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