GlueX Start Counter Meeting, January 10, 2019

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GlueX Start Counter Meeting
Thursday, January 10, 2019
10:00 am EST
CEBAF Center, Room L207
BlueJeans: 556 286 544


  1. Announcements
  2. Review minutes from the meeting on December 13
  3. Calibration and Efficiency
  4. *new z-dependent SC resolution parameterization (Sean)
  5. SiPM bias currents (Beni)
  6. NIM Paper
  7. Action Item Review


Talks can be deposited in the directory /group/halld/www/halldweb/html/talks/2019 on the JLab CUE. This directory is accessible from the web at .



  • FIU: Werner Boeglin, Mahmoud Kamel
  • JLab: Thomas Britton, Mark Ito (chair), Simon Taylor, Beni Zihlmann

There is a recording of this meeting on the BlueJeans site. Use your JLab credentials to authenticate.

Review minutes from the meeting on December 13

We went over the minutes and noted that the plan is to do the DIRC commissioning with the liquid hydrogen target and start the PrimEx run with beryllium.

Calibration and Efficiency

Sean recently implemented the use of Mahmoud's new z-dependent resolution parametrization in halld_recon] and halld_sim.

SiPM bias currents

Beni has looked into using the SiPM bias-voltage-supply current as a method to monitor radiation damage. He found that these currents have been recorded in the EPICS Archiver. The current if very small, there is a noticeable increase year-to-year by a few percent, roughly consistent from channel-to-channel. He reminded us that each supply channel serves then four SiPM's that read-out one start counter paddle.

We should compare the observed behavior with the BCAL. We should also check with Carl Zorn that the absolute magnitude of the current seen in the Archiver is reasonable.

Werner mentioned that another way to monitor dark rate is to look at pedestal widths of the ADC's.

NIM Paper

Mark reported that Eric Pooser has pushed the paper through the Lab approval process, submitted it the the arXiv, and submitted it to NIM. Just this morning Eric reported that the arXiv has assigned a temporary submission identifier, submit/2531925. He also reports that NIM has assigned a reviewer, Peter Krizan, and a manuscript number, NIMA-D-19-00031.


We discussed ideas for insuring reliable operation of the start counter going forward.