ANOMALOUS ION-TRANSPORT OF L-MODE PLASMAS IN JT-60

Local heat transport in auxiliary heated JT-60 plasmas has been analysed, with emphasis on the understanding of the deteriorated confinement observed in the L-mode. The dependence of the local thermal transport on plasma current, density and heating power have been studied in both divertor (single null, lower X-point) discharges and limiter discharges with hydrogen beam injection into hydrogen plasmas. The deterioration of the energy confinement time with increasing auxiliary heating power - the so-called power scaling - is mainly due to the stronger impact of the ion heat transport. It is found that the ion thermal diffusivity has a favourable density dependence. Experimentally obtained profiles of the ion temperature have been compared with the predictions of the theoretical model, especially with regard to the transport coefficients derived from the theory of the ion temperature gradient instability. For L-mode plasmas in JT-60, the theory has been found to be in good quantitative agreement with measurements over a wide range of plasma parameters, with the exception of limiter discharges with a plasma current of 1 MA.