During the first year of operation, the TCV tokamak has produced a large variety of plasma shapes and magnetic configurations, with 1 . O B J1.46T, I <800kA, ~S2.05, -0.7G%0.7. A new shape control algorithm, Eased on a finite element reconstruction of the plasma current in real time, has been implemented. Vertical growth rates of 800 sec-', corresponding to a stability margin f=l.IS, have been stabilized. Ohmic H-modes, with energy confinement times reaching 8 h s , normalized beta (p ,aB/I> of 1.9 and z P R 8 9 -P of 2.4 have been obtained in singlenuB X-point deuterium discharges with the ion grad B drift towards the X-point. Limiter H-modes with maximum line averaged electron densities of 1 . 7~1 0~~m -~ have been observed in D-shaped plasmas with 360kASIp&00kA.

Confinement in TCV electron cyclotron heated discharges was studied as a function of plasma shape, i.e. as a function of elongation, 1.1 < κ < 2.15, and triangularity, −0.65 ≤ δ ≤ 0.55. The electron energy confinement time was found to increase with elongation, owing in part to the increase of plasma current with elongation. The beneficial effect of negative triangularities was most effective at low power and tended to decrease at the higher powers used. The large variety of sawtooth types observed in TCV for different power deposition locations, from on-axis to the q = 1 region, was simulated with a model that included local power deposition, a growing m/n = 1 island (convection and reconnection), plasma rotation and finite heat diffusivity across flux surfaces. Furthermore, a model with local magnetic shear reproduced the experimental observation that the sawtooth period is at a maximum when the heating is close to the q = 1 surface.

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On the Tokamakà Configuration Variable (TCV), electron internal transport barriers (eITBs) can be formed during a gradual evolution from a centrally peaked to a hollow current profile while all external actuators are held constant. The formation occurs rapidly (<τ eE) and locally and, according to ASTRA modelling, is consistent with the appearance of a local minimum in the safety factor (q) profile. The eITB is sustained by non-inductively driven currents (including the off-axis bootstrap current) for many current redistribution times while the current in the tokamak transformer is held constant. The maximum duration is limited by the pulse length of the gyrotrons. The transformer coil can be used as a counter (or co-) current source with negligible accompanying input power. In established eITBs the performance can be enhanced (degraded) by altering solely the central current or q-profile. New experiments show that the same stationary eITB performance can be reached starting from discharges with centrally peaked current. A fine scan in surface voltage shows a smooth increase in performance and no sudden improvement with voltage despite the fact that q min must pass through several low-order rational values.

A steady-state, fully noninductive plasma current has been sustained for the first time in a tokamak using electron cyclotron current drive only. In this discharge, 123 kA of current have been sustained for the entire gyrotron pulse duration of 2 s. Careful distribution across the plasma minor radius of the power deposited from three 0. 5-MW gyrotrons was essential for reaching steady-state conditions. With central current drive, up to 153 kA of current have been fully replaced transiently for 100 ms. The noninductive scenario is confirmed by the ability to recharge the Ohmic transformer. The dependence of the current drive efficiency on the minor radius is also demonstrated.