Studies of nonneutral plasmas confined on helical magnetic surfaces of Heliotron J

Nonneutral plasmas confined on helical magnetic surfaces becomes have different characteristics from those of neutral plasmas. The most significant one observed in experiments is that both space potential φs and plasma density ne are not constant on closed magnetic surfaces. This strongly implies that such plasma parameters vary also along each magnetic field line (B-field line) with which closed magnetic surfaces are formed. In this paper, we have numerically estimated the variations of φs and ne along helical B-field lines of the Heliotron J machine, Data show that on the magnetic axis, variations of φs and ne are about 7 V and 2x107 m-3 for the case of B-0.3 kG. Other accessible B-field lines and the estimated variations of φs and ne on them are also presented. (author)