[Halld-pid] Time-of-Flight Meeting Minutes, December 13, 2016

[Mark Ito]

Folks,

Please find the minutes below and at 
https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_December_13,_2016#Minutes 
.

   -- Mark
_____________________________


    GlueX TOF Meeting, December 13, 2016, Minutes

Present:

  * *FSU*: Sasha Ostrovidov
  * *JLab*: Thomas Britton, Brad Cannon, Paul Eugenio, Mark Ito (chair),
    Simon Taylor


      Announcement

Beam is due in the Hall this afternoon. Shifts start today at 16:00.


      Lucite Shield

Paul has updated the run plan <https://logbooks.jlab.org/entry/3437900> 
in the logbook. We will need to talk to Alexandre Deur to incorporate it 
into the larger schedule.


      PMT Testing

Paul showed a page listing the steps used at FSU 
<http://hadron.physics.fsu.edu/wiki/index.php/Photomultiplier_tubes> to 
qualify the original order for PMTs for the Time-of-Flight. They are:

  * Preliminary assessment of the signal shape with a scope
  * Single photo-electron gain measurement
  * Americium source anode sensitivity measurement
  * NaI crystal quantum efficiency assessment

The plan is for Paul to drive back to Tallahassee with the new PMTs for 
testing. Mark will have to prepare the paperwork for this.


      PMT bases with Amplifiers

Mark reported on progress Beni has been making.

  * He has given specs to Vladimir Popov.
  * He measured time resolution of the new tubes with a laser as the
    light source and a scope using its built-in data acquisition
    functions. He sees a significant degradation in timing resolution
    when the tube is run at a lowered voltage, from about 50 ps RMS at
    1550 V to a few hundred ps at 1250 V.
  * If an external amplifier is used the resolution recovers to about 50
    ps, RMS.
  * He is preparing to do tests with different proportions of voltage
    drops from the voltage divider.


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