Table of contents

A non-relativistic formulation has been developed which calculates the whistler-mode electron cyclotron emission spectrum in the direction parallel to the magnetic field for a plasma containing an isotropic Maxwellian electron component and an anisotropic bi-Maxwellian electron component. The formulation is valid for arbitrary densities of both components and the model utilizes the radiation transfer equation to obtain the intensity of the emitted radiation. The calculations are intended for use with mirror devices and the motivation is to use cyclotron emission as an electron temperature diagnostic. The projected plasma parameters for the TMX-Upgrade machine have been considered as an example, where the plasma is assumed to have a cold- and a hot-electron component (n_e ∼ 10¹² – 10¹³ cm⁻³, T_cold ∼ 1 keV, T_hot ∼ 50 keV). A procedure is described by which the axial cold-electron temperature profile can be obtained from spectral measurements of the cyclotron emission. The effect of the hot-electron population has been considered in detail and it is shown that in certain circumstances their influence on the emitted spectrum is small. For those cases where hot electrons dominate the emission, the model can be used to obtain important information about hot-electron behaviour.

Ignoring the stability effect of a conducting shell or conductors, it is found that an oblateness parameter ∊ =−0. 3 and an aspect ratio closest to one give optimal stability properties for a spheromak. In the pressureless case, only the n = 1 tilting and, possibly, the n = 2 kink modes are unstable. If these two modes are actively stabilized, appreciable beta values of a few per cent can be obtained, the limiting modes being Mercier modes with very small growth rates.

Alpha-particle spectra have been measured with a time-of-flight detector in laser fusion experiments on the symmetrical illumination, six-beam ZETA laser system (Nd-doped phosphate glass, λ = 1.054 μm). For a series of fast imploding targets, upward mean energy shifts of alpha particles were observed. These energy shifts were attributed to a time-varying electric field which charged reaction products experience as they pass through the corona of the imploding microballoon. A one-dimensional, two-temperature hydrodynamics code was used to simulate both the expanding corona and the imploding glass. The corona simulation gave rise to an electric field with a decay time of the order of the laser pulse width. The acceleration of alpha particles by this field satisfactorily accounted for their observed alpha-energy shifts.

A model for the magnetic field strength along a stellarator field line has been developed which correctly describes the principal contributions to the field strength and which can differ substantially from the simple form commonly assumed. An analytically tractable form of the model is obtained and is compared with results from ray-tracing in real fields. A theoretical description of the drift motions of 'localized' particles (trapped in the helical ripples of the magnetic field) is then obtained for a more general class of stellarator field than previously possible. Orbits in real devices are considered for both ℓ = 2 and ℓ = 3, and differences between the predictions of the present work and of earlier investigations are pointed out. The application of the theory to particle guiding-centre orbit following is discussed, and other consequences of the improved model field are indicated.

The state of the art in the field of electron cyclotron emission and absorption of fusion plasmas confined by a magnetic field is reviewed. The general theory is described concisely, explicit results being given mainly for plasmas in local thermodynamic equilibrium. Moreover, the practical implications of these effects with respect to cyclotron radiation losses, the use of cyclotron emission as a diagnostic tool, and electron cyclotron heating and current drive are discussed with emphasis on tokamak plasmas.

Direct measurement of the fast magnetosonic wave near the hybrid resonance layer in a deuterium-hydrogen plasma by magnetic probes is described. Externally driven waves in the ion cyclotron range of frequencies (ICRF) are excited by a half-turn antenna located on the high-field side in the TNT-A tokamak. The amplitude and the phase shift of the fast magnetosonic wave are measured by magnetic probes in the equatorial plane of the plasma. The amplitude of the fast magnetosonic wave is damped in the ion-ion hybrid resonance layer, and the wavelength changes at the high-field side near this layer. The amplitude and the phase shift of the wave as measured by the probes agree with those calculated from a cold-slab model.