Particle confinement study in hot ion H mode discharges of JT-60U

Abstract

In order to understand the particle confinement properties of the hot ion H mode plasmas of JT-60U, the particle confinement time was estimated through analyses of the neutral particle behaviour based on measurements of the line emission intensity from the neutral particles combined with neutral particle transport simulations. The relationship between the properties of the particle confinement and the energy confinement was then examined. It was found that: (a) the particle confinement time depended strongly on the averaged electron density, (b) the ratio of the particle confinement time to the energy confinement time was in the range of 1-2 and (c) the particle confinement time was well correlated with the edge ion temperature. Furthermore, in order to clarify the roles of the particle confinement in the edge ion power balance, the charge exchange and convective losses were quantitatively evaluated using the distribution of the neutral particle density and the charged particle outflux, both of which were obtained through an analysis of the neutral particle behaviour. The conductive loss was estimated on the basis of the charge exchange and convective losses and the input power, and then the thermal diffusivity was estimated. From these estimates, it was found that the contributions of the charge exchange and convective losses in the edge power balance were small, and the increase of the edge ion temperature was caused by a decrease of the thermal diffusivity at the plasma edge