Microwave scattering from a turbulently heated plasma

Abstract

The electron density fluctuation spectrum during the turbulent heating of a toroidal plasma column is derived from the scattering of lambda ₀=2.4 mm and 8.8 mm microwave beams. A multi-antenna receiver array and heterodyne detection are used to obtain the frequency spectrum of fluctuations with wavevectors aligned across and parallel to the exciting plasma current. The minimum detectable fluctuation levels were S(k)=6*10⁴ (at lambda ₀=2.4 mm) and S(k)=2*10⁴ ( lambda ₀=8.8 mm), set by the plasma radiation level. Evidence is obtained of ion sound fluctuations with k perpendicular to B are observed whose origin has not yet been explained.