GlueX Start Counter Meeting, May 3, 2012

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GlueX Start Counter Meeting
Thursday, May 3, 2012
10 am EDT
JLab: CEBAF Center, Room 326/327


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

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, Puneet Khetarpal
  • JLab: Mark Ito (chair), Elton Smith, Tim Whitlatch, Beni Zihlmann


The sample counter has still not come in from McNeal. It has been built and now is "in finishing."


Mark reported on his conversation with Fernando. Fernando has started thinking about the design of the SiPM board.

  • Having three counters read-out by one board seems about right for the design. 3 sectors ok
  • We will have three bias voltages per board, one for each counter. The four SiPM's used for a single counter will be matched so they can use a single bias voltage.
  • Fernando is thinking about an out-rigger board that fits on a card-edge-like connecter on the SiPM board. The new card would contain the pre-amp and cable connectors. This is to have more real estate for components. Chuck Hutton will have to be consulted to see what fits.
  • We decided not to use the thermister voltage divider to stabilize that gain against temperature fluctuation since gain is not a big issue for this detector and to save real estate. That having been said, both Elton and Werner were in favor of including it if possible. One question is whether the set temperature needs to be known in advance of selecting the components used in the circuit. For the start counter that temperature is unclear.


The new geometry with 30 counters is ready. Remaining is the removal of the long light guides. Puneet is working on this and a version should be ready in the next few days. In the future we may want to add some material for the SiPM boards.


We discussed having a light pulsing system. Werner pointed out that it would be useful to check that the detector is working. In addition if the light intensity were variable, an efficiency check of sorts could be done. If the pulses were fast, timing resolution could be checked.

One possibility is to use an LED, mounted externally, and run the light into each counter with an optical fiber. Another is to have one LED mounted directly on each counter. A lot more thinking about this remains to be done on the mechanical issues as well as the basic calibration considerations.

Mechanical Design

  • We have a working concept of an inner foam support machined out of single piece, and no outer foam support.
  • We discussed issues of light tightness and optical independence of the counters. A firm design is not yet in place. If light tightness is not established on a counter-by-counter basis then some sort of overall enclosure is called for. At the same time the enclosure must accomodate sufficient air flow on the SiPM pre-amps to keep them at a stable temperature.