GlueX Start Counter Meeting, December 12, 2013

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GlueX Start Counter Meeting
Thursday, December 12, 2013
10 am EST
JLab: CEBAF Center F326/327


  1. Announcements
  2. Review minutes from previous meeting
  3. Counter Construction Status
  4. Support Structure Construction Status
  5. Electronics Status
  6. Contract

Communication Information

Video Conferencing

  • ESNet: 8542553
  • SeeVogh
    • Direct meeting link
    • Phone Bridge ID: 15 4136


  1. Dial
  2. enter access code followed by the # sign: 1833622#

Desktop Sharing

  1. Go to
  2. In the "join a meeting" box enter the Hall D code: 1833622
  3. Fill in the participant registration form.


Talks can be deposited in the directory /group/halld/www/halldweb/html/talks/2013-4Q on the JLab CUE. This directory is accessible from the web at .



  • FIU: Werner Boeglin, Eric Pooser
  • JLab: Chuck Hutton, Mark Ito (chair), Beni Zihlmann
  • Northwestern: Sean Dobbs

Counter Construction Status

Eric gave the report.

  • Eljen has been having yield problems due to scratches on the bent scintillator bars. The Q/A guy there has taken over production and since then, yield has improved. They have 25 bars of acceptable quality and should have all 50 by Christmas.
  • McNeal has been apprised of the delay. They think that their estimate of 4 weeks to do the work should hold.
  • FIU has decided on food grade aluminum to do the wrapping of the counters. The thickness is 16.5 μm.
  • Anthony (FIU student) has done several test wraps with good results on the barrel and nose sections. The technique on the dreaded bend region is the next hurdle.
  • The design of the assembly jig is largely done. The next step is to start ordering materials and running the design past the machine shop.
  • The exact mechanism for precise clocking of the inner mandrill still needs to be worked out.

Support Structure Construction Status

Chuck brought in the latest inner carbon fiber tube for show and tell. The length of the tube has been extended from the original plan to 12 inches. This still will not cover the nose region. We discussed whether three layers of carbon fiber was acceptable. Although a bit more material will be added than we expected, we thought that we could live with it.

[Added in press: Eugene Chudakov points out that we might want to look at the effect of the extra material on proton detection efficiency.]


Sean introduced the effort he has been leading to define the calibration constants sets that we will need, detector system-by-detector system. Today was the start counter's turn.

Werner went through the list.

  • time walk corrections
  • effective speed of light
  • parameters for attenuation corrections
  • gain constants
  • time resolution
  • time offsets

He will write down a specific set of constants for us to start with.