[Halld-pid] Minutes, GlueX TOF Meeting, November 10, 2011

[Mark M. Ito]

Folks,

Find the minutes at 
https://halldweb1.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_November_10,_2011#Minutes 
and as text below.

   -- Mark
   _____

GlueX TOF Meeting, November 10, 2011
Minutes

    Present: FSU: Sascha Ostrovidov JLab: Eugene Chudakov, Chuck Hutton,
    Mark Ito (chair), Beni Zihlmann

Mechanical Design

    Chuck presented the current status of [28]drawings on how to support
    the counters, in particular how to secure the light guides, phototubes,
    and shielding sleeves. Much more realism has been added, among other
    features, a set of collars to attach the steel shielding to the support
    structure.

Contract Status

    Mark reported that we have drafts of all documents needed to start the
    procurement process: statement of work, sole source justification,
    specifications for both PMT's and scintillator, and drawings. There are
    still some edits to do, however, and nothing has been signed yet.

Prototype Status

    Sasha reported work in three areas.

   Non-mixed set of splitters

    Measurements were done where the splitters were the same on all six
    channels of the prototype. He tried two configurations: a set of 50/50
    splitters and a set of 80/20 splitters. He measured the following time
    resoltions for mean time in a single layer:

    split resolution (ps)
    50/50 110
    80/20 107

   Reflections

    Sascha tried pulsing the electronics using a pulser in place of the
    phototube. No reflections were observed. He still sees reflections from
    phototube pulses with the standard 50 foot cable between the tube and
    the splitter, but if another cable is added to give a total of 100
    feet, the reflections are not present. He notes that in the latter
    case, the original and reflection are clearly separated in time. Not
    clear what is going on here.

   Eight-Stage PMT

    Sacha broke out the 8-stage tubes that FSU bought some time ago. With a
    test scintillator and an americium source he sees response with about a
    factor of 4 or 5 times less gain than with the 10-stage tubes, as
    expected, consistent with a gain of 5×10^5 as advertised on the data
    sheet.

    When looking at cosmics with the test scintillator, he does not see
    clear separation of pedestal and signal. He will try an amplifier on
    the output to see if that helps. Some details, for the record:
      * pedestal at 300 counts
      * signal at 400-500 counts
      * 150 ns gate
      * 0.25 pC/count

Retrieved from 
https://halldweb1.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_November_10,_2011

References

   28. https://halldweb1.jlab.org/talks/2011-4Q/tof_11_10_11.pptx