GlueX TOF Meeting, January 31, 2018

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GlueX Time-of-Flight Meeting
Wednesday, January 31, 2018
10:00 am EST
JLab: CEBAF Center, Room F226
BlueJeans Meeting number is 350 531 998


  1. Announcements
  2. Review of minutes from the previous meeting
  3. Calibration Status
  4. Low Efficiency in High-Rate Counters1
  5. Amplified Base Prototype (Beni)
  6. PMT testing
  7. NIM Paper (Paul)
  8. Action Item Recap


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.

Review of minutes from the previous meeting

We went over the minutes from the meeting on January 3 without significant comment.

Calibration Status

  • Beni performed a step-by-step calibration of recent data using run 40460, interactively on the ifarm. Comparison with previous constants show only small differences. Only a few channels show significant differences (50 to 100 ps). He characterized the agreement as "amazing". The database has not yet been updated with these constants.
  • Beni took the Spring 2017 constants for ADC vs. TDC time difference (channel-by-channel) and used them as the constants for recent running in the CCDB. Sean reported significant improvement in timing results. The relevant monitoring plots look good now.
  • Beni spoke to Ashley Ernst about her taking responsibility for the TOF calibration.

Low Efficiency in High-Rate Counters

Beni first did the analysis that showed this problem. There were no updates at this meeting.

Amplified Base Prototype

Beni has started to look at data taken recently with the test counter in the Hall. One end has a standard PMT, the other has a PMT with an amplifier in the base, designed and built by Vladimir Popov.

  • He looked at TDC times vs. ADC times to get time walk corrections for these two new channels.
  • After walk correction, the tTDC-tADC distribution of the amplified end looks better than that of the un-amplified end, the former with an RMS of 160 ps vs. 300 ps for the latter. Beni suspects that the HV is lower than optimal on the un-amplified end.
  • He plotted the time difference in the test counter vs. the time difference of a standard counter in the TOF (paddle 14, plane 0). These counters are in orthogonal orientations. There is a clear blob where coincidences appear. The RMS spread of the blob is worse for the test counter (220 ps) than for the standard counter (220 ps).
  • These results are preliminary. Beni has more to go on his first set of analysis ideas.

Overall the on-base amplifier seems to performing reasonably well. We await further results.

1. Beni's email from 2017-09-28.