Research And Design Of Staggered Double Grating Sheet Beam Traveling Wave Tubes

Terahertz(THz)wave is a kind of electromagnetic wave between the electronics and photonics area and its frequency is between 0.1 THz to 10 THz.This relative region has many attractive features including(1)strong penetration through a lot of dielectrics;(2)penetration dependent upon water concentration and tissue densities;(3)non-ionizing feature as compared with X-ray;(4)inherent wide bandwidth available due to its high frequency;(5)high definition benefiting from its high frequency;(6)low attenuation of millimeter wave electromagnetic radiation in rain and harsh weather conditions as compared to high signal attenuation at infra-red frequencies.These features benefit the THz wave a splendid prospect in the industrial area,scientific research,and national defense.However,subject to the restriction of the material,research methods and machining technology,the developing processes of the Terahertz device was very slow in last decades,this gives rise to what is known as the THz gap.As the material science,computation technology,and machining technology rapidly developing,Terahertz devices meet a new opportunity.Comparing with the Nuclear Magnet Resonance(NMR)and Low-Frequency Electron Paramagnetic Resonance(LF-EPR),the THz EPR system is much more sensitive and has higher resolution,so that,THz EPR system has better application prospects in medical examination,chemical research,and industrial production areas.But nowadays it meets a bottle-neck due to lack of middle power(tens watts)THz radiation sources.The main focus of this dissertation has been in conjunction with the staggered double grating(SDG)slow wave structure(SWS),broad bandwidth and large beam tunnel input/output coupling structure,hybrid modes transmission pill-box window,sheet beam electron gun and permanent periodic focusing system of the SB-TWT.Based on the previous research,a 263 GHz sheet beam traveling wave tube(SB-TWT)employed in the UC-Davis 260 GHz electron paramagnetic resonance(EPR)system has been analyzed and designed.At the beginning,based on the dispersive curve and the coupling impedance feature,the field distribution and the energy storage in the SDG SWS have been analyzed.The modified coupling impedance has been used to finish Pierce Gain analysis and the Back-Ward Wave analysis,which can generally estimate the performance of the SB-TWT.Employing the methods mentioned before,the main interaction structure of the 263 GHz SB-TWT has been designed.The particle-in-cell(PIC)simulation results show that driven by a 19 kV,0.15 A sheet beam,this 263 GHz SB-TWT can produce more than 50 W power over 20 GHz bandwidth.At the same time,the zero-driven PIC simulations show that this design can effectively suppress the Re-generation and Back-Ward Wave oscillation.Then,the electron gun and new PCM-TQM magnet for sheet beam TWT were analyzed and designed.The electrode tunable dual-mode gun can provide both 0.08666 A low current beam for continuous wave operation and 0.2126 A high current beam for pulse wave operation of 200 GHz dual mode SB-TWT.In the 0.8 teslas(T)uniform focusing magnetic field,both the low current beam and the high current beam can achieve 100% transmission ratio.The complex electrode gun for 263 GHz SB-TWT is designed to produce a 400 A/cm2 current density sheet beam.Although taking the beam bunching effect into consideration,the calculation shows that the transmission of this beam in the Permanent Cups Magnet – Tunable Quadrupole Magnet(PCM-TQM)focusing system is higher than 95.85%.After that,some other components of the 260 EPR system have been designed.At the beginning,the hybrid modes transmission pill-box window has been presented.By introducing the higher mode into the transmission band,this kind of windows can greatly extend the bandwidth of the single transmission mode pill-box windows.Both S-parameter and thermal analysis have been done to verify the feasibility of this design.The corrugated waveguide transmission line has been employed to reduce the attenuation of the high-frequency wave in the long distance standard waveguide.At the end of this chapter,a particular collection system for sheet beam has been carried out.Employing the tail dispersive magnet and the elliptical collector,this novel collection system can benefit the compact design of the whole device.At the last,some testing data of previously designed components has been reported.These data verified the previous design and will support our future research.