Pellet injection experiment on NBI current-free plasmas in Heliotron E

Abstract

The first pellet injection experiments on NBI-heated current-free plasmas in Heliotron E have been carried out. The pellet and plasma species are hydrogen. The increment of line-averaged density is up to 8.2 × 1019m−3, which is consistent with particle numbers of 1020 contained in a pellet used in the experiment. The behaviour of the plasma is studied in two cases of magnetic field strength, B = 1.9 T and B = 0.94 T. The density after pellet injection decays slowly (50–150 ms) in most cases, but in some cases with B = 0.94 T it decays rapidly (< 10 ms). This may be related to power balance.