Abstract
The magnetic island in the large helical device (LHD) shows the dynamic behaviour of the healing/growth transition with the hysteretic behaviour. The thresholds of plasma beta and poloidal flow for island healing are larger than that for growth. The threshold of resonant magnetic perturbation (RMP) for healing is smaller than that for growth. Furthermore, thresholds of the amplitude of RMP depend on the magnetic axis position Rax in the LHD. The RMP threshold increases as the magnetic axis position Rax increases. The poloidal viscosity may be considered as a candidate to explain the experimental observation from the viewpoint of the relationship between the electromagnetic torque and the viscous torque.
Highlights
For the good confinement of toroidal plasmas, nested flux surfaces are required
A small magnetic island might trigger a magnetohydrodynamic (MHD) instability called neoclassical tearing mode which leads to a deterioration of the confinement and may possibly lead to a locked mode in Tokamak plasmas [1], whereas a serious disruption never occurs even if the magnetic island grows in the large helical device (LHD) plasmas
It is observed that thresholds of the amplitude of resonant magnetic perturbation (RMP) for the healing/growth transition of the magnetic island depend on magnetic axis position Rax
Summary
For the good confinement of toroidal plasmas, nested flux surfaces are required. A small magnetic island might trigger a magnetohydrodynamic (MHD) instability called neoclassical tearing mode which leads to a deterioration of the confinement and may possibly lead to a locked mode in Tokamak plasmas [1], whereas a serious disruption never occurs even if the magnetic island grows in the large helical device (LHD) plasmas. The magnetic islands intrinsically disappear as they are stabilised during a plasma discharge under certain conditions [2, 3] and the grown magnetic island merely triggers a minor collapse when the magnetic shear becomes low [4].
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
