Beam Delivery System collimators for the International Linear Collider

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Beam Delivery System collimators for the
International Linear Collider
J. L. Fernandez-Hernando STFC/ASTeC Daresbury Lab
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The ILC collimation system is composed of a
spoiler and an absorber. The collimator mission
is to clean the beam halo from e- or e off orbit
which could damage the equipment, but mainly to
clean the beam from photons generated during the
bending of the beam towards the Interaction
Point. These photons, if not removed, would
generate a noise background that would not allow
the detectors to work properly.
Task 5.3 Programme

• Highlights
• T480 data analysis/test beam
• Mafia/GdfidL simulations of T480 Collimators
• Beam damage simulations
• Fluka/Geant4
• Ansys

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Specification of requirements for LC spoilers -
Complete Eurotev Report 2006-015 and ILC RDR

• Long, shallow tapers (20mrad?), reduce short
  range transverse wakes
• High conductivity surface coatings
• Require spoilers survive at least 2 (1) bunches
  at 250 (500) GeV
• Design external geometry for optimal wakefield
  performance, reduce longitudinal extent of
  spoiler if possible
• Design internal structure using materials found
  most appropriate from survey of material
  properties.

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Report on spoiler damage estimates and comparison
with test beam data Partially achieved
Simulations carried out with Fluka, Geant4 (EGS
with Keller), see EPAC06 and EUROTeV Reports
2006-015 and 2006-021 FEA studies in
ANSYS3D/Fluka of transient stress waves, see
PAC07, EPAC06 Beam test proposal (2007)
approved for ATF and in preparation, see PAC07
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UK a leading contributor on critical collimator
issues wakefields, survivability. Strong
collaboration with SLAC and EUROTeV groups.
Made most detailed Simulations of spoiler jaw
damage to date.
G. Ellwood, J. Greenhalt
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Material damage test beam at ATF

• The purpose of the first test run at ATF is to
• Make simple measurements of the size of the
  damage region after individual beam impacts on
  the collimator test piece. This will permit a
  direct validation of FLUKA/ANSYS simulations of
  properties of the materials under test.
• Allow us to commission the proposed test system
  of vacuum vessel, multi-axis mover, beam position
  and size monitoring.
• Validate the mode of operation required for ATF
  in these tests.
• Ensure that the radiation protection requirements
  can be satisfied before proceeding with a second
  phase proposal.
• Assuming a successful first phase test,
  the test would be to measure the shock waves
  within the sample by studying the surface motion
  with a laser-based system, such as VISAR (or
  LDV), for single bunch and multiple bunches at
  approximate ILC bunch spacing.

sample holder
Bunch sx?sy (mm2), material Estimated damage region, x Estimated damage region, y Estimated damage region, z
1.9?0.5, Ti alloy 11 (14) mm 4 (5.6) mm 5 (8) mm
20?2, Ti alloy 45 (90) mm 5 (9) mm 2 (7) mm
20?2, Cu 65 (100) mm 7 (10) mm 3 (7) mm
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Report on wakefield beam tests - Achieved
Analysis of 2007 and 2006 T480 data for
publication in progress, including BPM
uncertainties/calibrations, bunch length
monitoring Original plan was to use SCP and
established instrumentation See PAC07, EPAC06,
EUROTeV Reports 2007-044, 2006-059, 2006-060

• 3D simulation of wakefields for various candidate
  spoiler prototypes - Achieved
• For 16 ESA collimators, most recently using
  non-conformal moving mesh GdfidL
• Additional mesh dependence studies ongoing, esp.
  for smallest sz
• PAC07, EPAC06, EUROTeV-Reports 2006-055
  (GdfidL) and 2006-103 (MAFIA)

Report on applicability of bench tests for ILC
collimator design - Achieved Initial report
EPAC06/EUROTeV Report 2006-056 2007 work ?
method not useful for quantitative tests (for
collimator jaws), final report in preparation
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Variation of GdfidL predictions of transverse
kick as a function of mesh resolution, for T480
collimator 3 (depth 1m), for sz 1.0mm at an
offset from electrical centre of 0.4mm.
GdfidL calculated kick for collimator 3
(depth 1m) for z 1.0mm KF 4.09 0.80V/pC/mm
J. Smith, C. Beard
A. Bungau, R. Barlow
Merlin studies emittance dilution due to
wakefield
Looked at emittance dilution due to higher order
mode wakefields -gt get an increase in the beam
size and consequently a decrease in luminosity
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Beam Parameters at SLAC ESA and ILC
Parameter SLAC ESA ILC-500
Repetition Rate 10 Hz 5 Hz
Energy 28.5 GeV 250 GeV
Bunch Charge 2.0 x 1010 2.0 x 1010
Bunch Length 300 mm 300 mm
Energy Spread 0.2 0.1
Bunches per train 1 (2) 2820
Microbunch spacing - (20-400ns) 337 ns
possible, using undamped beam
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Designed, modelled and tested collimators at SLAC
ESA facility
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V/pC/mm
V/pC/mm
1.2 0.3 (1.7 0.4)
1.7 0.3 (2.4 0.9)
1.2 0.3 (3.1 0.8)
2.2 0.3 (2.7 0.5)
3.7 0.3 (7.1 0.9)
0.9 0.3 (2.4 1.1)
0.5 0.4 (0.8)
4.9 0.2 (6.8)
V/pC/mm
V/pC/mm
V/pC/mm
0.7 0.2 (2.4 1.1)
1.2 0.3 (1.2 0.3)
1.1 0.2
2.3 0.3
2.5 0.3
1.1 0.3
1.5 0.2
1.2 0.3
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a 324 mrad r 2 mm
Col. 1
a 166 r 1.4 mm
(r ½ gap)
Col. 6
Col. 3
a 324 mrad r 1.4 mm
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Optimal spoiler design to achieve requirements
(geometry, material, but not engineering)
Partially achieved We have designs for material
and geometry which can satisfy beam damage
requirements Outcome of ongoing wakefield
optimisation likely to require further iteration
on candidate designs
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Lead into LC-ABD2 (WP4)
LC-ABD1 result

• 3D wakefield simulations for collimator
  prototypes
• Simulations validated by our test beam data are
  used to predict transverse wakes for more
  realistic prototype collimator designs.
• Wakefield test results for collimator jaws
• This is an ongoing programme to ensure modelling
  capability is reliable in regimes where
  calculations are known to be inadequate..
• Data-validated material response simulations for
  BDS components
• Essential to test collimator materials/components
  under conditions which emulate instantaneous ILC
  bunch heating.
• Prototype damage detection system for collimators
• An unsolved problem ranked very highly, will
  become a major part of new project.  Closely
  linked with material response test above.
• Full engineering designs for BDS absorbers,
  protection collimators, masks
• Design of these various components, 20 different
  types
• Prototypes of critical subsystems of adjustable
  jaw collimators
• Deliver demonstration hardware of critical
  components.

GdfidL simulations
T480 beam tests
Damage simulation ATF test
Expertise in STFC