Untersuchungen zur Beschleunigung von Plasma mit elektromagnetischen Wanderwellen

Abstract

With regard to the application in plasma wind-tunnels or propulsion devices, the electrodeless generation and acceleration of plasma by an electromagnetic wave travelling along a special transmission line are investigated. Our first aim was to obtain information on the interaction of the wave with the plasma and to determine the initial parameters for effective operation. In the first experiments the efficiency of the process was not a primary concern. The transmission lines were terminated in matched loads where the whole electromagnetic energy at the output of the circuit, of the order of 100 MW, was dissipated. Such devices can be operated only in a pulsed manner, because it is practically impossible to maintain such high energies for long periods of time. Plasma pulses with a length of about 1 m, densities up to 1014 cm-3 and particle velocities between 5 ×106 cm/sec and 1.2 × 108 cm/sec could be produced. The interaction of wave and plasma could be described in good agreement with a simple model in which we assumed the ions of the plasma to be reflected elastically on a magnetic piston. For the production of longer or continuously streaming beams it appears necessary to go over to a feed-back circuit, where the energy at the output of the line is reinjected at the input by using an appropriate transformer. A high frequency oscillator is used to compensate the energy losses resulting from ohmic effects and from the plasma acceleration. The realization of such a circuit was studied theoretically and experimentally.