiPM read-out.

SiPM read-out geometry

We looked at drawings from Werner and some from Chuck showing concepts for placement and mounting of "custom" arrays of 3×3 mm SiPM's. Werner would prefer a configuration where no light guide is needed.

Beni noted that with no light guide, there will be non-linearity when hits are near the read-out end due to short-attenuation-length photons being detected. He also repeated Eugene Chudakov's point that some modularity in the mounting would be convenient if SiPM's ever had to be replaced.

Mark reported that the drawings on the wiki page have been sent to Hamamatsu, but no response has been received yet.

There was a basic question that came up: are the SiPM's individual surface-mount components that we place on a circuit board ourselves or are they packaged in the 1×5 configuration by Hamamatsu? More homework is obviously needed.