Advances and Challenges in Compton Radiation Sources*

Ongoing developments in Compton radiation sources are aimed toward a diversity of potential applications, ranging from university-scale compact x-ray light sources and metrology tools for EUV lithography, to positron sources for ee colliders. Novel conceptual approaches are pursued on different routes: One research direction lies in multiplying the source’s repetition rate and increasing its average brightness by placing the point of Compton interaction inside an optical cavity. Highgradient plasma-wakefield accelerators are fast becoming a practical reality, offering a new paradigm to compact all-optical Compton sources operating in x-rayand gamma-regions. Continuing improvement in the quality of the beam of plasma accelerators promises the achievement of fully coherent Compton x-rays, thereby prompting the evolution of the Compton source to an alloptical free-electron laser.