The Study Of Quasi-optical Cavity Device Based On Smith-purcell Radiation

Terahertz refers to an electromagnetic wave whose frequency is between 0.1 THz and 10 THz.Terahertz science and technology have extremely wide application prospects in many fields.However,a major problem in the application of the terahertz is the lack of high-power,compact terahertz sources.In this paper,faced with the very scarcity of terahertz radiation sources,a method combining theory and particle simulation was adopted to systematically study two devices based on Smith-Purcel radiation.The main work of this article:1.Theoretical and simulation studies of Smith-Purcel radiation and Smith-Purcel coherent radiation.The coherent radiation in the 90 degree direction was studied,and the influence of the single or double electron beams on the intensity of the coherent radiation was compared.It was found that the intensity of the coherent radiation can be significantly increased by 3 times as much as compared with single electron system.2.A dual electron beam oscillator based on Smith-Purcell coherent radiation with a confocal open quasi-optical resonator is proposed.The simulation results show that it is possible to modulate periodic electron bunches with the two-electron beam modulated by gratings.The electron clusters can effectively excite the Smith-Purcel coherent radiation and form a stable mode in the cavity.3.A confocal cylindrical cavity is designed to replace the conventional planar surface cavity,and the energy storage capability is 7 times lager and the Q-factor are higher 18.5%.the DC beam study shows that this source can generate 0.35 THz frequency while the voltage is 14.8ke V and current density is just 20A/cm2,while it is relative low input in THz band.4.A new type of oscillator based on Smith-Purcel radiation was studied.The design method of Obictron resonator is studied deeply.Firstly,the method of calculating the resonant field of the whole structure through single-cycle structure is studied.Afterwards,the influence of the resonant cavity parameters on the field shape was carefully studied.The design method of the desired resonant cavity was obtained,and the resonant cavity type that could easily couple the double electron beam was proposed.Afterwards,the influence of the resonant cavity parameters on the field was carefully studied.The design method of the desired resonant cavity was obtained.And the resonant cavity type that could easily couple the double electron beam was proposed.5.Then the interactions electron and wave were studied,and 37.5GHz and 340 GHz oscillators were designed.For a 37.5GHz oscillator,the output power can reach 18 W,the electronic efficiency can reach 5%,and its surface wave mode is found as the competitive mode and The output frequency is consistent with the previous high-frequency calculations.A 340 GHz model was obtained using the scale method,a terahertz output of 338 GHz was obtained,and its efficiency could reach 2%.Finally,it is studied excite other high-order modes by changing the position and voltage of the electron beam.The working principle of this device was further discussed,and the two devices studied in this paper were compared.