Improved source of cold plasma electrons and negative ions

A cold electron plasma has been produced, with a greater latitude in neutral pressure and plasma density than previously, by drifting plasma through an improved magnetic cusp cage. The motion across this cage has been characterized as a two-step process. First, the plasma between the cusps cools off as it loses contact with the primary ionizing electrons which are confined at the cusps and, second, the cold plasma electrons experience a ∇B×B drift across the cage barrier magnetic field. Large ambipolar fields are also seen across the region. A two-component, positive ion (Ar+)–negative ion (SF6−) plasma was created with the ratio of electron density (ne) to positive ion density (n+) continuously variable from 10−3