Formation of Plasma Structures Due to Local Production of Huge Negative Ions

点击翻译按钮获取中文摘要

Huge negative ions are locally produced by introducing "Buckminsterfullerene, C_<60>" particles into a low-temperature potassium plasma column confined by a strong magnetic field. Concerning phenomena parilel to the magnetic-field lines it is experimentally found that a mechanism of reflecting a part of the electrons and ions flowing along the plasma flow exists around the region of negative ion production, and that solitary pulses with negative potential are intermittently excited, propagating downstream at an acoustic speed of the negative ions. This result is also confirmed by means of a one-dimensional electrostatic particle simulation. The plasma becomes unstable for a large rate of negative ion production, being accompanied by a double-layer formation generating the solitary pulse.Concernig phenomena perpendicular to the magnetic-field lines positive inos are experimentally observed to strongly diffuse in the radial direction with a diffusion coefficient ten times larger than that in the absence of negative ion production. Much stronger diffusion of the negative ions is observed around the downstream exit of the region of the negative ion production. As a result, the negative ions are radially localized in the periphery region of the plasma column. A new-type drift-wave instability originating from a combination of positive and negative ions is excited around that region described just above, a radial amplitude profile of which is dominated by the negative ion profile, and which propagates in the direction of the positive-ion diamagnetic drift with the mode number 1 or 2. This drift wave excitation and the radial plasma diffusion are confirmed to be closely related.