Enhanced gamma-ray betatron radiation from laser accelerator and plasma radiator

A compact source of high-energy femtosecond photons stands as a transformative tool across diverse fields, attainable through betatron radiation generated in the laser wakefield acceleration process. The concurrent pursuit of photon energy and flux confronts a critical challenge, arising from the intrinsic discrepancy between the acceleration and radiation processes. To address this, we demonstrate a hybrid betatron scheme, driven by multi-petawatt laser pulses, using a two-stage gas medium to decouple acceleration from radiation. A low-density medium enables efficient acceleration, followed by a high-density plasma that markedly enhances betatron flux and photon energy. It yields gamma-ray pulses with a brilliance of ~5×10²⁴ photons∙s⁻¹∙mm⁻²∙mrad⁻²∙0.1%-BW at 180 keV, applied to radiography of a complex metallic structure. Particle-in-cell simulations confirm that the dense radiator stage efficiently converts high-energy electrons into high-brightness gamma rays. These results establish a simple, scalable route to compact, ultrabright betatron gamma-ray sources, opening new opportunities in photon-driven science and technology.