[Halld-pid] Start Counter Meeting Minutes, July 26, 2012

[Mark M. Ito]

Folks,

Find the minutes below and at

https://halldweb1.jlab.org/wiki/index.php/GlueX_Start_Counter_Meeting,_July_26,_2012#Minutes

   -- Mark
_____

GlueX Start Counter Meeting, July 26, 2012
Minutes

    Present:
      * FIU: Werner Boeglin, Puneet Khetarpal
      * JLab: Eugene Chudakov, Chuck Hutton, Mark Ito (chair), Sascha
        Somov, Beni Zihlmann

Prototype News

      * The new scintillator from Eljen has not been ordered yet. The 
order should
        go out next week.
      * Werner contacted Elgen and asked diamond-milled edges
      * Werner has been thinking of an alternate scheme for wrapping the
        scintillator to eliminate cross-talk. Eljen has a double-sided
        aluminized mylar, two microns thick total, used for entry windows
        for alpha detectors to make them light tight. He is thinking we
        could wrap the entire counter in this material. It has 1000
        Anstroms of aluminum on each side.
      * Chuck will send drawings of the individual counters to Werner.
        These will have the latest dimensions.

Read-Out Design

    FIU received the boards from Fernando Barbosa on Monday. They have two
    one-sector detectors, each with 4 SiPMs, one with 50 micron devices,
    the other with 100 micron devices. They are about to start testing
    them. Fernando is interested in the results so he can fix the gain in
    the design.

Simulation

Background Studies

    Puneet presented rate calculations done with the new start counter
    geometry (30 counters). See his [22]wiki page for details. He showed
    overall rates, the spatial distribution of the hits and energy spectra
    both for electromagnetic background and for hadronic events.

    There was some discussion of his results:
      * We need to understand the details of the digitization model.
      * Beni noted that HDGeant applies a threshold cut of 150 keV on hits.
      * HDGeant is assuming an attenuation length of 150 cm. It should be
        more like 60 cm.

Optical Simulations

    Puneet also described progess in modeling the optical response of the
    counters in Geant4, including different optical properties for
    different faces of rectangular counters. See [23]his wiki page for
    details. He find a reduction of the light output for a fixed sized
    sensor as the thickness of the counter the counter. The source for
    these studies is a point source of photons positioned at various
    distances from the sensor.

    The next step is to implement these features on the actual bent counter
    geometry.

Action Items

     1. Send new counter drawings to Werner. -> Chuck
     2. Test the SiPM start counter electronics.
     3. Start work on the SOW. -> Mark, Werner

    Retrieved from
"[24]https://halldweb1.jlab.org/wiki/index.php/GlueX_Start_Counter_Meet
    ing,_July_26,_2012"

References

   22. 
https://halldweb1.jlab.org/wiki/index.php/Start_Counter_Background_Studies
   23. https://halldweb1.jlab.org/wiki/index.php/Start_Counter_Simulations

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