AIAA 992861 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. Nomenclature B 0 background magnetic-flux density, T B LVTF magnetic-flux density in LVTF, T B E geomagnetic-flux-density vector, T B E geomagnetic-flux density, T B IGRF magnetic-flux density from IGRF model, T k Boltzmann's constant, 1.38 × 10 −23 J/K m e electron mass, 9.109 × 10 −31 kg m i ion mass, kg n e electron plasma density, m −3 n i ion density, m −3 q charge magnitude, 1.602 × 10 −19 C r ce electron gyroradius, m r ci ion gyroradius, m T e electron temperature, K v te electron thermal velocity, m/s v ti ion thermal velocity, m/s Z i ionization level, integer ε 0 free space permittivity, 8.85 × 10 −12 F/m θ e electron temperature, eV Introduction T HE capability of generating a plasma environment that closely approximates that of the iono-sphere is highly desirable to researchers wishing to examine ionospheric-plasma phenomena in a controlled setting. Such a capability would also be useful in testing and calibrating ionospheric probes without relying on scaling techniques. 1 The use of a hollow cathode assembly (HCA) in a large vacuum chamber, such as the University of Michigan's Large Vacuum Test Facility (LVTF), can provide just such a capability. The HCA provides a …