1. Towards Improved Collimation for the ILC
Jonathan Smith
(Lancaster University/Cockcroft Institute)

2. Outline Damage Studies Merlin Simulations Bench Tests T480@ESA
EM Simulation activity
Plans
LC-ABD WP5.3 (Nigel Watson)/EUROTeV WP2 (BDS)
Collimation is crucial for beam delivery and detector protection/performance

3. People “Spoiler Wakefield and Mechanical Design” task
Details on project web:
Birmingham: N.Watson
CCLRC: C.Beard,G.Ellwood,J.Greenhalgh,J.O'Dell,L.Fernandez
CERN: F.Zimmermann,G.Rumolo,D.Schulte
[DESY: I.Zagorodnov]
Lancaster: D.Burton,N.Shales,J.Smith,A.Sopczak,R.Tucker
Manchester: R.Barlow,A.Bungau,G.Kurevlev,R.Jones,A.Mercer
TEMF, Darmstadt: M.Kärkkäinen,W.Müller,T.Weiland
For ESA tests, working closely with
CCLRC on optics for wakefield and beam damage studies
SLAC Steve Molloy et al. for all aspects

4. Damage Studies EGS/Geant4/FLUKA in agreement
ANSYS modelling of temperature flow done.
Shockwave studies underway…
Focus now on manufacturability – wire erosion?
Search for a site to conduct damage tests (CERN? Discussions at EPAC… )
[L.Fernandez, ASTeC]
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).
L. Fernandez-Hernando, N.K. Watson, EUROTeV-report , FLUKA Simulations of Energy Density Deposition from a ILC Bunch in different Spoiler Designs,
A. Bungau, R.J. Barlow et al., EUROTeV-Report , GEANT4 Simulations of Energy Deposition in ILC Spoilers
L. Fernandez-Hernando et al.¸Shower Simulations, Comparison of FLUKA, GEANT4 and EGS4, Proc. EPAC'06, Jun 2006.
G.Ellwood, R.J.S.Greenhalgh, Beam Impact of the ILC Collimators, Proc. EPAC'06, Jun 2006.

5. Shockwave studies
This shows in 1 dimension waves of stress emanating from a heated zone (on the left, up to one unit of distance) The heated zone takes 1 picosec (0.1E-11) seconds to heat up. It then shows stresses in X (along the direction of motion of the wave) and in Y (perpendicular). The X stress propagates as a wave, leaving the Y stress in place. At the free end of the 1D region the stress wave reflects with a change in sign. The exact behaviour of the wave (disappearing and reappearing) is well explained by simple wave theory. The relationship between the X and Y stresses, and their magnitudes, are well explained by simple 3D stress theory. When the wave (now tensile) gets back to the heated zone we have a region with very high tensile stresses in one direction and high compressive stresses in the other direction. This is bad for the material. The SEQV line shows the "badness" of the combined effects; at its worst when the tensile and compressive stresses overlap (for techies it is the Von Mises equivalent stress). We developed this model in order to explore the minimum element and time step size we need to use and we are now applying the results to a 2D model of a slice through the collimator, importing heating loads from FLUKA. The notch visible in the SEQV line at about t=0.1E-11 is an artefact of the result plotting algorithm.

6. Merlin Simulations
Manchester University involved in wakefield simulations of the ILC collimators (R.Barlow, A.Bungau)
Merlin code development (includes higher order modes)
Simulation of bunch kicks for different modes at different offsets
EPAC 2006 Paper: “Simulation of High Order Short Range Wakefields”
A.Bungau and R. Barlow, The University of Manchester, EUROTeV

7. Bench “wire method” setup
Plot from S.F.Hill and M.J.Pugh, paper at EPAC'94
Bench “wire method” setup
Calculate impedence of structure
Simulate mode structure
Use where wire is not interfering with the mode, or use simulation results to subtract wire induced effects

