1. R. Cimino COULOMB’05, Senigallia, Sept 15, 05. 1 Surface related properties as an essential ingredient to e-cloud simulations. The problem of input parameters: a detailed analysis by a test case (the cold arcs of LHC). Results of relevance for LHC and DA  NE Future experiments and open problems R. Cimino LNF Frascati (Italy)

2. R. Cimino COULOMB’05, Senigallia, Sept 15, 05. 2 Cold Bore @ 1.9 K Beam Screen @ 5K< T <20K Extreme High Static Vacuum (<< 10 -13 Torr) Radial Distance T=0, without beam Static

3. R. Cimino COULOMB’05, Senigallia, Sept 15, 05. 3 Cold Bore @ 1.9 K Beam Screen @ 5K< T <20K Extreme High Static Vacuum (<< 10 -13 Torr) Radial Distance T=0, without beam Static

4. R. Cimino COULOMB’05, Senigallia, Sept 15, 05. 4 CB BS Radial Distance Time = 0 calculation + + + + + + + + + p + Synchrotron Radiation: Ec = 44 e V @ LHC

5. R. Cimino COULOMB’05, Senigallia, Sept 15, 05. 5 CB BS Radial Distance Time = 2 nsec + + + + + + + + + p + Photon reflectivity: SR & Surface Science Flat Cu Saw tooth N. Mahne et al. App. Surf. Sci. 235, 221-226, (2004).

6. R. Cimino COULOMB’05, Senigallia, Sept 15, 05. 6 CB BS Radial Distance Time = 5 nsec SR and Surface Science + + + + + + + + + p + Photoemission:  vs. h  E,T, B) R. Cimino, V. Baglin, I. R. Collins. Phys.Rev. ST-AB 2 63201 (1999).

7. R. Cimino COULOMB’05, Senigallia, Sept 15, 05. 7 SPS Radial Distance Time = 5 nsec observation + + + + + + + + + p + Even in absence of SR: e - from ionization of residual gas… etc Beam induced multipacting is observed in SPS where no e - are photoemitted. e-e- (M.Jimenez)

8. R. Cimino COULOMB’05, Senigallia, Sept 15, 05. 8 CB BS Radial Distance Time = 10 nsec simulation + + + + + + + + + Beam induced el. acceleration p + (F.Zimmermann)

9. R. Cimino COULOMB’05, Senigallia, Sept 15, 05. 9 CB BS Radial Distance Time = 15 nsec + + + + + + + + + e - induced e - emission Surface Science R. Cimino et al Phys. Rev. Lett. 93, 14801 (2004).

10. R. Cimino COULOMB’05, Senigallia, Sept 15, 05. 10 CB BS Radial Distance Time = 20 ns + + + + + + + + + e - induced e - emission vs. E Surface Science Energy Distribution Curves as function of Ep R. Cimino et al Phys. Rev. Lett. 93, 14801 (2004).

11. R. Cimino COULOMB’05, Senigallia, Sept 15, 05. 11 CB BS Radial Distance Time = 25 ns simulation + + + + + + + + + P + e - cloud Build-up + + + + + + + + + Time structure vs Simulations. P + (F. Zimmermann)

12. R. Cimino COULOMB’05, Senigallia, Sept 15, 05. 12 CB BS Radial Distance Time = 25 ns + + + + + + + + + p + e - induced heat load + + + + + + + + + p + Simulation R. Cimino et al Phys. Rev. Lett. 93, 14801 (2004).

13. R. Cimino COULOMB’05, Senigallia, Sept 15, 05. 13 CB BS Radial Distance Time = 25 ns + + + + + + + + + p + ph. or e - induced desorption + + + + + + + + + Dynamic pressure increase !!! p + Desorbed gas Surface Science and simulation It is a Vacuum issue!

14. R. Cimino COULOMB’05, Senigallia, Sept 15, 05. 14 CB BS Radial Distance Time = 25 ns + + + + + + + + + P + Beam scrubbing effect with e- + + + + + + + + + P + The nominal LHC operation relies on SCRUBBING Surface Science

15. R. Cimino COULOMB’05, Senigallia, Sept 15, 05. 15 CB BS Radial Distance Time = 25 ns + + + + + + + + + P + Beam scrubbing effect with photon + + + + + + + + + P + The nominal LHC operation relies on SCRUBBING Surface Science and SR See: R. Cimino et al Phys. Rew. AB-ST 2 063201 (1999)

16. R. Cimino COULOMB’05, Senigallia, Sept 15, 05. 16 1)0-1keV Electron induced el. emission yield (SEY) 2)and its angular dependence 3) Photoemission Yield and Photoemission induced el. energy distribution (also Angle resolved!) 4) Photon - reflectivity 5) Electron induced energy distribution curves 6) Heat load 7) Photon and electron induced desorption 8) Surface properties changes during conditioning. 9) Chemical modifications vs. conditioning. 10) Relation between photon and electron conditioning. … and this on all vacuum high tech. materials… To qualify a material for “e-cloud” simulations one need to perform the following experiments:

