[Halld-pid] Time-of-Flight Meeting Minutes, June 21, 2013

[Mark M. Ito]

Folks,

Find the minutes at

https://halldweb1.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_June_20,_2013#Minutes

and below.

   -- Mark
____________________________________________________________

GlueX TOF Meeting, June 20, 2013
Minutes

    Present:
      * FSU: Paul Eugenio, Sasha Ostrovidov
      * JLab: Chuck Hutton, Mark Ito (chair), Beni Zihlmann

Adding frame part machining to contract

    We decided to add the machining of parts for the TOF frame that FSU
    will undertake as an additional activity in the contract. This should
    not delay specification of the work or procurement of materials.

Iron shield drawings

    We looked at the drawings Chuck has done of the outer iron magnetic
    shields. There are two versions, [29]one for the standard counters and
    [30]another for the half-width counters. These will machined at FSU and
    Paul will show these to the shop folks at FSU to get the ball rolling.

    Color scheme for these shields was the subject of too much discussion.

Rail system for supporting the TOF

    Chuck showed the current [31]design for supporting the TOF from the
    FCAL frame. The weight is supported on rails that will allow the TOF
    move upstream from its running position by about two feet to allow
    access to the downstream face of the TOF and the upstream face of the
    FCAL. Note that the strain relief for the cables are not shown on these
    drawings.

    The TOF will be brought in on a crane and placed on the rails. There
    will be some guide rails at the bottom. The exact procedure for
    supplying the force to move it on the rails is TBD.

Review of minutes from the last meeting

      * The splitters have arrived at FSU.
      * The two LeCroy high voltage cards have arrived at FSU.
      * Paul will send us a set of links to the procedures so that we can
        capture a copy at JLab for archival purposes.
      * Chuck will look into finding a good time for an
        assembly/installation next week.

Construction News

      * Gluing fixture now accommodates 9 modules at a time.
      * 13 completely wrapped modules now.
      * 9 standard and 2 half-width glued with light guides, ready for
        wrapping, moving to storage. Will wrap in groups of eight.
      * Students being moved from polishing to wrapping work.
      * Will start gluing another nine bars soon.
      * Issue with light leaks: some modules had [32]Tedlar wrapping
        damaged during transport in moving structure. Light leak testing,
        based on PMT current, now instituted into the procedures. Once
        found leaks are easily fixed. Now all modules will be wrapped in
        felt after wrapping, and will remain so wrapped through shipping to
        JLab.
      * Rubber caps will be installed on the unused dynode BNC connector on
        the PMTs for marking ("do not use") and protection.
      * The test system is being modified to use the Flash-250.
      * Sasha now understands the [33]dip in the end-to-end time-difference
        spectrum seen with the linear fan-in/fan-out. It was due to a lack
        of efficiency introduced when the pulses were in coincidence as the
        FI/FO.
      * He also reports that he sees double pulses about 10% of the time
        when using the 50-50 passive splitters in the test set-up. He
        attributes this to signal reflections from the splitter. See his
        plots on the same wiki page as above. This will require further
        investigation.
      * Sasha proposes that we gain balance tubes in the test set-up (same
        wiki page) using dead reckoning rather that do a series of
        measurements to iteratively adjust the gains with cosmics, which
        may be quite time consuming. We thought that that was a reasonable
        proposal.

Shield at cathode voltage

    Paul looked up the [34]"HA" coating that comes with our Hamamatsu
    tubes. This obviates the need to do any external connection to cathode
    voltage on the shield or other surrounding metal structure.

    Retrieved from
"https://halldweb1.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_June_20,_2013"

References

   29. https://halldweb1.jlab.org/talks/2013-2Q/2006.pdf
   30. https://halldweb1.jlab.org/talks/2013-2Q/2007.pdf
   31. https://halldweb1.jlab.org/talks/2013-2Q/Presentation1.pptx
   32. 
https://halldweb1.jlab.org/wiki/index.php/Wrapping_with_protective_felt
   33. http://hadron.physics.fsu.edu/~ostrov/tof/20130620/
   34. 
https://halldweb1.jlab.org/wiki/index.php/PMT_Ground_Polarity_and_HA_Coating