Multi-objective Optimizations of a Novel Cryo-cooled DC Gun Based Ultra Fast Electron Diffraction Beamline

Abstract

We present the results of multi-objective genetic algorithm optimizations of a potential single shot ultra fast electron diffraction beamline 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 sample location have been performed for three different sample radii: 50, 100, 200 microns, for two final bunch charges: 100k and 1000k electrons. Analysis of the solutions is discussed, as are the effects of disorder induced heating. In particular, a coherence length per rms spot size of 0.27 nm/micron was obtained for a final bunch charge of 100k electrons and final rms bunch length of approximately 100 fs. For a final charge of 1000k electrons the cryogun produces a coherence length per rms spot size of 0.1 nm/micron for an rms bunch length of 100-200 fs and final spot size of 50 micron. These results demonstrate the viability of using genetic algorithms in the design and operation of ultrafast electron diffraction beamlines.

References in corpus (4)

• New electron source concept for single-shot sub-100 fs electron diffraction in the 100 keV range
• Cold electron beams from cryo-cooled, alkali antimonide photocathodes
• Demonstration of Cathode Emittance Dominated High Bunch Charge Beams in a DC gun-based Photoinjector
• Fundamental Photoemission Brightness Limit from Disorder Induced Heating

Cited by in corpus (4)

• A kiloelectron-volt ultrafast electron micro-diffraction apparatus using low emittance semiconductor photocathodes
• The Role of Low Intrinsic Emittance in Modern Photoinjector Brightness
• Point-to-Point Coulomb Effects in High Brightness Photoelectron Beamlines for Ultrafast Electron Diffraction
• Comparison of Multiobjective Optimization Methods for the LCLS-II Photoinjector