Table of contents

In the case of high-intensity plasmons, interaction processes among the plasmons are more probable than interaction processes of plasmons with plasma particles; plasma relaxation occurs in two stages: first, statistical equilibrium in the plasmon sub-system is established, characterized by a temperature different from that of particles, and then in a slower process equality of plasmon and particle temperatures is established.

The plasmon energy may be increased by slowly modulating the external magnetic field on which the plasmon frequencies depend. The energy pumped into the plasmon sub-system by this method — which may be called the method of magnetic pumping — may be much higher than the Joule heat immediately obtained by the particles. The energy obtained by plasmons will be transferred slowly to the particles; in the plasmon sub-system itself a stationary energy level will be established. Thus, in a non-isothermal plasma mainly the electrons will be heated.

Resonant heating by microwave power has been used to produce high β plasmas with electron temperatures near 1 MeV. Typically plasmas are produced with ω_pe∼ω_ce. Further experimental heating studies described here have shown that a large increase in stored plasma energy is produced by microwave power with a frequency higher than the cold-electron resonance frequency. This increase, caused by off-resonance heating, is attributed both to stochastic heating and to the control of an instability through changes in the electron distribution function. Alternatively, a decrease in the stored plasma energy is produced by microwave power at a frequency below the cold-electron resonance frequency. This effect is attributed in part to enhanced diffusion into the loss cone. However, a small fraction of the plasma is heated to high energies.

The behaviour of dense hydromagnetic plasmoids interacting with a non-uniform axially symmetric magnetic field has been calculated using a two-dimensional fully ionized two-temperature hydromagnetic model. A two-step second order finite difference scheme similar to the Lax-Wendroff method is used to integrate the equations. Comparisons are made with the plasmoid experiments of Azovskii et al. A good correlation is obtained for the density and induced magnetic field, although significant differences exist between computed and experimental electron temperatures. The computed results indicate that thermal conduction along field lines can be a dominant loss mechanism.

A description is given of experiments with the pulsed injection of a neutral gas during discharge in Tokamak-3 The electron concentration was measured by a method of multichord probing with 2 mm waves. The flow of neutral gas from the chamber walls and from the diaphragm was determined from measurements of the intensity of the hydrogen spectral line in three directions. The diffusion lifetime in the experiments described is in the range 20-30 ms and the halt in the reduction of the electron concentration observed in the intermediate discharge stage is not associated with an increase in the flow of neutral gas but with an improvement in the plasma confinement. The flows from the diaphragm and from the chamber walls are compared, as are the diffusion and energy life times.

The interaction of a plasma flow with a mirror field is studied by changing the mean free path of ion-ion collisions in the BSG-I_A device. In the case of a collision-dominated plasma, it has been shown in the BSG-I and II devices that a shock occurs when a supersonic plasma flow encounters a mirror field. When the mean free path is made longer than the characteristic length of the mirror field, shock effects no longer occur. The diamagnetic signal in front of the mirror still increases compared with that obtained in the case without a mirror. A particle orbit model given by Gilleo for the interaction of a plasma flow and a mirror field is refined and the increment of the diamagnetic signal explained by the refined model.

The interaction of a tenuous energetic test-particle species with a multispecies high temperature plasma is calculated. The Balescu-Lenard kinetic equation is used in order to include collective effects through the dielectric constant. Quantum corrections are made for close collisions. The theory is first applied to the slowing down of fusion born alpha particles in a mirror-confined plasma and theory and numerical results are compared to previous treatments and corrections are found. In Tokamak-like plasmas most of the alpha-particle energy goes into the electrons and the thermalization time is somewhat larger than the plasma lifetime but heating can nevertheless be substantial. Heating of a Tokamak-like plasma by injection of energetic neutrals is shown to be effective at injection energies ≤ 70 keV, possibly doubling the ion temperature when the injected particle density reaches 1% of the plasma density. For analytic estimates, a simple binary collision model for injection heating is given.

