[Halld-pid] Minutes, GlueX Start Counter Meeting, July 28, 2011

[Mark M. Ito]

People,

Find the minutes at 
http://www.jlab.org/Hall-D/software/wiki/index.php/GlueX_Start_Counter_Meeting%2C_July_28%2C_2011#Minutes 
and below.

   -- Mark

   ==

GlueX Start Counter Meeting, July 28, 2011

Minutes

    Present:
      * FIU: Werner Boeglin, Lei Guo, Eric Pooser
      * JLab: Eugene Chudakov, Mark Ito (chair), Puneet Khetarpal, Sascha
        Somov, Simon Taylor, Tim Whitlatch, Beni Zihlmann


Prototype Status

      * The dark box is in operation.
      * Current set-up uses the 140 cm solid light guide.
           + Previous tests showed a loss of a factor of two in time
             resolution when using the light guide vs. placing the
             phototube at the scintillator. That counter was 6mm x 10 mm.
           + Tests were done with and without reflective wrapping material.
           + Using optical grease helped; degradation was only a factor of
             1.5.
      * Scintillator from Plastic Craft has been tested.
           + By eye, the quality is not so great. There are scratches and
             some look milky.
           + Tried test with the piece (of five) that looked the worse.
           + With a FM-PMT directly on the scintillator got 300-400 ps
             resolution in the flat section and most of the tapered
             section, but see 600 ps at the forward point.
           + Judging from the previous tests, expect that with the light
             guide we will see a resolution range of 600 ps to 1 ns.
           + Light output may be improved by improving surface quality of
             the counters.
           + Want to measure all 5 counters to see if response if uniform
           + Vapor polishing looks like promising option.
      * Setting up to test fiber light guide
           + A new mounting scheme has been built.
           + These should have better light transmission.


Geometry

    Tim emphasized the need to have a good idea of the start counter
    geometry and support scheme now design of the target is progressing.
    One design cannot proceed without knowledge of the other.

    Werner will send Tim the drawing of the current design. The Plastic
    Craft pieces conform to this design.

Fiber Start Counter?

    Beni described ideas that have been discussed at JLab about using the
    excess fibers from BCAL reconstruction to build a start counter. There
    was a lot of discussion of possible design ideas. Werner pointed out
    that this idea was considered some years ago. The principal issue is
    how to transitions the fibers from the barrel section to the "nose
    cone" section or whether a nose cone is needed at all. Also raised was
    the idea that a more complicated design might be more appropriate for
    an upgrade. More discussion and some preliminary drawings are needed.

SiPM option

    Fernando Barbosa has recently reported tests with a new version of the
    pre-amp for the BCAL SiPM arrays that appears to give sub nanosecond
    intrinsic rise time. Werner has not been pursuing the SiPM option
    recently due to the disappointing results from tests last year. The
    device he tested before had a rise time of 20 to 22 ns. If there is a
    new device available with markedly better performance then he is
    interested in repeating some of those tests.

MOU

    The MOU is going around university administration at FIU for
    signatures.

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