Improved Modes and the Evaluation of Confinement Improvement

"Various improved confinement modes in tokamak are surveyed and their characteristics are reviewed. To search for the potentiality as a fusion core plasma in reactor, an examination to evaluate the core performance has been made. The fusion product near the ignition condition, where Q is large, is used for the evaluation. The dilution of the fuel ion and the profile effect are simultaneously examined together with the obtained tau_E. Because of the fuel dilution and of the bulk radiation, the good performance does not always correspond to the mode with long tau_E. If their time evolution is taken into account the problem becomes more serious. Further extensive research to control the fuel purity is surely needed to ensure the long pulse operation.