GlueX Start Counter Meeting, January 23, 2014

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GlueX Start Counter Meeting
Thursday, January 23, 2014
2:00 pm EST
JLab: CEBAF Center L207


  1. Announcements
  2. Review minutes from previous meeting
  3. Counter construction status
  4. Support structure construction status
  5. Support structure material study
  6. Electronics status
  7. 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/2014-1Q on the JLab CUE. This directory is accessible from the web at .



  • FIU: Werner Boeglin, Eric Pooser
  • JLab: Mark Ito (chair)


Eric gave the report.

  • McNeal will ship the machined scintillator counters starting tomorrow. The first shipment should arrive by the end of next week.
  • Assembly jig progress
    • The material for the clear cast acrylic rings for the assembly jig have been ordered. The rings will be machined by an outside vendor, Faulkner of Miami. It should take about a week to do the job. They will cut four rings, 8.5 in. OD, 8.0 in. ID, 1.0 in. thickness, with 30 tapped holes.
    • Eric is looking into two USB cameras to get a good look at alignment with the SiPMs.
    • The type of the pneumatic cylinders has been finalized. Also the valves have been chosen. A vendor has been identified: Bimba Manufacturing.
  • The design of the wrapping template is complete and the job submitted to the FIU machine shop. When the templates come back they will do some cutting practice.
  • There is possible problem with the SiPM on the scintillator test stand. This is still to be confirmed.
  • The current plan is the wrap the scintillators first, before testing. That will give protect them during subsequent handling. A study will be done to ensure that the test results are not affected by having the wrapping in place.


  • Eric is working on collecting the list of calibration constants we will need to run the start counter.
  • He will add a leading-edge discriminator to the test set-up to start studying time-walk corrections.


  • The foam for the support should arrive at JLab at the beginning of February.
  • The best estimate is that the start counter might be done by May.
  • Werner cautioned that until the final assembly of a few counters has started, it will be difficult to estimate the end date accurately. The time required to align the counters with the SiPMs is a big unknown at this point.

Data Acquisition at FIU

Werner is planning on putting together another data acquisition at FIU. He would like to refresh their CODA installation.

Material Study

Mark did a study to estimate the effect of the carbon fiber lining on the inner support on proton detection efficiency, as suggested by Eugene Chudakov. See his wiki page for details.

A material budget was collected for all significant structures from the beam line to the outside of the start counter and material was converted to scintillator-equivalent thickness. Several reactions were studied. Proton range and energy loss were calculated, and the efficiency for detection were tabulated for two distinct definitions of "detection."

Typically, the presence of the carbon fiber degrades proton detection efficiency by about 1.5 percent for most scenarios. We thought that this was acceptable, given the increased strength it adds to the structure.

Communication Announcements

  • We will move to ESNet channel 85554 to avoid conflict with the BCAL meeting.
  • Mark will move the Start Counter meetings back to the PID heading on the Meetings wiki page.