Meeting 11 May 2017

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HIPS with FLUKA (Jixie)

HCPS report (Gabriel)

Hall C WACS with HIPS (David H.)


  • Discussion about recent FLUKA simulation results
  • Simulation uses 2.5 uA beam current, 11.5 GeV electron beam energy, pivot at distance 60 cm to beam line
  • Discussion about the dump design, which is similar to JLab tune-up dump and includes a pair of quadrupoles to refocus the beam. Results are consistent with expectation
  • Discussion about recent GEANT4 simulation results
  • explored two-magnet options, different positions of radiator and shielding thicknesses. Diffusing is done by magnet and radiator. Main parameter that spreads beam is a 1mm raster vertical
  • simulation shows an integrated power deposition of 27 kW (10% radiator, 11 GeV beam) into ~40cm magnet. Power deposition is z-dependent.
  • Using power deposition results, a heat-flow/cooling calculation was performed. The results suggest a heat rise in the most central area of the power absorber of ~600 degC. The magnet iron, the pole is at about 140degC. The cooling water flow and change in water temperature of 20degC are manageable. Overall, heat removal appears doable and heat deposition can be managed in the magnet.
  • Discussion about WACS measurements (ALL and ALT) with NPS and SBS or BigBite
  • Trade-off between momentum resolution vs. science goals and distance/angle vs. solid angle are important considerations
  • As an example, in the case of BB and assuming 1.2 Tm and GEM chambers with 100 micron resolution and assuming one determines the track over a length of 40 cm, one would obtain 0.4% dp/p at 4 GeV and 0.6% resolution at 6 GeV. The distance/minimum angle relations for BB are: at 1.5 meter, minimum angle=30 degrees, at 2.25 meter, minimum angle~20 degrees, and at 3 meter, minimum angle~15 degrees
  • Simulations suggest that NPS+SBS is the best configuration, but NPS+BigBite would also be feasible
  • Simulations suggest that s scans at 90 deg and 70 deg at 8.8 GeV are possible, measurement at 120 deg and 8.8 GeV is difficult due to pion dilution. Measurement of ALT at 90deg and at 8.8 GeV might be difficult due to the target coil positions. Rotation as described in Jixie/Donal's earlier talks might help
  • Discussion about photon flux to use in the proposal
  • Assuming 2.5 uA at 11 GeV and a 10% radiator, the equivalent photon flux is equivalent 1.5x10^12 photons/s. For lower energy 8.8 GeV and taking into account the limitation of the polarized target, the result is similar.


  • Prepare WACS proposal for PAC. Discussion of draft during 18 May NPS meeting. This draft will focus on the science and include language on the photon source like in the KLong proposal
  • Check with Bob if it is ok to have a dedicated presentation on HIPS at the PAC
  • Simulations for 110 deg CM at 11 GeV, for 90 deg at 11 GeV
  • Prepare a write-up of the HIPS design