Abstract
We present the results of multiobjective genetic algorithm optimizations of a single-shot ultrafast electron diffraction beam line utilizing a 225 kV dc gun with a novel cryocooled photocathode system and buncher cavity. Optimizations of the transverse projected emittance as a function of bunch charge are presented and discussed in terms of the scaling laws derived in the charge saturation limit. Additionally, optimization of the transverse coherence length as a function of final rms bunch length at the sample location have been performed for three different sample radii: 50, 100, and , for two final bunch charges: electrons (16 fC) and electrons (160 fC). Example optimal solutions are analyzed, and the effects of disordered induced heating estimated. In particular, a relative coherence length of was obtained for a final bunch charge of electrons and final bunch length of . For a final charge of electrons the cryogun produces for and . These results demonstrate the viability of using genetic algorithms in the design and operation of ultrafast electron diffraction beam lines.
1 More- Received 18 April 2016
DOI:https://doi.org/10.1103/PhysRevAccelBeams.19.093402
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Published by the American Physical Society