8. T-480 Experiment
BPM
2 doublets
~40m
BPM
Two triplets
~16m
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…

9. T-480 Experiment
BPM
2 doublets
~40m
BPM
Two triplets
~16m
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…

10. ESA beamline layout (plan)
Wakefield box
Beam
Measure kick factor using incoming/outgoing beam trajectory, scanning collimator gap through beam
Stage 1, 5 rf cavity BPMs, 1 stripline BPM, 2 wire scanners
Downstream BPMs themselves R&D project …
Wakefield box, proposal for 2 sets of four pairs of spoiler jaws
Each set mounted in separate “sandwich” to swap into WF box
(Relatively) rapid change over, in situ – ½ shift for access
Commissioning run, Jan 4-9, 2006
Physics run, 24-Apr – 8-May, 2006

11. Magnet mover, y range = 1.4mm, precision = 1mm
Wakefield box
1500mm
Ebeam=28.5GeV
ESA sz ~ 300mm – ILC nominal
sy ~ 100mm (Frank/Deepa design)
Magnet mover, y range = 1.4mm, precision = 1mm

12. Successful commisioning and Beamline preparation at SLAC - Ray Arnold
ESA Test Beam for T-480
sy = 117 mm
Wire scanner measurement of vertical spotsize.
Successful commisioning and
physics runs in 2006
Wakefield box
Beamline preparation at SLAC - Ray Arnold

13. a Side view (“DESY sandwich”) Beam view 1, 1 2, 2 3, 3 4, 4
Collim. #, slot
Side view (“DESY sandwich”)
Beam view
Revised
4-May-2006
1, 1
a=324mrad
r=2.0mm
2, 2
r=1.4mm
3, 3
4, 4
a=p/2rad
r=4.0mm
h=38 mm
38 mm a
r=1/2 gap
As per last set in Sector 2, commissioning
Extend last set, smaller r, resistive WF in Cu
L=1000 mm
7mm
cf. same r, tapered

14. cf. collim. 7, and same step in/out earlier data
Collim.#, slot
Side view (“SLAC sandwich”)
Beam view
Revised
4-May-2006
8, 1
r1 =4.0mm
r2 =1.4mm a1=289mrad
a2=166mrad
7, 2
a1=p/2 rad
r1=4.0mm
r2=1.4mm
6, 3
a=166mrad
r=1.4mm
5, 4
a=p/2rad
133mm
cf. collim. 7, and same step in/out earlier data
38 mm
h=38 mm
31mm
cf. collims. 4 and 6
211mm
cf. collim. 2, same r
7 mm
cf. collim. 4 smaller r

15. L Fernandez: Collimator 2 Kick angle/(µrad/mm)
Wakefield box position/mm
L Fernandez:
Collimator 2
run588
No of events
Misallignment

16. L Fernandez: Collimator 8 Some plots not as clear! 1167
Bunch length ~400
Charge ~1.6E10
L Fernandez:
Collimator 8
Some plots not as clear!

17. Processing also at SLAC

18. EM Simulations with GdfidL4 5 2 7 1 6 8
Ensure collimator geometries are discussed, along with estimation of accuracy, and that experiment should correspond to this. 3

19.
Collimator number
Collimator number
(6 cells/sigma)

20.
Collimator number
Collimator number
(10 cells/sigma)

21. GdfidL & TBCI
TEMF working on ECHO/PBCI – 3D, moving mesh, conformal, non-dispersive solver
GdfidL
σ/Δz=6
PBCI
W║(s)/(V/pC)
With thanks to Mikko Kärkkäinen
s/σ

22. Next DRAFT ESA Runs provisionally beg. Feb07, Jul07.
Understand affect of conductivity and finish
Manufacturability studies
Still some simulation tuning
Simulation of new collimator geometry
Analysis fine tuning
Bench tests

23. Conclusion Now starting second iteration… Prediction of effect at IP
EM simulations:
MAFIA
GdfidL
ECHO
Now starting second iteration…
Bench Tests
(scaling?)
Prediction of effect at IP
(MERLIN)
New designs
Beam Tests
ESA
Damage Studies ?
Prediction of mechanical properties
Analytical Approach
(Lancaster Theory Group)