GlueX TOF Meeting, July 7, 2011

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Location, Time

NOTE: non-standard room, date, and time!

Thursday, July 7, 2011
10:00 am EDT
JLab: CEBAF Center, Room L207


  1. Announcements
  2. Minutes from the last meeting
  3. Prototype Status
  4. Contract Status
  5. Meeting time



  1. ESNet: 8542553
  2. EVO: EVO site


  1. dial:
  2. enter access code followed by the # sign: 3421244#


Talks can be deposited in the directory /group/halld/www/halldweb/html/talks/2011-3Q on the JLab CUE. This directory is accessible from the web at .



  • FSU: Paul Eugenio, Sasha Ostrovidov
  • JLab: Chuck Hutton, Mark Ito (chair), Beni Zihlmann


  • Paul sent the 3-D drawing of the light guides in step format to the email list. Chuck has looked at both versions and both look good.
  • Chuck asked for 3-D drawings of Ian's support scheme and any other drawings that Ian is working with.
  • Ian is currently working on the design for the light guides for the split counters (3-cm-wide counters).
  • Paul sent out the drawings of the Hamamatsu phototubes to the list.


Paul will send out a draft of the statement of work soon.

Prototype News

  • Paul received the UVT plastic from Polymer Plastics Corporation. It looks good. They can produce casts like it at the rate of four per week, which should be adequate. The price is comparable (or better) than commonly available UV-inhibiting material.
  • We talked about Elton's arguments for going with UVT material. Given the price, the choice is clear (clear...get it? ;-) ). Chuck reminded us

that the BCAL folks are using UVT for their light guides.

  • Paul has had his machine shop make a couple light-guides with the new design.
    • One has been polished.
    • Another will be sent for vapor polishing.
    • The plan is to test both and compare performance.
    • Beni also suggested looking at them with a laser pointer to get a qualitative feeling for the effect of polishing.
  • Paul raise a concern: there is a short section of the light guide

that, because of the bending, the cross-sectional area gets a bit larger before returning to the nominal size. He wonders whether this is something to worry about or not.

Time-Walk Corrections

Sasha has been working on applying Elton's time-walk correction prescription to data from the prototype set-up.

  • He re-arranged the trigger paddles so that their long axes are at right angles to that of the test paddle.
  • 400 k events have been collected with varying pulse height.
  • Time walk is evident for the low ADC values.
  • He is currently having some problems with the fit.