Progress of Positive-Ion-Based NBI for LHD

摘要

Two positive-ion-based neutral injectors for Large Helical Device (LHD), which are LHD-NBI #4 and #5, are overviewed. Those injectors are installed to enhance the ion temperature of LHD plasmas by producing low-temperature ions. Each beamline has four ion sources, and the injection power of NBI #4 is 6 MW at the energy of 40 keV.The NBI #5 is designed to provide the beam power of 6 MW at 45 keV for hydrogen beam and 9 MW at 80 keV for deuterium beam. Beam injection with NBI #4 has started with two ion sources in 2004 and with full of four sources in 2005. The maximum power of NBI #4 has reached 7 MW. The injector contributes to increase ion temperature, and is also applied to a diagnostic beam using charge exchange recombination spectroscopy (CXRS). The NBI #5 has been operational in 2010. After tuning a ratio of acceleration and deceleration voltages, the injection power reaches 5.8 MW at 40 keV so far.