Limited Laser Bandwidth Impact on electron dynamics in

Limited Laser Bandwidth Impact on electron dynamics in injector C. Limborg, P. Bolton Feb 13 -04 • Fourier Limited pulses – Plateau Ripple – Slope • PARMELA simulations of modulated beams – for 0. 280 nm UV BW – impact of rise time on emittance

Fourier Limited pulses with

Rise/Fall Time [ps] Fourier Limited pulses Total Bandwidth [GHz]

1. 2 THz 0. 280 nm

0. 7 ps rise/fall Gun Exit

0. 7 ps rise/fall Entr. Linac

0. 7 ps rise/fall Linac Exit

1 ps rise time 1. 5 ps rise time

The various Rise/Fall times, obviously, do not affect slice emittance Slope (10 -90%) 0. 7 ps 1. 5 ps 80% 0. 90 0. 93 without new optimization, no problem for downstream compression

Conclusion • A 1. 2 THz UV (0. 280 nm) Band. Width generates plateau ripples of rms 2%, 1% , 0. 4% for rise times (0. 9 , 1. 05, 1. 5 ps) with modulation wavelength =380 m 0. 9 ps case The 2% modulation is attenuated at the entrance of L 01 And generates not more than +/- 1 ke. V at the end of L 01 Slower rise times and larger BW are even safer w. r. t LSC The limited BW of the laser, as long as it is larger than 0. 280 nm (in the UV) will not generate any dangerous LSC instability Possible sources of noise with <100 m and amplitude larger than 2% are potentially dangerous w. r. t LSC Instability (tolerance still to be defined in the presence of laser heater ) Those sources of noise need to be identified