Summary 2/3/20

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  • No significant changes in design since ERR
  • Action item: steps towards assembly and commissioning:
  • Check and document interference for all kinematics again including those for the DVCS experiment from Hall A
  • dDocument time estimates for configuration changes, e.g. moving the NPS from one side to the other, rotating the magnet
  • Identify and document items that can be done in advance of installation, e.g. welding the plates on the SHMS (requires finishing the drawings)

MAGNET (Charles)

  • Magnet was energized to 25% (250A) of the max current
  • Simulations have shown that for DVCS/pi0 it would be sufficient to energize the magnet to 2/3 of the max current - this allows to relax the requirements for a full current test. However, note that for RCS need the full field to deflect electrons
  • Running at lower current also has an impact on the HMS optics design
  • Action Items:
  • Check measurements vs 3D calculations
  • Make table of fringe fields vs. current and check simulations for physics impact
  • Decide on what fraction of maximum current to run the magnet for first run group – will also impact HMS optics


  • Final design
  • support structure has been built
  • new shielding design was adapted
  • no change in cooling strategy
  • PMT assembly concept ready (see a prototype here)
  • attachment PMT-crystal through optical grease - some rotation is possible, note that it is important to check alignment from the front during installation
  • HV and LEMO connectors on top of the box as before
  • Parts manufacturing
  • Large fraction has been received or is expected to arrive in mid-February; some delay in parts related to new shielding strategy, but still expect delivery of frame by August 2020
  • Optical fibers: 28mm diameter quartz fiber
  • Cut and polishing will be done in Orsay
  • Carbon holders
  • radiation hardness was tested in Hall C near the scattering chamber (see log entries 3687981 and 3669952)- the samples are radiation hard
  • can support the crystals - note that the crystals, in particular the bottom row, also support themselves
  • Infrastructure
  • Temperature sensors (63 front + 63 side), PT 100 Ohm
  • goal is to measure crystal temperature, no feedback, no interlock, but should be in alarm handler
  • radiation concerns when operating in the hall
  • Chiller - radiation concerns
  • heat exchanger air flow - optimized, not much overall since many cables
  • Action Items
  • Finalize quotes, e.g. for quartz and mu metal
  • Implement the new magnetic shielding design – includes ordering all parts (honeycomb, mu metal, iron shielding, aluminum plates, supports), assembly, and testing
  • Send temperature control information to Brad to figure out readout (include in alarm handler, but no feedback, no interlock)
  • Determine needs for operating chiller in Hall C, e.g. shielding, order spares
  • Send crystal wrapping material for pre-shaping to JLab
  • Check uniformity of fiber transmittance after cut/polish
  • Test for LED system cross talk for adjacent PMTs
  • Check if Kapton tape should be used around the PMT to insulate it from the mu metal cylinder
  • Determine if there is a way to monitor thickness increase of crystals when adding tape


  • Built and assembled
  • Discussion about mounting holes to install the box on the JLab fixture (once installed, all lifting will be done from the JLab fixture)
  • Action items:
  • re-calculate center of gravity
  • decide on how to attach NPS frame to JLab fixture - bolts, weld?


  • Interface bases, HV-LED - Fischer connectors
  • HV cables (Samtec)
  • tested wires in each cable to detect short circuits, bad connections
  • tested HV on each cable
  • Anode cables - waiting for LEMO connector, SMA side done
  • Systec + LPC
  • LED cables tested in similar way as HV cables
  • developed special tool for these tests

CRYSTALS (Vladimir)

  • Have been receiving crystals from CRYTUR and characterizing - 100% acceptance
  • September 2020: expect to have ~630 crystals
  • April 2021: expect to have 900 CRYTUR crystals
  • rate of production is 30-40 crystals/month with PANDA or other production ongoing - most recently 30 pieces/month
  • fastest production rate was 250 crystals/3 months
  • slowest production rate is anticipated to be 15-20 crystals/month, e.g. with large PANDA order in parallel
  • Have 460 SICCAS crystals on site
  • 700 PMTs are on site
  • Action items:
  • Send 10 CRYTUR crystals and full-size glass to Orsay for irradiation tests
  • Decide on final stacking configuration – current nominal configuration is two outer layers SICCAS, rest CRYTUR
  • Check with CRYTUR if possible to expedite crystal production of outstanding 250 crystals with an early FY21 procurement

HV DIVIDERS (Fernando, Julie)

  • All dividers are assembled at OU and awaiting decision on specifics of the modification
  • Nonlinearity of bypassed amplifier is 1-2% depending on pre-amp gain (0.5, 1, 2 V to match fADC)
  • gain 3: nonlinearity increases to ~4% (2 V) and ~11% (0.5V)
  • Reasonably good linearity at gain 3 - still analyzing anode current
  • Action items:
  • Check on the method to measure anode current, e.g. in Hall C
  • Further analyze existing anode current data from Hall D
  • Decide on final HV divider gain
  • Determine need for additional resources and/or funding beyond what was planned


Additional Notes by Charles Hyde

•Summarize full to-do list in hall, and estimated time to completion
•Estimate time for configuration changes during beam running
•Document interferences between NPS, BeamLine, HMS
•Kinematic configurations are dynamic (addition of beam time from E12-06-114, uncertain beam energy in 2022)
• How is the Calorimeter, Cabling, etc assembled
•Do we run Sweep Magnet at full power or ~30%?
•DVCS, pi0 maybe OK at 30% power
•Future RCS will require full power (with NPS on outer side of SHMS)
• Do we mix-and-match Crytur and SICCAS crystals?
•Order ~200 more crystals from Crytur and wait ~1year for full delivery?