Highly Ionized Hollow Cathode Discharge

Abstract

A hollow cathode discharge (HCD) is described that produces a highly ionized steady-state plasma (ne≈1013−1014/cm3) at a temperature 1–10 eV, in a volume as large as 104 cm3, with background neutral gas density ≈1013/cm3. The HCD is generated by the prescription: gas flow (H2, He, A, or N2) 0.05–2 cc STP/sec through a refractory metal hollow cathode tube into a vacuum; any anode; 20–200 V dc applied. An axial induction 100–1000 G is used to collimate the discharge and to aid in starting by rf excitation. The HCD runs from the cathode interior, deep enough that p0d≈1 cm×mm Hg. Current range is 2.0–300 A. Various electrode configurations and a wide range of operating parameters have been studied. The external plasma density and temperature were measured by Langmuir probes. A discussion is given of the confinement mechanism and of the energy balance, both in the external plasma and in the region of the cathode itself.

Geometrical Aspects of a Hollow-cathode Magnetron (HCM)

“…7,8 One of the early studies on magnetized hollow cathode discharges was performed by Lidsky et al 9 These employed a uniform magnetic field parallel to the central axis of the hollow cathode tube. The aspect ratio was typically large, R a ~ 10 and the HCS diameter small, D ~ 1 cm.…”

A high efficiency ionizer using a hollow cathode discharge plasma

“…As an example, a 3 ma diameter cathode was operated in Ar from a few araperes to several nundred amps. 1 Plasma densities in the 10 13 to 10 l< * ca~3 range can be obtained, and the background pressure i3 typically in the 10 Torr range, or 10~s Torr with sufficient differential pumping. The length of t;ie plasma can be anywhere from a few centimeters to a few meters with almost no change in the discharge current and voltage.…”

Design data for hollow cathode gas-fed arcs

“…The early development of the hollow cathode gasfed arc was attributed t o Luce ( l ) = or Lidsky et al (2). Since then arcs have been studied by many investigators.…”