Abstract
Explosive emission cathodes (EECs) are adopted in relativistic backward wave oscillators (RBWOs) to generate intense relativistic electron beam. The emission uniformity of the EEC can render saturation of the power generation unstable and the output mode impure. However, the direct measurement of the plasma parameters on the cathode surface is quite difficult and there are very few related numerical study reports about this issue. In this paper, a self-developed three-dimensional conformal fully electromagnetic particle in cell code is used to study the effect of emission uniformity on the X-band RBWO; the electron explosive emission model and the field emission model are both implemented in the same cathode surface, and the local field enhancement factor is also considered in the field emission model. The RBWO with a random nonuniform EEC is thoroughly studied using this code; the simulation results reveal that when the area ratio of cathode surface for electron explosive emission is 80%, the output power is unstable and the output mode is impure. When the annular EEC does not emit electron in the angle range of 30°, the RBWO can also operate normally.
Highlights
The relativistic backward wave oscillator (RBWO) is one of the most promising high power microwave (HPM) sources,1,2 which is characterized by operating at high efficiency and high repetition
A self-developed three-dimensional conformal fully electromagnetic particle in cell code is used to study the effect of emission uniformity on the X-band RBWO; the electron explosive emission model and the field emission model are both implemented in the same cathode surface, and the local field enhancement factor is considered in the field emission model
As the area ratio of the electron emission (EEE) decreased to 80%, the numerical simulation results are presented in Fig. 6, we find that the saturation of the power generation is unstable, FIG. 3
Summary
The relativistic backward wave oscillator (RBWO) is one of the most promising high power microwave (HPM) sources, which is characterized by operating at high efficiency and high repetition. In the previous design of the RBWO, these factors have been overlooked in the previous numerical research of the MICDs and the RBWO, cathode plasma is considered to cover the whole cathode surface in the particle simulation, and it is very challenging to implement the parameters of the cathode in the particle code because of the dynamic change of cathode plasma and formation of a new emission center. Emission nonuniformity of EEC is implemented in our selfdeveloped conformal three-dimensional particle-in-cell (PIC) code, and the FE process and the EEC process are both considered in the same cathode surface, and the influences of nonuniform EEE on the RBWO are studied using this code.
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