Quasi-monoenergetic and tunable X-rays from a laser-driven Compton light source

The maximum achievable photon energy of compact, conventional, Compton-scattering X-ray sources is currently limited by the maximum permissible field gradient of conventional electron accelerators(1,2). An alternative compact Compton X-ray source architecture with no such limitation is based instead on a high-field-gradient laser-wakefield accelerator(3-6). In this case, a single high-power (100 TW) laser system generates intense laser pulses, which are used for both electron acceleration and scattering. Although such all-laser-based sources have been demonstrated to be bright and energetic in proof-of-principle experiments(7-10), to date they have lacked several important distinguishing characteristics of conventional Compton sources. We now report the experimental demonstration of all-laser-driven Compton X-rays that are both quasi-monoenergetic (similar to 50% full-width at half-maximum) and tunable (similar to 70 keV to >1 MeV). These performance improvements are highly beneficial for several important X-ray radiological applications(2,11-15).