Overview of TCV results

The TCV tokamak (R = 0.88 m, a < 0.25 m, BT < 1.54 T) is equipped with six 0.5 MW gyrotron sources operating at 82.7 GHz for second harmonic X mode ECH. By distributing the ECCD current sources over the discharge cross section, fully driven stationary plasmas with Ip = 210 kA, ne0 = 2×1019 m-3, Te0 » 4 keV, were obtained for the full discharge duration of 2 s. Highly peaked electron temperature profiles with Te0 up to 12 keV were obtained in central counter-current drive scenarios with off-axis ECH. Absorption measurements using a 118 GHz gyrotron have demonstrated the importance of suprathermal electrons for third harmonic absorption. A coupled heat-particle transport phenomenon known as `density pumpoutʹ, which leads to the expulsion of particles from the plasma core, has been linked to the presence of m = 1 modes, suggesting that it is due to the existence of locally trapped particles associated with the loss of axisymmetry. Highly elongated discharges have been developed with ohmic heating (k < 2.8) and off-axis ECH. The latter exhibit considerably improved vertical stability due to current profile broadening. A `gatewayʹ for ELMy H modes has been discovered, which allows stationary ohmic ELMy H mode operation over a wide range of elongation, triangularity and density. Divertor detachment experiments suggest the existence of recombination pathways other than three body or radiative processes.