Laser-Aided Plasma Diagnostics

The invention of the first laser followed by many others has led to a large amount of different plasma diagnostics using some aspect of the interaction between light and plasmas. In this paper a short review of these diagnostics is given, where the emphasis will be on Thomson scattering and Laser Induced Fluorescence. Thomson scattering is a very powerful diagnostic that is applied at nearly every magnetic confinement device. When the laser wavelength is much smaller than the plasma Debye length, the scattering spectrum is a reflection of the electron velocity distribution, from which local values for the electron temperature and density can be derived. Laser Induced Fluorescence enables to determine the neutral density of different species in the plasma.