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Collimator Damage. Adriana Bungau The University of Manchester. Cockcroft Institute “All Hands Meeting” , January 2006. What we do:. Collaboration between RAL, Manchester University and Daresbury Laboratory Goal:

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Collimator Damage

Adriana Bungau

The University of Manchester

Cockcroft Institute “All Hands Meeting” , January 2006


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 Keller’s results on spoiler survival (SLAC)
  • Study a range of geometry/material combinations that allows low wakefields and verify these experimentally

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)

Comparation between ANSYS simulations and analytic calculations (good agreement)

ANSYS used to predict stress induced in a 3d solid (apply to the collimator geometry)





Collimator geometry (modelled with Geant4)


x = 38 mm

y = 17 mm

z = 21.4 mm

Z = 122.64 mm

θ = 324 mrad


Ti alloy (Ti-6Al-4V)

 = 4.42 g/cm3

melting temperature 1649 C°

c = 560 J/kg C°

beam profile
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 ->2.9 mm range in Ti alloy

e+ kinetic energy cutoff = 2.0 MeV ->3.1 mm range in Ti alloy

 energy cutoff =100.4 KeV ->6.18 cm attenuation length

in Ti alloy


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 z≈14 mm: max energy deposition is 3 GeV/2e-3 mm3 -> ∆T = 215 K

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 z≈35 mm, the max Edep is 6.66 GeV/2e-3 mm3 -> ∆T = 430 K

e.m. shower for one 250 GeV e- at 2 mm depth

e.m. shower for one 250 GeV e- at 10 mm depth


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 -> ∆T = 517 K


e- : multiplicity ≈ 4

e+: multiplicity ≈ 3


e+ : multiplicity ≈ 4

e- : multiplicity ≈ 4


Direct Hits on Spoilers

Maximum ∆T/2x1010 bunch at Hit Location, °C/bunch

Geant 4 simulation

L. Keller

*with a spread in energy ∆E/E = 0.06 %


The instantaneous temperature rise at various depths were below the melting temperature of the Ti alloy ->collimators 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)