Beam Delivery System collimators for the International Linear Collider
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Transcript of Beam Delivery System collimators for the International Linear Collider
Beam Delivery System collimators for the
International Linear Collider
Beam Delivery System collimators for the
International Linear Collider
J. L. Fernandez-Hernando
STFC/ASTeC Daresbury Lab
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.
Highlights• T480 data analysis/test beam• Mafia/GdfidL simulations of T480 Collimators• Beam damage simulations
– Fluka/Geant4– Ansys
Task 5.3 Programme
• 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.
0.6
Specification of requirements for LC spoilers - CompleteEurotev Report 2006-015 and ILC RDR
Report on spoiler damage estimates and comparison with test beam data – Partially achieved Simulations carried out with Fluka, Geant4 (+EGS with Keller), see EPAC’06 and
EUROTeV Reports 2006-015 and 2006-021FEA studies in ANSYS3D/Fluka of transient stress waves, see PAC’07, EPAC’06Beam test proposal (2007) approved for ATF and in preparation, see PAC’07
beamMade most detailedSimulations of spoilerjaw damage to date.
Made most detailedSimulations of spoilerjaw damage to date.
UK a leading contributor on critical collimator issues: wakefields, survivability. Strong collaboration with SLAC and EUROTeV groups.
heated zone
compressive wavesReflected tensile waves
reflected shear waves
beam collimator
beam
G. Ellwood, J. Greenhalt
Bunch xy
(m2), material
Estimated damage region, x
Estimated damage region, y
Estimated damage region, z
1.90.5, Ti alloy
11 (14) m 4 (5.6) m 5 (8) mm
202, Ti alloy
45 (90) m 5 (9) m 2 (7) mm
202, Cu 65 (100) m 7 (10) m 3 (7) mm
sample holder
x
y
referencepin hole
guide channels
pin hole
low mass mounting
Cu Ti
target area
10mm
The purpose of the first test run at ATF is to:
1. 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.
2. Allow us to commission the proposed test system of vacuum vessel, multi-axis mover, beam position and size monitoring.
3. Validate the mode of operation required for ATF in these tests.
4. 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.
Material damage test beam at ATFMaterial damage test beam at ATF
Report on wakefield beam tests - AchievedAnalysis of 2007 and 2006 T480 data for publication in progress, including:
BPM uncertainties/calibrations, bunch length monitoringOriginal plan was to use SCP and established instrumentation See PAC’07, EPAC’06, 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 z
PAC’07, EPAC’06, EUROTeV-Reports 2006-055 (GdfidL) and 2006-103 (MAFIA)
Report on applicability of bench tests for ILC collimator design - Achieved
Initial report EPAC’06/EUROTeV Report 2006-0562007 work method not useful for quantitative tests (for collimator jaws), final
report in preparation
Merlin studies: emittance dilution due to wakefield
Looked at emittance dilution due to higher order mode wakefields -> get an increase in the beam size and consequently a decrease in luminosity
Variation of GdfidL predictions of transverse kick as a function of mesh resolution, for T480 collimator 3 (depth 1m), for σz = 1.0mm at an offset from electrical centre of 0.4mm.
GdfidL calculated kick for collimator 3 (depth1m) for z = 1.0mm: KF= 4.09 ± 0.80V/pC/mm
J. Smith, C. Beard
A. Bungau, R. Barlow
Beam Parameters at SLAC ESA and ILCParameter SLAC ESA ILC-500Repetition Rate 10 Hz 5 Hz
Energy 28.5 GeV 250 GeV
Bunch Charge 2.0 x 1010 2.0 x 1010
Bunch Length 300 m 300 m
Energy Spread 0.2% 0.1%
Bunches per train 1 (2*) 2820
Microbunch spacing - (20-400ns*) 337 ns
*possible, using undamped beam
T480“wakefield box”
ESA beamlineDesigned, modelled and tested collimators at SLAC ESA facility
Designed, modelled and tested collimators at SLAC ESA facility
Kic
k fa
ctor
(V
/pC
/mm
)
E.M. predictionsGdfidL vs. ECHO(ESA collims. 1- 8)
E.M. predictionsGdfidL vs. ECHO(ESA collims. 1- 8)
Col. 12 = 166 mradr = 1.4 mm
Ang
ular
kic
k (
V/p
C)
Collimator y (mm)
T480 (prelim.)2007 data
T480 (prelim.)2007 data
1.2 ± 0.3
(1.7 ± 0.4)
1.2 ± 0.3
(3.1± 0.8)
3.7± 0.3 (7.1 ± 0.9)
0.5 ± 0.4 (0.8)
1.1 ± 0.2
0.7 ± 0.2 (2.4 ± 1.1)
2.5 ± 0.3
1.5 ± 0.2
1.7 ± 0.3 (2.4 ± 0.9)
2.2 ± 0.3 (2.7 ± 0.5)
0.9 ± 0.3 (2.4 ± 1.1)
4.9 ± 0.2 (6.8)
1.2 ± 0.3 (1.2 ± 0.3)
2.3 ± 0.3
1.1 ± 0.3
1.2 ± 0.3
V/pC/mm V/pC/mm
V/pC/mmV/pC/mmV/pC/mm
Col. 1
Col. 3L=1000 mm
= 324 mradr = 2 mm
= 324 mradr = 1.4 mm
Col. 12 = 166 mradr = 1.4 mm
Col. 6 = r = 1.4 mm
(r = ½ gap)
Optimal spoiler design to achieve requirements (geometry, material, but not engineering) – Partially achievedWe have designs for material and geometry which can satisfy
beam damage requirementsOutcome of ongoing wakefield optimisation likely to require
further iteration on candidate designs
beam
Lead into LC-ABD2 (WP4)1) 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.
2) 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..
3) Data-validated material response simulations for BDS components Essential to test collimator materials/components under conditions
which emulate instantaneous ILC bunch heating.
4) 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.
5) Full engineering designs for BDS absorbers, protection collimators, masks
Design of these various components, ~20 different types
6) Prototypes of critical subsystems of adjustable jaw collimators Deliver demonstration hardware of critical components.
GdfidL simulations
T480 beam tests
LC-ABD1 result
Damage simulation + ATF test
Expertise in STFC