Confinement Problem Research Articles

Some engineering problems of thermonuclear reactors

The features of a hypothetical controlled thermonuclear reactor that today seem most crucial to its performance are considered: the plasma, the vacuum magnetic field, the divertor, the vacuum wall, the energy absorbing blanket and the current-carrying coils. Some of the conditions necessary for a successful reactor are discussed. On the basis of the present limited knowledge of the essentials for a nuclear fusion power plant, a model is selected and its economics examined. It may be concluded that, if the fundamental problem of plasma confinement can be solved and several teohnological requirements met, fusion power stations should be economically successful.

Fine structure in current sheaths

The general, exact theory of a collisionless planar current sheath is developed with the constants of integration method. Every quantity depends on a single space variable x alone; electric field, current, and magnetic field are mutually orthogonal. Appropriate approximation methods can be developed to investigate the structure of the deviations from charge neutrality when the Debye distance d is much smaller than the sheath thickness; they appear either as local spatial electrostatic oscillations, whose wavelength is proportional to d as d → 0; or as space-charge regions whose size is comparable to the scale of the magnetic transition itself. The general criterion for the presence of such oscillations is given and the investigation of their structure is reduced to quadratures. In the simple case of two mono-energetic beams turned around by a magnetic field they are discussed in detail. If their amplitude vanishes where the field is nil, we recover Rosenbluth's profile ( 1); but the solution deviates slightly from neutrality near the turning points of the particle motions which, in general, are separated. The problem of confinement by an external magnetic field is treated in detail in the case where in the plasma the particles all move only in the x-direction with a Maxwellian distribution; there are no oscillations and the potential jump across the sheath diverges logarithmically as d → 0.

Vlasov Instability in Longitudinal Plasma Oscillations

It is concluded from the sizable currents computed that Vlasov instabilities of the simple type considered will not play a major role in the problem of magnetic confinement and attendant diamagnetic currents. The situation investigated may have a valid application to the plasma of the sun's corona and possibly the simple types of Vlasov instabilities have some connection with solar prominences. (T.B.C.)