Electron cloud build up in the FCC HEB Update on simulation results

1. Electron cloud build up in the FCC HEBUpdate on simulation results L. Mether, G. Iadarola, G. Rumolo

2. FCC High Energy Booster (HEB) • Envisaged additional injector, accelerating beam from SPS to FCC • To be housed in current LHC or future FCC tunnel • We study electron cloud build up in the FCC-tunnel HEB using PyECLOUD Electron cloud meeting

3. Electron cloud simulations • We investigate the effect of beam pipe aperture and bunch spacing on the formation of e-cloud in HEB • Focus on arc dipoles, with beam at injection energy, 450 GeV • Consider circular beam pipe, scanning over aperture radii of 1.0 - 3.75 cm • Corresponding parameters: • Transverse emittancesεx ,εy : 2.5 µm • Beta functions βx ,βy : 67, 71 m Electron cloud meeting

4. Electron cloud simulations • Since most machine details unknown, consider simple scenario: • Uniform initial distribution of seed electrons, no other primary electron production • Single uniform bunch train • Study 3 different bunch spacings • Bunch intensities scaled to keep average current constant Bunch spacing [ns] Intensity [ppb] Train length [b] • 5ns train shorter, results scaled accordingly Electron cloud meeting

5. Simulation results Heat load as function of radius, 50 ns beam Heat load increases monotonically with R Electron cloud meeting

6. Simulation results Heat load as function of radius, 25ns beam Heat load decreases for large R Electron cloud meeting

7. Simulation results Heat load as function of radius, 5ns beam Heat load decreases with growing R, but oscillates Electron cloud meeting

8. Simulation results Heat load as function of SEY, 50 ns beam Heat load increases monotonically with R Electron cloud meeting

9. Simulation results Heat load as function of SEY, 25 ns beam Heat load decreases for large R Electron cloud meeting

10. Simulation results Heat load as function of SEY, 5 ns beam Heat load decreases with growing R, but rises non-linearly Electron cloud meeting

11. Simulation results - electron energy spectrum 50 ns • Peak energy of electrons impacting on the chamber wall, lies in the emitter region of SEY curve • For larger radius, peak closer to maximum SEY, δmax Electron cloud meeting

12. Simulation results - electron energy spectrum 50 ns • Peak energy of electrons impacting on the chamber wall, lies in the emitter region of SEY curve • For larger radius, peak closer to maximum SEY, δmax Electron cloud meeting

13. Simulation results - electron energy spectrum 50 ns • Peak energy of electrons impacting on the chamber wall, lies in the emitter region of SEY curve • For larger radius, peak closer to maximum SEY, δmax Electron cloud meeting

14. Simulation results - electron energy spectrum 50 ns • Peak energy of electrons impacting on the chamber wall, lies in the emitter region of SEY curve • For larger radius, peak closer to maximum SEY, δmax Electron cloud meeting

15. Simulation results - electron energy spectrum 50 ns • Peak energy of electrons impacting on the chamber wall, lies in the emitter region of SEY curve • For larger radius, peak closer to maximum SEY, δmax Electron cloud meeting

16. Simulation results - electron energy spectrum 25 ns • Peak energy of electrons impacting on the chamber wall, still lies mainly in the emitter region of SEY curve • For larger radii, the peak moves towards lower energies, outside of the emitter region Electron cloud meeting

17. Simulation results - electron energy spectrum 25 ns • Peak energy of electrons impacting on the chamber wall, still lies mainly in the emitter region of SEY curve • For larger radii, the peak moves towards lower energies, outside of the emitter region Electron cloud meeting

18. Simulation results - electron energy spectrum 25 ns • Peak energy of electrons impacting on the chamber wall, still lies mainly in the emitter region of SEY curve • For larger radii, the peak moves towards lower energies, outside of the emitter region Electron cloud meeting

19. Simulation results - electron energy spectrum 25 ns • Peak energy of electrons impacting on the chamber wall, still lies mainly in the emitter region of SEY curve • For larger radii, the peak moves towards lower energies, outside of the emitter region Electron cloud meeting

20. Simulation results - electron energy spectrum 25 ns • Peak energy of electrons impacting on the chamber wall, still lies mainly in the emitter region of SEY curve • For larger radii, the peak moves towards lower energies, outside of the emitter region Electron cloud meeting

