GlueX Start Counter Meeting, November 3, 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. SiPM configuration
    1. staggered 4x4 arrays
    2. two counters into one 4x4 array
    3. 2x4 arrays
  5. MOU status
  6. Simulation Status [1]

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


The MOU has been signed by all parties at FIU and at JLab and is thus official! The FIU copy on the way back to Werner.

Plastic Craft Pieces

The scintillator samples were sent back to Plastic Craft for re-polishing. No word yet from them on progress.

Mechanical Design

Eric showed several views of possible positions for the 4x4 SiPM arrays with respect to the start counter. See view 1, view 2, view 3, view 4, and view 5. This staggered arrangement has the disadvantage that the light guides come in two lengths.

We also discussed other arrangements

  • two counters into one 4x4 array. This is the arrangement that Fernando Barbosa suggested as a possibility. Each counter would be directed into a 2x4 sub-array of the 4x4 array being used by the BCAL. Each sub-array would be electrically independent, i. e., have a different summing circuit than that for the BCAL SiPM's. Fernando thought design of the accompanying pre-amp would not be difficult. No need to stagger the SiPM's in this case.
  • array that matches the start counter. Werner and Elton (independently) mentioned having an array that matches the area of the counters better, say 1x5 or 1x4. This would simplify the shape of the light guides and would fit inside the CDC without staggering.

We need to research what arrangements are available from Hamamatsu. No one at the meeting had a definite idea about what they offer. We were also not able to assess how hard it would be to build electronics for SiPM's with alternate array configurations.

Simulation Status

Puneet has surveyed and understood the processes we have in sim-recon now for hit generation (hdgeant), smearing (mcsmear), and reconstruction (dana). See his slides for details and plots obtained from events generated with the particle gun.