Recent Progress on Toroidal Nonneutral Plasmas Confined on Heliotron Magnetic Surfaces

Firstly, non-constant space potential phi(s) and electron density n(e) on magnetic surfaces of helical nonneutral plasmas are observed in CHS experiments. The variation of phi(s) has grown with increasing electron injection energy, implying that thermal effects are important when considering the force balance along magnetic Field lines. These observations confirm the existence of plasma equilibrium having non-constant phi(s) and n(e) on magnetic surfaces of helical nonneutral plasmas. Secondly, outward orbits that extend to inward part of closed helical vacuum magnetic region are found in three dimensional calculations which take into account two experimental findings. The pitch angle of electron injected into the stochastic magnetic region is scattered considerably due to the presence of shifted self space potential phi(s). Eventually, the injected electron turns to be a helically trapped particle, and start an inward movement along one of the vertical bar B-min vertical bar contours. Once penetrating deeply, the electron can never escape from the last closed flux surface because the negative phi(s) acts as a potential barrier. Thirdly, first data obtained from toroidal nonneutral plasmas confined on the quasi-poloidally symmetric magnetic surfaces having a helical-axis is described. It shows that externally produced plasmas are successfully observed, and moreover, the non-constant phi(s) and n(e) of helical nonneutral plasmas are ensured in the Heliotron J experiments, as well.