Excitation of parametric oscillations in a triode with a virtual cathode with an external electromagnetic wave

The electromagnetic radiation of an electron flow in a triode with a virtual cathode is studied from the viewpoint of a parametric resonance. It is shown that the phase modulation of the electrons and the radiation saturation take place due to the oscillations of the virtual cathode as a result of large space charge. An expression for the coherent radiation intensity of the electron flow in a resonator is derived. It is shown that the phase modulation depth and the radiation efficiency increase with an external electromagnetic wave. Tomsk Polytechnic University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 76–81, February, 2000.