GlueX PID Meeting, March 19, 2010
Minutes

   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

Target

     * Chris asked about purchasing the pulse tube refrigerator and
       compressor he described at the [22]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.


Time-of-Flight


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.
               o hits at far end only got to 97% efficiency
               o gain 1.5x10^6 and 1.1x10^6 for the two tubes tested vs.
                 1x10^7 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.


Rates

   Sascha S. showed results from a study of rates in the time-of-flight
   due to electromagnetic background. See [27]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.


MOU

   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.

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References

  22. http://www.jlab.org/Hall-D/software/wiki/index.php/Time-of-Flight/Start-Counter/Target_Meeting%2C_December_11%2C_2009#Minutes
  27. https://halldweb1.jlab.org/talks/2010-03/tof_rate.pdf