JEF meeting, June 28, 2019

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

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Magnetic shielding studies


Attendees: Wolfgan, Josh, Simon, Sasha, Zisis

  • Magnetic field studies more or less complete
    • From last time: Sasha suggested moving FCAL assembly 35 cm downstream to reduce field in PMT region for lead tungstate
      • Could stack lead glass blocks that we remove from the central region in the outer radius to improve acceptance
    • Studies with 350 micron mu-metal shielding + iron housing look promising -- added additional 50 micron mu-metal
      • For 60 Gauss longitudinal external field -> 2 Gauss in center of housing+mu-metal shield
      • PMT response in central position of 3x3 array flat up to about 40-50 Gauss longitudinal field
      • No saturation of mu-metal seen
      • Currently using 1020 steel, could be annealed for ~20-30% improvement
  • Stacking: insert needs to be well-leveled to distribute load
    • Consider adding ~few mm thick plates (above and below insert) in addition to shims
    • 1/2-1 FTEs next fiscal year to work on frame and other designs aspects
  • Cabling/connectors: Hall C style? (lemo for signals?)
  • Second arm of pair spectrometer now ready for use for parasitic measurements
    • Josh working on design for assembly to mount 12 crystals at a time
    • Need to consider magnetic field from fringe field of Hall-D solenoid
  • Zisis can provide summer undergrad students next year, considering putting graduate student of project