GlueX TOF Meeting, September 23, 2014

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GlueX Time-of-Flight Meeting
Tuesday, September 23, 2014
11:00 am EDT
JLab: CEBAF Center F326/7


  1. Announcements
  2. Review of the September 9 Meeting
  3. Collaboration Meeting
  4. Hot Check-Out
  5. Shift-Takers' Instructions
  6. Calibration
  7. More Data Taking
  8. Review of Action Items



Talks can be deposited in the directory /group/halld/www/halldweb/html/talks/2014-3Q on the JLab CUE. This directory is accessible from the web at .



  • FSU: Hussein Al Ghoul, Sasha Ostrovidov, Aristeidis Tsaris
  • JLab: Mark Ito, Beni Zihlmann

Review of Previous Meetings

We went over minutes from September 2 and from September 9.

  • Sasha reports that TDC inefficiency is still and issue. There is a factor of

two in the occupancy among certain channels.

  • Aristeidis continues work on the event display. He is now working on the TOF library, adjusting constants in the code, for example the time window for matching FADC and TDC hits. For the viewer, he needs a bit more information that that provided the TOF point object and is looking at how to get it.
  • FSU has been monitoring the rates in the TOF continuously. The high voltage has been on for about a month and a half now. There were two noisy channels at the beginning, but they have quieted down for unknown reasons.

Collaboration Meeting

Aristeidis will give the presentation at the meeting. Sasha and Hussein will also make the trip.

Hot Check-Out

We reviewed the list for the TOF. No comments were offered.

Shift-Takers' Instructions

We reviewed the instructions, which are still pretty basic. Sasha commented that we still need instructions on how to write the online monitoring code.

Commissioning Plan

We looked at the commissioning plan for the TOF that Sasha put together last month. It is rather complete. No comments were offered.


Sasha took another 2 million events a couple of weeks ago and transferred them to FSU. Data taking was at one point interrupted by the power outage in the Hall. Good data came from 6-8 hours of running and came to 150 GB. Using this data he has been developing the calibration procedure further.

First Step: Looking at each plane separately he fits straight lines to hit counters, getting the hit position with end-to-end time differences. He uses these fits to adjust the end-to-end timing offset and the speed of light in the counter and iterates.

Second Step: Here he obtains module-to-module mean time offsets. He has tried two approaches.

  1. Events with two counters in each plane. A line is fit to the trajectory, mean time offsets are obtained and the process iterated. For some counters he sees participation in very few such tracks (as low as 100).
  2. Events with one counter in each plane. This gives mean time offsets from counters in different planes by definition, but given all such pairs time offsets can be calculated for all counters in all planes. Here he is running into the ambiguity between cosmics which go back-to-front and those going front-to-back. This is introducing an ambiguity of about 100 ps.

Sasha thinks that with beam, a lot of these problems will disappear; calibration will be relatively easy with particles from a target.