Status and Perspectives of the Liquid Material Experiments in FTU and ISTTOK

The main goal of FTU lithium liquid metal experiments was to demonstrate the capability of the Capillary Porous System (CPS), firstly tested on T-11 tokamak, to confine liquid lithium avoiding sudden release as consequence of j×Β electromagnetic force on the surface. These latter should be balanced by the surface tension forces associated to the liquid lithium in capillary channels. Very encouraging results have been obtained: a new ohmic plasma regime is obtained characterized by spontaneous peaking of the electron density profile with line average values of the density near or beyond the Greenwald limit. Furthermore these discharges exhibit an increase of the energy confinement over ITER97 L mode scaling up to a factor 1.4 after transport analysis with the JETTO code. Although the lithium liquid limiter is 2 cm away from the last closed magnetic surface and FTU is a fully metallic device the only impurity detected by the survey spectrometer is lithium, i.e. lithization is quite uniform over all the metallic part directly exposed to the plasma. In these conditions, the application of additional power (ECRH plus LH) has shown that the formation of an internal transport barrier (ITB) can be easier probably due, to an increase of LH current drive efficiency in plasma with lower Zeff and/or different edge conditions with a reduction of the local turbulence.Furthermore a distinct approach is being investigated in the small size ISTTOK tokamak, where free flowing, fully formed, liquid gallium jets have been successfully exposed to the plasmas aiming at studying their power extraction capability as well as the effects of tokamak-like magnetic field on their behaviour. Preliminary results on these issues are presented.