DENSITY-FLUCTUATIONS IN JIPP T-IIU TOKAMAK PLASMAS MEASURED BY A HEAVY-ION BEAM PROBE

Multiple and small sample volume measurements of the density turbulenc e and potential profile measurements in tokamak plasmas were conducted using a heavy ion beam probe. The obtained waver lumber-frequency spe ctrum S(k, w) shows that the cross-sections of neutral beam injection (NBI) heated plasmas are divided into three regions of different turbu lence characteristics. Outside the layer where the direction of the de nsity turbulence propagation reverses, a low frequency and low wavenum ber mode travelling in the ion diamagnetic drift direction dominates. The region enclosed by this reversal layer is divided into two parts d uring nearly perpendicular NBI heating: a region where the propagation velocity is near the E-r/B-t poloidal rotation velocity and a bad cur vature region of very smell wavenumber and high propagation velocity. The region of high propagation velocity, found in NBI plasmas, disappe ars in the ohmic plasmas. In addition, a small component that propagat es in the ion diamagnetic drift direction is observed in NBI plasmas.