| Summary: | Approved for public release; distribution is unlimited === As interest in high power free electron lasers (FELs) has increased, the FEL and accelerator communities have been faced with the need to develop high bunch charge, high repetition rate, low emittance electron sources for use as the driving accelerators for FELs. A novel superconducting, radio-frequency (SRF) gun/booster has been designed by and built for the Naval Postgraduate School (NPS) FEL Beam Physics Lab in collaboration with Niowave, Inc., for studying this electron source regime. The NPS SRF gun/booster operates at 500 MHz and is based upon a quarter-wave structure. It incorporates many features that make it desirable for studying the cathodes and transport regimes necessary to explore high bunch charge beams, including adjustable field focusing, short transport out of the gun, and the ability to change cathode types and materials. After attaining "first beam" in June 2010, the NPS gun has been established as the first SRF electron gun in the United States. Initial results show excellent agreement with simulation with bunch charges of 110 pC and transverse emittance estimates of 4 mm-mrad. Additionally, a modal analysis tool for the NPS FEL simulation software is developed based upon the Hermite-Gaussian basis set. Using a minimization of mode coefficients approach, we decompose output optical fields for amplifier FEL designs and experiments for FEL optimization and comparison of laser output fields.
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