US 4,684,848 A · Broad-beam electron source

Abstract

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.

Claims23

Dependent claims

An electron source comprising:

a chamber;
means for introducing an ionizable gas into said chamber;
means for developing a plasma throughout a region within said chamber and the size of which region is large compared to the Debye length in said plasma;
and a selective means constituting a bounding wall of said chamber effectively defining a screen with an array of apertures transmissive of electrons produced from said plasma together with means, including the impressing of a potential on said screen, to enable broad extraction from said chamber of a defined broad beam of said produced electrons, while screening flow of ions from within said chamber, said selective means accelerating an effective plurality of electron beamlets which exhibit balanced electron-emlssive characteristics that coalesce into a defined beam.

1 more element

Dependencies are inferred from the claim text.

Broad-beam electron source

Life of this patent

Broad-beam electron source

Life of this patent

Abstract

Claims23