GlueX TOF Meeting, January 30, 2014

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GlueX Time-of-Flight Meeting
Thursday, January 30, 2014
10:00 am EST
JLab: CEBAF Center, L207 non-standard room


  1. Announcements
  2. Review of meeting on January 16
  3. Calibration
  4. Installation Update
  5. Testing Results [?]
  6. Fast Shutdown



  1. ESNet: 8542554

Desktop Sharing

  1. Go to
  2. In the "join a meeting" box enter the code: 1833622
  3. Fill in the participant registration form.


To connect by telephone:

  1. dial:
  2. enter access code followed by the # sign: 1833622#


Talks can be deposited in the directory /group/halld/www/halldweb/html/talks/2014-1Q on the JLab CUE. This directory is accessible from the web at .



  • FSU: Sasha Ostrovidov
  • JLab: Mark Ito (chair), Beni Zihlmann
  • NWU: Sean Dobbs


There was a significant change int the configuration of the support structure over the past week based on experience laying down the first layer of the TOF. In summary the aluminum holders ("cheese pieces") that surround the cylindrical portion of the light guides turned out to be too constraining, especially when used on the outer counters. The inner counters have their position defined by the beam hole box, but the tolerances built up going outward and turned out in sum to be too much. Said another way, the counters as-built were a bit wider than as-drawn, with manufacturing and wrapping variation all tending to go towards more width. Alignment was off by about 1/4 inch for the outer counters.

The solution is to remove the aluminum holders; they were not meant to hold the weight of the modules. That support is provided by the long steel C-channel which clamp around the lightguides near the scintillator joint. Also only every other bolt for the C-channel clamp will be installed to allow more space for the light light guides. In addition, the non-threaded shaft of the bolts that pass by the light guides will be re-machined to a smaller diameter. The bolts have gone back to the FSU shop to have this done to realize a not insignificant cost savings.

Paul was traveling during the meeting (snow-storm-induced travel plan modification) so we did not discuss this at length.

For Hussein is going to start testing the first layer in situ, applying high voltage and looking for light leaks with a scope.


We went through the questions raised in Sean's email and the accompanying list of constant sets for the TOF. These are based on Sasha's original list.

  • We thought that we should include ADC energy correction constants, as is traditional.
  • We will begin an effort to plan for simulation data to use for developing calibration code. Sasha has been using a stand-alone code so far to study time-walk corrections. Only single hits are simulation; it is not a full event simulation. We need to understand if there is any further development needed in HDGeant to support calibration practice at an appropriate level of detail. One task that we know about is updating the geometry to describe the half-width counters.

Action Items

  1. Check into monitoring the scalers on the discriminators.
  2. Update geometry to describe the half-width counters. -> Beni