Measurement of Dispersion and Damping of Drift Waves in a Potassium Plasma

Abstract

Drift waves have been excited by signals applied to a plasma through an exciter consisted of four mesh grids. The waves have been distinguished from an edge oscillation which is simultaneously excited in a stable potassium plasma immersed in a uniform magnetic field. Dispersion relations including damping rates of the drift wave have been measured experimentally in a frequency range extended up to higher frequencies than the drift wave frequency. Since the fluid equation cannot be used due to the fact that the wave is considerably affected by resonant ions at the frequency range we are studying in a low-temperature potassium plasma, we have solved a linearized drift kinetic equation with taking the collision in an approximate from into account and derived the local dispersion relation. The experimental results for both the real and imaginary parts of the dispersion relation are well interpreted by the theory.