Invited paper: particle confinement in ISX-B

A number of experiments have been performed on ISX-B to help in the understanding of particle behavior. These include: single parameter scans allowing the dependence of global particle confinement on external variables to be determined, edge plasma measurements, recombination measurements at the wall, to help in the modelling of recycling, and pump limiter experiments, to control global recycling. Because of the difficulties in measuring the total source of neutrals, emphasis has been placed on the modelling of recycling of neutrals from the walls. The results are then used in both the analysis (ZORNOC) and predictive (PROCTR) transport codes, to derive the particle fluxes necessary to produce the observed density behavior. Much work in ISX-B has been devoted to understanding the reduction of global energy confinement time with increasing neutral beam power and β /sub p/ . One phenomena observed on coinjection, the density clamp, is the necessity to increase the external gas required to maintain a given density, suggesting a reduction in particle confinement time, and a possible role of convection in the observed degradation of energy confinement time. This possibility is strengthened by the observation that the scalings of energy and profile confinement times are very similar (I /sub p/ /sup 3/2/ P /sub b/ /sup -2/3/ ). However, detailed transport analysis using ZORNOC and PROCTR show that within 3/4 of the plasma radius, convection plays an insignificant role, and the observed energy confinement times are controlled by conduction losses. A model explaining these results is described