Magnetic separatrix configurations have been produced in JET for plasma currents of up to 3 MA. Experimental results obtained with these configurations show that some features can be achieved that are common to divertor tokamaks. In Ohmic discharges, high recycling regimes can be produced. In neutral beam heated discharges, substantial improvement of the energy confinement time is achieved together with the characteristic signatures of an H-mode. These characteristics include improved particle confinement, flatter density profile, and an increase in electron temperature especially at the edge, leading to a characteristic pedestal feature. At higher neutral beam power, higher plasma densities are reached, with deterioration of beam penetration and strong radiation losses in the outer region of the plasma. The global energy confinement time in the H-mode is observed to degrade with additional power. However, results of radial power balance analysis suggest that in the central region, where the radiation is not important, the degradation of confinement is small.
Energy confinement of beam-heated divertor and limiter discharges in Doublet III