[Halld-pid] GlueX TOF Meeting Minutes, June 23, 2011

[Mark M. Ito]

Find the minutes at 
http://www.jlab.org/Hall-D/software/wiki/index.php/GlueX_TOF_Meeting%2C_June_23%2C_2011#Minutes 
and below.

   ==

GlueX TOF Meeting, June 23, 2011
Minutes

    Present:
      * FSU: Sasha Ostrovidov
      * JLab: Paul Eugenio, Chuck Hutton, Mark Ito, Simon Taylor, Tim
        Whitlatch, Beni Zihlmann


Minutes from the Last Meeting

    We reviewed the [33]minutes from the May 27th meeting.
      * Paul's students are back in Tallahassee after attending HUGS.
      * Mark purchased the raw light guide material as requested by Paul.
        It has been received at FSU.


Mantis task tracker project for TOF

    Mark pointed out that he has created a project to track TOF action
    items in the [35]Mantis Bug Tracker. Any collaborator can create an
    account that uses your JLab password and add, modify, or remove
    entries.

Design and Prototyping


Drawings

    We had a discussion centered around the [38]design drawings enumerated
    by Paul and reserved in Oce by Chuck. Some of the issues discussed:
      * light guides must be bent to accommodate the diameter of the PMT's
        with their shielding, what is the best way to do this?
      * how to best support the counter-light-guide-tube-cable assemblies
      * two options for manufacturing the bent light guides
          1. heat and bend the Lucite
          2. machine entire 3-D shape out of single piece of Lucite
      * Paul is looking into the single-piece option.
           + This method requires a 3.5" diameter Lucite rod, unfortunately
             3" is the largest "stock" size at McMaster. The price goes up
             by a factor of 2.5 if a custom size is ordered.
      * We discussed whether UV-transparent Lucite was necessary.
           + Tests with both UVT and non-UVT light guides at FSU gave
             similar results, as expected.
           + Elton thought that UVT plastic was important for the BCAL; we
             will have to talk to him about this issue.
      * Paul raised the possibility of using vapor polishing on the
        machined light guides. He has identified a company that will do a
        trail piece at no cost.

    We will have a meeting in a week, tentatively Thursday, June 30 at 10
    am, with engineering and design folks at FSU and JLab to discuss how to
    proceed with producing drawings. Mark will send an announcement.

Tests

    Sasha led us through [40]some plots showing results from recent tests
    at FSU. Quoting from his presentation:
      * Good news: Switch to a leading-edge discriminator (LED) from a
        constant-fraction discriminator (CFD) has eliminated multiple
        timing peaks. We confirmed the presence of these peaks with both
        CAEN 812 VME CFD and Phillips 715 NIM CFD. Peak positions were
        strongly correlated with the value of internal CFD delays.
        Apparently, the CFD method of inverting, delaying and subtracting
        part of the signal does not work well with signals of certain
        magnitude/shape.
      * Problem: While time differences with the LED do not show extra
        timing peaks, the shape of the time-difference spectrum when using
        2 short trigger paddles is somewhat puzzling, with a dip in the
        middle rather than at both ends. This results in highly
        non-Gaussian timing distributions. Time-walk corrections improve
        overall timing resolution from 180 ps to 115 ps but we hope to
        improve this number if the shape of distribution is better
        understood.


Contract

    We looked at the [schedule (i. e., the APP)]. We have slipped over a
    month from where we said we will be. Getting the drawings done is the
    next big step; it will force some decisions.

    Paul will write a draft statement of work. The required drawings and
    specifications will be called out if not detailed. He will send it to
    Mark who will pass it around for review.

Meeting Time

    We decided on regular time for future meetings: bi-weekly, 10 am on
    Thursdays.

New Action Items

     1. Paul will send chuck specification of PMT geometry.
     2. Talk to Elton about UVT light guides.
     3. Schedule TOF design meeting for Thu. June 30.
     4. Order 3.5" diameter Lucite rod for light guide machining tests.
     5. Distribute reference on vapor polishing.
     6. Find out if PMT's need specification in FSU contract if they are
        being bought by JLab.

    Retrieved from
    
"http://www.jlab.org/Hall-D/software/wiki/index.php/GlueX_TOF_Meeting%2C_June_23%2C_2011"

References

   33. 
http://www.jlab.org/Hall-D/software/wiki/index.php/GlueX_TOF_Meeting%2C_May_27%2C_2011#Minutes
   35. https://halldweb1.jlab.org/mantisbt
   38. https://halldweb1.jlab.org/talks/2011-2Q/chuck.pdf
   40. 
https://halldweb1.jlab.org/talks/2011-2Q/Latest%20on%20TOF%20prototype_110623.html