@article{oai:nifs-repository.repo.nii.ac.jp:00000663,
 author = {IKEDA,  Katsunori and NAKANO,  Haruhisa and TSUMORI,  Katsuyoshi and KISAKI,  Masashi and NAGAOKA,  Kenichi and OSAKABE,  Masaki and TAKEIRI,  Yasuhiko and KANEKO,  Osamu},
 journal = {Plasma and Fusion Research},
 month = {Apr},
 note = {We developed a new imaging spectroscopy diagnostic tool for Hα  emission and installed it on a negative hydrogen ion (H?) source to investigate the H? dynamics in the extraction region. During beam extraction, the Hα emission dropped; the same drop also appeared in the H? density (as measured by cavity ring-down spectroscopy). The reduction in the Hα emission results from the reduction in the excited hydrogen population caused by mutual neutralization processes between H+ and H? ions, which in turn are due to a decrease in the H? density. We find a reduction structure in Hα that is observed inside the plasma farther than 20 mm from the plasma grid (PG) surface. The result indicates that H? ions produced at the PG surface accumulate in the extraction region, so we conclude that they flow toward the PG apertures.},
 title = {Visualization of H? Dynamics in Extraction Region of Negative-Ion Source by Hα Imaging Spectroscopy},
 volume = {Vol.8},
 year = {2013}
}