[Halld-pid] Minutes, GlueX Start Counter Meeting, Jan. 27

[Mark M. Ito]

Find the minutes at 
http://www.jlab.org/Hall-D/software/wiki/index.php/GlueX_Start_Counter_Meeting%2C_January_27%2C_2011#Minutes 
and below as text.

   ==

GlueX Start Counter Meeting, January 27, 2011
Minutes

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


Wrapping Material

    The ESR sheets from FSU have still not arrived.

Materials and Construction

      * Lei reports a price of $190 a piece for the scintillator from
        Elgin. They will have with diamond milled edges.
      * The pieces will be sent to Plastic Craft for cutting, bending, and
        polishing.


Neutrons and SiPM Damage Rates

    Sasha recommended that we look at Richard's [31]recent note on the
    effect of SiPM dark current on the microscope counters. Some points
    from that note:
      * Timing resolution is not much affected by dark rate.
      * Looked at rates up to a gigahertz.
      * Photonique devices with a slow recovery rate gives fluctuation in
        timing resolution due to non-constant exposure to beam.
      * Hamamatsu devices have a faster recovery rate and a steadier
        response.


Measurements with the New SiPM

    Werner and Eric reported on tests that have done the Hamamatsu SiPM
    that Carl Zorn sent them comparing its performance with a fine-mesh
    tube that Werner had on hand.

    Timing resolution for the SiPM was a bit disappointing. Tests were done
    with a new scintillator bar from Elgin. The measurements were done with
    a Sr90 source where the timing was done between the test counter and a
    trigger counter. Using the PMT, light output and attenuation length
    measurements were done and repeated with the SiPM. It appears that even
    with the same amount of light, the resolution for the SiPM is a factor
    of 1.5 to 2 worse than for the FM-PMT. See [Eric's plots] for details.
    More study is under-way.

    Some other remarks:
      * Pulses generated with an led worked well with the SiPM.
      * They cannot see the single p.e. peak; pedestal is too wide.
      * For the SiPM, there is a 50 mV-ish signal, amplified to 200 mV-ish
        before being discriminated. The PMT set-up uses the direct signal.
      * They played a bit with bias voltage, nominally 71 V.
      * They are using a constant-fraction discriminator.

    Werner also mentioned that if a spare Peltier junction was lying around
    somewhere, he would be interested in borrowing it.

JLab/FIU MOU

    Mark send Werner a revised version last week incorporation wording that
    Werner provided. Werner will send a version back with some
    already-planned modifications to JLab in the near future.

    Retrieved from
    
"http://www.jlab.org/Hall-D/software/wiki/index.php/GlueX_Start_Counter_Meeting%2C_January_27%2C_2011"

References

   31. 
http://argus.phys.uregina.ca/cgi-bin/private/DocDB/ShowDocument?docid=1662