[Halld-pid] Start Counter Meeting Minutes, November 15, 2012

[Mark M. Ito]

find the minutes below and at
 
https://halldweb1.jlab.org/wiki/index.php/GlueX_Start_Counter_Meeting,_November_15,_2012#Minutes
_____

GlueX Start Counter Meeting, November 15, 2012
Minutes

    Present:
      * FIU: Werner Boeglin, Puneet Khetarpal, Eric Pooser
      * JLab: Chuck Hutton, Mark Ito (chair), Beni Zihlmann

SiPM Gain Measurement

    Eric has done a single photo-electron measurement on a tube to
    determine its gain as a precursor to measuring the SiPM gain. Fernando
    Barbosa is waiting on this measurement to finalize his design.

Scintillator Quality

    After about a month, the scintillator bars (those that were not broken)
    are showing visible signs of deterioration, with crazing on many areas
    of the surface. FIU showed photos of bars illuminated from one end by a
    diffuse laser light source. Loss of light is clearly seen.

    image:laser test
    image:laser test, close-up

    Werner has been in contact with McNeal about their handling practices.
    Recall that instructions on how to properly handle scintillator had
    been sent the the company and they claim that those procedures were
    followed. Yet some samples of the same scintillator material retained
    at FIU do not show any degradation.

    FIU will go ahead and test the bars in any case. They are considering
    how to proceed. The quality of the machining done at McNeal is fine.
    The question is whether or not the material handling problem can be
    solved.

Light Yield Studies

    Puneet showed [20]further studies of light collection efficiency. He
    has improved the geometry to insure adequate coverage of the "detector"
    regardless of scintillator dimensions. He also can vary the intensity
    of the source so that it scales with path length and is physically
    spread along a "track" in the scintillator.

    Lately he has been looking at the dependence of the light collection
    efficiency on the thickness of the counter when the roughness of the
    edges is greater than that of the faces, as we expect it is in the real
    counters. With a constant number of photons from the source he hees no
    dependence on thickness. Studies continue.

Equipment Difficulties

    The LeCroy 1454 high voltage mainframe that FUI has been using for PMTs
    has died. They now only have the capability, using other means, of
    running a couple of channels. A full cosmic ray run requires six tubes
    in their set-up. They do have a CAEN SY2527 mainframe, but the only
    cards they have on hand are for wire chambers.

    We will all explore options for getting them going again.

Contract

    Mark submitted the purchase requisition for start counter construction
    to JLab Procurement yesterday. We have to get started on the proposal
    next.

    Retrieved from
 
"https://halldweb1.jlab.org/wiki/index.php/GlueX_Start_Counter_Meeting,_November_15,_2012"

References

   20. 
https://halldweb1.jlab.org/wiki/index.php/Start_Counter_Simulations#Side_Test:_Thickness_Variation

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