Simulation Meeting July 9 2020 10AM ET

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Simulation Task List Updated 2019


  1. New source of radiation load on the upstream coils - Ciprian slides
  2. Progress on the Priority list
    1. Light guide light generation - Cameron slides
  3. Beam Generator update (vertex cut and track id) - Garrett Leverick (UoM) slides
  4. Geometry optimizations - Chandan, Sakib
  5. AOB


Rakitha, Garrett Leverick, David Kashy, Juliette Mammei, Krishna Kumar, Seehrar, David Flay, Chandan Ghosh, Ciprian Gal, Hanjie Liu, Sakib, nazanin roshanshah, Cameron Clarke, Dustin McNulty, Jim fast, Sandesh Gopinath, Michael Gericke, Kent Paschke


  • Upstream magnet hot-spots, Ciprian:
    • positrons from the acceptance channel slam into the coils is the dominant source. The track trajectory hit them on the side of the coil surface. e+ sources are the target (high energy), col-1 and 2 (low energy)
    • the energy deposit in G4 plot showing rad length needs better understanding. Do a back of the envelope calculation and first-principle calculation to check these results.
    • The plan is to shield the coils on the side using 2mm tungsten plates. The hot spot rad load goes down from 320 Gy to 37 Gy
    • is there an alternative to epoxy impregnated copper, Jim F.
    • dE/dx in W-Cu is about 3 MeV/mm for beta~1 particles so I think you are seeing the full stopping of the low energy positrons in 2 mm. As they slow the beta will drop and the dE/dx will increase so seeing this up to ~10 MeV for 2 mm makes sense. Jim F.
    • due to the grazing angles the 2mm of W is effectively much longer Ciprian
    • yes - so you will deposit up to a few 10's of MeV just by dE/dx energy loss, then the positron will annihilate on an electron. The gammas may escape so another 1 MeV goes into those photons. Jim F.
    • It is interesting that you are degrading the 100 MeV e+ so effectively. This must be that they are making EM showers and the secondaries are getting absorbed pretty efficiently. Jim F.
    • make sure to get CW90 or CW95 with no iron or any other impurities to prevent magnetic issues
  • Light guide light generation, Cameron:
    • G4 optical physics update where Cameron is using Remoll to reproduce the Qsim
    • compared the NIM paper results with Qsim running again so we know Qsim is reproducible.
    • The reflectivity plots shows differences between Remoll and Qsim. Extra bounces allowed in remoll could explain this. Cameron will look into this further.
    • Will generate lookup table to get PE count for angle vs position that can be used in the main simulation
    • Cameron will make these into a new branch in remoll. The scripts will be in the Analysis directory.
  • Beam Generator update (vertex cut and track id) - Garrett Leverick
    • hit.mtrid==0 should apply to all primaries, including both mollers but track id is not associated with Beam generator since particle generator is associated only with event generators.
    • the "second" moller electron will have mtrid == 1
    • so in principle you can have trid == 1 (to get half of your mollers) and then select the target pid for the second moller: Cip.
    • for the rest of the processes (like ep elastic) trid == 1 should be sufficient .. i think
    • correct. for the beam, it's safer to use the vertex cut to get the rate relatively right at least for the default magnetic field scale. : Sakib
  • Geometry update: Sakib, what to merge to develop
    • epoxy update to coil
    • merged col
    • two bounce shield
    • changes to Col-1
    • we will discuss this next week. Ciprian prefers these to be on the development branch.

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