GlueX PID Meeting, March 19, 2010

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Location, Time

Friday, March 19, 2010
2:00 pm EDT
JLab: CEBAF Center, Room F326/7
ESNet: 8542553
EVO: direct meeting link
Conference Group: 800-377-8846, participant code: 77438230
Slides: talks can be deposited in the directory /group/halld/www/halldweb/html/talks/2010-03 on the JLab CUE (you have to be a member of the "halld" group). This directory is accessible from the web at .


  1. Announcements
    • Meeting name change progressing
  2. Minutes from the last meeting
  3. Time-of-Flight Status: Paul
  4. Rates in the TOF: Sascha S.
  5. Start Counter Status: Werner
  6. Target Status: Rory
  7. Action Items


FSU: Sasha Ostrovidov
JLab: Eugene Chudakov, Paul Eugenio, Mark Ito (chair), Chris Keith, Elton Smith, Sascha Somov, Simon Taylor, Elliott Wolin, Beni Zihlmann
UMass: Rory Miskimen


  • Chris asked about purchasing the pulse tube refrigerator and compressor he described at the December 11th meeting. He had a cost estimate of 40 k$. He will get a quot and pass it on to Eugene.
  • Tim noted that on the p3e schedule, we will purchase cryogenic supply lines for the target in January 2012. This system obviates the need for those lines.
  • Rory reported that Aram Teymurazyan is no longer with UMass. We wish Aram well with his new position at the University of Toronto. A new post-doc search is being organized. Hall D instrumentation will be a major part of the job description. If you know of strong candidates, let them know about the position.

Start Counter

  • Werner working on hiring for the new bridge position and the...
  • ...MOU.
    • Elton asked about signatures at FIU. Werner reported concerns from the Provost, though not of a alarming nature.
  • He wants to talk to Tim about mechanical issues, including machining the scintillator after bending so that they fit nicely into a close-packed array.
  • Seema has gone on to a new position. Werner is going to hire another post-doc.
  • Werner would like to get one of the new SiPM arrays. Testing should take about a month.
  • We were reminded that the nominal cross section of the counters is now 10 mm x 3 mm.


FSU status

  • Paul reminded us that their recent effort has been to choose a PMT
    • The thrust was comparison of the new Hamamatsu tubes vs. the Photonis XP2020 (the latter being no longer available)
    • The new tubes performed better for timing, but are 10 stages (R10534) vs. the 12 stages of the XP2020's and so gain is a question.
      • hits at far end only got to 97% efficiency
      • gain 1.5x106 and 1.1x106 for the two tubes tested vs. 1x107 for the XP2020's
    • The Hamamatsu tubes cost about $800 with base and shield, half the cost of the XP2020
  • Sasha O. is now working on CFD vs LE (with time-walk correction) discriminator comparisons
  • Paul and Sasha want to add more paddles and study half-length paddles
    • Need 6 more tubes for the set-up they have in mind.
    • Paul will get quotes, send them to Mark, who will pass them by Eugene
  • Paul is thinking of studying whether light can be coupled around hole to get two-ended read-out for the short paddles.
    • Elton commented that schemes like that often have difficulty channeling enough light to make them work.
  • Paul described their preparations to test flash ADC readout (VXS crate, cutting the pins to accomodate the Flash250, etc.)
    • Given scarcity of the FADC's, Paul and Sasha will explore using integrating ADC's.


Sascha S. showed results from a study of rates in the time-of-flight due to electromagnetic background. See his note for details.

  • The main message: the estimated rate of 12 MHz in the inner double-ended counters is probably too high to be acceptable.
  • These counters may have to be "split" longitudinally.
  • Beni remarked that these rates are higher than in previous studies. Those gave rates more like 3 or 4 MHz
  • Richard found 5 MHz was the limit for the tagger counters.
  • Elton asked why low energy stuff in ADC specturm was not larger in comparison the the minimum ionizing signal in the background.
  • Sascha complained that in the reconstruction it is often difficulty to correlate hits with the Monte Carlo particles that produced them.
  • Eugene suggested that we also look at the current going through tubes and whether they can stand it. If not we might have to go to amplifiers.


Paul gave a report.

  • Comments from others have been incorporated.
  • He will talk to his chair.
    • Recent changes in the department make a designer available.
  • Paul will send the latest version to everyone.