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.