The effect of a metallic reflector upon cyclotron radiation

Abstract

A careful study of the effect of a metallic reflector upon cyclotron radiation emanating from a uniform plasma is made in which the angular, polarization, and frequency dependence of both the cyclotron radiation and the metallic reflector is taken into account. The properties of the metallic reflector then enter in a natural way and share equal status with the properties of the plasma. The radiation coefficient, the ratio of the cyclotron radiation absorbed by the reflector to that generated by the plasma, becomes a function of the two parameters: Te, the electron temperature, and ℓne/B(Bρ)1/2, the plasma depth to cyclotron radiation, where ℓ is the perpendicular distance across the reflector, ne is the electron density, B is the magnetic field, and ρ is the resistivity of the reflector. The radiation coefficient is determined for both slab and cylindrical geometries for the range of values 20 ≤ Te ≤ 120 (keV) and 1019 ≤ ℓne/B(Bρ)1/2 ≤ 1027(MKS). A simple analytic approximation is given for the radiation coefficient for each geometry, and the results are then applied to a low-β thermonuclear device based on the D-D reaction. For β of the order of 1 to 2%, and for devices of moderate size (ℓ of the order of a few metres), the metallic reflector is incapable of reducing the cyclotron radiation loss below that required for a self-sustained D-D reaction.