GlueX Start Counter Meeting, March 21, 2019

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GlueX Start Counter Meeting
Thursday, March 21, 2019
10:00 am EST
CEBAF Center, Room L207
BlueJeans: 556 286 544


  1. Announcements
  2. Review minutes from the last meeting
  3. Calibration and Efficiency
  4. SiPM dark rate measurement
  5. NIM Paper
  6. 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 .



  • JLab: Sean Dobbs, Mark Ito (chair), Simon Taylor, Beni Zihlmann

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


The Start Counter NIM paper has been published. The record in JLab's publication database has been updated as has the GlueX wiki's list of publications.

Review minutes from the meeting on February 7

We went over the minutes. Sean plans to talk to Mahmoud Kamel about the status of the comparison between data and Monte Carlo.

SiPM dark rate measurement

Beni has analyzed data taken under the following conditions

  • read-out threshold set below pedestal
  • read-out of all SiPM detector systems (start counter, BCAL, etc.)
  • random trigger at 2 kHz
  • raw mode

He integrates over all samples and normalizes to the number of events. Histograms are fit to a Gaussian from the low side to just over the peak on the high sides. The idea is to count events in the high-side tail of the distribution. The data from two runs are shown. The red points were taken in the middle of the Beryllium target run, the blue points are from yesterday. He showed some representative channels from the start counter.

H4.gif H5.gif
H19.gif H20.gif

He believes that there is an effect seen, but more analysis is needed.

Beni wants to talk to Carl Zorn about what expectations for dark rate are. Also he has yet to look at other detector systems.

He also mentioned that there is a procedure to anneal the SiPM to partially cure an elevated dark rate due to neutron radiation damage. We could consider this if the damage is severe.