Emission Features and Structure of an Electron Beam versus Gas Pressure and Magnetic Field in a Cold-Cathode Coaxial Diode

The structure of the emission surface of a cold tubular cathode and electron beam was investigated as a function of the magnetic field in the coaxial diode of the high-current accelerator. The runaway mode of magnetized electrons in atmospheric air enabled registering the instantaneous structure of activated field-emission centers at the cathode edge. The region of air pressure (about 3 Torr) was determined experimentally and via analysis, where the explosive emission mechanism of the appearance of fast electrons with energies above 100 keV is replaced by the runaway electrons in a gas.

Влияние анодной и катодной плазмы на работу электронного диода со взрывоэмиссионным катодом

The results of modeling and experimental investigation of the formation of anode and cathode plasmas in a vacuum diode with an explosive-emission cathode during the generation of a pulsed electron beam with a current density of 0.3-0.4 kA/cm^2 and an accelerating voltage of 300-500 kV are presented. It is shown that the concentration of the anode plasma does not exceed 10^10 cm^-3 and it does not significantly contribute to the operation of the diode. However, the complete desorption of molecules from the working surface of the explosive-emission cathode and the high efficiency of shock ionization of atoms ensure the formation of a cathode gas plasma with a concentration of 10^16 cm^-3. It is found that the charge of the explosive-emission plasma layer is significantly less than the charge of the electron beam and the main source of electrons is not an explosive-emission plasma, but a cathode gas plasma. In this case, the electron current is limited by the concentration of the cathode plasma. The use of a cathode with a developed surface (a cathode with a carbon fabric coating) allows increasing the total charge of the electron beam by more than 1.5 times without changing the cathode diameter and the anode-cathode gap.

Токовые характеристики сильноточной электронной пушки с многоканальным инициированием взрывной эмиссии пробоем по поверхности диэлектрика

Current characteristics of a plasma-filled, high-current electron gun with a new cathode assembly which can be named as a controlled explosive-emission cathode have been investigated. Multi-gap initiation of explosive emission is performed with the use of parallel operated, resistively decoupled arc plasma sources which electrodes and tube ceramic isolators are built-in to the explosive-emission cathode. The initiation of explosive emission was performed using 69 operating in parallel arc plasma sources whose electrodes and tubular ceramic insulators are inserted to the disk explosive-emission cathode. Experiments have demonstrated operability of high-current electron gun with a new cathode assembly at accelerating voltage up to 30 kV and its good emissivity (average in area current density) which was approximately 1.4–2.4 times higher than an emissivity of traditional electron gun with plasma anode and multi-wire copper cathode.