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Study on Setting BC1 Energy Set Point for LCLS-II Accelerator Design

This study by J. Wu at SLAC focuses on setting the BC1 energy set point for the LCLS-II accelerator. It covers updated design distances, undulator effects, and accelerator stability. The research includes profiles, dipole field integrals, chicane strength analysis, and jitter tolerance investigations. Detailed comparisons and analysis are provided between different energy set points to optimize the accelerator performance.

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Study on Setting BC1 Energy Set Point for LCLS-II Accelerator Design

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  1. Study on the BC1 Energy Set Point J. Wu working with T.O. Raubenheimer LCLS-II Accelerator Physics meetingMay 09, 2012 LCLS-II Accel. Phys. , J. Wu, SLAC

  2. outline • Continue from the talk I gave on April 11, 2012 • Updated to LCLS-II design distance and also modeled the undulator resistive-wall wakefield effect and by-pass line wakefield effect • Pros of setting BC1 @ 300 ~ 350 MeV for LCLS-II • More accelerator tubes before BC1: lower the amplitude, avoid any breakdown related problem; more stable simply due to 1/sqrt(2) statistics; … • One concern about the chicane strength (looked into) • More knowledge about the stability and tolerance (on-going) LCLS-II Accel. Phys. , J. Wu, SLAC

  3. Layout: according to LCLS-II mad deck • BC1 @ 250 MeV • Set points • BC1: R56 = 46 mm, Energy 250 MeV, peak current 176 Amp • L1S: – 20 degree • L1X: – 160 degree; 19 MeV • L2: – 31.4 degree • BC2: R56 = 29 mm, Energy 4.5 GeV, peak current 3 kA wire scanner 4 wire-scanners L0 L1X L1S gun DL1 135 MeV BC1 250 MeV BC2 4.5 GeV TCAV3 L3-linac By-pass 13.5 GeV L2-linac UND LCLS-II Accel. Phys. , J. Wu, SLAC

  4. Profiles BC1END UNDBEG CSR, LSC included in LiTrack, good agreement with Elegant [Bosch, Kleman, Wu, PRSTAB, 2008] LCLS-II Accel. Phys. , J. Wu, SLAC

  5. Bc2 CSR and L3 RF + wake BC2END L3END CSR, LSC included in LiTrack, good agreement with Elegant [Bosch, Kleman, Wu, PRSTAB, 2008] LCLS-II Accel. Phys. , J. Wu, SLAC

  6. By-pass line and Undulatorwake Implement wakefield UNDBEG UNDEND LCLS-II Accel. Phys. , J. Wu, SLAC

  7. Layout: higher energy • BC1 @ 335 MeV • Set points • BC1: R56 = 44.4 mm, Energy 335 MeV, peak current 207 Amp • L1S: – 16 degree • L1X: – 160 degree; 30 MeV • L2: – 32 degree • BC2: R56 = 27 mm, Energy 4.5 GeV, peak current 3 kA wire scanner 4 wire-scanners L0 L1X L1S gun DL1 135 MeV BC1 355 MeV BC2 4.5 GeV TCAV3 L3-linac By-pass 13.5 GeV L2-linac UND LCLS-II Accel. Phys. , J. Wu, SLAC

  8. Profiles BC1END UNDBEG CSR, LSC included in LiTrack, good agreement with Elegant [Bosch, Kleman, Wu, PRSTAB, 2008] LCLS-II Accel. Phys. , J. Wu, SLAC

  9. Bc2 CSR and L3 RF + wake BC2END L3END CSR, LSC included in LiTrack, good agreement with Elegant [Bosch, Kleman, Wu, PRSTAB, 2008] LCLS-II Accel. Phys. , J. Wu, SLAC

  10. By-pass line and Undulatorwake Implement wakefield UNDBEG UNDEND LCLS-II Accel. Phys. , J. Wu, SLAC

  11. Rematch the optics LCLS-II Accel. Phys. , J. Wu, SLAC • Twiss-function through BC1 @ 335 MeV

  12. EmittANCE GROWTH T.O. Raubenheimer • Due to ISR • E = 0.335 GeV; q = 6.43o; LB = 0.2035;DL = 2.44572; ; • Dgex = 5.5E-13  negligible • CSR and Space Charge: reported last time with Impact-T simulation  small LCLS-II Accel. Phys. , J. Wu, SLAC

