GlueX TOF Meeting, February 21, 2017

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GlueX Time-of-Flight Meeting
Tuesday, February 21, 2017
11:00 am EST
JLab: CEBAF Center, Room F326/327


  1. Announcements
  2. Review of minutes from the previous meeting
  3. Run Status
  4. Calibration Status
  5. New PMT bases (Beni)
  6. NIM Paper (Paul)
  7. 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, Mark Ito (chair), Sasha Ostrovidov, Simon Taylor, Beni Zihlmann

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


  • Lucite Shield Simulation. Thomas has had a possible issue with his environment. He is rerunning the simulation now.

Review of minutes from the previous meeting

We went over the minutes from February 7. There were no significant comments.

Run Status

  • Sasha is the run coordinator until tomorrow.
  • He reported the the occupancy plots look good, one set of scalars [ADCs?] for the TOF is missing in EPICS.
  • Even with the Lucite shield, the upstream plane shows a higher scalar rate than the downstream, by 50%. It will be interesting what the Monte Carlo has to say about this.


Beni reported that the timing calibrations are being re-run now for all runs.

Also we need to get started on comparisons of efficiency and resolution between data and Monte Carlo. Simon has been working on improving the matching between charged tracks and the TOF.

New PMT bases

Beni presented results from tests with the new base with on-board amplifier from Vladimir Popov. (See his wiki page for details and plots.)

He did the tests with a standard PMT and one with a modified base. He reproduced the collapse of pulse height for the standard base at 1300 V and a rate of 10 MHz from the laser. The amplitude was adjusted to be that of a minimum ionizing TOF hit. The modified base went to 10 MHz with signal collapse but only after the voltage on the tube was reduced to 1000 V. Under those conditions a 18 mV DC offset appears on the baseline. We need to ask Vladimir about the inductive coupling scheme he proposed at one point.

Vladimir suggested a test in the Hall. We discussed options. Beni suggested shipping a half-width counter from the mini-TOF from FSU to JLab and mounting it in the Hall, location to be determined. In front of the TOF? Behind the FCAL? Paul thought that we could get it here with a week's notice so doing it this run seemed not impossible. We will have to talk to Tim Whitlatch and Tom Carstens about the feasibility of mounting and possible locations.

We would also like to know if the PMT gains have remained stable during the current run with the new reduced voltages.

PMT Replacement

Several comments were made and questions asked.

  • Can amplifiers be added to the bases in situ, i. e., without dismounting the planes from the FCAL carriage?
  • Can the gain loss suffered by the inner PMTs be compensated by running them at higher voltage?
  • Has the performance of the PMTs deteriorated during the current run now that they are being run at lower voltage?
  • Which PMTs do we want to replace?
  • Do we need to build more gluing fixtures to facilitate PMT replacement?
  • What are the schedule constraints for producing the amplifier electronics?