New source technologies and their impact on future light sources

Emerging technologies are critically evaluated for their feasibility in future light sources. We consider both new technologies for electron beam generation and acceleration suitable for X-ray free-electron lasers (FELs), as well as alternative photon generation technologies including the relatively mature inverse Compton scattering and laser high-harmonic generation. Laser-driven plasma wakefield acceleration is the most advanced of the novel acceleration technologies, and may be suitable to generate electron beams for X-ray FELs in a decade. We provide research recommendations to achieve the needed parameters for driving future light sources, including necessary advances in laser technology.