ANOMALOUS TRANSPORT IN TOKAMAKS - EXAMPLES OF ITS SUPPRESSION

Studies conducted towards an understanding of improved plasma confinem ent in small and large tokamaks are presented In STOR-M, Ohmic H-modes can be induced by various means. The most recent finding is that inje ction of a high density compact torus triggers a sustained II-mode. Fo r bias induced H-mode, direct evaluation of fluctuation induced partic le flux has been made for Ohmic H-modes. The particle flux is intermit tent and the average changes its sign from radially outward in L-mode to radially inward in H-mode. The direction and magnitude of the flux are predominantly determined by the phase difference between the densi ty and potential fluctuations. Nonlinear correlation studies have also been made between two radial positions. In L-mode, the inner region b ehaves as a master and outer region as slave. In H-mode, the relations hip is reversed. For high performance negative shear discharges in lar ge tokamaks, the radial derivative of the Shafranov shift Delta' is sh own to have efficient stabilizing influence on the trapped electron dr ift mode and kinetic ballooning mode (KBM). The ion temperature gradie nt (ITG) mode is well stabilized at a modest alpha (the ballooning par ameter).