Dependence of tokamak edge conditions on global plasma parameters in JET

Abstract

Measurements of the plasma parameters have been made in the boundary layer of JET for Ohmic discharges with discrete limiters over a wide range of operating conditions. The plasma currents have been varied from 1 MA to 5 MA and the average density from 1 to 5 X 1019 m−3. It has been observed that the edge density increases with line average density and that the edge temperature decreases. Emphasis has been placed on testing data under steady state conditions of plasma current and density. The temperature and density at the last closed flux surface have been modelled using global particle and energy balance. Good quantitative agreement has been obtained with the experimental data for the density and the total particle flux. In a second stage, using the global energy balance, a crude attempt has been made to estimate the impurity influx and hence the radiation from the plasma. The results give the right order of magnitude and the correct trends for the variation of the edge temperature with density and input power.