BETATRON X-RAYS FROM A LASER WAKEFIELD ACCELERATOR IN THE IONIZATION INDUCED TRAPPING REGIME

Betatron x-rays with multi-keV photon energies have been observed from a GeV-class laser-plasma accelerator. The experiment was performed using the 200 TW Callisto laser system at LLNL to produce and simultaneously ob-serve GeV-class electron beams and keV Betatron x-rays. The laser was focused into various gas cells with sizes rang-ing from 3 to 10 mm, and containing mixed gases (He, N, CO2, Ar, Ne) to accelerate large amounts of charge in the ionization induced trapping regime. KeV betatron x-rays were observed for various concentrations of gases. Elec-tron spectra were measured on large image plates with the two-screen method after being deflected by a large 0.42 Tesla magnet spectrometer