Experimental and theoretical studies were made of the decrease in the degree of ionization of shock-heated agron resulting from radiative emission. the studies were based on measurment of the time history of the electron density by means of optical interferometry used in conjunction with a rotating mirror camera. These measurments apply to the quasi-euilibrium region which follows the short electronic relaxation zone behind strong shocks. Loss of energy by rediation led to cooling of the gas as evidenced by the decreasing electron density. The analytical studies were based on the assumption that the dense plasma readiated throught both continuu, emission and emission from spectral lines. Comparison was made with experimental results, and theory and experiment were in good agreement, for a realistic choice of the parameters contained in the continuum theory. The analysis indicated that line radiation losses could not be disregarded. Sizeable loss resulted from lower level bound-bound transitions even though these lines experienced absorption.

In a previous paper, the R.F. characteristics of a spherical probe immersed in a hot, low-density plasma using a realistic sheath model were considered, and a few results of computations presented. The remainder of these results are given in this paper. The dependences of R.F. admittance, and rectified current on probe radius, d.c. bias, and electron neutral collision frequency are exhibited and shown to be qualitatively in accord with the predictions of simple slab-sheath/dielectric models. It is shown how in principle, analysis of resonance rectification characteristics using curves included in the paper can yield values of electron density ne temperature Te, and electron-neutral collision frequency ν. Two methods of reduction are applied to some laboratory results obtained at Slough and are shown to give reasonably consistent values of ne and ν, but the values of Te, show considerable scatter. These methods could complement the Langmuir probe which gives more reliable values of Te than of ne in low density plasmas with ne ≾108 cm−3. Effects of magnetic fields are not included in this paper.

A simple single-fluid model is presented which accounts for the behaviour of MHD shock producing devices in which the shock and the driving current sheet are unseparated. By means of both characteristic and similarity solutions, it is shown that unusual plasma behaviour is a simple consequence of the fluid equations of motion. The important parameters in determining the performance of MilD shock tubes are the width of the current sheet at breakdown (related to the magnetic Reynolds number) and the current sheet Mach number with respect to the gas at rest. It is shown that, under many conditions, separation is more likely to be achieved with a decrease, rather than an increase, in current sheet speed. Lowering the Mach number is more influential in causing the shock to form at the front of the current sheet than raising the magnetic Reynolds number.

The thermal conductances in a collisionless gas between coaxial cylinders and concentric spheres have been obtained for arbitrary thermal accommodation coefficients. This exact theory is based on the general theory of thermal conduction of collisionless gas developed recently by Wu which has been established according to his revised theory of thermal transpiration. The classical theory of thermal conductance between coaxial cylinders by Knudsen and Von Smoluchowski is only accurate to the first power of the temperature difference in which the velocity distribution in the system is assumed to be nearly Maxwellian. However, in the present paper, it is unnecessary to make this usual assumption and the exact theory has been established according to the revised theory of thermal transpiration.

A simple model of an ionizing detonation wave is studied in which the electrical conductivity jumps from zero to infinity across the wave at which a net release of exothermal energy occurs and which propagates with magnetoacoustic speed relative to the products of combustion. The upstream electric and magnetic fields are mutually orthogonal and transverse to the direction of propagation. The ratios of downstream flow parameters to those upstream and the detonation speed are presented for a range of values of the upstream electromagnetic field. It is surmised that, for a specified upstream magnetic field, physically realistic detonation waves exist only for a limited range of values of the electric field strength of invariant sign.

This paper considers the steady two-dimensional ‘magnetic bottle’ in which a moving, compressible and electrically conducting plasma is confined by a horizontally aligned magnetic field. It is assumed that dissipation by viscosity and resistivity is negligible and that the plasma-magnetic field interface is free from instabilities of all kinds.

The beam-plasma interaction which has been proposed by Stix is examined both by approximate analysis and by integration of the non-linear equations of motion which describe the interaction of an individual electron with a monochromatic large amplitude electrostatic plasma wave. The quasi-stochastic model of the large amplitude plasma waves, introduced by Stix (1964), has been used in the calculations by programming a random phase function into the argument of the periodic plasma wave function. It is found that electrons are subject to a quasi- cyclotron acceleration which proceeds to a higher energy in the stochastic case than the limit found in the non-stochastic case (a phase-coherent plasma wave). This behaviour is interpreted in terms of a limit cycle phenomenon, and the stochastic phase shift appears to push electrons across these limit cycles. It is also found that favoured groups of electrons in a 2eV plasma excited by a 5 keV beam in a2000 Gauss field can achieve energies in the range 85 to 170 keY in less than a nanosecond by a single acceleration occurring in one plasma wave coherence length L‖ as defined by Stix.

Numerically exact solutions of the problems of heat transfer between concentric circular cylinders and spheres have been obtained.