Physical analysis and numerical simulations of ultra widebandplasma relativistic microwave noise amplifier br

The physical mechanism and output properties of the plasma relativistic microwave noise amplifier(PRNA) are studied numerically by using the all electromagnetic particle-in-cell (PIC) code. Firstly, thedispersion relation between the operating mode and the slow space charge wave of relativistic electron beamwithout coupling is simulated and analyzed. Simulation results show that both the plasma density np and radialthickness Drp affect the dispersion characteristics markedly and their increasing can lead the frequency at thebeam-wave resonant point to be enhanced. The beam voltage and current also affect the resonant frequency,but the effect is relatively slight. Secondly, variation of the linear growth rate and the bandwidth are thenevaluated by using the linear theory. Calculations show that the PRNA has the virtue of wideband output. Itsbandwidth can reach a GHz level. By adjusting the plasma parameters np and Drp, the relativistic electronbeam voltage and current, the operating frequency can be tuned over a wide frequency range. Therefore thePRNA also has virtue of fine frequency tunability. Based on the above calculation results, the whole PICsimulations of the PRNA are then carried out to verify the virtues of wideband microwave output andfrequency tunability. The basic features of the field distributions of the operating in the evolution process andout coupling process are given. The bunching process and the energy release process of relativistic electron beamare also plotted. Simulations show that with a plasma density of 1.4x1019 /m3, beam voltage and current of500 kV and 2 kA and applied magnetic field of 2.0 T, 200 MW output microwave with efficiency about 20% canbe obtained. The frequency ranges from about 7.0 to 9.0 GHz, the band width reaches 2 GHz. And the outputmode is the TEM mode of the coaxial waveguide. Both np and Drp affect the dispersion relations markedly andthe output frequency increases clearly with np and Drp increasing. The influence of beam voltage and current onthe output frequency are both relatively small and the gap distance between the plasma and electron beam haslittle effect on the output frequency. The research results will provide useful reference for further designing thePRNA