[Halld-pid] Start Counter Meeting Minutes, September 5, 2013

[Mark M. Ito]

Friends,

Find the minutes below and at

https://halldweb1.jlab.org/wiki/index.php/GlueX_Start_Counter_Meeting,_September_5,_2013#Minutes 
.

   -- Mark
____________________________________________

GlueX Start Counter Meeting, September 5, 2013
Minutes

    Present:
      * FIU: Werner Boeglin, Eric Pooser
      * JLab: Chuck Hutton, Mark Ito (chair), Tim Whitlatch

Meeting Recording

    You can find a [23]recording of the meeting at the ReadyTalk site. It
    will be there for about a month.

Review of the Last Meeting

    We reviewed the [24]minutes of the meeting we had on August 22.
      * Mark discussed the issue of SiPM placement tolerance with Fernando.
        He thinks he can hold the placement to about a mil which is much
        better than we require (the scintillators are 3 mm thick).
      * We discussed when would be a good time for Nick Sandoval to do the
        initial electronics installation at FIU, as Fernando has proposed.
        This depends on how construction of the counters proceeds and what
        we want to get out of Nick's trip. We will have to discuss further
        in the future, with Fernando in the loop.

Foam Support Construction

    Chuck spoke to Steve Christo of Hall B about what type of foam to use.
    Although they used Last-A-Foam for their start counter support, Steve
    recommended using [25]Rohacell instead. Chuck contacted the company and
    obtained a quote for the 51 HF foam. The structure would be made of two
    "half-pipes" glued together. We are also considering the 71 HF which is
    mechanically stronger, but because of the size of their stock it would
    have to be made of three sections. The total cost is about $5,000,
    where the costs are dominated by engineering and set-up costs. An
    additional complete support assembly would only be another $300.

    Tim has done some stress calculation and we would have to be somewhat
    careful that we do not apply too much "bending" force on the support
    cylinder. Werner mentioned to support a scintillating fiber array for
    Fermilab's D0 detector, a layer of carbon fiber was glued to a foam
    structure to increase strength. Tim will study adding a 1/2 mm carbon
    fiber layer. Although it would do more good on the outside of the foam,
    construction would be easier if it were placed on the inside. Werner
    pointed out that the carbon fiber could stop before the nose part of
    the counters and still add a lot of strength.

    Werner mentioned that the position of each counter may have to be
    shimmed to get good alignment with the SiPMs. This can be done with
    layers of reflective material, probably VM2000. The nominal position
    increment to be added needs to be calculated and sent to Chuck soon so
    that he can put that into the design.

Construction News

    Eric gave us an update.
      * The test stand is being constructed now. The SiPM case is done, the
        outer frame is being machined now. The holder for the scintillator
        and PMT case are next. It should be done by next week.
      * A new quote was obtained from Eljen for the scintillator. For
        quantity 50 they will be $197 each, which is a bit better than the
        previous quote. FIU is nearly ready to proceed with the
        procurement.
      * Eric spoke with Robert McNeal about buffing scratches observed on
        the broad faces of the prototype counters. The protective plastic
        that was applied by Eljen had to be removed to place the
        scintillator into the machining fixture. After machining, a new
        protective plastic film was applied before shipping to FIU. The
        claim is that the broad faces were never touched during this
        process. The quality of the edges, the surface that is actually
        machined, is very good. Eric also asked about how they verify
        dimensions and was told they use a [26]coordinate-measuring machine
        that they have on hand there.

Electronics

    Construction of the SiPM boards will start very soon according to
    Fernando. Nick Sandoval will be doing the work. They have already done
    the bias-voltage-requirement matching of the SiPMs in groups of five,
    only four of which are needed for a particular channel. Recall that the
    design uses one bias voltage for all four SiPMs.

    Retrieved from
"https://halldweb1.jlab.org/wiki/index.php/GlueX_Start_Counter_Meeting,_September_5,_2013"

References

   23. http://cc.readytalk.com/play?id=4mo9my
   24. 
https://halldweb1.jlab.org/wiki/index.php/GlueX_Start_Counter_Meeting,_August_22,_2013#Minutes
   25. 
https://halldweb1.jlab.org/talks/2013-3Q/ROHACELL%20HF%20Product%20Information.pdf
   26. http://en.wikipedia.org/wiki/Coordinate-measuring_machine

-- 
Mark M. Ito, Jefferson Lab, (757)269-5295, marki at jlab.org