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LSC in drifts Simulations for Injector Case of 100  m modulation

Simulations of LSC in the LCLS Injector C é cile Limborg-D é prey, P. Emma, Z. Huang, Juhao Wu March 1st, 2003. LSC in drifts Simulations for Injector Case of 100  m modulation Other wavelengths [ 50 ,150 ,200 , 300]  m Conclusion. Simulations of LSC in drifts.

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LSC in drifts Simulations for Injector Case of 100  m modulation

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  1. Simulations of LSC in the LCLS Injector Cécile Limborg-Déprey, P. Emma, Z. Huang, Juhao Wu March 1st, 2003 • LSC in drifts • Simulations for Injector • Case of 100 m modulation • Other wavelengths [ 50 ,150 ,200 , 300] m • Conclusion Cécile Limborg-Déprey, SLAC

  2. Simulations of LSC in drifts • Simulations description • 40k/200k particles • Distribution generated using the Halton sequence of numbers • Longitudinal distribution • 2.65 m of drift • With 3 cases studied • 6MeV, 1nC • 6 MeV , 2nC • 12 MeV, 1nC +/- 5% Cécile Limborg-Déprey, SLAC

  3. Cécile Limborg-Déprey, SLAC

  4. Cécile Limborg-Déprey, SLAC

  5. Comparison with theory Summary 100m • Transverse beam size evolution along beamline taken into account • (Radial variation of green’s function for 2D ) • Evolution of peak current NOT taken into account yet • Absence of dip in 6MeV curve : • “Coasting beam “ against “bunched beam” with edge effects • Intrinsic energy spread Cécile Limborg-Déprey, SLAC

  6. ASTRA Simulations of LSC along Injector Beamline • Nominal Tuning • 10 ps pulse (rise/fall time 1ps ) • 1 nC 0MeV 6MeV 60MeV 150MeV Linac0-1 Linac0-2 Laser + Gun Cécile Limborg-Déprey, SLAC

  7. ASTRA Simulations for modulation of 100 m • Modulation Wavelength = 100 m , with  8% amplitude peak-to-peak “Noise of  8% amplitude around flat top is likely to be present “ P.Bolton • FWHM = 3mm • Longitudinal bining = 200 points (~ more than 6 bins per period) • 1 Million particles with modulation = 100 m Region of interest Fourier Analysis Current density Position (mm) Position (mm) Cycles per mm Cécile Limborg-Déprey, SLAC

  8. Longitudinal Phase Space After removal of correlation up to order 5 Longitudinal Phase Space z = 0.15 m E = 6MeV Gun Exit Fourier transform E = 0 → 0.35 keV Energy  Current modulation = 5.65% → 3% Fourier transform Current Fit up to 3rd order Substract and Fit Amplitude + rms w.r.t reference level Cécile Limborg-Déprey, SLAC

  9. z = 1.4 m E = 6MeV Entrance L01 Fourier transform E = 0.35 keV → 1 keV Energy  Current modulation = 3% → 1.5% Fourier transform Current Cécile Limborg-Déprey, SLAC

  10. Exit L01 z = 4.4 m E = 60MeV Exit L01 Fourier transform E = 1 keV → 3 keV Energy  Current modulation = 1.5 % → 1.5% Fourier transform Current Cécile Limborg-Déprey, SLAC

  11. Exit L02 z = 8.4 m E = 150MeV Exit L02 Fourier transform E = 3 keV → 3.9 keV Energy  Current modulation = 1.5 % → 1.6% Fourier transform Current Cécile Limborg-Déprey, SLAC

  12. Summary 100m Cécile Limborg-Déprey, SLAC

  13. Summary 50,100,150,300m Attenuation by factor More than 5 for  <100m ~ 5 for  >100m Cécile Limborg-Déprey, SLAC

  14. Same results with PARMELA At end LCLS injector beamline: • Current density modulation strongly attenuated • residual energy oscillation has amplitude between 2 keV and 4 keV for wavelengths [50 m, 500 m] • Impedance defined by Cécile Limborg-Déprey, SLAC

  15. Conclusion • Good agreement Simulations / Theory for drift and Acceleration • Solutions to handle Numerical Problems • Noise Problem ( high number of particles) • Shorter wavelengths (new option in ASTRA) • Clear “Attenuation” in gun makes situation less critical than first thought • But not enough attenuation : • for wavelengths >100 m : attenuation line density modulation by factor of~5 • for wavelengths <100 m : attenuation line density modulation by factor of more than 5 • To reach less than 0.1% at end of beamline requires less than 0.4% rms on laser so +/- 0.56% = far beyond what is achievable by laser • Also large energy modulation in all cases (“large” = of the order or more than intrinsic energy spread) • Heater is required as microstructure present in all wavelengths cases and in particular those < 100 m Cécile Limborg-Déprey, SLAC

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