Transition of fluctuation characteristics observed by a heavy ion beam probe in the JIPP T-IIU tokamak

As the sample volume of a heavy ion beam probe (HIBP) is swept from the centre to the plasma boundary in the JIPP T-IIU tokamak, we observe that the correlation time of the density turbulence increases appreciably and the dominant frequency decreases appreciably. The transition is located near rap = 0.6 in a low density gas-puffed plasma and an NBI-heated (neutral beam injection) plasma. Its position moves outwards in an R.F. heated plasma.