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| THPPH026 |
Design of a Two-Stage Laser Pulse Shaping System for FEL Photoinjectors
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617 |
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- M. B. Danailov, A. A. Demidovich, R. Ivanov
ELETTRA, Basovizza, Trieste
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Temporal pulse shaping is one of the most important requirements to photoinjector lasers needed in the majority of FEL projects. The laser pulses commonly requested for excitation of the photocathode are in the UV (around 260 nm) and have flat-top shape of duration in the 5-10 ps range. More complex pulse shapes like "water-bags" and ramps have also been proposed recently, indicating that the pulse shaping scheme must offer flexibility in generating different shapes. In this paper we present an approach which combines the two main pulse shaping techniques, namely acousto -optic dispersive filter (DAZZLER) and Fourier-based 4-f system. The DAZZLER is inserted between the seed mode-locked oscillator and the amplifier and is used for preliminary shaping in the infrared, while the final pulse shape and duration are determined by a 4-f system incorporating deformable mirror positioned after the harmonic conversion to UV. The paper provides simulations and experimental results on designed and measured pulses of both flat-top and asymmetric (ramp) type, comparing solutions based on different distribution of amplitude and phase shaping between the two parts of the shaping setup.
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