RADIAL ION-TRANSPORT MEASUREMENTS IN A NONAXISYMMETRIC MAGNETIC-MIRROR

Experimental radial ion transport rates and diffusion coefficients are presented for the Constance-B magnetic mirror [Phys. Rev. Lett. 58, 1853 ( 1987)]. The transport experiments are performed by measuring steady state equilibrium radial profiles of plasma density, ionization source, end loss current, electric field, electron temperature, and ion temperature. A charge coupled device (CCD) camera system [Rev. Sci. Instrum. 60, 2835 (1989)] is used to measure the two-dimensional radial density, source, and electron temperature profiles. End loss diagnostics including movable Faraday cups, electrostatic end loss analyzers, and an ion time-of-flight analyzer [Rev. Sci. Instrum. 59, 601 (1988)] are used to measure radial profiles of potential and ion temperature. The ion confinement time perpendicular to the magnetic field is found to be an order of magnitude shorter than predicted by classical and neoclassical transport theories. The radial profiles of the perpendicular diffusion coefficient (D⊥) are presented for hydrogen, helium, and argon plasmas. The coefficients are a factor of 10 larger than the maximum classical and neoclassical coefficients in all three plasmas. Plasma fluctuations resulting from whistler mode microinstability [Phys. Rev. Lett. 59, 1821 (1987)] as well as nonaxisymmetric potentials are suggested as possible explanations for the experimentally measured radial transport rate. © 1990 American Institute of Physics.