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Intensive MOGA Optimizations of LCLSII configurations

Intensive MOGA Optimizations of LCLSII configurations. L. Wang Work with T.O. Raubenheimer, J. Wu LCLS-II Accelerator Physics meeting Jan 15th, 2013.

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Intensive MOGA Optimizations of LCLSII configurations

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  1. Intensive MOGA Optimizations of LCLSII configurations L. Wang Work with T.O. Raubenheimer, J. Wu LCLS-II Accelerator Physics meeting Jan 15th, 2013 Many thanks to J Wu for useful discussion and help on the Litrack set-up, thanks F. Zhou for his help on IMPACT simulation data, M. Woodley and Y. Nosochkov for providing the R56 data. LCLS-II Accel. Phys. , L. Wang, SLAC

  2. Problem Layout Gun to L0, using IMPACT (thanks to F. Zhou) Particle Tracking start from L0 to beginning of the Undulator using LiTrack Nominal R56@BC1= 46 mm (thanks M. Woodley, Y. Nosochkov) Nominal R56 @BC2= 29 mm Nominal R56@Bypass Dogleg= -0.115 mm Nominal R56@HBEND= -0.383/0.479mm (HXR/SXR) Wake field is included wire scanner 4 wire-scanners L0 L1X L1S gun DL1 135 MeV BC1 250/335 MeV BC2 4.5 GeV TCAV3 BSY 10/13.5 GeV L3-linac L2-linac LCLS-II Accel. Phys. , L. Wang, SLAC

  3. Wake All surface material are SS (except Undulator) LCLS-II Accel. Phys. , L. Wang, SLAC

  4. Optimization Method • MOGA(Multi-Objective Genetic Algorithm) • Variables: • Phase and Voltage of L1,LX,L2,L3 • R56@BC1 • R56@BC2 • … • Objectives & constrains • Energy spread • Jitters(RF Voltage and phase jitter, Charge jitter, Laser timing jitter) • Energy at BC1(250MeV/335MeV) • Energy at BC2(4.5GeV) • Energy at the beginning of undulator (13.5GeV/10GeV) • Peak current at the beginning of undulator (3kA/4kA) • …second order curvature LCLS-II Accel. Phys. , L. Wang, SLAC

  5. Objectives • The Objective of sensitivity to jitters is the total normalized one For instance (I/I)0=12%, (E/E)0=0.1%, ()0=100fs • The energy spread is normalized by 0.03% • Simplified Jitter model in MOGA Various Jitters LCLS-II Accel. Phys. , L. Wang, SLAC

  6. The range of RF phase A larger range may be need for more studies! L1 Phase: [-30, -10] LX phase: [-162, -156] L2 phase: [-36, -31] L3 phase : [-10,0] (based on study at 250pC) LCLS-II Accel. Phys. , L. Wang, SLAC

  7. Benchmarked with design report LCLS-II Accel. Phys. , L. Wang, SLAC

  8. Complexity LCLS-II Accel. Phys. , L. Wang, SLAC • Only About 10 variables, but with many constrains • The bunch profile (also the peak current) is not easy to be satisfied. Many efforts have been taken to make the optimization converge fast and well. • Wake field and residual R56 after L3 Wake field couples with bunch profile and add energy chirp in the phase space, therefore it can change the bunch profile/peak current ; the non-zero R56 also rotate the phase space, which causes the variation of the bunch profile/peak current after L3. • CPU

  9. results LCLS-II Accel. Phys. , L. Wang, SLAC • 250pC HXR • 250pC SXR • 150pC HXR • 40pC HXR • 20pC HXR • 20pC SXR

  10. MOGA optimization of 250pC HXR(BC1@335MeV) Converge after 100 generations LCLS-II Accel. Phys. , L. Wang, SLAC

  11. Objectives @250pC HXR The slope in z-profile shows the dI/dz near bunch center. ( thanks J. Wu) It doesn't mean anything for Gaussian shape bunch Total Jitters H T 150pC 20pC LCLS-II Accel. Phys. , L. Wang, SLAC

  12. Parameters @250pC HXR---Solutions Green Zone Red zone Small jitter zone Small energy spread zone Nominal R56 @BC1= 46 mm Nominal R56 @BC2= 29 mm Large range with LX phase <-162? LCLS-II Accel. Phys. , L. Wang, SLAC

