Study On Large Power Broadband Energy Transmission System Of Terahertz Electronic Vacuum Devices

With the outlook for the application of terahertz technology,the electric vacuum devices as the terahertz source get much attention,and many researchers of this filed at home and abroad are studying on it.The window as one of the important components of it undertakes the task of separating the vacuum and atmosphere and energy transmission.The wider working bandwidth and higher power capacity are important research directions for the window.The pill-box window,which is used commonly,is a resonant window,which means it can not achieve ultra-broadband transmission.Due to the size co-dimensioning effect,the increasing working frequency leads to the problem of decreasing device power capacity and increasing waveguide loss.To deal with these problems,this thesis studis on the 220 GHz diamond pill-box window,220 GHz mode conversion,W-band metamaterial window,and 1 THz Brewster window and overmodedBrewster window.The specific studis of this thesis is as follows.1.Design and processing of 220 GHz diamond pill-box window.The dimensions of the diamond box window is designed with the electromagnetic simulation software.The reflection coefficient S₁₁ is better than-20 dB and transmission coefficient S₂₁ is better than-1 dB at 210-230 GHz.The metallization process of the diamond window slice was explored with magnetron sputtering.After the welding of the diamond slice and the window frames,the airtightness and transmission characteristics was tseted.2.Design of 220 GHz TE₁₀-TE₁₁-HE₁₁ mode converter.In order to meet the requirements for source of terahertz energy radiation,the energy output from the window should be converted to a quasi-Gaussian distributed HE₁₁ mode.The mode requirements of the HE₁₁ mode was met in turn by means of a diamond pill-box window,a rectangular-circular transition section and a radius tapering circular waveguide,and the phase was adjusted by the circular waveguide.The conversion efficiency of the structure without the diamond pill-box window is 98.22%,and the conversion efficiency of the whole system,of which the reflection coefficient S₁₁ is better than-18 dB,is 94.16%.3.Design of W-band metamaterial window.The working bandwidth was extented by adding a specific mental structure on the surface of the window slice of sapphire window.The reflection coefficient S₁₁ is better than-20 dB in 70-104GHz and the transmission coefficient S₂₁ is better than-0.4 dB in 70-112 GHz.The mental structure is verified to have a good tolerance of dimensional error.4.Design of 1 THz Brewster window and overmodedBrewster window.Based on the principle of zero reflection by Brewster angle,the Brewster window of 0.95-1.05 THz was designed.The reflection coefficient S₁₁ is better than-20 dB and the transmission coefficient S₂₁ is better than-2.5 dB.Then,the overmodedBrewster window is designed to achieve the reflection coefficient S₁₁ better than-20 dB and the transmission coefficient S₂₁ better than-1.1 dB in 0.9-1.1 THz.With the transition section from the standard waveguide to the overmoded waveguide,the reflection coefficient S₁₁ is better than-18dB and the transmission coefficient S₂₁ is better than-2.7 dB.