Thomson scattering of intense lasers from electron beams at arbitrary interaction angles

Analysis of nonlinear Thomson scattering of intense lasers from relativistic electron beams is extended to describe off-axis scattering geometries. Electron trajectories are calculated for the case of a plane electromagnetic wave of arbitrary intensity, either circularly or linearly polarized, interacting with a relativistic electron beam at an arbitrary interaction angle. The trajectories are used to derive analytic expressions for the intensity distribution of the scattered radiation. These expressions are valid in the nonlinear regime (arbitrary laser intensity) and include the generation of harmonics. The effect of interaction angle on the intensity distribution is discussed and spectra are plotted numerically for the specific cases of head-on and transverse scattering. The dependence of x-ray frequency, pulse duration, and photon flux on interaction geometry are also examined. Applications to the laser synchrotron source are discussed. There are potential advantages of both head-on and transverse interaction geometries: head-on scattering results in the generation of higher frequencies and higher photon fluxes; normal incidence scattering can result in ultrashort x-ray pulses.