Table of contents

One measure of the viability of any power producing system is the thermal efficiency — a quantity which reflects the extent to which waste heat is rejected into the surroundings. Using an efficiency of 50% as basis for comparison we calculate the thermal efficiency of a mirror fusion reactor with direct conversion for two fuel cycles. It is shown that a D-T mirror reactor may be marginally competitive if current estimates of direct conversion and injection efficiencies prove realistic. The D-³He mirror reactor appears less hopeful unless these efficiencies can be significantly improved or the required injection power greatly reduced.

A class of sufficient stability criteria is derived among which the sufficient criteria known as yet are contained as special cases. In this class, there is an optimum criterion. For equilibria periodic along the magnetic field lines (i.e. having some symmetry or closed field lines) its application requires calculating the lowest eigenvalue of a Sturm-Liouville problem. Various more convenient criteria have been obtained from lower bounds of this eigenvalue. These appear well suited for a calculation of lower bounds of a critical β. Some consequences for symmetric equilibria are discussed.

The authors consider the interaction of a plasma column in a constant magnetic field H_z with a system of two counter-rotating high-frequency magnetic fields whose axis of rotation is directed along a constant magnetic field. Both the first and the second wave are uniform along the axis of rotation. The configuration of the high-frequency field is such that the electrical component of the field is directed along the constant magnetic field, while the latter does not influence the effectiveness of the action of the high-frequency field on the plasma.

It is assumed that the collision frequency ν of the charged particles in the plasma is non-zero. Taking into account entrainment of the plasma by the high-frequency field, one can use — instead of the second wave of the alternating field — the constant magnetic field of a multipole configuration, which behaves as a high-frequency field relative to the rotating plasma. The distribution of the plasma rotation velocity v_φ, the charged particle concentrations N and the strength of the alternating fields _φ, and _r along the plasma column radius are determined by a system of Maxwellian equations and equations of motion for the ions and electrons. A system of equations with boundary conditions is solved by computer, and the radial dependences of the angular velocity of rotation, the plasma concentration and the high-frequency fields for different values of the multipole magnetic field and the plasma concentration are ascertained. If the ratio of the field strengths at the plasma boundary is of the order of unity, then the plasma column has a tubular structure.

In the case of a rotating plasma, the radial distribution of the high-frequency field is of a peculiar type.

The authors calculate the radiation intensity of a hydrogen plasma containing small amounts of impurity in the form of bare nuclei and hydrogen-, helium-, lithium- and beryllium-like ions with a nuclear charge Z in the range 5 ≤ Z ≤ 18. They consider electron concentrations of 10¹⁶ ≤ n_e ≤ 10²⁰ cm⁻³ and electron temperatures of 0.05 ⩽ kT/Z² Ry ⩽ 3 (Ry = 13.6eV), which are typical of the radiating zone of the plasma focus. The results show, among other things, that the radiation from the impurities may substantially limit the life-time of the high-temperature zone in the plasma focus.

The paper summarizes the basic information on the equilibrium of a toroidal plasma column in systems of the Tokamak type. It considers the methods of maintaining a plasma in equilibrium with the help of a conducting casing, an external maintaining field and the iron core of a transformer. Attention is paid to the role of the inhomogeneity of the maintaining field. It is shown in particular how the shape of the column cross-section depends on the curvature of the lines of force of the maintaining field. For the case (which has practical importance) weak asymmetry of the field distribution in the transverse cross-section, this paper describes a uniform method of consideration, which takes into account the influence of different factors on the equilibrium position of the column. This method is used for calculating plasma equilibrium in a Tokamak model with a conducting casing. Account is here taken of the effect of gaps in the casing and of finite electrical conductivity. Some cases of plasma equilibrium which are outside the standard Tokamak scheme are also considered, such as equilibrium in a conducting shell having the shape of a racetrack, equilibrium where the whole current is transferred by relativistic runaway electrons and equilibrium at high plasma pressure β_I ∼R/a.

After briefly recalling the main features of laser-produced plasmas and the problems involved in the production of nuclear DD-reactions, the author deals with the fundamental data on heating mechanisms. Experimental results and heating limitations are then presented. Finally, a review of present and future possibilities of both laser and plasma parameters is given.

The Working Sessions were attended by over 150 people and comprised eight informal whole-day meetings arranged in two parallel sessions on each of four days, together with two evening meetings and a summary day. Each day's meeting was introduced by a state-of-the-art presentation by the chairman, and followed by informal papers and discussion. The evening meetings were aimed at a more general discussion of the future prospects for fusion. A Proceedings will be published in about two months containing the summary papers given on the final day by the session chairmen.

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