The low to high confinement transition has been observed on the large helical device fA. Iiyoshi, A. Komori, A. Ejiri et al., Nucl. Fusion 39, 1245 s1999dg, exhibiting rapid increase in edge electron density with sharp depression of Ha emission. The transition occurs in low toroidal field sBt =0.5-0.75 Td discharges and are heated by high power neutral beam injection. The plasma thus has a relatively high value s,1.5%d of the volume averaged b value. The electron temperature and density profiles have steep gradients at the edge region which has high magnetic shear but is at a magnetic hill. Formation of the edge transport barrier leads to enhanced activities of the interchange type of modes with m=2/n=3 sm,n are the poloidal and toroidal mode numbersd in the edge region. At present, these magnetohydrodynamic activities limit the rise of the stored energy; the resultant increment of the stored energy remains modest.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics