[Halld-pid] Start Counter Meeting Minutes, May 3, 2012

[Mark M. Ito]

Find the minutes at 
https://halldweb1.jlab.org/wiki/index.php/GlueX_Start_Counter_Meeting,_May_3,_2012#Minutes 
and below.
_____

GlueX Start Counter Meeting, May 3, 2012
Minutes

    Present:
      * FIU: Werner Boeglin, Puneet Khetarpal
      * JLab: Mark Ito (chair), Elton Smith, Tim Whitlatch, Beni Zihlmann

Prototype

    The sample counter has still not come in from McNeal. It has been built
    and now is "in finishing."

Read-Out

    Mark reported on his conversation with Fernando. Fernando has started
    thinking about the design of the SiPM board.
      * Having three counters read-out by one board seems about right for
        the design. 3 sectors ok
      * We will have three bias voltages per board, one for each counter.
        The four SiPM's used for a single counter will be matched so they
        can use a single bias voltage.
      * Fernando is thinking about an out-rigger board that fits on a
        card-edge-like connecter on the SiPM board. The new card would
        contain the pre-amp and cable connectors. This is to have more real
        estate for components. Chuck Hutton will have to be consulted to
        see what fits.
      * We decided not to use the thermister voltage divider to stabilize
        that gain against temperature fluctuation since gain is not a big
        issue for this detector and to save real estate. That having been
        said, both Elton and Werner were in favor of including it if
        possible. One question is whether the set temperature needs to be
        known in advance of selecting the components used in the circuit.
        For the start counter that temperature is unclear.

Simulation

    The new geometry with 30 counters is ready. Remaining is the removal of
    the long light guides. Puneet is working on this and a version should
    be ready in the next few days. In the future we may want to add some
    material for the SiPM boards.

Calibration

    We discussed having a light pulsing system. Werner pointed out that it
    would be useful to check that the detector is working. In addition if
    the light intensity were variable, an efficiency check of sorts could
    be done. If the pulses were fast, timing resolution could be checked.

    One possibility is to use an LED, mounted externally, and run the light
    into each counter with an optical fiber. Another is to have one LED
    mounted directly on each counter. A lot more thinking about this
    remains to be done on the mechanical issues as well as the basic
    calibration considerations.

Mechanical Design

      * We have a working concept of an inner foam support machined out of
        single piece, and no outer foam support.
      * We discussed issues of light tightness and optical independence of
        the counters. A firm design is not yet in place. If light tightness
        is not established on a counter-by-counter basis then some sort of
        overall enclosure is called for. At the same time the enclosure
        must accomodate sufficient air flow on the SiPM pre-amps to keep
        them at a stable temperature.

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-- 
Mark M. Ito
Jefferson Lab (www.jlab.org)
(757)269-5295