發(fā)布時(shí)間：2018-11-23 13:10

【摘要】：太赫茲(THz)波是介于微波和紅外之間、頻率在0.1THz-10THz之間的電磁波。太赫茲波具有:(1)對大多數(shù)非金屬的介質(zhì)有著較強(qiáng)的穿透力;(2)太赫茲波的穿透性會(huì)隨著水和組織密度的改變而改變;(3)相較于X-射線,太赫茲波具有很小的電離性;(4)由于其中心工作頻率較高,相對于中心頻率較低的器件其絕對帶寬具有很大優(yōu)勢;(5)采用太赫茲波作為探測源的器件,得益于較高的頻率,通常具有更高的分辨率;(6)相較于紅外線,在雨中或者其他惡劣氣象條件下,其損耗相對較小等優(yōu)點(diǎn)。這些優(yōu)點(diǎn)使得太赫茲波在工業(yè)、科研和國防上有著誘人的應(yīng)用前景。但由于材料科學(xué)、研究手段以及精密加工水平等條件的限制,長期以來太赫茲器件的發(fā)展極為緩慢,以致于出現(xiàn)了所謂的太赫茲間隙(THz Gap)。近年來材料科學(xué)、計(jì)算機(jī)科學(xué)以及精細(xì)加工等方面的快速發(fā)展,為開展高增益、寬帶寬以及小型化的太赫茲器件的研究提供了前提條件,為填補(bǔ)太赫茲間隙,促進(jìn)太赫茲科學(xué)技術(shù)的發(fā)展奠定了基礎(chǔ)。相較于核磁共振與低頻段(頻率低于100GHz)電子順磁共振檢測技術(shù),太赫茲頻段的電子順磁共振檢測儀在分辨率和靈敏度方面具有很大的優(yōu)勢,在醫(yī)學(xué)檢測、化學(xué)研究以及工業(yè)生產(chǎn)中都具有良好的應(yīng)用前景。但由于中等功率(幾十瓦)太赫茲信號源的匱乏,太赫茲頻段的電子順磁共振技術(shù)的發(fā)展遇到了瓶頸。本論文對帶狀束器件的交錯(cuò)雙柵周期慢波結(jié)構(gòu)、大電子通道寬帶耦合器、混合模式輸出窗、高電子發(fā)射密度帶狀束電子槍以及周期永磁聚焦磁體等重要部件都進(jìn)行了探索性的研究;并在相關(guān)研究的基礎(chǔ)上設(shè)計(jì)了一支太赫茲波段(263GHz)帶狀束行波管。論文首先從交錯(cuò)雙柵周期慢波結(jié)構(gòu)的色散與耦合阻抗特性的理論出發(fā),深入地研究了這種慢波結(jié)構(gòu)中場分布以及能量儲(chǔ)存特性,并在此基礎(chǔ)上對通常使用的耦合阻抗進(jìn)行了修正。結(jié)合Pierce小信號增益分析理論、返波振蕩分析理論對交錯(cuò)雙柵帶狀束行波管互作用線路的性能進(jìn)行了總體的評估。在理論分析與仿真模擬的輔助下,為加州大學(xué)-戴維斯分校(UC-Davis)260GHz順磁共振探測系統(tǒng)設(shè)計(jì)了中心頻率為263GHz、工作帶寬大于20GHz的太赫茲輻射放大器。模擬結(jié)果顯示,在19000V、0.15A的帶狀束驅(qū)動(dòng)下,在工作頻帶內(nèi)該真空電子器件可輸出50W的功率,實(shí)現(xiàn)30dB的增益;且其零驅(qū)PIC粒子模擬顯示,所設(shè)計(jì)的帶狀束行波管有效地抑制了再生振蕩與返波振蕩的產(chǎn)生,可以穩(wěn)定的工作。其次本文詳細(xì)地研究了帶狀束電子槍以及可調(diào)式周期永磁聚焦磁體。分別為200GHz雙模帶狀束行波管與263GHz帶狀束行波管設(shè)計(jì)了可調(diào)式帶狀束電子槍與高電流密度電子槍。通過調(diào)節(jié)橫向聚焦極的距離,200GHz可調(diào)式電子槍可以發(fā)射出0.0866A的低電流帶狀束來驅(qū)動(dòng)低增益、連續(xù)波工作模式的200GHz帶狀束行波管;也可以產(chǎn)生0.2126A的高電流帶狀束來驅(qū)動(dòng)200GHz帶狀束行波管來產(chǎn)生高增益的脈沖電磁輻射。與此同時(shí),在1.2T的均勻磁場的聚焦作用下,低電流帶狀束與高電流帶狀束均實(shí)現(xiàn)了良好的電子流通率。263GHz帶狀束電子槍采用了復(fù)雜曲面陰極來壓縮電子束,來產(chǎn)生高質(zhì)量的帶狀束、提高帶狀束的流通率。與此同時(shí),還對帶狀束的傳輸理論進(jìn)行了分析,研究了帶狀束的流通性以及其影響因素。在理論分析的基礎(chǔ)上,為了約束263GHz帶狀束電子槍發(fā)射出的電子束,本文設(shè)計(jì)了可調(diào)式周期永磁-可調(diào)式四極磁體(Permanent Cups Magnet Tunable Quadrupole Magnet,PCM-TQM)。模擬結(jié)果顯示,即使考慮電磁波對電子束的調(diào)制作用與磁塊剩磁波動(dòng)的影響,263GHz帶狀束電子槍發(fā)射的電子束在該聚焦系統(tǒng)的約束下也可實(shí)現(xiàn)高達(dá)95.85%的熱電子傳輸效率。接著本文詳細(xì)介紹了帶狀束行波管的其他相關(guān)部件的研究與設(shè)計(jì)。首先介紹了通過混合模式傳輸來擴(kuò)寬傳輸帶寬的盒型窗,并通過S參數(shù)仿真以及熱分析兩方面來驗(yàn)證了該設(shè)計(jì)的可行性。為了降低高頻率電磁波在傳統(tǒng)波導(dǎo)傳輸線路上的損耗,本文為260GHz順磁共振系統(tǒng)設(shè)計(jì)了低損耗、高純度的波紋波導(dǎo)遠(yuǎn)距離傳輸系統(tǒng)。最后,根據(jù)帶狀束的特點(diǎn)為263GHz帶狀束行波管設(shè)計(jì)了相應(yīng)的電子收集系統(tǒng)。通過尾端引導(dǎo)磁體的引入、橢圓形收集極的采用,新的收集系統(tǒng)大大縮短了帶狀束收集系統(tǒng)的長度,提高了電子的收集效率。本文的最后給出了部分前文所設(shè)計(jì)的器件的加工實(shí)物與測試結(jié)果。測試結(jié)果驗(yàn)證了前面的部分設(shè)計(jì),并為進(jìn)一步改進(jìn)設(shè)計(jì)、修正加工誤差指引了方向。
[Abstract]:The terahertz (THz) wave is an electromagnetic wave between the microwave and the infrared and the frequency is between 0. 