Confinement studies in the TJ-II stellarator

ECR (electron cyclotron resonance) heated plasmas have been studied in the low magnetic shear TJ-II stellarator (R = 1.5 m, a<0.22 m, B = 1 T, f = 53.2 GHz, PECRH = 300 kW, power density = 1-25 W cm-3). Recent experiments have explored the flexibility of the TJ-II across a wide range of plasma volumes with different rotational transforms and rational surface densities. In this paper, the main results of this campaign are presented and, in particular, the influence of iota and rational surfaces on plasma profiles is discussed.