Extension of the Operating Space of High-Beta N Fully Noninductive Scenarios on TCV Using Neutral Beam Injection

The fully non - inductive sustainment of high normalized beta plasmas ( ? N ) is a crucial challenge for the steady - state operation of a tokamak reactor. In order to assess the difficulties facing such scenarios, steady - state regimes have been explored on the Tokamak à Configuration Variable (TCV) using the newly available 1MW Neutral Beam Injection (NBI) system. The operating space i s extended towards plasmas that are closer to those expected in JT - 60SA and ITER, i.e. with significant NBI and Electron Cyclotron Resonance Heating and C urrent D rive (ECRH/CD) , bootstrap current and F a st I on (FI) fraction . ? N values up to 1.4 and 1.7 are obtained in lower single null L - mode (H 98 (y,2)~0.8) a nd H - mode (H 98 (y,2)~1) plasmas, respectively, at zero time averaged loop voltage and q 95 ~6 . Fully non - inductive operation i s not achieved with NBI alone, whose injection c an even increase the loop voltage in the presence of EC waves. A strong contribution to the total plasma pr essure of bulk and FIs from NBI is experimentally evidenced and confirmed by interpretative ASTRA and NUBEAM modelling , which further predict s that FI charge - exchange reactions are the main loss channel for NBH/CD efficiency. Internal t ransport b arriers, which are expected to maximize the boo t strap current fraction, are not formed in either the electron or the ion channel i n the plasmas explored to date, despite a significant increase in the toroidal rotation and FI fraction with NBI, which are known to re duce turbulence. First results on scenario development of high - ? N fully non - inductive H - mode plasmas are also presented.