21. Simulation results - electron energy spectrum 5 ns • For 5 ns beam, no clear energy peak • Electrons interact with several bunches before reaching chamber wall • Behavior very radius dependent in non-monotonic fashion Electron cloud meeting

22. Simulation results - electron energy spectrum 5 ns • For 5 ns beam, no clear energy peak • Electrons interact with several bunches before reaching chamber wall • Behavior very radius dependent in non-monotonic fashion Electron cloud meeting

23. Simulation results - electron energy spectrum 5 ns • For 5 ns beam, no clear energy peak • Electrons interact with several bunches before reaching chamber wall • Behavior very radius dependent in non-monotonic fashion Electron cloud meeting

24. Simulation results - electron energy spectrum 5 ns • For 5 ns beam, no clear energy peak • Electrons interact with several bunches before reaching chamber wall • Behavior very radius dependent in non-monotonic fashion Electron cloud meeting

25. Simulation results - electron energy spectrum 5 ns • For 5 ns beam, no clear energy peak • Electrons interact with several bunches before reaching chamber wall • Behavior very radius dependent in non-monotonic fashion Electron cloud meeting

26. Simulation results - electron energy spectrum 5 ns • For 5 ns beam, no clear energy peak • Electrons interact with several bunches before reaching chamber wall • Behavior very radius dependent in non-monotonic fashion Electron cloud meeting

27. Simulation results - electron energy spectrum 5 ns • For 5 ns beam, no clear energy peak • Electrons interact with several bunches before reaching chamber wall • Behavior very radius dependent in non-monotonic fashion Electron cloud meeting

28. Simulation results - electron energy spectrum 5 ns • For 5 ns beam, no clear energy peak • Electrons interact with several bunches before reaching chamber wall • Behavior very radius dependent in non-monotonic fashion Electron cloud meeting

29. Simulation results - electron energy spectrum 5 ns • For 5 ns beam, no clear energy peak • Electrons interact with several bunches before reaching chamber wall • Behavior very radius dependent in non-monotonic fashion Electron cloud meeting

30. Simulation results - electron energy spectrum 5 ns • For 5 ns beam, no clear energy peak • Electrons interact with several bunches before reaching chamber wall • Behavior very radius dependent in non-monotonic fashion Electron cloud meeting

31. Simulation results - electron energy spectrum 5 ns • For 5 ns beam, no clear energy peak • Electrons interact with several bunches before reaching chamber wall • Behavior very radius dependent in non-monotonic fashion Electron cloud meeting

32. Simulation results - electron energy spectrum 5 ns • For 5 ns beam, no clear energy peak • Electrons interact with several bunches before reaching chamber wall • Behavior very radius dependent in non-monotonic fashion Electron cloud meeting

33. Simulation results - electron energy spectrum 5 ns Electron cloud meeting

34. Simulation results - electron energy spectrum 5 ns Electron cloud meeting

35. Simulation results - electron energy spectrum 5 ns Electron cloud meeting

36. Simulation results - electron energy spectrum 5 ns Electron cloud meeting

37. Simulation results - electron energy spectrum 5 ns Electron cloud meeting

38. Simulation results - electron energy spectrum 5 ns Electron cloud meeting

39. Simulation results - electron energy spectrum 5 ns Electron cloud meeting

40. Simulation results - electron energy spectrum 5 ns Electron cloud meeting

41. Simulation results - electron energy spectrum 5 ns Electron cloud meeting

42. Simulation results - electron energy spectrum 5 ns Electron cloud meeting

43. Simulation results - electron energy spectrum 5 ns Electron cloud meeting

44. Simulation results - electron energy spectrum 5 ns Electron cloud meeting

45. Summary & conclusions • Electron cloud formation in the FCC HEB has been studied, varying chamber radius and bunch spacing • 50 ns beam • Larger radii produce more e-cloud, peak electron energy resides around δmax • 25 ns beam • e-cloud production grows with R until SEY-dependent threshold, where peak e-energy moves into absorber part of δ(E)curve • Cloud production then decreases as R grows further • 5 ns beam • Electrons interact with multiple successive bunches before hitting chamber wall more complex behavior • General trend is more e-cloud for smaller radii • For SEY ~ 1.2-1.5 very non-linear behavior Electron cloud meeting