SOURCES OF FLUCTUATING FIELD ON FIELD-REVERSED CONFIGURATION PLASMA

Fluctuating azimuthal fields, B(theta), are detected during a lifetime of a Field-Reversed Configuration plasma. The maximum strength reache s to 70 G which corresponds to about 1.5% of a confining field. Source s of the fields are discussed with relation to such plasma motions as radial shifting and tilting motions, and elliptical deformation of the plasma column triggered by a rotational instability. Analytic formula s of the B(theta), are derived from disturbance of the confining field due to these motions. Estimated values from the formulas agree well w ith field profiles obtained from a magnetic probe array.