Meeting 19 December 2017

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CPS Radiation Study using FLUKA (Jixie)

[ CPS Radiation Study (Parker)]

CPS Studies Update (Bogdan)

Rotating Target Raster (Dustin)


'Homework for next year: make a list of what needs to be done for removing conditional approval (Thia/Tanja?) and circulate for discussion'

Discussion of Jixie's update on CPS radiation studies using FLUKA

  • Two configurations were investigated: 1) pure electron beam, 2) pure photon beam created with 2.7uA electron beam incident on 10% radiator and a) with UVa target and NO CPS and b) with NPS and NO target
  • the target in the simulation now has real thickness of the chamber and the real geometry of the coils (based on Hall B design)
  • Total accumulated heat load is ~0.3 W for both cases - a little larger for pure photon case
  • Activation at the target chamber boundary 1 hour after beam off after 1000 hours of beam is for: (1) < 1mrem/hr and (2) ~4 mrem/hr - both are acceptable
  • Analysis of neutron flux at various boundaries shows that 10cm thick 30% borated plastic reduces the neutron flux significantly
  • Heat power in CPS (Cu core) is 584 W/cm^3 - important for cooling design considerations
  • Accumulated damage (1 MeV neutron equivalent damage) is less than 10^13 (dose where electronics get damaged) at: i) 20cm away from the beam line in the pivot area, ii) outside at dipole - all looks good
  • Activation profile after 1000 hours of beam comparison:
  • Pure electron beam with target: all safe
  • Pure photon beam with target and no CPS: high background radiation, need more shielding backward from CPS
  • Pure photon beam with CPS and no target:contribution from CPS in target area is small and comparable to that from electron beam (1) scenario
  • CONCLUSION: CPS doesn't create much activation in target area - what comes out is from the target itself
  • Prompt dose rate comparison for pure photon beam with 1) Target and no CPS and 2) CPS and no target shows that CPS contributes very little in target area
  • Overall Conclusions and next steps:
  • Shielding design looks good overall - radiation contribution from CPS is at most the same as from the target
  • Next: put target in with CPS and repeat all studies
  • Longer term: investigate backward region shielding
  • How much is needed? - depends to some extent on experiments.
  • NPS requirements - related to crystal radiation hardness. Requirement specifies that ideally want to run experiment without annealing (~1000 hrs). Could check that with simulation creating conditions for DVCS (no target/radiator)

Discussion about Parker's model

  • Easy to use interface
  • Good way to cross check and to run quick tests for Hall D

Discussion about CPS update (Bogdan)

  • Top of CPS seems most important for soft neutron shielding - might impact design
  • Discussion about additional physics with a CPS and different target configurations

Discussion about rotating target raster (Dustin)

  • A few comments/suggestions are made to optimize slides for NPS/CPS meeting in January:
  • NMR - explain how to practically do that
  • more on rotate vs. non-rotate field scenarios, include a slide with target and rotation to remind people what trying to do
  • Add field gradient profile - this question came up earlier
  • Radiation considerations - this is good
  • Connection to additional physics - this is good

NEXT MEETING: tentative 9 January 2018, as needed.