The effects of the dielectric properties of the plasma on the cyclotron radiation spectrum from a tokamak discharge are investigated for propagation perpendicular to the magnetic field. At the cut-offs and at the upper hybrid resonance the cold-plasma dispersion relation is assumed to be valid. It is shown that the presence of evanescent regions, cut-off surfaces, and an upper hybrid resonance surface in the plasma distorts the line shape at the lower harmonics when ωp ∼ ωc. The first-harmonic extraordinary-mode emission is suppressed as ωp/ωc at the centre of the discharge increases owing to the de-coupling of the electromagnetic wave from the plasma electrons. A computer study is made of the changes in the spectrum as (ωp/ωc)r=0 is increased. The anisotropy of the cyclotron radiation spectrum about the minor axis of the torus is also investigated. Both line width and shape depend on the viewing direction.
Investigation of the electron energy distribution by cyclotron radiation into Tokamak plasmas