X-band Relativistic Backward Wave Oscillator

Backward wave oscillator(BWO) is one of the microwave devices having the highest output power,but a voluminous guiding magnetic field system,which is also an undesirable energy-consumer is needed.The BWO with small radial dimension and low magnetic field is studied here.The dissertation mainly involves three parts:In part one,consisting of chapter 2 and chapter 3,the BWO is theoretically studied.The analytical formula,which uncovers the relationship between microwave frequency and parameters of electron beam and slow wave structure(SWS),is derived.The formula is very exact for sinusoidal SWS.Simultaneity,based on the linear Vlasov equation,the relationship between output power and guiding magnetic field,which accords with the experimental results,is gained.In part two,consisting of chapter 4 and chapter 5,a relativistic BWO is investigated. Firstly,the BWO with 7 periods SWS is designed by particle in cell(PIC) simulation.When the average radius and thickness of annular electron beam is 0.95cm and 1mm,the voltage and current of electron beam is 900kV and 6.7kA,the strength of guiding magnetic field is 3.2T, the performance of 1.2GW microwave output power at 9.4GHz microwave frequency and 22%conversion efficiency are obtained.Secondly,the relativistic BWO is experimentally investigated.Under the condition that the electron energy is 790keV,the beam current is 7.6kA and the guiding magnetic field is at 2.3T,the performance of 1.4GW microwave output power at 9.4GHz microwave frequency with 30ns pulse width and 26%conversion efficiency are obtained and consistency of microwave waveforms is very good.In part three,consisting of chapter 6 and chapter 7,a relativistic BWO with low magnetic field is investigated.Firstly,the BWO is simulated by the particle in cell(PIC) code KARAT. When the voltage and current of electron beam is respectively 760kV and 7.2kA,the strength of guiding magnetic field is 0.73T,the performance of 1.2GW microwave output power at 9.3GHz microwave frequency and 25%conversion efficiency are obtained and the mode of the microwave is TM₀₁.Secondly,the relativistic BWO with low magnetic field is experimentally investigated.Under the condition that the electron energy is 740keV,the beam current is 7kA(the total current,which includes the beam current and the loss current,is 12KA) and the guiding magnetic field is at 0.68T,the performance of 1.15GW microwave output power at 9.1GHz microwave frequency with 22ns pulse width and 22%conversion efficiency are obtained and the mode of the microwave is TM₀₁.The BWO is on the same level with other microwave devices with low magnetic field in the world,but it has the smallest radial dimension.So it is possible to develop practical HPM source guided by a permanent magnetic field.