UHF Reflectometry Study of the Plasma Oscillations Arising During RF Heating in Uragan-3m Torsatron

In Uragan-3M torsatron one or two high-power waves are used for plasma production and heating. Powerful RF waves excite different types of plasma fluctuations. In this work, two kinds of oscillations caused by Alfven waves in plasma are presented. These oscillations were observed by UHF reflectometry. Spectral analysis of reflected microwaves showed an existence of plasma density fluctuations when two heating waves were used simultaneously. The ion Bernstein waves (IBW) manifested themselves as plasma density fluctuations and have been observed by microwave backscattering in the vicinity of ion gyro frequency harmonics. Experimental observation of IBW gives a tool for studying predicted link between IBW amplitude and ion temperature. Measurement of ion cyclotron harmonics frequency for different values of probing frequency allows the determination of their cut-off radius and radial profile of electron density.