Energy confinement time and heat transport in initial neutral beam heated plasmas on the large helical device

The confinement characteristics of large net-current-fret plasmas heated by neutral-beam injection have been investigated in the Large Helical Device (LHD). A systematic enhancement in energy-confinement times from the scalin g derived from the medium-sized heliotron/torsatron experiments have been o bserved, which is attributed to the edge pedestal. The core confinement is scaled with the Bohm term divided by the square root of the gyro radii. The comparative analysis using a dimensionally similar discharge in the Compac t Helical System indicates gyro-Bohm dependence in the core and transport i mprovement in the edge region of LHD plasmas.