| During the recent decades, a sheet electron beam is preferred over a pencil beam for its merits of high power radiation density and high beam-wave interaction efficiency due to the larger interaction area, stronger heat dissipation capacity and lower current density, which can enable the utilization of permanent magnet. These advantages make the sheet beam vacuum devices of great interest in the microwave, millimeter and terahertz regimes for the applications such as satellite communications, airborne, ship borne and ground based radar, ja mming, decoy and material processing due to their high beam-wave ef?ciency, high output power, broad bandwidth and compact size. At present, two main development tendencies for the sheet beam devices are respectively high frequency and high power operation. For the first one, radiation sources in the terahertz band(0.1-10THz) can fuel the high-data-rate commucation, high- resolution radar, explosives detection, pulse imaging and spectroscopy. For the high power devices, they will promote the developments of national defense and economy.In this Ph D thesis, two different sheet beam devices including a backward wave oscillator(BWO) operating in G-band and a high power travelling wave tube(TWT) operating in K u-band are designed, simulated, cold and hot tested. The BWO was driven by a pesudospark discharge(PSD) hollow cathode, which can generate a very high current density and bright intense electron beam. Meanwhile, no external confined magnetic field is needed due to the existing ion tunnel. In our final hot test experiment, we successfully got terahertz pulse signal. In addition, a Ku-band sheet beam TWT operating with pulse and continuous wave(CW) state was detailed studied. Components for wide band operation were designed, fabricated and cold tested. Dual mode operation was proposed to extend the TWT bandwidth, which can increase the bandwidth twice of the single mode operation. The study of beam-wave interaction efficiency improvement based on the genetic algorithm, velocity taper theory and curved DSGWs was deeply discussed. Besides, water-cooling configrations were proposed, and thermal and mechanical analysis also for the tubes was performed.Main work and innovation for this dissertation are as followed:(1) Pierce small signal theory considering the c ircuit loss, space charge effect and velocity factor was used to analyze the starting condition and growth rate of theBWO and TWT. Performance from the theory had a good agreement with the PIC simulation.(2) An intense sheet beam with high current density and brightness was produced by the pseudospark discharge to drive the BWO. The beam can propagate a long distance without any external magnetic field due to the ion channel. BWO hot test caught a very pure beam spot and also successfully detected the terahertz output signal.(3) Curved Bragg reflector and multi-staged step were introduced to the design of wideband input and output coupler for our K u-band sheet beam TWT. Good performance was achieved to broaden the bandwidth and suppress the oscillations caused by the reflections.(4) A segmented lossy dielectrics loaded in the H-plane of the SWS was proposed to suppress the parasitic osclllations. Not only it will not increase the circuit length and additional reflections leading to oscillations, but also it can extend the attenuation and water-cooling path without the limit of the confined magnetic.(5) In order to extend the TWT operating bandwidth, dual- mode TE10 and TM11 respectively operation with the-1 and-2 harmonics was proposed and verified by the PIC simulation. It can effectively extend the bandwidth nearly twice of our original design.(6) The shapes of the DSGWs were curved and optimized to match the elliptical sheet beam and non-uniform coupling impedance. And based on the genetic algorithm and velocity taper theory, the efficiency and gain was optimized. Moreover excellent beam wave interaction improvement was achieved.(7) Different water-cooling paths for CW TWT aiming at microwave attenuation and electron interception were demonstrated. Thermal and mechanical analysis of the slow wave structures and output window were also given in this thesis.
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