PLASMA DYNAMICS XVIII. PLASMAS AND CONTROLLED NUCLEAR FUSION A. Waves and Radiation

The major goal of this group is to generate a basic understanding of various types of oscillations and waves in ionized gases that are relevant to problems in thermonuclear fusion and space research. The experimental and theoretical studies fall roughly into three main groups. a. Investigations of electromagnetic radiation emitted spontaneously by the plasma, because of thermal and nonthermal fluctuations of the free charges. At present, particular attention is being paid to emission at long infrared wavelengths and to radiation generated as a result of many-body (collective) interactions between the charges. b. Studies of the dispersion characteristics of small amplitude stable and unstable waves. We are now looking at the properties of ion and electron cyclotron oscillations, low-pressure striations, and ion sound waves. c. Investigation of nonlinear plasma phenomena is one of our major goals for the next few years. In this connection, we are particularly interested in the properties of large-amplitude waves, particle trapping, nonlinear Landau damping, parametric coupling of three or more waves, and the coupling of waves with particles. The effects of boundaries and finite plasma geometry are considered. We attempt to carry out these projects under well-controlled experimental conditions. This often entails the construction of new plasma sources. During the past year, for example, we have constructed two quiescent, collisionless, plasma facilities (PF 1 and PF 2) on which many of the studies described will be carried out. QUIESCENT PLASMA FACILITY (PF 1) Using electron cyclotron heating in a mirror geometry, Lisitano and his co-workers1 have produced an almost collisionless, quiescent plasma column that is useful in studying a variety of problems, such as wave propagation, instabilities, nonlinear phenomena, and turbulence. In this report we describe the construction of a similar system (called PF 1) and the modifications that we have made to obtain a more uniform plasma column than that reported by Lisitano. In studying the plasma characteristics, we have used Langmuir probes. In Sections XVIII-C. 1 and XVIII-C. 2, we describe some optical and probe studies that were made on a facility (called PF 2) that differs essentially from PF 1 only in the overall length of the machine. Overall System This system, shown in Fig. XVIII-1, is made almost entirely of stainless steel. The backbone of the system is a stainless-steel tube, 5 inches in diameter, in which the plasma is generated and confined. This tube, 8 1/2 ft long, has an inside …