Simulated performance of a compact water-window FEL driven by a structure wakefield accelerator

Free-electron lasers (FELs) send an accelerated electron beam through a magnetic undulator to provide a source of continuously tunable, short (10s of fs), high-peak power (GW-scale) radiation. FELs have found many applications, particularly in the infrared, extreme ultraviolet (EUV) and X-ray regimes. However, current EUV and X-ray FELs are large (100s of m) and expensive facilities, limiting the accessibility of these sources. In this work, we present FEL simulations driven by a compact accelerator combining high-gradient short pulse two-beam wakefield accelerators [1] and short-period superconducting undulators [2]. An FEL demo based on a GeV-scale accelerator is discussed as a driver for a water-window ( 2.3-4.4 nm) FEL with a ≈ 50 m length. Such a proof-of-principle integrated facility would serve the dual purpose of supporting user-based research in the water-window regime, and providing a proving ground for these new technologies to later be applied to shorter wavelength FELs. Here, we present early design and simulation efforts with a focus on FEL-process modeling.