CONTRIBUTION OF PLASMA DIELECTRIC PROPERTIES TO THE CYCLOTRON RADIATION SPECTRUM FROM A TOKAMAK PLASMA

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/Ħc)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. © 1979 IOP Publishing Ltd.