GlueX Start Counter Meeting, August 21, 2014

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GlueX Start Counter Meeting
Thursday, August 21, 2014
10:00 am EDT
CEBAF Center, Room F326/327


  1. Announcements
  2. Review minutes from the August 7 meeting
  3. Construction Status (Eric)
  4. Light Tightening
  5. Start-Counter/FIU-folks at JLab
    1. space: Hall, ESB, EEL, CC
    2. test equipment
    3. training
    4. property check-in
    5. office space
    6. radiation badge location




Talks can be deposited in the directory /group/halld/www/halldweb/html/talks/2014-3Q on the JLab CUE. This directory is accessible from the web at .



  • FIU: Anthony Llodra, Eric Pooser
  • JLab: Fernando Barbosa, Mark Ito (chair)

Construction Status

Eric showed some slides detailing the status of assembly and testing. He also wrote a report for yesterday's GlueX meeting since he could not attend.

The slides show measurements of timing resolution for the 30 paddles selected for the detector. Average resolution over the entire length is 360 ps improving to 275 ps in the nose. This is better than the best prototypes tested.

He also showed photographs illustrating the procedure used to shim the ends of the scintillators to bring them into alignment with the SiPMs. About 30 mils of shimming is needed, and the technique allows variation from counter to counter.

Next week work on the transportation crate will begin.

Delivery to JLab is planned for September 2. The MPOD will be shipped back separately so that it will not crowd the start counter in Eric's SUV.

[Added in press] Mark talked to Tim and Beni and at present the plan is to put the start counter in EEL 126 where it can be light-tight'ed and tested in the dark box there.

Electronics Status

We decided to go ahead with the gain adjustment on the ST-2s back to their original values, a factor of five less than the previous version. We also decided to reduce the gain on the TDC side of the split on ST-3 by a factor of 2 to avoid saturation on the output of the split.

Nine of the ten ST-2 boards are at JLab and will be modified there. They will stay at JLab and will be installed when the start counter arrives.

The modification on the ST-3 will be made on the spare board and then swapped into the enclosure.

The cables going from the ST-3 to the read-out electronics have not been strung yet. Nick Sandoval and Tim Whitlatch have a plan to run them downstairs through the same penetration used by FDC/CDC cables.