Simulating ionospheric plasma with a hollow cathode in a large vacuum chamber

A plasma environment closely approximating the ionosphere can be generated by a hollow cathode assembly in a large vacuum chamber. This capability allows examinations of ionospheric-plasma phenomena in a controlled setting without, in most cases, relying on scaling techniques. The hollow cathode provides a low-temperature, low-density, fairly uniform plasma in its far field, and the large chamber provides ample room such that the effects of plasma confinement are reduced to a minimum. Most previous studies of hollow cathodes have concentrated on their plasma environment in the near field, i.e., within a few tens of centimeters. This work, however, examines their far-field plasma environment, i.e., 1-2m. This characterization shows that the hollow cathode provides, in the far field, a fairly uniform ionospheric-level plasma environment. The hollow cathode was operated at nine different operating conditions consisting of three different gases (argon, krypton, and xenon) each at three different flow rates. Results from these nine operating conditions are summarized, and the corresponding far-field plasma environments are analyzed. Comparison of the hollow cathode's plasma environment parameters with typical ionospheric values is presented. Uses of the facility, such as full-scale scientific instrument verification, are presented.