Investigation of a novel virtual cathode oscillator with decelerating electric field

Traditional virtual cathode oscillators require extremely high operating voltage to generate beam currents exceeding the space charge limiting current to form virtual cathodes, which significantly limits their repetitive operation capability and application fields. In this paper, the impact of brake voltage on the space charge limiting current in the diode gap is first analyzed, and it is found that brake voltage can effectively “relax” the limit of current required to form a virtual cathode. On this basis, a prototype experiment of a new type of virtual cathode oscillator with a braking electric field was designed. The results show that the braking electric field can effectively reduce the electron beam current required to form the virtual cathode and reduce the input power. The use of appropriate braking voltage can effectively suppress the chirping phenomenon of radiation frequency and improve the radiation pulse width and radiation efficiency. This provides a reference for the design of new narrow-band imaginary cathode oscillators with low voltage and high efficiency.