X-ray radiation emitted from the betatron oscillation of electrons in laser wakefields

An ultra-intense short laser pulse incident on a plasma generates a blowout-regime wakefield, where almost all of the electrons are expelled radially by the ponderomotive force. Electrons injected in an off-axis position of the blowout-regime wakefield experience transverse oscillations as well as longitudinal acceleration, and emit intense X-rays from betatron oscillations. In order to investigate the conditions for X-ray generation, we simulated the relativistic electron motion from wakefield profiles pre-calculated with a two-dimensional particle-in-cell code. The maximum energy of the off-axis injected electrons reaches 900 MeV for a propagation time of 20 ps and the electron emits intense X-ray radiation with energies up to 13 keV.