Mikrowellendiagnostik von Instabilitäten des Säulenplasmas Elektronendichte, -temperatur und Helligkeitsverlauf in selbsterregten laufenden Schichten einer Wasserstoffentladung

Microwave methods are used to obtain the periodic variations in time and space of some plasma parameters. The electron density is obtained using a time-display of the reflection coefficient due to a plasma-perturbed cavity, and the electron temperature from the noise signal of a Dicke radiometer gated periodically. Assuming simple one-dimensional sinusoidal variations of temperature and density, the fundamental convolution integrals relating the appropriate cavity parameters to the plasma properties are solved and formulas are obtained to calculate the real fluctuating quantities. Also in that case where the lenghth of the cavity field region equals the dimension of the variations the correct phase relation between electron temperature and density is obtained. The method is used for diagnostics of self exited moving striations in hydrogen. The striations (frequency 24 kHz, striation lenghts ～1 cm) move from cathode to anode and the sequence of the different maxima for an observer in rest is electron density, temperature and light-emission. The phase shift between density and temperature is about 90 degrees, the appropriate density variation is 10:1 and the temperature variation >2:1.