| As an important part of high-power microwave generation system,high-power microwave source is highly concerned and researched.In order to expand the application prospects,high-power microwave sources need to develop towards compact,light and small-scale to adapt to different platforms.At the same time,when high-power microwave devices work under long pulse conditions,their single pulse energy and the overall operation efficiency of the system will be greatly improved,so as to greatly improve their effectiveness.Ku band high-power microwave has great application potential,but due to the size of high-frequency devices,it usually needs strong magnetic field and low power capacity.Therefore,it is urgent to reduce the required magnetic field strength and increase the internal power capacity of the device.Among the reported highpower microwave sources,the transit time oscillator has many advantages,such as low magnetic field,high power capacity,stable mode,wide working voltage range and so on.Therefore,this paper is mainly divided into the following aspects based on the research of the transition time oscillator in Ku band.First of all,the linear theory of modulation cavity and the factors that affect the characteristics of modulation cavity are studied.By studying the linear theory in the axial modulation cavity,the basic operation principle of the modulation cavity is studied.In addition,the linear theory of the modulation cavity is improved to apply to different types of modulation cavity such as the axial bending modulation cavity.Finally,for the modulation cavity with different drift width,the influence of its working characteristics,including the starting vibration ability and power capacity,is studied.Secondly,based on the different elements of the transit time oscillator,the simulation modeling and optimization design are carried out respectively.In order to reduce the magnetic field and reduce the weight of the magnetic field,it is important to optimize the cathode structure and the excitation device;at the same time,in order to improve the long pulse working ability,it is necessary to improve the internal power capacity of the device,and reduce the risk of the microwave cut-off phenomenon caused by the plasma,it is vital to optimize the beam wave interaction structure and the collector structure.In order to reduce the intensity of magnetic field,the uniformity of the electric field at the cathode tip is improved to reduce the dependence of electron beam on the intensity of magnetic field.On the one hand,the inner axis of the anode in the coaxial structure is stretched to the inner part of the cathode,so as to balance the radial electric field at the cathode tip.On the other hand,the focusing ring is improved,and a set of methods for analyzing and designing the focusing ring is put forward.For another thing,the weight of the excitation device is reduced.In order to reduce the energy consumption of the excitation device,the light and small permanent magnet structure is designed.In the axial modulation cavity,the empty part in the center of the anode inner cylinder is fully utilized,and the coaxial permanent magnet device is set,which can produce a uniform magnetic field of 20 cm length and 0.35 T magnetic weight In the aspect of long pulse,the power capacity is increased by using the wide drift section modulation cavity,and the reflection cavity is set at both ends of the wide drift section modulation cavity,so as to improve the vibration starting ability;the large radius electron collector is designed to reduce the possible influence of the plasmon at the collector,and the electron beam is directed to a larger radius through the magnetic field,in order to increase the surface area of the electron beam collection.The results show that the energy deposition on the collector surface is greatly reduced,so as to reduce the possibility of plasma generation.Thirdly,based on the particle simulation software,PIC simulation is carried out for the above research model,and the specific physical picture is given and analyzed.The simulation results show that under the input of 620.0 k V voltage and 13.3 k A current,under the guidance of 1.0 T bending magnetic field,12.43 GHz and 3.37 Gw microwave can be generated,with an efficiency of 41.0%.Compared with the traditional coaxial transit time oscillator structure,the required uniform magnetic field length is reduced by60.0%,effectively reducing the weight of the excitation magnet.Aiming at the traditional axial transit time oscillator,the focusing ring structure is adopted to effectively reduce the required magnetic field strength.Under the condition of 0.38 T low magnetic field,the output of 12.61 GHz and 1.65 GW can be generated,with the efficiency of 33.1%;the wide drift channel is adopted to improve the internal power capacity of the device,and the maximum field strength of 11 mm wide drift section is 770 k V/ cm,while 8mm wide drift section is used to output the same power microwave The maximum field strength in the moving section is 987 k V/ cm,which decreases by 22.0%;using large radius electron collector reduces the risk of plasma generation.Under 65 ns simulation condition,the surface energy deposition of traditional collector is 43.51 J,while that of large radius collector is only 17.63 J,which decreases by 59.5%.Finally,the preliminary experimental engineering design is carried out,and the experimental research on the focusing ring is carried out.The engineering design of the magnetic field of the compact light and small Ku band long pulse transit time oscillator is carried out,and the consistency between the solenoid magnetic field and the design is verified by the experiment.At the same time,the transmission and emission experiment of the electron beam is carried out on the cathode loaded with the focusing ring,and the beam is collected and diagnosed by the Faraday cylinder.In the experiment,it is found that there is obvious breakdown trace at the focusing ring,which leads to Faraday The current detected by the cylinder is reduced;in the high-power microwave experiment,the microwave output is not measured after the cathode of the focusing ring is loaded.The preliminary experimental analysis shows that the maximum field strength of the polymer material used in the focusing ring in the simulation has been reduced to within 350 k V/cm,but it still exceeds the maximum breakdown field strength of the polymer material.Therefore,the next step will be passed Step by step,the structure of the focusing ring is improved,and the materials with higher breakdown field strength are used to further study the actual working ability of the focusing ring. |
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