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CSR Benchmark Test-Case Results

Evaluation of Chicane CSR test case results based on the transient model in LCLS-TN-01-12, discussing second-order compression effects, beta and dispersion functions, energy spread, and emittance. The impact of chicane CSR wakefields on phase space and emittance growth is analyzed using Gaussian and uniform distributions. ####

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CSR Benchmark Test-Case Results

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  1. CSR Benchmark Test-Case Results Paul Emma SLAC January 14, 2001 BERLIN CSR Workshop

  2. Chicane CSR Test-Case Use line-charge CSR  transient model described in LCLS-TN-01-12… (Stupakov/Emma, Dec. 2001) [same now used in Elegant] …based on TESLA-FEL-96-14 (Saldin et al., Nov. 1996) (T566 included, no ISR* added) * incoherent synchrotron radiation

  3. Initial Gaussian Distribution Prior to Chicane perfectly linear correlation sE/E0 = 0.72 %  bunch head ss = 200 mm E0 = 5 GeV

  4. Second Order Compression Included: T566 /mm T566 -3R56/2 leads to slight bunch shape distortion after drift-3 before drift-3

  5. Beta and Dispersion Functions B2 B3 B1 B4 ‘CSR-altered’ bx ‘linear’ bx hx-max 267 mm ‘linear’ hx

  6. Bunch Length and R56 B2 B3 B1 B4 ss0 = 200 mm ss = 20 mm B2 B4 B3 B1 R56 = -25 mm

  7. Final s-d phase space (gaussian input) sE/E0 = 0.716 %  bunch head ss = 20.3 mm

  8. Energy Spread and Emittance (gaussian) B2 B4 B3 B1 E /E0 -0.043% sd 0.021% B2 B4 B3 B1 gex 1.52 mm

  9. Total RMS Relative Energy Spread (including ‘chirp’) B2 B4 B3 B1

  10. Chicane CSR-wake Movie (gaussian)

  11. Chicane CSR-integrated-wake (gaussian)

  12. Final x-x Phase Space (gaussian input) ge 1.52 mm geCSR 0.145 mm ge0 = 1.00 mm bopt 1.37 m aopt-1.10

  13. Final x-x Phase Space (gaussian & optimalb0, a0) emittance growth can be reduced by choosing optimal b-functions ge 1.15 mm geCSR 0.145 mm bbopt aaopt ge0 = 1.00 mm

  14. Beta and emittance (gaussian & optimalb0, a0) too big? bmin 0.6 m bbopt aaopt gex 1.15 mm

  15. CSR wakefields (gaussian  bend-1 to drift-2) bend-1 (10) L = 0.4 m drift-1 (20) L = 5 m Nbin = 600, smoothed over 4 bend-2 (10) L = 0.4 m drift-2 (10) L = 1 m

  16. CSR wakefields (gaussian  bend-3 to drift-4) bend-3 (20) L = 0.4 m drift-3 (40) L = 5 m drift-4 (20) L = 2 m bend-4 (20) L = 0.4 m

  17. Compressing Uniform Distribution

  18. Final s-d phase space – Uniform input dist. sE/E0 = 0.720 % ss = 20.2 mm

  19. Energy Spread and Emittance (uniform) E /E0 -0.046% sd 0.007% emittance growth reduced compared to gaussian gex 1.12 mm

  20. Chicane CSR-wake Movie – Uniform Dist.

  21. Chicane CSR-integrated-wake – Uniform Dist.

  22. Final x-x Phase Space (uniform input) ge 1.12 mm geCSR 0.07 mm ge0 = 1.00 mm bopt 3.9 m aopt-0.51

  23. CSR wakefields (uniform bend-1 to drift-2) bend-1 (10) L = 0.4 m drift-1 (20) L = 5 m Nbin = 600, smoothed over 4 bend-2 (10) L = 0.4 m drift-2 (10) L = 1 m

  24. CSR wakefields (uniform bend-3 to drift-4) bend-3 (20) L = 0.4 m drift-3 (40) L = 5 m drift-4 (20) L = 2 m bend-4 (20) L = 0.4 m

  25. Betatron Amplitude per Bunch Slice gaussian l(s) uniform l(s)

  26. Final s-d phase space - Single-Bend sE/E0 = 0.011 % ss = 20.1 mm

  27. Energy Spread and Emittance – Single Bend (24ssR2)1/3 sd = 0.011% steady-state bend magnet

  28. CSR-Wake Movie - Single-Bend

  29. LCLS BC2 CSR-integrated-wake (tracked dist.)

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