The energy confinement in the NBI plasmas has been investigated in the helical-axis heliotron device, Heliotron J. The configuration control experiments for bumpiness (εb), being one of the side-bands of the helical component, show that the plasma performance in NBI plasmas depends on not only the effective helical ripple (εeff) but also the bumpiness. The preferable enhancement factor of the e...

We demonstrate magnetic confinement of an ultracold neutral plasma (UCNP) created at the null a biconic cusp, or quadrupole field. Initially, UCNP expands due to electron thermal pressure. As encounters stronger fields, expansion slows and density distribution molds electrons are strongly magnetized over most plasma, while ion magnetization is only significant boundaries. Observations suggest t...

In this paper measurements of short wavelength electron density fluctuations using collective scattering of infrared light are presented. The Wendelstein 7-AS (W7-AS) stellarator (Renner H et al 1989 Plasma Phys. Control. Fusion 31 1579) and the diagnostic are briefly described. A series of plasma discharges with reproducible confinement transitions was created by ramping up the plasma current....