GLOBAL CONFINEMENT IN NBI PLASMAS OF THE TJ-II STELLARATOR UNDER LITHIUM-COATED WALL CONDITIONS

parameters (plasma radius, heating power, density, rotational transform) in rough agreement with the ones obtained from stellarator inter-machine scaling studies, like ISS04 [1, 2]. Subsequent local transport studies extracted dependencies of the thermal diffusivity on the mentioned parameters, which confirmed and qualified the results of the global 0-dimensional study [3]. During 2008, NBI operation under lithium-coated wall has given access to a new operational regime as compared to the previous NBI plasmas with boron-coated wall. This new NBI scenario is characterized by enhanced, long-lasting density control, impurity reduction and improved confinement [4, 5]. The details of the lithiumization process and the physics behind the observed boosted performance are described in these references. The present analysis concentrates in the global confinement of a set of 343 plasma discharges with pure NBI heating produced in 2008. The lithium wall plasma performance of an appropriate subset of discharges is compared to a set of boron wall NBI discharges produced in 2007 with one neutral beam injector.