GlueX Start Counter Meeting, March 22, 2012

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GlueX Start Counter Meeting
Thursday, March 22, 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/2012-1Q on the JLab CUE. This directory is accessible from the web at .

Chair's Cell Phone




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

Prototype Report

We are still waiting for a prototype counter from McNeal.

Readout Design

Since the last meeting, we had a meeting with Fernando to answer some basic mechanical questions. At that meeting we decided on a segmentation of 10, to aid alignment and to simplify fabrication of the circuit board. Since then Chuck has done some work on the design and we reviewed his slides showing the latest version. He showed a new scheme for attaching the start counter to the target vacuum chamber and a circuit board concept showing the location of the individual SiPM SMD components.


We had a short discussion on cooling. Fernando reported that in the case of the BCAL readout it was recently discovered that non-uniformity in the contact pressure between the cooling elements and the SiPM arrays was causing temperature variation channel-to-channel with attendant gain variation. For the start counter we plan to cool with air flow so the details of maintaining a stable temperature are different. Fernando suggested that we could use some sort of heat-sink/heat-spreader/radiator to make sure there are no hot spots among the read-out elements.

Discussion of Design

  • Chuck asked Fernando for some details on the non-SiPM side of the boards, e. g. a rough profile of components, connectors, cabling, etc.
  • Werner suggested an alternate scheme for mounting where the entire start counter array, including electronics, is assembled on a separate rigid mounting collar independent of the target. The current design has the counters mounted on the vacuum chamber first and then the SiPM's aligned and fastened to the vacuum chamber as well. In the alternate scheme there would be simple way to bolt the mounting collar rigidly to the vacuum chamber. It would have the advantage of providing a simple way to detach the start counter from the target when/if that is required. The scheme would require modification of the current design of the vacuum chamber, but it was thought that this could be accommodated.
  • We realized that now we are at the stage where the many details of the mechanical design that need to be worked out, especially related to supporting and light-tighting the scintillators and SiPM read-out. We will try to arrange a meeting with Youri Sharabian to review how some of these issues were solved for the Hall B start counter.

New Action Items

  1. Get some details of circuit board design to Chuck. -> Fernando
  2. Arrange a meeting with Youri to discuss design details. -> Mark