Towards Improved Collimation for the ILC

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

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 http://hepunx.rl.ac.uk/swmd/talks/

3. People • “Spoiler Wakefield and Mechanical Design” task • Details on project web: http://hepunx.rl.ac.uk/swmd/ • 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-2006-015, FLUKA Simulations of Energy Density Deposition from a ILC Bunch in different Spoiler Designs, http://www.eurotev.org/e158/e1365/e1378/e2167/EUROTeV-Report-2006-015.pdf • A. Bungau, R.J. Barlow et al., EUROTeV-Report-2006-021, 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

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-2006-051

7. 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. 2 doublets Two triplets BPM BPM BPM BPM ~40m ~16m 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…

9. 2 doublets Two triplets BPM BPM BPM BPM ~40m ~16m 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…

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

13. 38 mm h=38 mm L=1000 mm a r=1/2 gap As per last set in Sector 2, commissioning Extend last set, smaller r, resistive WF in Cu 7mm cf. same r, tapered

14. 38 mm 7 mm cf. collim. 4 smaller r h=38 mm cf. collim. 2, same r 211mm 31mm cf. collims. 4 and 6 133mm cf. collim. 7, and same step in/out earlier data

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

16. 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 GdfidL 4 5 2 7 1 6 8 3

19. Wakefields @300µm (6 cells/sigma) Collimator number Collimator number

20. Wakefields @500µm (10 cells/sigma) Collimator number Collimator number

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 • 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)