Ambipolar Electric Fields and Turbulence Studies in the Wisconsin Levitated Toroidal Octupole.

The turbulence structure was measured by correlation techniques which were carefully described. In these experiments, signals were studied which are aperiodic in time and space, short lived compared to the decay times of the bulk plasma parameters, short ranged compared to the machine size, and were therefore classified as microturbulence structures. The resulting spatial and temporal correlation functions were well fitted to a Gaussian function and the associated correlation lengths or times were the half width at half maximum of the CFs. The correlation length was measured to be the ion gyro radius for the hot hydrogen plasma and somewhat less for the helium plasma. The measured correlation time was comparable to the disassembly time of such a cell from the influence of the magnetic gradient and curvature drifts.