@techreport{oai:nifs-repository.repo.nii.ac.jp:00010464,
 author = {"Yokoyama,  M. and Ida,  K. and Sanuki,  H. and Itoh,  K. and Narihara,  K. and Tanaka,  K. and Kawahata,  K. and Ohyabu,  N. and LHD, experimental group"},
 month = {May},
 note = {"The radial electric field (E_r) properties in LHD have been investigated to indicate the guidance towards improved confinement with possible E_r transition and bifurcation.   The ambipolar E_r is obtained from the neoclassical flux based on the analytical formulae. This approach is appropriate to clarify ambipolar E_r properties in a wide range of temperature and density in a more transparent way. The comparison between calculated E_r and experimentally measured one has shown the qualitatively good agreement such as the threshold density for the transition from ion root to electron root. The calculations also well reproduce the experimentally obesrved tendency that the electron root is possible by increasing temperatures even for higher density and the ion root is enhanced for higher density. Based on the usefulness of this approach to analyze E_r in LHD, calculations in a wide range  have been performed to clarify the parameter region of interest where multiple solutions of E_r can exist. This is the region where E_r transition and bifurcation may be realized as already experimentally confirmed in CHS. The systematic calculations give a comprehensive understandings of experimentally observed E_r properties, which indicates an optimum path towards improved confinement."},
 title = {Analysis of Radial Electric Field in LHD towards Improved Confinement},
 year = {2001}
}