Zeeman-Effect Magnetic Field Measurement of a High-Temperature Plasma

Distortions of magnetic field measurements caused by material probes in hot plasmas can be avoided by measuring the Zeeman splitting of impurity spectral lines. The problem of the line breadths being large compared to the magnetic field splitting is solved by using the opposite circular polarization characteristics of the symmetrically displaced Zeeman components in a longitudinal field. This, however, limits the technique to wavelengths longer than 2000 Å, where there is a scarcity of intense allowed transitions from the highly ionized species which originate in the hot plasma. Successful measurements have been made on the Scylla I theta pinch device. These indicate approximately zero magnetic field in the hot plasma and set a lower limit of 79% on $\beta$, the ratio of plasma to magnetic pressure.