Linewidth-modulated motional Stark effect measurements of internal field structure in low-field configurations

Motional Stark effect measurements of internal field structure in low-field magnetic confinement configurations are considered for both magnitude and direction of the local magnetic field. The amplitude and phase delay of an oscillating spectral linewidth driven by a rotating polarizer provides a me ans of determining the magnitude and direction of the total field simultane ously while avoiding difficulties of neutral beam energy drift. Photon-nois e limit estimates for a diagnostic beam on the low-field PEGASUS toroidal e xperiment indicate sensitivities of roughly 20 G and 0.2 degrees for the ma gnitude and direction angle. These values are sufficient to provide signifi cant constraints on magnetic equilibrium reconstructions. (C) 2001 American Institute of Physics.