Gamma-ray production from resonant betatron oscillations in plasma wakes

ABSTRACT The laser-plasma wakefield accelerator is a novel ultra-compact particle accelerator. A very intense laser pulse focused on to plasma can excites plasma density waves. Electrons surfing these waves can be accelerated to very high energieswith unprecedented accelerating gradients in excess of 1 GV/cm. While accelerating, electrons undergo transverse betatron oscillations and emit synchrotron-like x-ray radiation in to a narrow on-axis cone, which is enhanced when electrons interact with the electromagnetic field of the laser. In this case, the laser can resonantly drive the electro nmotion, lading to direct laser acceleration. This occurs when the betatron frequency matches the Doppler down-shifted frequency of the laser. As a consequence, the number of photons emitted is strongly enhanced and the critical photon energy is increases to 100 ¶s of keV. Keywords: betatron radiation, resonance , laser , plasma accelerator 1. INTRODUCTION In a laser-plasma wakefield accelerator