GlueX TOF Meeting, February 18, 2011

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Location, Time

Friday, February 18, 2011
2:00 pm EST
JLab: CEBAF Center, Room F326/7


  1. Announcements
  2. Minutes from the last meeting
  3. Report from trip to U. of South Carolina: Paul
  4. Prototype Status
  5. Contract Status
  6. TOF Schedule
  7. Meeting time OK?



  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/2011-1Q on the JLab CUE. This directory is accessible from the web at .



  • FSU: Paul Eugenio
  • JLab: Mark Ito (chair), Yi Qiang, Elton Smith, Sascha Somov, Simon Taylor, Tim Whitlatch, Beni Zihlmann

Minutes from the last meeting

We reviewed the minutes from the meeting on January 21.

The Hamamatsu PMT arrived at JLab from FSU. Beni has been looking at it and has reported his findings in a series of email messages to the PID list. He concludes that the tube performs as advertised and its contribution to timing resolution is small compared to other factors, as well as compared to our spec for the TOF.

Report from trip to the University of South Carolina

Paul and Sasha Ostrovidov travelled to Columbia to visit Ralf Gothe and discuss his work on the forward time-of-flight for CLAS12. Some notes on their trip:

  • Goals
    • compare and contrast design choices between USC and FSU
    • identify factors limiting factors in resolution in the FSU set-up
    • look at contradictory experiences with ESR wrapping at the two institutions
  • Ralf reviewed his construction and QA procedures with Paul and Sasha
  • time-walk corrections
    • Sasha trying to fit all parameters at once
    • USC using an iterative approach, not letting all parameters float
    • without time walk corrections, USC resolution a factor of two worse
    • Elton: 1/sqrt(p.h.) may not be the right functional dependence
  • TDC's
    • resolution from electronics at FSU gives get something like the 55 ps value of the least significant bit
    • Ralf gets the same thing (lsb value) except in his case it is 25 ps from his CAEN device
    • Why not go to CAEN TDC?
      • Paul will get from a loaner from Mark Kibilko
      • readout protocol should be OK for GlueX pipelined DAQ
  • PMT choices
    • USC using 8-stage, not the 10-stage, Hamamatsu PMT
    • 10-stage tube perhaps not available when they made the decision
  • ESR
    • improved light collection: results from FSU
    • SC had poorer performance with ESR
    • material USC was ESR: looks like white Tedlar, not specular
    • Ralf had some mylar that he could not use for his counters, gave it to Paul
  • Tour of USC lab
    • saw alignment devices
    • saw glueing tools, jigs
  • Contract
    • Paul got a copy of the assembly and testing document from Ralf that was part of USC's 12-GeV contract with JLab.


Elton reminded us of the issue of the geometry of the TOF counters that has been discussed previously. Some notes from the discussion:

  • making the counters wider may lose light
  • mounting PMT directly on the scintillator like USC is doing is attractive
  • Paul has not finalized a proposal yet
  • need to talk about it at the next meeting
  • outside diameter with mu-metal 6 cm
  • USC using 6 cm x 6 cm counters
  • current GlueX design with steel tube more than adequate for magnetic shielding


Tim walked us through the schedule in the current project plan. Again some notes:

  • PMT's are the kind of thing JLab would buy, scintillator as well
  • other items would likely be bought by FSU
  • contract has to be awarded before PO goes out, say 7 months from now

The overall message is that decision making on the TOF will have start now to make this schedule.

Other items

  • Tim will test the mu-metal shield that came on the Hamamatsu tube that Beni has been looking at.
  • Elton reminded us that rates for inner-most paddles near the beam hole are problematic. We need to decide how to address that.