Ultrahigh intensity Compton scattering focused X-ray source

Summary form only given, as follows. At ultrahigh intensities, where the normalized vector potential associated with the laser wave exceeds unity, the electron axial velocity modulation due to radiation pressure yields nonlinear Compton backscattered spectra. For applications requiring a narrow Doppler upshifted linewidth, such as the future /spl gamma/-/spl gamma/ collider or focused X-ray generation, this can pose a serious problem. It is shown that temporal laser pulse shaping using spectral filtering at the Fourier plane of a chirped pulse laser amplifier, or similar approaches, can alleviate this problem, and that this technique can be scaled to the required multi-TW range. Compton backscattered spectra are derived in three cases: hyperbolic secant, hybrid pulses (hyperbolic secant transient and flat-top), and square optical pulses similar to those experimentally obtained by Weiner et al. It is found that the optimum laser pulse shapes correspond to square pulses, yielding a high contrast ratio between the main spectral line and the transient lines. The corresponding spectral filter function is also determined, and its practical implementation in a CPA laser is addressed.