JET-P(99)61
Characteristics of Internal Transport Barriers from the JET Optimised Shear Database
The general features of the Internal Transport Barriers (ITBs) obtained in the JET "Optimised Shear" regime are deduced from the analyses of a large database of discharges including the experiments performed with a mixture of Deuterium-Tritium (D-T) ions. The coupled and complex spatio-temporal dynamics of the ITBs are studied from the radial profiles measurements of the thermal ion and electron temperatures. The spatial locations of the ITBs inside the plasma column are deduced from the radial derivatives of the plasmas profiles. In particular, our analyses show that the radial positions of the ITB follow the same evolution for both the electron and ion temperature profiles. Among the JET "Optimised Shear" database, we propose to distinguish two categories of discharges depending on the edge conditions: the ITBs are triggered either with an L-mode edge or simultaneously with an edge transport barrier (H-mode). The characteristics of the ITBs and plasma performances of these two categories are compared. Experimental conditions to successfully combine the edge and core transport barriers are given. In particular, emphasis is given on the description and analyses of the "Optimised Shear" discharges which combine an ITB with an ELMy edge since this operating mode opens the route to high performance regimes which could be extrapolated towards steady-state conditions.