Keith H. Burrell

Transport theory of tokamak plasmas with large toroidal rotation

The neoclassical transport theory for tokamak plasmas in the plateau to Pfirsch–Schluter regimes is extended to cases in which the parallel flow can become comparable to the ion thermal velocity. Important changes are found in the qualitative structure and the quantitative predictions of the theory. Solutions for both pure and impure plasmas in the plateau regime are obtained.

Effect of particle and heat sources on impurity transport in tokamak plasmas

Local particle injection or heating can affect the transport of impurities. Proper source configurations can oppose the natural inward impurity drift, thus providing a means for controlling impurity influx.

Resonance cones in a warm plasma for finite magnetic fields

The resonance cone structure excited by a localized source is studied theoretically and experimentally for a warm plasma with a finite, uniform magnetic field. The electrostatic Green’s function is evaluated by asymptotically expanding it in the limit where the observation point is far from the source. Results are obtained that are valid for all angles and for all frequencies below the upper hybrid. The theory predicts the functional dependence of the angular location of the main resonance cone peak and the angular spacing between interference peaks on the physical parameters. Experimental parameter studies were made to check the predicted functional dependence; it was found to produce a good fit to the data. Both density and temperature can be found from these measurements; thus, resonance cone measurements are a useful diagnostic technique in any magnetoplasma in which antennas can be inserted.

Low frequency resonance cone structure in a warm anisotropic plasma

Asymptotic analysis of the electrostatic Green’s function for an antenna in a warm, anisotropic, nearly collisionless plasma reveals the presence of new resonance cone structures which exist in addition to the cold plasma resonance cone for frequencies below the lower hybrid frequency. These new cones, the ion acoustic resonance cones, occur for frequencies 0 ⩽ ω ⩽ min(ωpi, ωci) and max(ωpi, ωci) ⩽ ω ⩽ ωlh; they exist only when the electron temperature is nonzero and are important when Ti/Te ≪ 1. The interference structure associated with this cone is quite sensitive to the ion temperature and could be the basis of an ion temperature diagnostic technique for plasmas that meet the conditions of the theoretical derivation: Ti/Te ≪ 1 and ωci ≫ ωpi.

Kinetic theory of neutral hydrogen atoms in a bounded hydrogen plasma slab

The transport of neutral hydrogen atoms in a hydrogen plasma slab is considered. After making a reasonable approximation for the charge exchange rate, analytic solutions for the neutral distribution function are obtained which depend on one spatial and three velocity variables. To obtain these, a condition must be imposed that implies uniform electron and ion temperatures. Specular reflection of the neutrals at the boundaries is considered. Solutions associated with the diffusion approximation are also given and the condition for its validity is discussed. The solutions are evaluated for the case of Maxwellian ion distribution functions.

Solid‐state traveling‐wave amplification in the collisionless regime

Traveling‐wave interaction between flowing plasma and electromagnetic wave supported by external slow wave structure is analyzed in the collisionless regime. The plasma is described with the collisionless Boltzmann equation and the interaction is analyzed using the coupled‐mode approach. The analysis is applied to a plasma consisting of drifiting charge carriers in a solid. Illustrative examples demonstrate interaction leading to wave growth for frequencies in the far‐infrared regime. It is suggested that experimental measurement of wave growth or damping due to this effect can provide information about the velocity distribution of drifting carriers in the solid.

Algorithm 484: Evaluation of the modified Bessel functions K 0 (Z) and K 1 (Z)for complex arguments

This procedure evaluates the real and imaginary parts of the modified Bessel functions K_0(z) and K_1(z) for values of the complex argument z = x + iy in the half plane x ≥ 0. (The notation K_n(z) is fairly standard; the exact definition of the function is given in [1]).

Transport of a trace impurity in a dirty plasma in the Pfirsch–Schlüter regime

Particle transport rates for a trace impurity are calculated for a Pfirsch–Schluter regime plasma consisting of a main ion and all the charge states of a background impurity. The main ion is taken to be much lighter than all impurities, but masses and charges are otherwise arbitrary. Qualitative trends of the transport rates with variations in the trace impurity mass and background impurity concentrations are discussed.

Kinetic theory of neutral hydrogen atoms penetrating a hydrogen plasma half-space: Analytic solution

Transport of neutral hydrogen atoms in uniform temperature hydrogen plasma half‐spaces is considered. Using arbitrary ion distribution functions, analytic neutral solutions are found depending on one spatial and three velocity variables. These are evaluated for a Maxwellian distribution.

Alteration of Pfirsch–Schlüter transport in tokamaks by all four external sources

Tokamak energy and particle transport are calculated for a plasma in the Pfirsch–Schluter regime containing all possible external sources: particle, momentum, heat, and heat momentum. The effect of the last source has never been considered previously; its presence makes possible simultaneous control of the impurity flux into the plasma and of the heat flux from the plasma. Examples are given showing that such control is possible with existing neutral beam or rf sources.