Femtosecond X-rays from 90° Thomson scattering

We report on progress on the femtosecond X-ray pulse generation experiment. The experiment involves a relativistic electron beam (50 MeV) with an rms bunch length of 10 ps containing 1 -2 nC of charge, and a ultrashort pulse (50-200 fs), high power (<4 TW) 0.8 μm laser beam from a Ti:Al₂O₃ laser system. Both beams are focused down to about a 50 μm waist size and intersect at 90°. The laser field acts as an electromagnetic undulator for the relativistic electron beam generating radiation upshifted by 2 γ ² and a pulse length given by the transit time of the laser beam across the electron beam. For a 50 MeV electron beam we expect 10 ⁵ photons at 0.4 Å (25% bandwidth) in a cone angle of 6-10 mrad in about a 200 fs pulse