Development of plasma cathode electron guns

Abstract

The status of experimental research and ongoing development of plasma cathode electron guns in recent years is reviewed, including some novel upgrades and applications to various technological fields. The attractiveness of this kind of e-gun is due to its capability of creating high current, broad or focused beams, both in pulsed and steady-state modes of operation. An important characteristic of the plasma cathode electron gun is the absence of a thermionic cathode, a feature which leads to long lifetime and reliable operation even in the presence of aggressive background gas media and at fore-vacuum gas pressure ranges such as achieved by mechanical pumps. Depending on the required beam parameters, different kinds of plasma discharge systems can be used in plasma cathode electron guns, such as vacuum arcs, constricted gaseous arcs, hollow cathode glows, and two kinds of discharges in crossed E×B fields: Penning and magnetron. At the present time, plasma cathode electron guns provide beams with transverse dimension from fractional millimeter up to about one meter, beam current from microamperes to kiloamperes, beam current density up to about 100 A/cm2, pulse duration from nanoseconds to dc, and electron energy from several keV to hundreds of keV. Applications include electron beam melting and welding, surface treatment, plasma chemistry, radiation technologies, laser pumping, microwave generation, and more.

Plasma Cathode Electron Sources

“…Later, in 1989, Plasma Processes in Technological Electron Guns was published [2], with contributions from several authors. The problems and promises of the development of plasma emission electronics have been addressed in various collections of articles [3-5], reviews papers [6][7][8][9][10], and the [11]. The formation of large-cross-section electron beams, including those produced in plasma-cathode systems, is discussed in [12].…”

Electron beam generation in a diode with a gaseous plasma electron source II: Plasma source based on a hollow anode ignited by a hollow-cathode source

“…To ignite the main hollow anode discharge, a HC 3,4 placed at the bottom of the HPA was used ͑see Fig. 1͒.…”

“…Indeed, the increase in the plasma potential should lead to a decrease in the electron emission capability of the HPA. 4 In order to avoid a diode plasma prefilled mode, the diode operation was checked with a decreasing time delay of the accelerating pulse application relative to the beginning of the HPA discharge. Namely, the accelerating pulse was applied at the rising front of the HPA discharge current.…”

Low-pressure, high-current hollow cathode with a ferroelectric plasma source

“…1,2 However, in order to achieve a high-current HC discharge (I HC Ͼ100 A), one has to keep a high gas pressure (10 Ϫ2 -10 Ϫ3 Torr) and to have a large ratio between the cathode and anode areas. 1 The latter is necessary to avoid arcing inside the HC cavity. In addition, the increase of the gas pressure results in a breakdown inside the accelerating gap.…”

“…͓DOI: 10.1063/1.1527695͔ Hollow cathodes ͑HC͒ have important advantages compared with other types of plasma cathodes. 1 The HC can produce a plasma with a density of 10 12 cm Ϫ3 and an emitting area of several tens of square centimeters that is sufficient for the production of electron beams with current amplitudes up to hundreds of amperes. 1,2 However, in order to achieve a high-current HC discharge (I HC Ͼ100 A), one has to keep a high gas pressure (10 Ϫ2 -10 Ϫ3 Torr) and to have a large ratio between the cathode and anode areas.…”