Drift wave maps, area preserving maps that describe the motion of charged particles in drift waves, are derived. The maps allow the integration of particle orbits on the long time scale needed to describe transport. Calculations using the drift wave maps show that dramatic improvement in the particle confinement, in the presence of a given level and spectrum of E x B turbulence, can occur for q(r)-profiles with reversed shear. A similar reduction in the transport, i.e. one that is independent of the turbulence, is observed in the presence of an equilibrium radial electric fieId with shear. The transport reduction, caused by the combined effects of radial electric field shear and both monotonic and reversed shear magnetic q-profiles, is also investigated.

No abstract

The authors derive the guiding center equations of motion from the phase space Euler–Lagrange formulation for the motion of a charged particle in toroidal magnetic confinement geometry. The guiding center equations are numerically solved together with the Monte Carlo Coulomb collisional pitch angle scattering. The numerically calculated microscopic diffusion coefficients for various values of collisionality ν* in the case of no electrostatic potential agree well with the results of neoclassical theory. The diffusion coefficient is then measured in the presence of a model electrostatic drift wave fluctuation and an equilibrium potential. The diffusion coefficient increases with increasing fluctuation amplitude while the equilibrium potential diminishes the diffusion processes through both the orbit squeezing and the Er×B shear flow of the poloidal velocity.

The effects of dual coplanar electrodes on a Hg-free flat fluorescent lamp were studied. For a dual coplanar lamp, brightness and efficacy were improved by 80% compared to a conventional coplanar lamp. The improvement is regarded as the result of reduced diffusion loss and the effective usage of the discharge volume in the dual coplanar lamps. An efficacy of 35.9 lm/w (14900 cd/m 2) was achieved for 250 torr of a Xe(30%)/Ne(70%) gas mixture, by a 20-kHz ac pulse driving.

Pure MgO powders were synthesized using wet chemical and thermal processes. Purity and crystallinity were used as indicators determining the synthesis. From this, we obtained highly pure and crystalline MgO powders. Using these powders, we could achieve 15~20V lower firing voltage and 10 ~ 15% higher efficiency, depending on the extent of the partly covered area and on sealing temperature. The improvement was proved to be due to surface states that were absent in an MgO film.