GlueX Start Counter Meeting, June 28, 2012

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GlueX Start Counter Meeting
Thursday, June 28, 2012
10 am EDT
JLab: CEBAF Center F326/327


  1. Announcements
  2. Review minutes from previous meeting
  3. Mechanical Design
  4. Read-out Design
  5. Simulation: Start Counter Background Studies
  6. Contract

Communication Information

Video Conferencing


Talks can be deposited in the directory /group/halld/www/halldweb/html/talks/2012-2Q on the JLab CUE. This directory is accessible from the web at .



  • FIU: Werner Boeglin
  • JLab: Eugene Chudakov, Chuck Hutton, Mark Ito (chair), Beni Zihlmann

Prototype Testing

Eugene asked how Werner's recent timing resolution measurements were done, with cosmics or a source. Werner used a Sr90 source with a trigger counter on the opposite side of the start counter paddle from the source. The end-point of the beta spectrum is 2.2 MeV, so the 3 mm thick start counter filters out the low energy electrons. Werner has done tests before on different counters using both cosmic rays and the Sr90 source and those have been consistent with each other.

Werner is still planning to buy two or three counters from McNeal.

Werner expressed some concern in using the relatively think VM2000 material to isolate the counters from each other. He was concerned that the thickness might add mechanical pressure and degrade the reflectivity of the edge surfaces. He will try various materials in the three-counter prototype to see if other materials do better, for example double-sided aluminized mylar.

Read-Out Design

The circuit boards for the SiPM read-out have come back and Nick Sandoval has assembled some using the 50 micron SiPM's we have on hand. The plan is to use 100 microns in the final detector; some of those are due in this week. Fernando Barbosa reported that we are still waiting for the mini-coax cable that routes connections to the break-out board.

Mechanical Design

Mark talked to Youri Sharabian about the Hall B start counter:

See Mark's email for details.

Werner has been thinking about the jig for assembling the complete detector. He is thinking of using pneumatically driven pins to hold the counters in place before an outer wrapping is done. That way the pressure can be controlled more easily than with set screws. Tim will look into candidate parts for doing this.


Mark will send the TOF Statement-of-Work to Werner as an example of what we need.


Puneet Khetarpal has been working on background studies; there are some consistency checks that need to be done. We should hear from him at the next meeting.