EFFECT OF ASPECT RATIO ON MAGNETIC-FIELD FLUCTUATIONS IN THE REVERSED-FIELD PINCH

The effect of aspect ratio on magnetic field fluctuations in reversed- field pinches is investigated using a three-dimensional magnetohydrody namic code. Configurations with aspect ratios of 1.1, 2.2, and 4.4 are modeled. The results are extrapolated to aspect ratio 8.8 for compari son with the Extrap T1 experiment [Nucl. Fusion 34, 427 (1994)]. It is found that the average modal amplitudes decrease with aspect ratio. H owever, the spectrum broadens correspondingly, resulting in negligible effect on the magnetic fluctuation level. The computed spectrum dynam ics are found to be in good agreement with experimental observations o n the T1 experiment. Quantitative evaluations of the field line stocha sticity indicate no dependence of the mean magnetic field diffusion ra te on aspect ratio. (C) 1995 American Institute of Physics.