Abstract
The non-uniform annular electron beam models are established based on the annular cathode explosive emission luminescence images. The influence of electron beam uniformities on the microwave characteristics of an annular structure S-band relativistic klystron amplifier output cavity is investigated with particle-in-cell simulations. The electron beam non-uniformities are simulated using four different electron emission models: (1) continuous area without emission, (2) spaced emission, (3) enhanced emission, and (4) current density variation emission. The simulation results with the first emission model show that the output power decreases as the continuous area without emission increases, while the continuous area without emission has little effect on the frequency and pulse width. The simulation results with the second emission model show that the output power of the spaced emission is related to the distribution of non-emission areas. The more evenly the areas without emission are distributed on the annular cathode, the greater the output power is. The simulation results with the third emission model show that the higher the current density in the local area is, the smaller the output power is. The simulation results with the fourth emission model show that the fluctuation of current density causes the fluctuation of frequency and output power. The larger the change area of the current density is, the greater the fluctuation amplitudes of the output power and frequency are. The larger the fluctuation amplitude of current density is, the greater the fluctuation amplitudes of the output power and frequency are.
Highlights
High power microwave technology has important applications in directional energy weapons, radars, high energy accelerators, plasma heating, laser pumping, etc,1–3 O-type devices such as a relativistic backward wave oscillator4–7 (RBWO) and relativistic klystron amplifier8–10 (RKA) generally require annular electron beams for beam–wave interactions
The non-uniform annular electron beam models are established based on the annular cathode explosive emission luminescence images obtained using a framing camera
The simulation results with the first emission model have shown that the output power of the S-band RKA output cavity decreases as the continuous non-emission area increases, while the continuous non-emission area has little effect on the frequency and pulse width of the S-band RKA output cavity
Summary
High power microwave technology has important applications in directional energy weapons, radars, high energy accelerators, plasma heating, laser pumping, etc, O-type devices such as a relativistic backward wave oscillator (RBWO) and relativistic klystron amplifier (RKA) generally require annular electron beams for beam–wave interactions. The authors of Ref. 20 used the PIC code to investigate the influence of different emission areas on an X-band RBWO. The results show that the output power is unstable and the microwave mode is not pure when the ratio of the explosion emission area on the cathode surface is below 80%. The authors of Ref. 21 used PIC software to study the effect of a non-uniform annular electron beam on the microwave characteristics of an RBWO. All the above research studies focus on RBWO devices, and there is hardly any research done on the influence of electron beam’s uniformities on the microwave characteristics of an annular structure S-band RKA. It is meaningful to establish nonuniform electron beam models to study the influence of the annular electron beam non-uniformities on the microwave characteristics of an annular structure S-band RKA. The influence of electron beam non-uniformities on the microwave characteristics of an annular structure S-band
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