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S2E in LCLS Linac M. Borland, Lyncean Technologies, P. Emma, C. Limborg, SLAC

S2E in LCLS Linac M. Borland, Lyncean Technologies, P. Emma, C. Limborg, SLAC. LCLS. 150 MeV  z  0.83 mm    0.10 %. 250 MeV  z  0.19 mm    1.8 %. 4.54 GeV  z  0.022 mm    0.76 %. 14.35 GeV  z  0.022 mm    0.01 %. 6 MeV  z  0.83 mm    0.1 %.

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S2E in LCLS Linac M. Borland, Lyncean Technologies, P. Emma, C. Limborg, SLAC

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  1. S2E in LCLS Linac M. Borland, Lyncean Technologies, P. Emma, C. Limborg, SLAC

  2. LCLS 150 MeV z  0.83 mm   0.10 % 250 MeV z  0.19 mm   1.8 % 4.54 GeV z  0.022 mm   0.76 % 14.35 GeV z  0.022 mm   0.01 % 6 MeV z  0.83 mm   0.1 % Lh L =0.6 m rf=180 rf gun L0 L = 9 m rf = -38° L = 330 m rf = -43° L = 550 m rf = -10° L = 6 m undulator L = 120 m L1 L2 L3 X ...existing linac BC-1 L = 6 m R56= -36 mm BC-2 L = 22 m R56= -22 mm DL-1 R56  0 DL-2 R56 = 0

  3. Nominal LCLS Optics…

  4. LCLS LCLS Start-to-End Tracking Simulations • Track entire machine to evaluate beam brightness & FEL • Track machine many times with jitter to test stability budget • See C. Limborg talk for injector • See Fawley, Reiche talks for FEL Parmela Elegant Genesis space-charge compression, wakes, CSR, … SASE FEL with wakes

  5. Initial Beam from Parmela Tracking • 1 nC • 10-psec FWHM • 0.7-ps rise/fall • 120 MV/m gun • getherm 0.3 mm • 150 MeV gex gex,y < 1 mm gey 2105 to 2106 macro-particles z, DE/E x, y

  6. Sliced e- Beam to Evaluate FEL (Dz 0.7 mm) gex,y sE/E Ipk

  7. centroid match FEL wavelength b mismatch variation slice 4D centroid osc. amplitude

  8. FEL parameter gain length FEL power ‘Ming Xie method’ see S. Reiche, B. Fawley talks…

  9. LCLS Longitudinal Jitter Tolerance Budget LCLS. note, Elegant simulations use 0.5 ps rms X- X-band

  10. DsE/sE0 0.01% DE/E0 0.1% 2D tracking used to develop tolerance budget DI/I0 8.6% Dtfw/tfw 12.5% Dtrms 125 fs Dsz/sz0 12.5%

  11. Now add component transverse misalignments… • Misaligned randomly in x and y: • All quadrupoles: 300 mm rms • All rf structures: 300 mm rms • All BPMs: 300 mm rms Transverse wakefields induce projected emittance growth and couple charge jitter to emittance jitter

  12. trajectory before steering gex 10000 mm x-y screen • Misaligned randomly in x and y: • All quadrupoles: 300 mm rms • All rf structures: 300 mm rms • All BPMs: 300 mm rms

  13. trajectory after steering Steered using Elegant’s ‘global’ algorithm gex 5 mm gey 2 mm after

  14. after steering coils Now let Elegant optimize both x and y emittances with two x- and two y-steering coils (pairs separated by Dyp/2) gex 1.02 mm gey 1.09 mm

  15. M. Borland optimized 100 random seeds… De/e 20% (projected)

  16. gex (mm) x-position of feedback set-point (mm) Real Emittance Minimization Using Trajectory ‘Bumps’ in SPPS H. Schlarb, P. Emma ~10 minutes (Ne 3.5 nC, sz 1 mm)

  17. Now run 200 S2E simulations, including Genesis runs, but with a distorted and ‘emittance-tuned’ trajectory… M. Borland, PE, J. Lewellen, C. Limborg, M. Woodley SC-wiggler is ON

  18. I 3.91 kA, rms  10% gex 2.29 mm, rms  5% projected x-emittance peak current gey 0.93 mm, rms  4% E 14.36 GeV, rms  0.04% projected y-emittance e- energy

  19. Dt 0, rms  49 fs gexs 0.76 mm, rms  2% sliced x-emittance bunch arrival time geys 0.67 mm, rms  2% sE/E 710-5, rms  0.810-5 sliced y-emittance sliced energy spread

  20. x 0, rms  9 mm (30% sx) x 0, rms  0.55 mrad x-position mean values set to zero for Genesis runs x-angle y 0, rms  1.5 mm y 0, rms  0.21 mrad y-position y-angle

  21. Lg 4.1 m, rms  5% lr 1.5 Å, rms  0.09% Gain length wavelength Lg ? m, rms  5% P 4 GW, rms  25% ??? gain length

  22. Final Comments* • Fairly realistic simulations with jitter demonstrate tight, but achievable tolerances – SPPS experience very helpful • Transverse wakefields are correctable – not a major issue (lower charge, shorter linac, and shorter bunch vs. SLC) • LCLS still deciding on SC-wiggler at BC2, or laser system at injector (as proposed at DESY for TTF-2; Saldin et al.) • LCLS entering engineering stage – detailed design must be ‘nailed’ down very soon (CD-2b in March 2004) * Special thanks to M. Borland: working for free!

  23. CSR gain (1D-model) in LCLS without wakefield or long. space-charge SC-wig OFF SC-wig ON initial modulation period prior to BC1 see Z. Huang talk Tuesday

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