RHIC Experiment Shielding at RHIC Retreat

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RHIC Experiment Shielding at RHIC Retreat

• Status
• Some Fermilab experience (for comparison)
• Some of our studies/results
• Minutes and presentations of the RHIC Experiment
  Shielding Working Group are kept at
• http//www.c-ad.bnl.gov/kinyip/Radiation/RHIC_Shie
  lding.html

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cylindrical tunnel
cylindrical tunnel
Shielding is much harder in the forward direction
than sideway
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• Sources of the background PHENIX, STAR and
  BRAHMS all have evidence to believe that their
  backgrounds are due to beam scraping at the
  magnet triplets (Q2 or Q3), rather than beam
  gas. 
• PHENIX has not had background problem until the
  beams are steered into collision. 
• For BRAHMS, changing the  ? from 2 to 3 during
  the dAu run decreased their backgound by a
  factor of 10 to 20. 
• PHOBOS also did not have background problem when
  the ? was set to 3 and their background seems to
  be strongly correlated to the beam gas pressure
  increase.
• PHENIX and PHOBOS (at least) have seen
  backgrounds considerably more on the outside of
  the ring during the deuteron-gold runs.

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Status

• Have good ideas as to where is the best place to
  put the shielding in front of PHENIX (the most
  desirable/doable expt.)
• ie., closer to the beampipe and closer to PHENIX
  MuID
• We have checked (within MCNPX)
• energy cuts change the absolute fluxes/energy
  deposition but doesnt change the ratios
• different physics models dont have big impact
• source at Q2 source at Q3
• turning on ?o,??, ? (in addition to
  neutrons/protons) to check that there is no major
  difference
• Charlie Pearson and I are working together to
  come up with a practical plan

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A

• FERMILAB-FN-629
• What is the effect of a
• reduced 1.8 m conrete wall
• (in the narrower tunnel)
• against the Tevatron
• halo related background.
• For high luminosity at the
• outermost layer, it is 10.
• A is the innermost layer and
• C the outermost layer of the
• D? muon PDT).

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3 layer sandwich shielding
? concrete wall filled with sandbags and
polybeads
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Nicholai Mokhovs suggestion for CDF
(FERMILAB-TM-2045)
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Mesh Tallies in MCNPX (2.5.c) ? without shielding
Vertical ?? (cm)
Horizontal ?? (cm)
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Cross-sectional view
The rest of the blocks are shields.
100/65 cm
platform
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DX closer to the beampipe
coffin shielding with steel-polyethylene-lead
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Near PHENIX MuID
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Source from Q3
Gap 4 (closer to magnets)
Gap 3
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Energy spectrum --- the energies of the
particles which contribute to the fluxes at the
volume of consideration
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Reduction factors on the fluxes due to different
kind of shieldings
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Looking forward

• Experiments may spend more time in locating the
  sources of backgrounds (eg. CDF CAL? vacuum
  problem roman pot 50 m away http//ncdf67.fnal.
  gov/tesarek/halo/joint_physics_020503/index.html)
  .
• Better knowledge about the source ? better
  shielding
• Detector and accelerator groups should work
  together do the detective works
• Backgrounds from the IP may be an issue, too
• In the future, we may use MARS to do more
  thorough simulation (eg. including the use of
  magnetic field and the asymmetric magnet
  positions)

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• Simulation aspects
• Tool MCNPX (newest version 2.5.c)
• Sources protons (100 GeV) scraping the inner
  radii of Q2/Q3 magnets
• Only turned on protons/neutrons at the moment
• Major problem (!) MCNPX does NOT have magnetic
  field.
• Plan to learn/use MARS for a more
  complete/realistic simulation but this probably
  will take some time