Plasma Conductivity and Temperature in a Theta Pinch

Using a new balanced magnetic probe technique the plasma magnetic field in a theta pinch has been measured independently of the drive field. The measurements allow a determination of the total plasma current versus time and the plasma current radius versus time. The current radius determined in this manner agrees well with the visible sheath radius from streak photographs. The measurements also allow determination of the plasma conductivity in the sheath, as well as the leakage of trapped flux through the sheath. Temperatures have been calculated from the conductivity, using the ``weak field'' and ``strong field'' conductivity expressions. An independent spectroscopic temperature measurement for the same plasma is consistent with the ``weak field'' conductivity expression. Finally, it is shown that the apparent validity of the ``weak field'' expression is consistent with the average magnetic field strength within the sheath.