The excitation of longitudinal oscillations by an external h.f. field is investigated in a non-homogeneous magneto-active plasma. It is shown that when the frequency of the subharmonic of the external h.f. field approaches one of the plasma hybrid frequencies, the plasma develops a parametric-type resonance.

The interaction of extraordinary waves with an inhomogeneous anisotropic plasma column at the lower hybrid frequency is investigated within the framework of the cold plasma theory. Numerical results for the wave absorption efficiency are presented for a wide range of plasma densities, magnetic field strengths, effective collision frequencies and column dimension values. Strong wave absorption occurs when the magnetic field strength approaches the value which corresponds to the ion cyclotron frequency. The plasma column exhibits a series of geometric resonances in the medium frequency range and a main absorption resonance in the h. f. range. The influence of temperature and nonlinear effects on the obtained absorption efficiency in the lower hybrid frequency range is discussed.

A discussion is given of the relative merits of the D-D, D-T,or D-³He mirror fusion power systems. As a basis for discussion we have used a simple approach for estimating the ratio of Q(D, He) to Q(D, T). When needed, the value of Q(D, T) is considered to be of the order of that calculated by Marx and by Kuo-Petravic, Petravic and Watson. The systems are compared at different assumed plasma temperatures in the range 200 to 1000 keV on the basis of several criteria: the investment costs in dollars per kilowatt, the ratio of waste power to power output, and the tritium and neutron production. We have concluded, based on the estimates of the ratio of Q-values, that subject to these criteria the D-T system appears the more favoured system. On the other hand, should a means be found to enhance the Q-values the D-³He system would be preferred on all but the first criteria. We consider the three-component D-T-³He system and its optimization. Finally, the possibility of further enhancing the D-T system by utilization of tritium breeding in the plasma is discussed.

A review is given of theoretical and experimental investigations on rotating plasmas. The basic equations are discussed from the microscopic and macroscopic points of view, including the balance of matter, momentum, and heat, as well as associated stability problems and limiting effects. Various types of devices are described, and obtained experimental results are compared with theoretical predictions. The review also summarizes the applications of rotating plasmas to fusion research, cosmical physics, and special technical arrangements such as plasma centrifuges, adjustable plasma condensers, and plasma gun and propulsion systems.

In the three years that have elapsed since the last Symposium on Magnetohydrodynamic (MHD) Electrical Power Generation, held in Warsaw, substantial progress has been made in the research and development of plasma and liquid-metal closed-cycle MHD systems. Both of these systems have relevance to the potential application of advanced, high-temperature nuclear power reactors as heat sources for MHD energy conversion. For fossil-fuelled open-cycle systems, engineering development has advanced to the prototype stage. Such were the conclusions made at the Fifth International MHD Conference, which was held in Munich from 19 to 23 April 1971 and attended by over 250 participants from 25 countries. At this conference, which brought together experts from all the major MHD development programs in the world, notably those in the USSR, USA, F.R. of Germany and Japan, 115 papers were presented.

The Fourth International Conference on Plasma Physics and Controlled Nuclear Fusion Research, organized by the International Atomic Energy Agency, was held during the summer of this year in the United States of America - in the small university town of Madison, in the state of Wisconsin. Some 500 scientists from about 30 countries took part in the Conference and approximately 140 papers were discussed, considerable use having been made of the rapporteur system. As at the earlier conferences in this series, most of the papers described experimental work.

The Fourth Symposium on Engineering Problems of Fusion Research was held at the US Naval Research Laboratory in Washington, D. C., 20–23 April, 1971. This was the fourth engineering symposium held in the United States since 1966. The purpose of these symposia is to present the engineering aspects of controlled fusion and serve as a meeting ground for the engineers working in the field. The Fourth Symposium was attended by approximately 90 engineers and scientists, representing the four major US Atomic Energy Commission laboratories, several universities, and a few industrial concerns. The Culham Laboratories in England and the Institute for Plasma Physics in Jülich, West Germany, were also represented. Fifty-eight papers were presented. The proceedings will be published by the IEEE Nuclear Science Group in the fall of 1971.

A translation of the abstracts of all the articles for this issue into French, Russian and Spanish.