1. Jonathan Smith, 1 st March, COLSIM, CERN 1 Recent Developments with ILC Collimator Wakefield Calculations Jonathan Smith (Lancaster University/Cockcroft Institute)

2. Jonathan Smith, 1 st March, COLSIM, CERN 2 Introduction/Project Objectives ● LC-ABD WP5.3 (Nigel Watson)/EUROTeV WP2 (BDS) ● Collimation is crucial for beam delivery and detector protection/performance of a particle accelerator ● Quantification of longitudinal and transverse wakefield effects of collimators on the beam ● Optimization of collimator design ● Use and understanding of simulation tools, potential improvements and support of other projects ● Verification by test beam measurement

3. Jonathan Smith, 1 st March, COLSIM, CERN 3 Wakefield box ESA  z ~ 300  m – ILC nominal  y ~ 100  m (Frank/Deepa design) Magnet mover, y range =  mm, precision = 1  m 1500mm E beam =28.5GeV Slide reproduced from talk by Nigel Watson

4. Jonathan Smith, 1 st March, COLSIM, CERN 4  =  /2rad r=4.0mm 4, 4  324mrad r=1.4mm 3, 3  324mrad r=1.4mm 2, 2  =324mrad r=2.0mm 1, 1 Revised 4-May-2006 Beam viewSide view (“DESY sandwich”) Collim. #, slot h=38 mm 38 mm L=1000 mm 7mm  r=1/2 gap As per last set in Sector 2, commissioning Extend last set, smaller r, resistive WF in Cu cf. same r, tapered Slide reproduced from talk by Nigel Watson

5. Jonathan Smith, 1 st March, COLSIM, CERN 5  =  /2rad r=1.4mm 5, 4  166mrad r=1.4mm 6, 3  1 =  /2 rad  2 =166mrad r 1 =4.0mm r 2 =1.4mm 7, 2 r 1 =4.0mm r 2 =1.4mm   =289mrad   =166mrad 8, 1 Revised 4-May-2006 Beam viewSide view (“SLAC sandwich”) Collim.#, slot h=38 mm 38 mm 7 mm cf. collim. 4 smaller r 211mm cf. collim. 2, same r 31mm cf. collims. 4 and 6 133mm cf. collim. 7, and same step in/out earlier data Slide reproduced from talk by Nigel Watson

6. Jonathan Smith, 1 st March, COLSIM, CERN 6 Small improvement on the Chisq/n Run 1206 (ref. 1207) Multiplying each bunch by its ebpm_x ADC value

7. Jonathan Smith, 1 st March, COLSIM, CERN 7 Analytical estimate ● Stupakov says: ● Stupakov asserts that the h»b is met, but is this really valid?

8. Jonathan Smith, 1 st March, COLSIM, CERN 8 For SLAC collimators...

9. Jonathan Smith, 1 st March, COLSIM, CERN 9 Assessment/Familiarization of Simulation Tools ● MAGIC (easy to use tool for first comparison with new calculations) ● ECHO/ECHO3D – Thomas Weiland, Mikko Karkkainen (TEMF, Darmstadt) Igor Zagorodnov (DESY). Code development as part of EUROTeV project ● MAFIA – CDB and JS working on comparison with Cho Ng’s results (PAC 2001) ● GdfidL – Overlapping interest with David Miller and Alexei Liapine (UCL) as part of EUROTeV WP5 (Spectrometry) ● Additional software for research if required: – BCI/TBCI/ABCI (old CERN tools), XWAKE, XOOPIC – Tau3P, Omega, T3P (next generation SLAC codes) – Boundary Element (BEM) codes (Sapporo, Japan)

10. Jonathan Smith, 1 st March, COLSIM, CERN 10 EM Simulations with GdfidL1 2 3 5 6 7 4 8

11. Jonathan Smith, 1 st March, COLSIM, CERN 11 Wakefields @300µm (6 cells/sigma)

12. Jonathan Smith, 1 st March, COLSIM, CERN 12 Wakefields @500µm (12 cells/sigma)

13. Jonathan Smith, 1 st March, COLSIM, CERN 13 Mesh stability: Collimators 1&2 ● Only 3 decent points at 300µm for most collimators ● More at 500µm ● 1mm ~ OK – can use spline fit on data to get an estimate – not done so far – further analysis to see if this takes us closer to ECHO/PBCI.

