Research on an improved explosive emission cathode

Abstract

This paper presents a physical description of the cathode plasma process of an explosive emission cathode (EEC) and experimental results on a type of oil-immersed graphite EEC. It is believed that the generation of a cathode plasma is mainly dependent on the state of the cathode surface, and that adsorbed gases and dielectrics on the cathode surface play a leading role in the formation of the cathode plasma. Based on these ideas, a type of oil-immersed graphite EEC is proposed and fabricated. The experiments indicate that the oil-immersed cathodes have improved emissive properties and longer lifetimes.

Emission Uniformity of an Annular Graphite Cathode With a Focusing Electrode in a High Power Vacuum Diode

“…The explosive electron emission process depends mainly on the status of the cathode surface hence the surface morphology of the cathode has a profound effect on the emission characteristics of EECs [14]. In the proposed diode structure, with the introduction of the focusing electrode, the electric field on the cathode surface would decrease greatly, which would increase the emission delay and hence have an unfavorable effect on the uniformity of the emission.…”

“…This requirement is especially important in HPM devices that are operated with a low guiding magnetic field (GMF). Consequently, great efforts have been made to improve the emission uniformity of EECs [14]- [17]. Moreover, for a cathode with focusing electrodes [18], [19], the introduction of the focusing electrodes is…”

“…However, the distribution of the initial emission micro-points is random and non-uniform, consequently, the emission points might be discrete and of relatively large size due to cathode plasma expansion [18], [21], [22], which would result in the azimuthal uniformity of the electron beam. Graphite as a cathode material is widely used in HPM generation and many reports have demonstrated excellent emission characteristics such a very short explosive emission delay time, long lifetime and good emission uniformity [14], [15], [23]- [25]. However, for operation of the graphite cathode with a focusing electrode, the emission threshold of graphite is quite high and this is not conducive to achieving good emission uniformity.…”

A Long Pulse Relativistic Klystron Amplifier Driven by Low RF Power

“…10. An annular electron beam of voltage 700 kV, current 6 kA, and pulse length 200 ns is injected into a 4.8-cm-diameter drift tube from a cold-cathode (graphite) explosive emission diode which is driven by the linear-transformer-driver accelerator [10], [11]. The beam is modulated by a modulating cavity driven by an external RF source at a frequency of 2.88 GHz.…”

Research on effect of emission uniformity on X-band relativistic backward oscillator using conformal PIC code

“…In order to improve the output power of the RBWO to reach or exceed the gigawatt level, magnetically insulated coaxial diodes (MICDs) are widely adopted to generate an intensive relativistic electron beam (REB), where explosive emission cathodes (EECs) are used to provide an annular electron beam of multi-kiloampere. In the explosive electron emission (EEE) process of the EECs, 3,4 the EEE nonuniformity is unavoidable due to the cathode surface morphology, which may result in the excitation of asymmetric modes or mode competition. 5 The nonuniformity of the EEE lies in the explosions of the micropoints in the cathode surface and the subsequent formation of the cathode plasma.…”