Thomson Scattering

Thomson scattering is a very powerful diagnostic which is applied at nearly every magnetic confinement device. Depending on the experimental conditions different plasma parameters can be diagnosed. When the wave vector is much larger than the plasma Debye length, the total scattered power is obtained by an incoherent summation over the scattered powers of the individual electrons. The scattering spectrum in this case is a reflection of the electron velocity distribution, from which local values for the electron temperature and density. and in some special experimental set-ups also the local current density, can be derived. For wave vectors which are in the same order of magnitude as or smaller than the Debye length the scattered powers of the electrons have to be added coherently. In this regime especially fluctuations in the electron density can be studied. Moreover, it becomes possible to diagnose the ion velocity distribution and, hence, the ion temperature.