Patent ID: 9633813
Date: 2017-04-25
CPC Classifications: H01J

Claim:
1. An ion source for use in a radiation generator tube comprising: a back passive cathode electrode; a passive anode electrode downstream of the back passive cathode electrode; a magnet adjacent the passive anode electrode; a front passive cathode electrode downstream of the passive anode electrode, the front passive cathode electrode and the back passive cathode electrode and defining an ionization region therebetween; and at least one ring-shaped ohmically heated cathode configured to emit electrons into the ionization region, wherein the ring-shaped ohmically heated cathode is centered about a longitudinal axis of the ion source to reduce exposure to backstreaming electrons; a cathode grid downstream of the at least one ring-shaped ohmically heated cathode; the back passive cathode electrode and the passive anode electrode, and the front passive cathode electrode and the passive anode electrode, having respective voltage differences therebetween, and the magnet generating a magnetic field, such that a Penning-type trap is produced to confine the electrons to the ionization region; at least some of the electrons in the ionization region interacting with an ionizable gas to create ions.