GlueX TOF Meeting, March 1, 2012

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Thursday, March 1, 2012
10:00 am EST
JLab: ARC, Room 428


  1. Announcements
  2. Minutes from the last meeting
  3. Sasha's talk at the Collaboration Meeting (for reference)
  4. Mechanical design: Tim, Chuck
  5. Prototype status: Paul, Sasha
  6. TDC choice: all
  7. Contract Status: Mark, Paul



  1. ESNet: 8542553
  2. EVO: EVO site


Talks can be deposited in the directory /group/halld/www/halldweb1/html/talks/2012-1Q on the JLab CUE. This directory is accessible from the web at .

Chairman's Cell Phone




  • FSU: Paul Eugenio, Kurt Koetz, Sasha Ostrovidov, Ian Winger
  • JLab: Chuck Hutton, Mark Ito (chair), Tim Whitlatch

Mechanical Design

Note: Chuck brought his PC into the meeting room so we were able to look at the 3-D I-DEAS drawings.

  • The TOF detector modules are clamped between two U-channels that run along the entire edge of the array.
  • Tim proposed lengthening the long scintillators by 1 cm, so that the edges protrude another 0.5 cm. This is to make the clamp share load equally between scintillator and light guide.
    • [Added in press] Elton Smith pointed out that it is not a good idea to put any pressure on the scintillator surface. That practice promotes crazing. So it looks like in fact we want to make the counters shorter.
  • Tim proposed building a 1/4-scale model of the entire frame, including some of the detector modules, to see if there are any assembly issues with the current design.
  • Paul proposed building a full-scale model of one corner of the frame, to test whether mechanical tolerances in the assembled array are sufficient.
  • Kurt expressed some skepticism that the clamping U-channels could be made with enough precision to both hold the scintillator and provide a suitable mounting surface for the outer steel magnetic shields. In fact the current design does not have a provision for adjusting the angle of the long axis of the shields so that they miss the PMT's and their bases. That would have to be added.
  • Kurt advocated a different approach, where the support for each end of each module is a separate mechanical assembly, each assembly supported on a common backbone. These assemblies would allow adjustment of more of the degrees of freedom and would have greater precision in doing so. Ian had drawn up a [??? concept] some months ago.

We decided that a lot of issues had been raised that require some study and further discussion. We agreed to meet again, in a week, Thursday, March 8, at 10 am (in ARC 428, so Chuck can bring his PC again).

next measure light transmission, loss in light guides

Paul: full scale of corner

adjusting angle of steel shield

paul would like to use CAEN TDC's

bring Eugene, Fernando into the conversation