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Chopper. Longitudinal dynamics.

Chopper. Longitudinal dynamics. May 26, 2010 Nick Perunov , Nikolay Solyak. Input beam parameters after RFQ. Beam distribution after HINS RFQ . (Simulation for 10 mA ). Beam distribution after HINS RFQ (Simulation for 10 mA ).

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Chopper. Longitudinal dynamics.

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  1. Chopper. Longitudinal dynamics. May 26, 2010 Nick Perunov, NikolaySolyak

  2. Input beam parameters after RFQ

  3. Beam distribution after HINS RFQ. (Simulation for 10 mA)

  4. Beam distribution after HINS RFQ (Simulation for 10 mA)

  5. Beam parameters after RFQ, used in TraceWin for matching between RFQ and chopperc Note : Beam parameters used in lattice design is slightlydifferent from RFQ simulations in TRACK (previous slide)

  6. Objectives: In the first design, presented in May 19, 2010 we have observed longitudinal emittance growth after SSR0 section caused by non-linearity in the cavity. Reason is large bunch length (>90 deg for 3 sigma) in the location of buncher cavities.Goal: minimize emittance growth at the end of SSR0 section and halo formation, by reducing bunch length in chopper cavities. Revision of the longitudinal beam dynamics in Choppersection.

  7. Chopper geometry & parameters. • Periodic structure (4 periods) • Each period = chopper, triplet, bunching cavity, beam dump. Phase advance μX=180°; μY=120°; μz~90°; • Apertures: • Chopper: 15mmx25mm; cavity Ø30mm; triplet = Ø40mm; beam dump 10-14mm • Chopper: • 0.5m long; Voltage: ±375 V; gap=15mm

  8. Input beam parametersBeam: 325 MHz; 2.5 MeV; 10mA-peak Estimation for minimum longitudinal beam size in cavity location: where: εz- emittance; z = L perod/2 In our case: εz = 0.49 mm*mrad; z = 1.3 m: σmin = 4.2 mm = 22.5 deg (RMS)

  9. Longitudinal 3σ envelopes • Four cases are presented here: • Version 0 (Initial) – shown May 19 presentation • V1-V4 is new versions with different cavity voltages and bunch lenghts Initial V4 V2 V1 V3 • Transverse beam dynamics are the same: • Phase advance in x-plane = 180 deg; • Phase advance in y-plane ≈ 120 deg;

  10. Beam distribution in the exit of the chopper Initial version Version 1 Version 2 In all cases the distribution in the entrance of the chopper was Gaussian( 3 independent planes, max_size = 3.1 rms_size ) Version 4 Version 3

  11. Halo definition

  12. Beam halo. Version 1 Version 2 Initial version Version 4 Version 3

  13. 99% Emittance. Initial version Version 2 Version 1 Version 4 Version 3

  14. Version 3 looks as the best choice. • Let’s compare two versions: Ver.0 vs. Ver.3 Details of longitudinal phase space see in next slides.

  15. Initial version vs. Version 3

  16. Initial version vs. Version 3

  17. Initial version vs. Version 3

  18. Initial version vs. Version 3

  19. Initial version vs. Version 3

  20. Initial version vs. Version 3

  21. Initial version vs. Version 3

  22. Initial version vs. Version 3

  23. Initial version vs. Version 3

  24. Initial version vs. Version 3

  25. Initial version vs. Version 3

  26. Initial version vs. Version 3

  27. Initial version vs. Version 3

  28. Initial version vs. Version 3

  29. Initial version vs. Version 3

  30. Initial version vs. Version 3

  31. Initial version vs. Version 3

  32. Initial version vs. Version 3

  33. Initial version vs. Version 3

  34. Initial version vs. Version 3

  35. Initial version vs. Version 3

  36. Initial version vs. Version 3

  37. Initial version vs. Version 3

  38. Initial version vs. Version 3

  39. Initial version vs. Version 3

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