Study of Current-Driven Magnetohydrodynamic Instability in the Heliotron-D Device

Ohmic-current-driven magnetohydrodynamic instabilities in the Heliotron-D device, which has large external rotational transform ($t_F>1\mathrm{}$) and strong shear ($\theta >0.5\mathrm{}$), have been studied experimentally. Since those instabilities satisfy the regular relations between the external and the ohmic-current transforms ($t_{\mathrm{OH}}$), kink and resistive tearingmode instabilities are supposed to exist. The strong shear plays a major role to suppress the magnetohydrodynamic instabilities, and the Ohmic current exceeds the $t_{\mathrm{OH}}$ limit stably.