Collimator Damage

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Collimator Damage
Adriana Bungau The
University of Manchester
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What we do

• Collaboration between RAL, Manchester University
  and Daresbury Laboratory
• Goal
• determine optimal material and geometry for ILC
  collimators in order to
• maximize the collimation efficiency and minimize
  the wakefield effects
• Investigate the heating effects caused by various
  patterns of energy deposit using ANSYS (G.
  Ellwood -RAL, G.Kourevlev Manchester Univ.)
• Simulate the energy deposition in a spoiler of
  specified geometry due to a beam being
  mis-steered using FLUKA ( L. Fernandez
  Daresbury) and Geant4 (A.Bungau Manchester
  Univ. )
• Cross-check these studies with Lewis Kellers
  results on spoiler survival (SLAC)
• Study a range of geometry/material combinations
  that allows low wakefields and verify these
  experimentally

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Update report on material damage
Geant4/Fluka results Model of an isometric view
of the collimator (geometry, material)
Simulations of the energy deposition along z at
several depths distributions in various 2D
projections of the energy density Calculations of
the corresponding increase in temperature Kinetic
energy of the outgoing particles Results passed
on for ANSYS studies
ANSYS results
Studies of steady state heating effects (3d
isothermal contours-consistent) Comparison
between ANSYS simulations and analytic
calculations (good agreement) ANSYS used to
predict stress induced in a 3d solid (apply to
the collimator geometry)
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Collimator geometry (modelled with Geant4)
Dimensions x 38 mm
y 17 mm z 21.4 mm
Z 122.64 mm ? 324 mrad
Material Ti alloy (Ti-6Al-4V)
? 4.42 g/cm3 melting
temperature 1649 C c 560 J/kg C
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Beam profile

• Ellipsoid with ?x 111 ?m ?y 9 ?m
• Simulated particles 104 electrons/bunch
• E 250 GeV
• Energy cutoff
• e- kinetic energy cutoff 2.0
  MeV -gt2.9 mm range in Ti alloy
• e kinetic energy cutoff 2.0
  MeV -gt3.1 mm range in Ti alloy
• ? energy cutoff
  100.4 KeV -gt6.18 cm attenuation length
• 
  in Ti alloy

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Energy deposition in Ti alloy at 2 mm depth

• the beam is sent through the collimator along z
  at 2 mm depth
• Edep max in the second wedge at 14 mm
• the mesh size should be smaller than the beam
  size for realistic results
• at z14 mm max energy deposition is 3 GeV/2e-3
  mm3 -gt ?T 215 K

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Energy deposition at 10 mm depth in Ti alloy

• the beam goes through the collimator at 10 mm
  depth
• max Edep at 10 mm depth is at 35 mm along
  z (second wedge)
• at z35 mm, the max Edep is 6.66 GeV/2e-3 mm3 -gt
  ?T 430 K

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e.m. shower for one 250 GeV e- at 2 mm depth
e.m. shower for one 250 GeV e- at 10 mm depth
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Energy deposition at 16 mm depth in Ti alloy
spoiler

• the beam is sent through the collimator at 16 mm
  depth
• max Edep is at 55 mm
• max Edep 8 GeV/2e-3 mm3 -gt ?T 517 K

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e.m. shower for one 250 GeV e- at 16 mm depth
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Summary
Depth (mm) ?T for Ti ?T for Ti alloy
2 226 215
10 452 430
16 581 517
e- multiplicity 4 e multiplicity 3
L.Keller e multiplicity 4 e-
multiplicity 4
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Direct Hits on Spoilers
Maximum ?T/2x1010 bunch at Hit Location, C/bunch
L. Keller
Geant 4 simulation
Steering Condition Beam Size (µm) sx sy Max T 500 GeV CM Max T 1 TeV CM Max T 500 GeV CM Max T 1 TeV CM
0.6 rl Ti spoiler 28 6 1020 2887 1380 2770
0.6 rl Ti spoiler 111 9 302 761 290 560
1.0 rl Ti Spoiler 104 15 295 - 260 720
with a spread in energy ?E/E 0.06
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Conclusion
The instantaneous temperature rise at various
depths were below the melting temperature of the
Ti alloy -gtcollimators are not in danger in case
of a direct hit from one bunch Little energy
deposition in the material a large fraction of
the energy appears as photons emerging from the
collimators
Future plans
Compare the Geant4 results with Fluka
predictions Carry out a survey of materials (so
far only Ti and Ti-6Al-4V were used) Pass on the
energy deposits files for ANSYS studies ( RAL)