Resonant side-coupled cavity electron accelerators: E A Knapp et al,Rep LA-DC-8834; MP-3-4, Sept 1967, 18 pages ( Sci Tech Aerospace Reps, 6 (5), 643, N68-14324).

Abstract

The chapter presents a short review on hollow cathode, penning, and electron-beam excitation sources. A type of discharge that has been found particularly suitable as a vacuum ultraviolet (VUV) radiation source is the windowless high-current hollow cathode source. Hollow cathode discharges are a special type of glow discharge. The characteristic feature of these sources is its dominant negative glow. Because the pressure is chosen so that the mean free path of the electrons is larger than the diameter of the hollow cathode these electrons, the so-called “beam electrons,” oscillate between the two opposing cathode falls until their kinetic energy is transferred to the gas atoms by collision. Hollow cathode discharges are typically non-LTE plasmas. Penning discharges were originally investigated for use as ionization gauges for low-pressure measurements. The characteristic feature of a Penning discharge is the application of a strong magnetic field parallel to the electric field of the cathode fall. When the high-energy beam electrons in the hollow cathode or Penning discharge are replaced by electrons produced from an electron gun no erosion of the electrode takes place and a highly stable source of VUV line radiation can be created. With known excitation cross sections the absolute flux emitted by such a source can be determined from the operating parameters and the geometry of the source.