The plasma-cathode electron gun

Abstract

The development of a new type of plasma-cathode electron gun suitable for pulsed as well as CW operation with <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e</tex> -beam lasers is reported. This device employs a plasma generated within a low-voltage hollow-cathode discharge rather than a thermionic emitter as the source of electrons. Electrons extracted from the plasma pass through a triode-type control grid structure and are accelerated to high energies in a plasma-free region prior to emerging from the gun through a thin foil window (the foil window was replaced by a solid collector in the tests described here). A plasma-cathode device producing a beam of up to 30 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> in area has been evaluated at beam energies up to 140 keV, at 100-μs pulsed beam current densities up to 1 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , and at CW current densities of greater than 0.7 mA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The beam current uniformity has been evaluated and the beam has been measured to be monoenergetic to better than 3 percent at the foil-window location. The major life-limiting factors have been shown to be minimal. Devices capable of producing beams of arbitrarily large areas should he possible.