Statistical Analysis on Particle Confinement of Hydrogenic Ions in Large Helical Device

Particle transport in NBI and ECH heated plasmas has been investigated on Large Helical Device (LHD). The control of hydrogenic isotope concentration, i.e, tritium and deuterium (D) is a critical issue to maximize fusion power output. Recently, D plasma experiment has begun in LHD, and measurement separating hydrogen (H) and D density profiles has become available by bulk charge exchange recombination spectroscopy (b-CXRS). Global particle confinement time in steady state has been compared for H, D and H/D mixture plasmas in order to characterize the isotope effect on particle transport. It has been found that the global particle confinement time deteriorates from H to D. The transient decay time of H/D ratio after H and D pellet injection has been also analyzed. In contrast to global particle confinement time, significant difference of the decay time between H and D particles has not been recognized.