Measurement of time development of local conductivity of turbulent plasma in a magnetic mirror bottle

The measurement of time development of plasma conductivity in a turbulent heating is done at various radial positions in a plasma by using an electric probe and a Rogowsky coil by which the quasi static electric field strength and current density are measured. In the early phase of the discharge, the plasma conductivity in the current penetrating domain shows anomalously low value ranging from 1.7 to 7 Ω-1 cm-1, that is of the order of one tenth of the classical one at 2 eV in electron temperature, despite that the overall voltage waveform does not show any resistive hump. After the full penetration of the current to the column axis the conductivity begins to drop rapidly at all radial points and the resistive hump of the overall voltage waveform begins to rise, and the macroscopic instability grows. (auth.)