GlueX TOF Meeting, May 19, 2015

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GlueX Time-of-Flight Meeting
Tuesday, May 19, 2015
11:00 am EDT
JLab: CEBAF Center, Room F326/327


  1. Announcements
    • Hall B: no calibration of 25 ps for CAEN TDCs
  2. Review of minutes from May 5
  3. Calibration Status FSU
  4. Calibration Status JLAB



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, Paul Eugenio, Sasha Ostrovidov, Aristeidis Tsaris
  • JLab: Mark Ito (chair), Simon Taylor, Beni Zihlmann


  • Mark spoke to Sergey Boyarinov of Hall B. Turns out they did not do the bin-equalizing calibration on their CAEN TDCs. Beni reminded us that Bryan Moffit has released the library functions we need to do the calibration. We decided that it is worth doing for Hall D and the group will form a plan for doing it before the next run. Beni suggested that we talk to Sergey Furletov and see if we can get him to help since the code will have to be maintained by the online group in any case. As a first step Beni suggested downloading the values recommended by CAEN.

Review of minutes from May 5

We went over the minutes.

Mike Staib is on board with the re-arrangement of the meaning of the timing calibration constants that we discussed last time. This clears the way for using our constants for the channel-to-channel time offsets.

Calibration Status FSU

Sasha has been looking at recent data with multiple hits per channel in both the FADCs and the TDCs. The second hit is often a cable reflection. For these events, he is exploring doing a time-walk correction by comparing the time difference measured by the ADCs and comparing it to the TDCs. When the second pulse is small reflection, the effect of time walk should be much greater for the second TDC hit.

Calibration Status JLab

Beni led us through recent work documented on his wiki page. See the page for details.

  • He sees the expected correlation between positions determined by end-to-end time difference in the TDCs and positions determined by the ratio of ADC amplitudes from the two ends of a counter.
  • After at time difference cut to select hits near the center of a counter, he sees clear Landau distributions in the energy deposition.
  • Added in press: he is also able to extract attenuation lengths from each counter. These show a long-range and short-range component in the relation of amplitude vs. distance from the PMT.

All of the these observation can serve as a basis for gain calibration and for future gain adjustments via high-voltage changes.