JEF meeting, May 31, 2019

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Meeting time and location= 1:00 pm EST (JLab time) F228

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FCAL-II tasks


Attendees: Josh C., Liping G., Zisis P., Sasha S., Simon T.

  • Update on contract with Shanghai Ceramics Institute: JLab in the process of procuring 500 crystals
    • Anticipated delivery: November'19-January'20
    • Liping plans to visit the institute in August, possibly Sasha will join? Idea is to go over specs and QA.
    • Would be nice to identify Chinese collaborators to help out with this.
    • JLab also procuring 64 crystals from Czech republic supplier (these are supposed to be more rad hard than the Chinese crystals).
  • First goal for summer work: finish magnetic shielding design for PMTs
    • Set thickness, length, position of mu-metal with respect to the face of the iron, etc.
    • Tests with magnetic field are about to start -- Helmholtz coils, Hall probe, LEDs all in hand for tests.
    • Will be using 3x3 prototype
  • Second goal for summer work: finalize PMT base design
    • Base divide/amplifier prototype design from V. Popov had too high amplification of 25 requiring operation of HV far below Hamamatsu recommendation
    • Fernando B. confirmed linearity issues observed by Sasha
    • Studies suggest 3x amplification is more suited to our application
    • LED setup is available for studying linearity for modified base designs
    • Want to be ready by the fall in order to do studies with beam
  • Issues with brazing of brass straps leading to breakage after some time have been observed, possibly due to corrosion?
    • Possible alternate brazing compound has been identified -- Josh will perform some tests.
  • Light guides will be needed to couple between crystal and PMT faces
    • Length will be about 3.5 cm, material likely to be acrylic, possibly glass if rad hardness is an issue?
    • Method of coupling needs to be decided (glue? cookies? RTV?)
  • Frame design for full FCAL-II in progress
  • Second slit in shielding downstream of PS in Hall-D is in the works.
  • Beam hole sized needs to be optimized (2x2 crystals? 3x3 crystals?)
  • Need to identify "clean" space for crystal work