[Halld-pid] Time-of-Flight Meeting Minutes, November 3, 2015

[Mark Ito]

Folks,

Please find the minutes below and at 
https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_November_3,_2015 
.

   -- Mark
_______________________________________________________________


  GlueX TOF Meeting, November 3, 2015, Minutes

Present:

  * *FSU*: Hussein Al Ghoul, Brad Cannon, Sasha Ostrovidov, Aristeidis
    Tsaris
  * *JLab*: Mark Ito (chair), Simon Taylor


      Calibration with Cosmics

Sasha gave a report on recent work.

  * He has succeeded in taking cosmic data, but had a couple of
    difficulties:
     1. He needed to attempt to start runs several times before getting
        any triggers at all. He suspects that with multi-block readout
        of the CAEN TDCs, the token passing between modules would stop,
        hanging the system.
     2. ROCTOF1, which houses the FADCs, would crash in minutes from the
        start of the run. A hard reboot was needed to get things going
        again.
          o This problem has resolved itself recently.
      o In the end he got a few times 100 k events.
  * The trend of higher gains at the edges of the arrays seen in beam
    data is also seen in cosmic data.
      o This rules out the magnetic field, or a systematic problem using
        beam tracks.
      o Possible culprits:
          + Different HV supplies than those used at FSU.
          + Different HV cables.
      o He is working on a program to adjust HV to equalize gains. Data
        will be taken, gains measured, HV adjusted, and process iterated.
      o He is also seeing a difference in the gain when comparing a hit
        in the middle of the paddle versus one near the ends, even after
        accounting for attenuation. The gain is about 10% higher near
        the ends.
  * He is trying to judge the effect of gain calibration using a set of
    "tracks" in the TOF in cosmic data. He requires 5 counters minimum.
    The yield of such events is extremely low, about one part in ten
    thousand.
      o The trigger rate is about 600 Hz.
      o The threshold for a single FADC channel to be read out is 500
        counts. The trigger threshold on the sum is about 50,000
        typically, but other values have been tried.


      Calibration

  * Brad is in contact with Sean Dobbs about a plug-in to be used in the
    calibration challenge.
  * He is also cleaning up the script to drive the calibrations already
    done.

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  * This page was last modified on 4 November 2015, at 20:58.


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