Electrode biasing experiments were carried out in various magnetic configurations on the Large Helical Device (LHD). The transitions of poloidal viscosity, which were accompanied with bifurcation phenomena characterized by a negative resistance in an electrode characteristic, were clearly observed on LHD by the electrode biasing. The critical external driving force required for transition was compared with the local maximum in ion viscosity, and the radial resistivity before the transition also compared with the expected value from a neoclassical theory. The critical driving force increased and the radial resistivity decreased with the major radius of the magnetic axis Rax going outwards. The configuration dependence of the transition condition and the radial resistivity qualitatively agreed with neoclassical theories. The radial electric field and the viscosity were also evaluated by the neoclassical transport code for a non-axisymmetric system, and estimated electrode voltage required for the transition, which was consistent with the experimental results.
様々な磁場配位において、大型ヘリカル装置（LHD）上で電極バイアス実験を実施した。電極特性における負性抵抗を特徴とする分岐現象を伴うポロイダル粘性の遷移が、LHD上で電極バイアスにより明確に観測された。遷移に必要な臨界外部駆動力は、イオン粘性の極大値と比較され、遷移前の径方向抵抗率も新古典理論からの予想値と比較された。臨界駆動力は増加し、径方向抵抗率は磁気軸の主半径Raxが外側に向かうにつれて減少した。遷移条件と径方向抵抗率の配位依存性は、新古典理論と定性的に一致した。径方向電場と粘性は、非軸対称系に対する新古典輸送コードによっても評価され、遷移に必要な電極電圧の推定値は実験結果と一致した。