Collimation%20in%20the%20ILC%20BDS

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Collimation in the ILC BDS

• Carl Beard
• ASTeC Daresbury Laboratory

• People
• Requirement
• Recent Successes
• Future Aims

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People

• Task Leader Nigel Watson (Bham)
• Damage Studies
• L. Fernandez (ASTeC), A.Bungau (Manc) R. Barlow
  (Manc) G. Elwood (RAL), J. Greenhaulgh (RAL).
• Wakefield Simulation and TDR
• C. Beard (ASTeC), J. Smith (Lanc), R. Jones
  (Manc), R.Carter (Lanc), S Jamison (ASTeC), P
  Corlett (ASTeC)
• I. Zagorodnov (DESY),
• M.Kärkkäinen, W.Müller, T.Weiland (TEMF)
• Beam Tests (T-480 Experiment)
• Frank Jacksonplus most of the above
• SLAC ESA Team Steven Malloy, Mike Woods

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Need for Collimation

• Reduce the background levels in the detector, by
  removing halo particles built up over the long
  linac.
• Machine Protection, in the event of a beam
  miss-steer.

Collimators are introduced, as a result of this
the change in impedance has detrimental effects
to the beam quality.
The collimators have to be robust to withstand
the full impact of several ILC Bunches.
Design / optimisation of spoiler jaws (geometry
and materials) for wakefield and beam damage
performance
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Objectives

• Development of Advanced EM modelling methods
• Benchmarking of wakefield calculations against
  experiments
• SLAC ESA beam test / data analysis
• RF bench tests (training/code comparisons)
• Tracking simulations with best models of
  wakefields
• Simulations of beam damage to spoilers
• Material studies using beam test

Submitted 7 papers at EPAC, several EUROTeV
reports/memos
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Collimator Parameter and Beam Parameters
Beam Energy, GeV 250, 500
Material Cu, Ti, C
Penetration (mm) 2 to 10
e- Particles/bunch 2 x 1010
Copper Fracture temperature 200 C (473
K) Melting temperature 1085 C (1357.77 K)
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Collimator Proposals
250, 500 GeV e-
2 mm, 10mm
Ti/C
0.6 Xo of Ti alloy leading taper (gold), graphite
(blue), 1 mm thick layer of Ti alloy
0.3 Xo of Ti alloy each side, central graphite
part (blue).
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CuGraphite spoiler
Carbon zones
Cu zones
250 GeV sx 111 µm, sy 9 µm
500 GeV sx 79.5 µm, sy 6.36 µm
?T K 250 GeV e- ?T K 500 GeV e-
2 mm from top 465 K 860 K
10 mm from top 440 K 870 K
Difference -5 1
Fracture temp.
Melting temp.
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Ti / Graphite Spoiler
Temperature data in the left only valid the
Ti-alloy material. Top increase of temp. in the
graphite 400 K. Dash box graphite region.
540 K
405 K
400 K
270 K
?Tmax 575 K per a bunch of 2E10 e- at 500
GeV sx 79.5 µm, sy 6.36 µm
2 mm deep from top Ti alloy and graphite spoiler
L.Fernandez, ASTeC
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Fluka Benchmark
Fluka Prediction of beam Damage (Evaporated
material not considered
Measurements of Beam damage crater in cooper on
the FFTB.
Measurements courtesy of SLAC, Marc Ross et al.
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Damage Studies

• Beam tests are being planned to benchmark the
  Fluka/Geant Simulations
• No electron beam is available with sufficient
  intensity
• Or probability to hit the same point due to beam
  jitter.
• Dynamic Simulations in ANSYS are being studied in
  support of the FLUKA/GEANT Simulations

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Wakefield Analysis
Instant solution for only simple geometry
Analytical Formula
Simulation
Bench Tests (TDR)
Good indicator poor resolution
Fast Results Limited by Resolution/ confidence
Tests with Beam
Real life measurements, slow turnaround time for
measurements
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Simulation and Wire tests
TDR and TDT are being used to measure the
Impedance of a vessel and its loss factor
Current TDR and TDT measurements are limited to
10 ps Pulse lengths.
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Achieving a 1 ps Pulse (In development)
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MAFIA Simulations
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Limitations / Advances
Limiting the simulations to short structures or
only sufficient resolution for gtgt300 um bunch
length.
MAFIA/HFSS
A new technique is being applied to allow full
structures to be simulated with substantially
higher resolution
GDFIDL / ECHO 2 3D
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Beam Tests in ESA

• Simple Shapes to allow benchmarking with
  Calculations/Code
• Geometric Wakefields
• Resistive Wall Wakefields
• Surface Roughness

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T-480 Experiment
Vertical mover

• Wakefields measured in running machines move
  beam towards fixed collimators
• Problem
• Beam movement ? oscillations
• Hard to separate wakefield effect
• Solution
• Beam fixed, move collimators around beam
• Measure deflection from wakefields vs.
  beam-collimator separation
• Many ideas for collimator design to test

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T-480 Experiment
Vertical mover

• Wakefields measured in running machines move
  beam towards fixed collimators
• Problem
• Beam movement ? oscillations
• Hard to separate wakefield effect
• Solution
• Beam fixed, move collimators around beam
• Measure deflection from wakefields vs.
  beam-collimator separation
• Many ideas for collimator design to test

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Wakefield Box
ESA sz 300mm ILC nominal sy 100mm
(Frank/Deepa design)
Ebeam28.5GeV
Magnet mover, y range ?1.4mm, precision 1mm
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Initial Comparison of Results
Analytical 0.562 V/pC/mm MAFIA 0.408
V/pC/mm Beam Test 0.556 V/pC/mm
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Future Work

• Continue study into beam damage/materials
• In the process of designing a 4th beam test
• Collimators designed and built in EU, to be
  installed at SLAC ESA.
• 3rd Physics run Mar/April 2007
• Application of the Moving Mesh Technique
• TDR Measurements with Optically generated 1 ps
  Pulse.
• Combine information on geometry, material,
  construction, to find acceptable baseline design
  regarding all of
• Wakefield optimisation
• Collimation efficiency
• Damage mitigation