Increase of Central Ion Temperature After Carbon Pellet Injection in Ne-Seeded NBI Discharges

A cylindrical carbon pellet with a size of 1.0 mm φ × 1.0 mm L was injected into low-density (ne = 0.3‐0.5 × 10 13 cm -3 ) neon-seeded NBI plasmas of the Large Helical Device (LHD). When the two NBI beam pulses were delayed just after the pellet injection, a large increment of central ion temperature up to 5 keV was observed with the appearance of a peaked density profile (ne0 /〈ne〉~2.5) and enhanced toroidal rotation speed up to 35 km/s. Improvement of the ion transport is expected with the suggestion of a new operational scenario for confinement improvement in the LHD.