Dynatron modulator

A new scheme of compact dynatron modulator is proposed. The modulator with transverse dimensions of several centimeters can work as an RF-avtogenerator or RF-amplifier in wide range of frequencies. The modulator works on the dynatron effect inside vacuum inverted coaxial diode with magnetic isolation supplied by an external pulsed high-voltage source connected to the modulator via RL-circuit. Under conditions of permanent emission of primary electron beam from an external electrode (cathode) and the growth of the voltage at the diode the storage of primary electrons arises inside the gap. Oscillations of the voltage due to oscillating regime of diode charging and/or azimuthal instability of rotating electron flow stimulates back-bombardment flow electrons to the cathode and leads to power spikes of secondary emission current exceeding primary one. As the result, the amplitude of oscillations in quasi-resonant circuit grows and the system can turn to self-supporting oscillations, i.e. like to avtogenerator. The amplitude, the average voltage and the frequency of oscillations can be changed by varying a part of parameters. Results of computer simulations are given for 2-D geometries (r,theta; rz) to illustrate the main physical processes inside the modulator and its possible applications