Forming and maintaining a potential well in a quasispherical magnetic trap

The formation and maintenance of an electrostatic potential well by injecting electrons into a quasispherical cusped magnetic confinement geometry is studied experimentally, as a function of plasma fill density and of the energy and current of the injected electrons. A model is developed to analyze the experiment. It is found that the potential is comparable to the energy of the injected electrons at low density, and decreases as an increasing density of cold plasma fills the device because of ionization or wall bombardment. Implications for fusion based on electrostatic/magnetic confinement are discussed.