17. R. Cimino COULOMB’05, Senigallia, Sept 15, 05. 17 Some of those experimental input parameters have strong relevance to Simulation results: 3 examples 1)0-1keV Electron induced el. emission yield (SEY) 2)and its angular dependence 3) Photoemission Yield and Photoemission induced el. energy distribution (also Angle resolved!) 4) Photon - reflectivity 5) Electron induced energy distribution curves 6) Heat load 7) Photon and electron induced desorption 8) Surface properties changes during conditioning. 9) Chemical modifications vs. conditioning. 10) Relation between photon and electron conditioning. … and this on all vacuum high tech. materials…

18. R. Cimino COULOMB’05, Senigallia, Sept 15, 05. 18 …. And its impact to simulations. Measure of Secondary e - YIELD

19. R. Cimino COULOMB’05, Senigallia, Sept 15, 05. 19 A systematic study is necessary to give values. Measure of low energy part of the Secondary e - YIELD of Cu It is clear that the reflected component plays a major role in  at low energy. The value for the minimum, its energy and width vary with sample, sample spot, scrubbing and T.

20. R. Cimino COULOMB’05, Senigallia, Sept 15, 05. 20 Implication of the SEY low energy part : Simulated average heat load in an LHC DM as a function of Nb, considering the elastic reflection (dashed line) or ignoring it (full line) R. Cimino et al Phys. Rev. Lett. 93, 14801 (2004). Calculation done extrapolating measured SEY to :  M =1.7 E M  240 eV

21. R. Cimino COULOMB’05, Senigallia, Sept 15, 05. 21 Implication of the SEY low energy part : Simulated EC density for the GSI-SIS18 with (dashed line) and without (full line) elastic reflection. R. Cimino et al Phys. Rev. Lett. 93, 14801 (2004).

22. R. Cimino COULOMB’05, Senigallia, Sept 15, 05. 22 Implication Low energy electrons have a long survival time. This may explain observations at KEK, SPS, PSR, LANL…. Implication

23. R. Cimino COULOMB’05, Senigallia, Sept 15, 05. 23

24. R. Cimino COULOMB’05, Senigallia, Sept 15, 05. 24 Dependence of Secondary Emission Yield on Impact Angle  Frank Zimmermann (CERN) and Giulia Bellodi (Rutterford) implemented the code with the only available data on such dependence reducing the simulated Heat-load for LHC by 40%

25. R. Cimino COULOMB’05, Senigallia, Sept 15, 05. 25 Single beam energy0.51GeV Number of particles per bunch 8.9x10 10 Number of bunches per ring up to 120 Crossing frequencyup to~ 368 MHz Horizontal emittance1.0 mm.mrad Vertical emittance0.01 mm.mrad Bunch length30 mm r.m.s. Horizontal beam size at crossing 2.0 mm r.m.s. Vertical beam size at crossing 0.02 mm r.m.s. Maximum stored current per ring 5.2 A Maximum luminosity5.310 32 cm -2 s -1 E-cloud @ DA  NE

26. R. Cimino COULOMB’05, Senigallia, Sept 15, 05. 26 e - cloud studies at DA  NE Vacuum pressure read-out vs total current as recorded in four straight section locations for the electron (blue dots) and positron (red dots) rings. C. Vaccarezza et al PAC 05

27. R. Cimino COULOMB’05, Senigallia, Sept 15, 05. 27 e - cloud studies input parameters at DA  NE : Photo-electron Yield N. Mahne et al PAC 05 mean e-cloud linear density in the storage ring calculated for two different photoelectron yield values (0.2 and 0.1) with a reflectivity of 50%.

28. R. Cimino COULOMB’05, Senigallia, Sept 15, 05. 28 e - cloud input parameters studies at DA  NE Studying : Reflectivity N. Mahne et al PAC 05 mean e-cloud linear density plotted changing the value of the reflectivity (85%, 50%, and 20%) with a ph.e - yield of 0.1.

29. R. Cimino COULOMB’05, Senigallia, Sept 15, 05. 29 Open problem & DA  NE as a working test bench for e-cloud studies a)Need to validate simulations vs “real machine” behaviour! b)Can we directly measure properties of the e-cloud in the DA  NE ring? (an important measurement could be the energy gained by the low electrons when they interact with the beam) (Scrubbing!) and use DA  NE and its wigglers (of importance for future DR) as a bench mark machine of “general” interest? c)Can we refine surface analysis aiming towards more realistic input parameters to be used in the simulations? (SEY for Al, low energy SEY, its angular dependence etc,,,?)

30. R. Cimino COULOMB’05, Senigallia, Sept 15, 05. 30 Acknowledgments: - C. Vaccarezza, M. Biagini, S. Guiducci, M. Zobov, A. Drago and the LNF-INFN accelerator group - I.R Collins A. G. Mattewson O. Gröbner, V. Baglin, and the CERN vacuum Group. - F. Zimmermann, F. Ruggero, M. Pivi, M. Furman, G. Bellodi, G. Rumolo, etc..