GlueX TOF Meeting, January 10, 2017

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GlueX Time-of-Flight Meeting
Tuesday, January 10
11:00 am EST
JLab: CEBAF Center, Room B101 non-standard room


  1. Announcements
  2. Review of minutes from the previous meeting
  3. Lucite Shield Results (Paul)
  4. PMT Testing (Paul)
  5. NIM Paper (Paul)
  6. Action Item Recap



Talks can be deposited in the directory /group/halld/www/halldweb/html/talks/2016 on the JLab CUE. This directory is accessible from the web at .



  • FSU: Paul Eugenio
  • JLab: Thomas Britton, Brad Cannon, Mark Ito (chair)

Lucite Shield Results

Paul led us through his logbook entry (shown below) tabulating the results of the test of a Lucite shield for the counters closest to the beamline. Data were taken at the end of the Fall run. Substantial rate reduction was observed with the TOF discriminator scalers. For example, the 2.25 inches of Lucite (17% of a radiation length) reduced the rate in S:21 by about 35% and that in S:22 by about 45%, independent of the beam rate used in the measurement.


We concluded that the Lucite would not do harm to the TOF measurement and gives a substantial rate reduction, reducing the current load on the last dynode of the PMTs. The hypothesis is that low energy electrons and positrons are getting ranged out in the additional shielding. Now that a significant effect has been observed, the next step is to see what a Monte Carlo study says. Pending results of that study, the proposal is to leave the configuration of shielding used in the study in place for the next run. It appears to be doing more good than harm.

PMT Testing

Paul drove the 25 PMTs to be tested down to FSU. Five were retained at JLab for studies. Ashley Ernst, an FSU grad student, will execute the testing procedure.

PMT Voltage Scan Analysis

Brad has been hampered in his efforts by the Lustre disk problems at JLab. This remains work in progress.

Collaboration Meeting

Brad will give the TOF report at the upcoming meeting.