Light Scattering

Abstract

Light incident on a laboratory plasma interacts with all constituents of the plasma (electrons, ions, atoms and molecules), and the fraction re-radiated into all directions usually is referred to as scattered radiation. Various scattering processes are possible, and by selecting suitably the wavelength of the incident radiation, one may achieve one process to dominate. The analysis of the scattered radiation yields a wealth of information on plasma parameters, plasma composition and plasma phenomena, and these diagnostic possibilities have been the prime motivation for the strong interest in these processes during the past two decades. Quite a number of different experimental methods have evolved: the differences arise from different incident radiation, from different interaction processes being effective or from different experimental techniques used specifically with regard to the detection and analysis of the radiation. Figure 1 reveals one great advantage of most of these methods: as the incident radiation traverses the plasma, the “scattering volume” may be selected by the detection optics. Scattered radiation thus is received only from this volume although the plasma radiation is collected along the total line of sight. Light scattering methods allow, therefore, spatially resolved measurements.