Scattering diagnostics of low-temperature plasmas (Rayleigh scattering, Thomson scattering, CARS)

Diagnostics of low-temperature plasmas suitable for plasma processing appli cations using light scattering techniques is a research field of growing im portance. The three scattering diagnostic techniques discussed in this pape r may be applied to a variety of industrially used thermal and nonthermal p lasma processing techniques. These methods are nonintrusive with high tempo ral and spatial resolution and could help to analyse the absolute compositi on of a plasma, where as many species as possible in different excitation a nd ionization states should be included. They furthermore deliver informati on about the energy of particles under investigation, their temperature, de nsity and fluxes. The scattering theory in random media is summarized very briefly and this approach is applied to Rayleigh and Thomson scattering. Th e difference between incoherent and coherent scattering is figured out. A s hort overview over the process of coherent anti-Stokes Raman scattering (CA RS) and an introduction into experimental techniques is given, which are re quired to detect Rayleigh, Thomson and CARS signals from a plasma. Finally, applications of these three diagnostic techniques to miscellaneous plasma experiments are shown.