FTU results with a liquid lithium limiter

Since the end of 2005 most of the plasma–wall interaction experiments on FTU have been focused on the possible use of liquid lithium as the plasma facing material. Liquid lithium limiter is an active method to deposit, during the plasma discharge, a lithium film on the walls with prolonged beneficial effects. Reliable operation with very clean plasmas, very low wall particle recycling, spontaneous peaking of the density profile for line-averaged density values ne > 1.0 × 1020 m−3 have been obtained. These results have allowed us to extend the density limit to the highest value so far obtained (n̄e = 4.0 × 1020 m−3 at Ip = 0.7 MA and BT = 7.1 T, qa = 5.0, by gas puffing only) and to increase the energy confinement time by almost 50% with respect to the average value of 50 ms of the old ohmic FTU database. An accurate analysis of these plasmas has been carried out by means of a gyrokinetic code to establish the role of collisionality and density gradients on the observed phenomenology. (Some figures in this article are in colour only in the electronic version)