GlueX Start Counter Meeting, September 22, 2011

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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. Simulation Status [1]

Communication Information

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

Prototype Testing

Eric has been looking at more of the scintillator pieces from Plastic Craft. They have poor surface quality and an attenuation length 4 times worse than when they arrived from Eljen. He is getting a time resolution in the range 230 ps to about 600 ps, going from the upstream end out to the nose. He is using the SiPM as a detector, with no light guide. All of the pieces will be assessed, shipped back to Plastic Craft for resurfacing, and then re-tested.

Mechanical Design

Tim has been trying hand-layouts of the SiPM's. If the SiPM's are packed side-by-side inside the CDC, then only 24 can be accommodated. He is also looking at a staggered arrangement (alternate SiPM's offset upstream and then downstream). Also if the light guides can be made 60 centimeters (roughly) long, then any azimuthal segmentation is OK (say 30 or 40). Going to 24 counters will increase the per counter rate which was estimated by Sasha and Seema at about 200 kHz for 40 counters, with the nose going down to 2 cm radius, at 108 γ/s

Eugene wondered whether we don't need to bring the SiPM's out from the CDC bore in order to place them farther from the beam line and in a more benign radiation environment.

Eugene also asked about the thinking on using scintillating fibers. The plan now is to continue with the scintillator paddles and think about an upgrade with the fibers.


Puneet has started working with the simulation. He showed proof-I-have-started plots of generated distributions, occupancy, and deposited energy. See his plots for details.


The changes suggested by FIU to the draft approved by the Concurrence Chain were passed by Rhonda Scales and Allison Lung at JLab. They had no further suggestions, so Werner will proceed with collecting signatures at FIU.