The information provided by different diagnostics has been combined in order to characterize the fast electron distribution function in lower hybrid current drive experiments on JET. In particular, X ray and electron cyclotron emission data are complementary in defining the fast electron energy contents in the directions parallel and perpendicular to the magnetic field. A numerical analysis chain has been developed which identifies the main moments of the distribution function of the current carrying fast electrons and allows simulations based on these moments to be compared with X ray emission, electron cyclotron emission and magnetic data. The method of analysis and the associated diagnostics are described, and results are presented which have been obtained during the lower hybrid current drive campaign on JET.

Radial profiles of the ion temperature have been measured on PLT by using neutron flux Doppler broadening of oxygen, carbon and helium line radiations, and charge exchange. The ion temperature (⪅ 1.2 keV) is consistent with Hinton-Rosenbluth neoclassical heat conduction in the plateau regime as the dominant energy loss from the plasma with central ion energy confinement times ⪅ 0.1 s.

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.

jET results are presented which show a "profile consistency'' of the electron temperature under a variety of plasma conditions.This experimental fact is interpreted as due to a topology of the magnetic field lines where ordered structures such as laminar surfaces and magnetic islands coexist with ergodic domains.The development of this concept identifies different plasma regions according to the value of the safety factor and relates the observed degradation in confinement time. when Additional Heating is applied. to the plasma entering a multiphase state where the electron temperature gradient is limited by a critical value defined by the global plasma parameters. A preliminary scaling law for the electron temperature is proposed which indicates a strong fa\ ourable dependence on major radius and plasma current.Losses due to atomic processes at the plasma edge give rise to thernial instabilities with low m numbers. which induce ergodic regions. Plasma disruptions could be considered as the effect of these very low number instabilities ini = 7 . 3).The near future JET experimental programme is briefly described and possible ways or improving the plasma confinement are presented.