Numerical computation of Thomson scattering spectra for non-Maxwellian or anisotropic electron distribution functions

Monte Carlo techniques applied to Thomson scattering (TS) power spectrum computation have been extended so as to include non-Maxwellian and anisotropic electron distribution functions (EDFs). First, a simple model has been selected for the spatial (angular) anisotropy of electron velocities (uniformly distributed around an axis of angular symmetry on a cone of semiaperture θanis), while the energies are distributed according to a lower-hybrid-like model function. Spectra have been computed, and their dependence with the EDF model parameters has been given. The most noticeable changes in the spectrum with respect to the isotropic Maxwellian are the broadening and blue-shift of the spectrum due to suprathermal electrons, and the presence of satellite or additional maxima (that can be either red-shifted or blue-shifted with respect to the thermal Maxwellian maximum) coming from the anisotropy of the EDF. Also, extensive numerical computations have been carried out on angularly non-separable EDFs (meaning that the sampling of the distribution function cannot be done independently on angle and energy variables), like the relativistic bi-Maxwellian (with or without drift). The connection of these results with some recent TS measurements reported by Yamada et al (2010 Rev. Sci. Instrum. 81 10D522) and more generally, with the possibility of detecting non-Maxwellian or anisotropic EDF features with TS, has been discussed.