14. Jonathan Smith, 1 st March, COLSIM, CERN 14 What do we do about it? (1)

15. Jonathan Smith, 1 st March, COLSIM, CERN 15 What do we do about it? (2)

16. Jonathan Smith, 1 st March, COLSIM, CERN 16 Effect of mesh filtering…

17. Jonathan Smith, 1 st March, COLSIM, CERN 17 Misallignment

18. Jonathan Smith, 1 st March, COLSIM, CERN 18 Further collimator designs semi-circle, with[9]/without[10] flat, opposing demi-circles[10], 8 with flat[11].

19. Jonathan Smith, 1 st March, COLSIM, CERN 19 More possible collimators 7 with flat [13], half exponential[14], 13 with shallower angle[15] exponential profile[16], 13 with ellipse connecting 4mm and 1.4mm aperture[17] 13 with ellipse connecting beam pipe radius and 1.4mm aperture (also see 9) [18] half cosine taper [19], raised cosine taper [20], tanh tapers [21] (set typically to the length of collimator 6)

20. Jonathan Smith, 1 st March, COLSIM, CERN 20  166mrad r=1.4mm 12  =166mrad r =1.4mm 11  =166mrad r =1.4mm 10  166mrad r=1.4mm (1/2 gap) 6 Revised 27-Nov-2006 Beam viewSide view Collim.# h=38 mm 38 mm Roughened surface, compare with 12 As 10, in Ti-6Al-4V, polished, cf. 12 As 10, in OFE Cu, polished, cf. collim. 6, 13 Runs 3, 2007 Exists, from 2006 runs. For reproducibility ~211mm 1.4mm  =21mm   

21. Jonathan Smith, 1 st March, COLSIM, CERN 21 non-linear taper r=1.4mm 16?  1 =  /2 rad  2 =50mrad r 1 =4.0mm r 2 =1.4mm 15  1 =  /2 rad  2 =166mrad r 1 =4.0mm r 2 =1.4mm 14  1 =  /2 rad  2 =166mrad r 1 =4.0mm r 2 =1.4mm 13 Revised 27-Nov-2006 Beam viewSide view Collim.# h=38 mm 38 mm cf. ? Polished, cf. collim. 13 Polished, cf. collims. 7, 11, 13 Polished, cf. collim. 7, 12, 13 Ti6Al4V OFE Cu =21 mm Form t.b.d. = 0.6    Ti6Al4V Runs 3, 2007 ~52 mm =21 mm  ~52 mm =21 mm   ~125 mm =21 mm

22. Jonathan Smith, 1 st March, COLSIM, CERN 22 Variation of collimator kick with bunch length

23. Jonathan Smith, 1 st March, COLSIM, CERN 23 WB's suggestion: Chop this bit off as beam will never see wake that has travelled this far from the bunch

24. Jonathan Smith, 1 st March, COLSIM, CERN 24 Two possibilities: s_ma x s_maxs_max “colimator 23” “colimator 22”

25. Jonathan Smith, 1 st March, COLSIM, CERN 25 Longitudinally Asymmetric?

26. Jonathan Smith, 1 st March, COLSIM, CERN 26 Results...

27. Jonathan Smith, 1 st March, COLSIM, CERN 27 Cylindrical jobs... ● W modal decomposition ● See Adriana's talk... ● Jobs still running ● w(s,r,r', θ, θ')→w(s,r,θ,m ) ● Useful for rectangular geometry?

28. Jonathan Smith, 1 st March, COLSIM, CERN 28 GdfidL & PBCI ● TEMF working on ECHO/PBCI – 3D, moving mesh, conformal, non-dispersive solver s/σ σ/Δz=6 W ║ (s)/(V/pC) GdfidL PBCI With thanks to Mikko Kärkkäinen