Towards steady-state tokamak operation with double transport barriers

Internal Transport Barriers characteristic for the Optimised Shear regime and an edge transport barrier of an ELMy H-mode regime have been superposed in the Double Barrier mode. In DT discharges the Double Barrier mode has resulted in 50% higher fusion power output and a factor 2 higher fusion gain Q than in conventional sawtoothing steady-state ELMy H-mode plasmas. Steady-state conditions in temperature and density profiles have been approached in Double Barrier discharges in deuterium. The Double Barrier mode has been routinely established in the new Gas Box divertor configuration on JET. Off-axis LHCD has been used for current profile control during the high performance phase. In preparation of a new DTE2 campaign on JET the potential of the Double Barrier mode for sustained high fusion performance has been explored in modelling studies. Steady-state operation on ITER has been studied in transport code modelling for Advanced Tokamak scenarios in the Double Barrier mode. (author)