GlueX Start Counter Meeting, December 13, 2018

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GlueX Start Counter Meeting
Thursday, December 13, 2018
10:00 am EST
CEBAF Center, Room L207
BlueJeans: 556 286 544


  1. Announcements
  2. Review minutes from the meeting on November 29
  3. Calibration and Efficiency
  4. NIM Paper
  5. Action Item Review


Talks can be deposited in the directory /group/halld/www/halldweb/html/talks/2018 on the JLab CUE. This directory is accessible from the web at .



  • JLab: 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 target will not be changed from LH2 to beryllium for the CompCal commissioning period. The start counter will not be disturbed in the near future.

Review minutes from the meeting on November 29 (SiPM Monitoring)

We looked over the minutes from the previous meeting.

Since the last meeting Mark spoke to Carl Zorn about monitoring the health of the SiPMs. He remembers having concerns about the neutron dose so near the beamline. Carl pointed out two monitoring methods:

  1. Measuring the dark rate directly by measuring the rate of single-pixel events with the beam off. In the lab this is done by looking at ADC data and observing the the distribution of 1-, 2-,..., n-pixel events. It is not clear if this can be done in situ in the Hall with the FADC-250s. The scalar rates with beam off might show something; this is not clear either. We need to see if the EPICS scalars were recorded in the Archiver.
  2. Measure the bias voltage supply current. This will be roughly proportional to the dark rate. These currents might be in the Archiver as well.

We need to do more research on these approaches.

NIM Paper

The December 7th deadline for comments has come and gone. Eric has produced a new draft, incorporating comments from Simon, Beni, and Mark. It has been posted on the DocDB as Version 4. Note there are some minor technical problems with references, but all text modifications are present.

After technical corrections, the plan is to announce this as a final draft to the PID email list and then:

  1. Submit it to the JLab approval process.
  2. Post it the the arXiv.
  3. Submit it to Elsevier.