Broad-beam electron source

A broad-beam electron source has a chamber into which is introduced an ionizing gas. Electrons are emitted between a cathode and an anode assembly to ionize that gas. The electrons within the plasma are drawn outwardly from the chamber through an apertured wall, which constitutes a screen, and thereafter are accelerated toward a target in a well-directed beam. A comparatively copious supply of electrons is developed, while yet requiring only low voltages in connection with its generation and resulting in correspondingly low electron energies. Ions produced external to the electron source itself are utilized to assist in neutralizing the charge density of the electron beam in order to help maintain its definition. For insulative targets, secondarily emitted electrons permit conservation of surface charge.