GlueX TOF Meeting, April 14, 2015

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GlueX Time-of-Flight Meeting
Tuesday, April 14, 2015
11:00 am EDT
JLab: CEBAF Center, Room F326/327


  1. Announcements
  2. Review of minutes from March 31
  3. Calibration Status [1]
  4. Preparations for Spring Run (All)
  5. Meeting participation:
    1. Daily Planning Meeting
    2. Bi-Weekly Calibration Meeting



Talks can be deposited in the directory /group/halld/www/halldweb/html/talks/2015 on the JLab CUE. This directory is accessible from the web at .



  • FSU: Hussein Al Ghoul, Brad Cannon, Sasha Ostrovidov, Aristeidis Tsaris
  • JLab: Eugene Chudakov, Mark Ito (chair), Simon Taylor, Beni Zihlmann

Calibration Status

Sasha showed a page with a plot where he compares longitudinal position measured by end-to-end time differences in a chosen counter (one of the thin counters) with the known geometric position of counters in the other layer, where the counters are perpendicular to the chosen counter. Details of cuts and criteria are described on the page. There is a clear correlation in the position of the two measurement methods, but the plot is dominated by uncorrelated hits, with most of those coming from near the beam line, as expected.

There were several suggestions on how to over come this background.

Beni has a new approach to calibration that depends on starting by calibrating mean times and time differences and then transforming the results to constants to apply to individual channels. Simon is working on evaluating these new constants. Beni will give is a talk on his method at a future meeting.

TDC Time-Scale

Paul Mattione has discovered that our nominal setting of 25 ps for the time bin of the CAEN TDCs does not give the correct separation between successive RF timing pulses. He is seeing a time bin about 7% smaller.

Added in press: careful reading of the CAEN manual indicates a time bin width of 23.4375 consistent with what Paul found.


Sasha Ostrovidov will start attending the Wednesday bi-weekly calibration meetings.

Mark will remind Paul about the upcoming Run Planning meeting on Thursday.