Electrostatic fluctuations and related transport in the edge and core plasma of the Keda Tokamak-5C

Abstract

Using the swept double probe and triple probe technique, temperature, density and potential fluctuations have been measured in both the plasma edge and core of the Keda Tokamak-5C (KT-5C) [World Survey of Activities in Controlled Fusion Research, Nuclear Fusion Special Supplement (International Atomic Energy Agency, Vienna, 1991). p. 190]. The fluctuation-driven particle and energy fluxes were also estimated from the correlations of (ñe,Ẽθ) and (T̃rẼθ). Evidence has been found that there exist substantial electron temperature fluctuations of T̃e/Te=O.4ñe/ne in both regions. At the edge of KT-5C. many of the fluctuation features, such as the velocity shear stabilization of turbulence, the non-Boltzmann relation and the role of fluctuations in the edge confinement, are very similar to those obtained from other tokamaks. In the plasma interior, the fluctuations do obey the simple Boltzmann relationship and the profiles of the normalized fluctuating levels ñe/ne and Φ̃p/Te vary roughly as ñe/ne∞ne-3/2 and Φ̃p/Te∞ne-1/2T e-1, respectively. In addition, a spiky, radially intermittent structure in the particle and energy fluxes with large levels at the low-q resonances and lower levels in between was found. The experimental results provide some new evidence, particularly in the plasma core, for a better understanding of the basic mechanism of turbulence. © 1996 American Institute of Physics.