General Meeting Summary 3/7/19

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MAGNET (Charles, Bogdan)

  • Safety and Operations documents
  • OSP for mapping is being prepared - expected to be complete in week 3/11
  • More detailed documents needed for ERR
  • Details of mapping plan for ERR
  • Planning to bring mapper to JLab in week 3/11
  • Fringe fields
  • Additional calculations made for downstream of magnet with passive shielding - sent this information to Jay Benesch
  • Action item: redo calculations of front of HMS (snout) for ERR - this is relevant for the optics
  • Paulo redid distances
  • need set of kinematic positions
  • Action item: determine sensitivity of experiments to up/down asymmetry due to magnetic field
  • magnet horizontal field changes up/down position of detector - for measurements only matters if sensitive to up/down asymmetry
  • DVCS measures up/down - need to think about and have answer for ERR
  • Is the power supply reversible? - need to include in ERR


  • Working on full prototype for tests of movable boards for PMT access
  • Deciding on cable lengths and work distribution
  • clarifying quotes and prices, e.g. labor and part per cable
  • Testing fibers

HV DIVIDERS (Vladimir, Alex S., Fernando)

  • Discussion of recent ComCal/NPS prototype results
  • Best solutions for NPS HV dividers seems to either bypass amplifier or to reduce the amplification - both are practically easy to do
  • slight preference to bypass the amplifier - 100uA is average anode current, peak anode current is 100mA/pulse, so have some dynamic range available --> bypass should be ok
  • practically bypass means directly connect signal to output
  • Planned tests with sample dividers with bypassed amplifier and reduced amplification
  • idea: compare gains (e.g. 1=bypass, 2=...) and rates and choose best option experimentally
  • test with beam in Hall D
  • test bench either after or instead of beam tests - expect to put all together in lab in 2-3 weeks
  • Planned test with 3x3 prototype and Crytur crystals
  • idea: test dependence of saturation on crystals (SICCAS vs. Crytur)
  • space and opportunity in Hall D
  • A few notes on PMT, divider, and fADC
  • R4125 is rated for 1500 V operating voltage, maximum anode current is 100 uA
  • fADC dynamic range for earlier 3x3 prototype tests was 1 V
  • ComCal/NPS prototype has different crystals than the 3x3 prototype
  • For original HV divider design assumed 8 pe/MeV light output

CRYSTALS (Vladimir, Tanja)

  • Received 160 replacement crystals from SICCAS - inspection ongoing
  • In contact with Crytur about procurement of additional crystals


  • Created Wiki page NPS ERR for people to start filling in