[Halld-pid] Time-of-Flight Meeting Minutes, January 30, 2014

[Mark Ito]

Colleagues,

Find the minutes below and at

https://halldweb1.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_January_30,_2014#Minutes

   -- Mark
_____________________________________________________

GlueX TOF Meeting, January 30, 2014
Minutes

    Present:
      * FSU: Sasha Ostrovidov
      * JLab: Mark Ito (chair), Beni Zihlmann
      * NWU: Sean Dobbs

Installation

    There was a significant change int the configuration of the support
    structure over the past week based on experience laying down the first
    layer of the TOF. In summary the aluminum holders ("cheese pieces")
    that surround the cylindrical portion of the light guides turned out to
    be too constraining, especially when used on the outer counters. The
    inner counters have their position defined by the beam hole box, but
    the tolerances built up going outward and turned out in sum to be too
    much. Said another way, the counters as-built were a bit wider than
    as-drawn, with manufacturing and wrapping variation all tending to go
    towards more width. Alignment was off by about 1/4 inch for the outer
    counters.

    The solution is to remove the aluminum holders; they were not meant to
    hold the weight of the modules. That support is provided by the long
    steel C-channel which clamp around the lightguides near the
    scintillator joint. Also only every other bolt for the C-channel clamp
    will be installed to allow more space for the light light guides. In
    addition, the non-threaded shaft of the bolts that pass by the light
    guides will be re-machined to a smaller diameter. The bolts have gone
    back to the FSU shop to have this done to realize a not insignificant
    cost savings.

    Paul was traveling during the meeting (snow-storm-induced travel plan
    modification) so we did not discuss this at length.

    For Hussein is going to start testing the first layer in situ, applying
    high voltage and looking for light leaks with a scope.

Calibration

    We went through the questions raised in [23]Sean's email and the
    accompanying [24]list of constant sets for the TOF. These are based on
    [25]Sasha's original list.
      * We thought that we should include ADC energy correction constants,
        as is traditional.
      * We will begin an effort to plan for simulation data to use for
        developing calibration code. Sasha has been using a stand-alone
        code so far to study time-walk corrections. Only single hits are
        simulation; it is not a full event simulation. We need to
        understand if there is any further development needed in HDGeant to
        support calibration practice at an appropriate level of detail. One
        task that we know about is updating the geometry to describe the
        half-width counters.

Action Items

     1. Check into monitoring the scalers on the discriminators.
     2. Update geometry to describe the half-width counters. -> Beni

    Retrieved from
"https://halldweb1.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_January_30,_2014"

References

   23. https://halldweb1.jlab.org/talks/2014-1Q/tof_calibration_email.pdf
   24. https://halldweb1.jlab.org/talks/2014-1Q/TOF_v0.1.pdf
   25. http://hadron.physics.fsu.edu/wiki/index.php/TOF_Calibrations