LAUSR

In order to investigate the confinement physics of the energetic particles (EPs) in the Large Helical Device (LHD), the neutral particle analyzer (NPA) array is newly developed using single crystal CVD diamond detectors. The diamond detectors are adopted because of their high radiation hardness which is suitable to withstand the high-neutron flux expected in the deuterium experiments. For the initial experimental campaign, two detectors were installed at z=−7.77 m for perpendicular lines of sight to measure helically trapped EPs generated by perpendicular neutral beam injectors (NBIs). As the result of the diamond NPA (DNPA) commissioning in the last LHD experimental campaign, the DNPA successfully detected the EPs. The signal pulse counting rate due to the neutron-induced noise is several kcps in the highest neutron flux discharge in LHD, this noise counting rate is sufficiently low compared to the neutral signal counting rate.