Overview of TCV Results

The Tokamak `a Configuration Variable , TCV, addresses scientific questions to improve our understanding of magnetically confined plasmas and our ability to control them in ITER relevant scenarios, and explores avenues to improve the plasma performance on the way to a conceptual fusion power plant that cannot necessarily be investigated in ITER. The unique flexibility of its shaping and control systems is matched by that of its Electron Cyclotron Heating (ECH) and current drive (ECCD) systems. These include 3 MW from six 82.7 GHz gyrotrons used at the second harmonic in X-mode (X2), and 1.5 MW from three gyrotrons at 118 GHz (X3). This overview highlights the progress accomplished on TCV during the 2004–2006 campaigns, focussed on five main themes: 1) particle, energy and momentum transport in shaped plasmas, investigated over a large range of normalized temperature gradients and including peaked density profiles measured even in the absence of a Ware pinch or a core particle source; 2) plasma edge physics, addressing the question of the origin of anomalous cross-field transport in the SOL; 3) H-mode physics under strong electron heating at reactor relevant beta, e.g. using third harmonic X3 heating (1.5 MW); 4) ECH and ECCD physics, including phase space fast electron transport and electron Bernstein wave heating, demonstrated in the O-X-B scheme; 5) physics of improved steady-state tokamak regimes with internal transport barriers, with or without inductive currents, and with large (over 70%) bootstrap current fractions, confirming the key role of the current profile in the transition to improved confinement and the necessity of a negative core magnetic shear for obtaining eITBs.