Confinement studies of plasmas in boronized Heliotron E

In helical systems, the increase of beta values and confinement studies in the low collisionality regime are the most important subjects. In order to obtain high beta plasmas the magnetic field strength is often reduced and the electron density is increased. These plasmas can be severely restricted by radiation collapse. In the low collisionality regime low density, high temperature operation is essential and the reduction of recycling is necessary. For the above purposes, a new boronization with low H/B atomic ratios has been applied to Heliotron E since July in 1993. After this boronization, the operational region in the density and temperature extended widely and the reproducibility of plasmas was greatly improved due to the reduction of the light impurities. In this paper the confinement study of plasmas heated by the neutral beams after boronization is presented. (author) 5 refs., 5 figs