The Research Of Y-band Extended Interaction Oscillator Based On Pseudospark-sourced Electron Beam

Recently,powerful and mobile terahertz sources of electromagnetic radiation are mainly concerned with research however the lack of compact and reliable sources has hindered applications in high data rate communications,molecular spectroscopy,biological spectroscopy and biomedical diagnostics etc.The extended interaction oscillator(EIO)is a kind of important terahertz radiation source under development.It is a novel vacuum electronic high power source which combine the ruggedness,high power capability of a klystron and the wide bandwidth of a travelling wave tube.As the development direction of the operating frequency of the EIO is submillimeter and terahertz,at the same time the device structure as compact as possible,how to improve the power density has become priority research areas of EIO.The main contents of this thesis include as the following: The systematical introduction of terahertz and pseudospark(PS)discharge;The summary of the development and current situation of EIO,and the outline of the related model and small-signal theory of EIO;The design and optimization of the Y-band EIO based on PS-sourced electron beam and the analysis and discussion of the simulation results of the Y-band EIO;The effect of velocity spread of PS-sourced electron beam to Y-band EIO performance.The research contents and innovation points include as the following:(1)Using the PS-sourced electron beam instead of an electron beam produced by a more conventional thermionic cathode is a novel way to generate millimeter and terahertz waves.PS-sourced electron beam generated from the PS discharge process is self-focused by the positive-ion channel,eliminating the need for external magnetic guide field.EIO operation in the terahertz range puts greater demand on current density and brightness of the electron beam.The PS-sourced electron beam is a good candidate to drive such high frequency EIOs as it has a very high combined beam current density(up to 108 A/ m2)and brightness(up to 1012 A/ m2 rad2).(2)With the help of the high frequency electromagnetic simulation software CST and CHIPIC,the design and optimization of the Y-band EIO based on PS-sourced electron beam(main operating frequency of 283.7 GHz)are discussed in detail.The dc pencil beam was designed for an accelerating energy of 36 keV,a current density of 800 A/cm2(total beam current of 0.25 A),and a beam diameter of 0.2 mm was adopted.The peak output power was about 1.85 kW with an averaged efficiency of ~10%,and the centre frequency was 283.7 GHz.(3)The PS-sourced electron beam can have an inherent velocity spread unless some form of post acceleration is used.It was found that the Y-band EIO circuit can operate with a relatively wide velocity spread range when a high beam current density is used.Based above simulation results,a peak power over 1.67 kW at 283.7 GHz was achieved using an electron beam,which can be generated by PS discharge,with velocity spread of 12.5%.For an electron beam current density of 1 kA/cm2,the output power is not less than 0.9 times of the power obtained with an electron beam with no velocity spread when the velocity spread is within the range 0~15%.