Microwave Diagnostics of Plasmas

The theory of wave propagation in plasma media where temperature and collision effects are important is formulated by combining the wave equation and Boltzmann´s equation for average electron velocity. Usually it is assumed that the electron collision frequency is independent of velocity, but most gases are characterized by a velocity-dependent collision cross section and the electron collision frequency is velocity dependent. It has been shown that when the velocity dependence of the collision frequency is neglected, electron density predictions are in considerable error. A wave theory which accounts for the velocity-dependent electron collision frequency has been worked out and applied to the measurement of electron density, temperature, and collision frequency in a rocket exhaust plasma.