  13. BC1 dipole field integral • BC1 energy set point to be as high as 350 MeV • Assuming the set point range is from 200 MeV to 350 MeV • Assuming the BC1 chicane can provide R56 from 15 mm to 65 mm for the above mentioned energy range (200 – 350 MeV) • With the same geometry as in CDR • Then the maximum field integral of each dipole is 1.31 kG m (350 MeV and R56 of 65 mm) • Details are plotted in the next page LCLS-II Accel. Phys. , J. Wu, SLAC

  14. BC1 dipole field integral 1.31 kG m 1.10 kG m LCLS-II Accel. Phys. , J. Wu, SLAC • BC1 energy set point: 200 -- 350 MeV • BC1 chicane R56: 15 (red curve) – 46 (green curve) – 65 (blue curve) mm

  15. Setpoint Comparison between setting BC1 @ 250 and 335 MeV Next, look at the jitter and tolerance LCLS-II Accel. Phys. , J. Wu, SLAC

  16. L1S phase jitter: UNDbegcentroid energy 250 MeV 335 MeV LCLS-II Accel. Phys. , J. Wu, SLAC

  17. L1S phase jitter: UNDbeg residual energy chirp 250 MeV 335 MeV LCLS-II Accel. Phys. , J. Wu, SLAC

  18. L1S phase jitter: UNDbeg peak current 250 MeV 335 MeV LCLS-II Accel. Phys. , J. Wu, SLAC

  19. L1X phase jitter: UNDbegcentroid energy 250 MeV 335 MeV LCLS-II Accel. Phys. , J. Wu, SLAC

  20. L1x phase jitter: UNDbeg residual energy chirp 250 MeV 335 MeV LCLS-II Accel. Phys. , J. Wu, SLAC

  21. L1x phase jitter: UNDbeg peak current 250 MeV 335 MeV LCLS-II Accel. Phys. , J. Wu, SLAC

  22. L1X amplitude jitter: UNDbegcentroid energy 250 MeV 335 MeV LCLS-II Accel. Phys. , J. Wu, SLAC

  23. L1x amplitude jitter: UNDbeg residual energy chirp 250 MeV 335 MeV LCLS-II Accel. Phys. , J. Wu, SLAC

  24. L1x amplitude jitter: UNDbeg peak current 250 MeV 335 MeV LCLS-II Accel. Phys. , J. Wu, SLAC

  25. Injector timing jitter: UNDbegcentroid energy 250 MeV 335 MeV LCLS-II Accel. Phys. , J. Wu, SLAC

  26. Injector timing jitter: UNDbeg residual energy chirp 250 MeV 335 MeV LCLS-II Accel. Phys. , J. Wu, SLAC

  27. Injector timing jitter: UNDbeg peak current 250 MeV 335 MeV LCLS-II Accel. Phys. , J. Wu, SLAC

  28. Jitter sensitivities and tolerance 250 MeV case from CDR LCLS-II Accel. Phys. , J. Wu, SLAC

  29. Jitter sensitivities and tolerance 335 MeV case on-going: L1S phase, L1X phase, timing LCLS-II Accel. Phys. , J. Wu, SLAC

  30. L1X phase jitter BC1@ 335 MeV: UNDBEG L1X: -160.5o L1X: -160o L1X: -159.5o LCLS-II Accel. Phys. , J. Wu, SLAC

  31. discussion • Linear compression study with optimization for BC1 @ 300 -- 350 MeV up to undulator end • Longitudinal profile up to undulator end • Tolerance study: centroid energy, residual energy chirp, peak current on timing and LINAC phase jitter up to undulator entrance • Looked into BC1 dipole magnet design for BC1 @ 335 MeV • The maximum field integral of each dipole is 1.31 kG m (350 MeV and R56 of 65 mm) • Full machine lattice in Impact code is on going • Strong focusing on sec. 11-2 • More tolerance study is needed. LCLS-II Accel. Phys. , J. Wu, SLAC

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