Alternating current operation with one full cycle at a plasma current level of 2.5 kA has been achieved in the CT-6B tokamak. The poloidal magnetic field in the plasma is measured with two internal magnetic probes in repeated discharges. The plasma current distribution is reconstructed with an inversion algorithm. The reversed plasma current first appears on the low field side due to decreasing poloidal beta. Two plasma current components flow in opposite directions when the net current vanishes. The existence of the magnetic surfaces and rotational transform provides particle confinement in the current reversal phase.

Electron cyclotron wave current startup has been investigated in a wide range of toroidal magnetic fields on the CT-6B tokamak. Two kinds of drive mechanisms of current startup have been identified experimentally, according to the dependence of the wave started current on the vertical field. Their contributions to the current have been estimated quantitatively for different resonance scenarios. The wave started current may occur at a downshifted resonance frequency even if the resonance layer is located outside the vacuum vessel.

A novel method of electron cyclotron wave current startup has been proposed, in which a discharge between a pair of electrodes is introduced and forms a magnified toroidal plasma current in a strong toroidal field and a weak vertical field. The method has been demonstrated on the CT-6B tokamak. The experimental results are consistent with a model that is suggested.

Alternating current operation with one full cycle and a current level of 2.5 k A have been achieved in the CT-6B tokamak. The poloidal magnetic field in the plasma is measured with two internal magnetic probes in repeated discharges. The current distribution is reconstructed with an inversion algorithm. The inversed current first appears on the weak field side. The existence of magnetic surfaces and rotational transform provide particle confinement in the current reversal phase.

We propose a method to determine the scaling law of the electron thermal conductivity xZT: with modulating heat pulses. Relation between temperature phase lag and parameters (xZ, A) is established, from which the electronthermal conductivity in center region of CT-6B tokamak is determined.