Numerical study of x-ray emission from electrons in a magnetically dominated plasma channel

We propose a scheme for generating high-brilliance, high-energy x-ray radiation using a compact NCD-plasma radiator formed by an intense laser pulse in near-critical-density (NCD) plasma. The mechanism exploits the intense azimuthal magnetic wakefield within the channel, driven by the return current along the channel wall, to induce high-amplitude, short-period betatron oscillations of injected electrons. Particle-in-cell simulations show that for a magnetically dominated plasma channel driven by a 40 TW laser, a 200 MeV electron beam produces x-rays with a peak brilliance of 2.3×1026 photons/(s mm2 mrad2 0.1%BW) at 300 keV and yields 4.5×1011 photons above 200 keV. A series of parameter scans confirms the robust performance across a practical range of laser and plasma conditions. The proposed NCD-plasma radiator can be realized with a 10-TW-class laser and a supersonic gas nozzle, enabling high-repetition-rate operation. Combined with emerging high-repetition-rate laser-plasma accelerators, this scheme may establish a practical path toward compact x-ray sources that are simultaneously high-repetition-rate, high-brilliance, and high-energy.