  13. Example of the best solution@250pC HXR Nominal R56 @BC1= 46 mm Nominal R56 @BC2= 29 mm H T Beginning of Undulator End of BC1 LCLS-II Accel. Phys. , L. Wang, SLAC

  14. Jitters distributions(250pC HXR run 2553 ) • Energy jitter and Timing jitter is small • Current jitter is dominated by LX phase, L1 voltage, L2 phase • Time jitter is dominated by L2 phase and voltage • Energy jitter widely distributed. (L3 Voltage; voltage and phase of L1,L2 and LX, Laser timing) • Energy jitter is insensitive to charge jitter and L3 phase jitter (I/I)0=12%, (E/E)0=0.1%, ()0=100fs LCLS-II Accel. Phys. , L. Wang, SLAC

  15. L2 Voltage jitter LCLS-II Accel. Phys. , L. Wang, SLAC

  16. L2 Phase Jitter LCLS-II Accel. Phys. , L. Wang, SLAC

  17. LX phase jitter LCLS-II Accel. Phys. , L. Wang, SLAC

  18. Example: L3 phase effect (slightly reduces the energy jitter with redistributed jitters @BC1250Mev) Phase= -10o Phase=0 LCLS-II Accel. Phys. , L. Wang, SLAC

  19. MOGA optimization of 20pC HXR LCLS-II Accel. Phys. , L. Wang, SLAC

  20. Objectives @20pC HXR Ip=3kA LCLS-II Accel. Phys. , L. Wang, SLAC

  21. Parameters @20pC HXR Ipk=3kA Red zone has small jitter Green zoon has small energy spread LCLS-II Accel. Phys. , L. Wang, SLAC

  22. example@20pC HXR Ipk=3.2kA End of L3 Beginning of undulator LCLS-II Accel. Phys. , L. Wang, SLAC

  23. Jitters distributions • Current jitter is dominated by LX phase, L1 voltage • Time jitter is dominated by L2 phase and voltage • Energy jitter widely distributed. (L3 Voltage; voltage and phase of L1,L2 and LX, Laser timing) • Energy/timing jitters are insensitive to L3 phase jitter LCLS-II Accel. Phys. , L. Wang, SLAC

  24. MOGA optimization of 40pC HXR (Ipk=4kA) LCLS-II Accel. Phys. , L. Wang, SLAC

  25. Objectives @40pC HXR Ip=4kA Converges slowly with large energy spread & jitter LCLS-II Accel. Phys. , L. Wang, SLAC

  26. Parameters @40pC HXR Ipk=4kA many islands Red zone has small jitter Green zoon has small energy spread LCLS-II Accel. Phys. , L. Wang, SLAC

  27. example@40pC HXR Ipk=4.4kA End of L3 Beginning of undulator LCLS-II Accel. Phys. , L. Wang, SLAC

  28. Jitters distributions • Current jitter is dominated by LX phase, L1 voltage and L2 phase • Time jitter is dominated by L2 phase and voltage • Energy jitter widely distributed. (L3 Voltage; voltage and phase of L1,L2 and LX, Laser timing) • Energy/current/timing jitters are insensitive to L3 phase jitter LCLS-II Accel. Phys. , L. Wang, SLAC

  29. Non-zero R56 after BC2 The non-zero R56 after BC2 can be important for low charge beam, especially when the bunch is close to full compression. However, there are no clear evidences at this time that the non-zero R56 have serious side effects LCLS-II Accel. Phys. , L. Wang, SLAC

  30. Summary of Configurations Nominal R56 @BC1= 46 mm Nominal R56 @BC2= 29 mm LCLS-II Accel. Phys. , L. Wang, SLAC

  31. Summary LCLS-II Accel. Phys. , L. Wang, SLAC • Intensive MOGA optimization, which provides a useful tool for the design • The energy jitter and timing jitter are small (compared with current jitter): • The time jitter is always dominated by the L2 phase and voltage • LX phase always contributes to a large current jitter; • The energy jitter is widely distributed • The best solutions of R56@ BC1 and BC2 are close to the design values. • The non-zero R56 after L3 is ok, although it complicates the design

  32. Next steps LCLS-II Accel. Phys. , L. Wang, SLAC With larger phase variation range to find better solution? More studies are need for 40 pCcase, which has peak current of 4kA Trading between energy jitter and phase jitter(L3 phase); Study at LCLS to test the sensitivity and ability trade dependence.

  33. Colleration Joe mingXie—Yang LCLS-II Accel. Phys. , L. Wang, SLAC

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