The far-field plasma environment of a hollow cathode assembly
Using a hollow cathode assembly (HCA) in a large vacuum chamber, such as the University of Michigan’s Large Vacuum Test Facility (LVTF), provides the capability of generating a plasma environment that closely approximates that of the ionosphere. This capability allows examinations of ionospheric-plasma phenomena in a controlled setting without, in most cases, relying on scaling techniques. The HCA provides a low-temperature, low-density, fairly uniform plasma in its far-field, and the LVTF provides ample room such that the effects of plasma confinement can be reduced to a minimum. Most previous studies on the HCA have concentrated on its plasma environment in the near-field, i.e. within a few 10’s of cm. This work, however, examines the far-field (i.e., 1-2 m) plasma environment of the HCA. This characterization shows that the HCA provides, in the far-field, a fairly uniform ionospheric-level plasma environment. The HCA was operated at nine different operating conditions consisting of three different gases (argon, krypton, and xenon) each at three different flow rates. In this paper, results from these nine operating conditions are summarized and the corresponding far-field plasma environments are analyzed. Comparison of the HCA’s plasma environment parameters with typical ionospheric values is presented.
