Brightness Optimization of Ultra-Fast Thomson Scattering X-ray Sources

We present simple scaling relations of the brightness a Thomson x-ray source on the electron and laser beam parameters in the case of a head (180 degree) interaction geometry. In particular, it is shown that a direct relation exists between the x-ray brightness and the electron beam brightness. These relations are discussed in the context of the PLEIADES Thomson x-ray source, where 107 photons per pulse, with photon energies as high as 140 keV, have been produced by colliding a 0.25 nC, picosecond electron bunch with a 500 mJ, 50 fs, 800 nm laser pulse. The estimated peak brightness of the source is about 1016 photons/s/mm2/mrad2/0.1 %b.w. A comparison of the current performance of the source and the predicted performance using optimized parameters is presented.