1THz and 10THz. The terahertz wave has the advantages that: (1) the medium with most non-metals has a strong penetrating power; (2) the penetration of the terahertz wave can be changed with the change of water and tissue density; (3) the phase is smaller than that of the X-ray and the terahertz wave has very little ionicity; (4) due to its high center operating frequency, the absolute bandwidth of the device with a lower center frequency has a great advantage; (5) a device employing a terahertz wave as a source of detection benefits from a higher frequency, typically having a higher resolution; (6) the phase is less than infrared, The loss is relatively small in the rain or in other severe weather conditions. These advantages make the terahertz wave attractive for industrial, scientific research and national defense. The so-called Terahertz Gap (THz Gap) has been developed for a long time due to the limitations of materials science, research methods, and precision processing levels. In recent years, the rapid development of the material science, computer science and fine processing has provided a prerequisite for the research of the terahertz device with high gain, wide bandwidth and miniaturization, and lays a foundation for the development of the terahertz science and technology to fill the terahertz gap. Compared with the electronic paramagnetic resonance detection technology of the nuclear magnetic resonance and low-frequency section (frequency lower than 100GHz), the electronic paramagnetic resonance detector in the terahertz frequency band has a great advantage in terms of resolution and sensitivity, and has good application prospect in medical detection, chemical research and industrial production. However, due to the lack of the medium power (tens of watts) of the terahertz signal source, the development of the terahertz frequency band has encountered a bottleneck. This paper makes an exploratory study on the staggered double-grid periodic slow wave structure, the large electronic channel wide band coupler, the mixed mode output window, the high electron emission density ribbon beam electron gun and the periodic permanent magnet focusing magnet of the ribbon beam device. A terahertz band (263GHz) band-beam traveling wave tube is designed on the basis of the relevant research. In this paper, based on the theory of the dispersion and the coupling impedance of the slow-wave structure of the staggered double-gate period, the field distribution and the energy storage characteristics of the slow-wave structure are studied in-depth, and the commonly used coupling impedance is modified. In this paper, the performance of the cross-acting line of the staggered double-grid band-beam traveling-wave tube is evaluated by the theory of the small-signal gain analysis and the back-wave oscillation analysis. Under the aid of theoretical analysis and simulation simulation, a terahertz radiation amplifier with a center frequency of 263GHz and a working bandwidth of more than 20GHz is designed for the UC-Davis 260GHz paramagnetic resonance detection system. The simulation results show that in the band-shaped beam drive of 19000V, 0. 15A, the power of 50W can be output by the vacuum electronic device in the working frequency band, and the gain of 30dB can be realized; and the zero-drive PIC particle simulation shows that the designed band-shaped beam-wave tube effectively suppresses the generation of the regenerative oscillation and the return wave oscillation, a stable operation. Secondly, the beam-beam electron gun and the adjustable periodic permanent-magnet focusing magnet are studied in detail. An adjustable band-beam electron gun and an electron gun with high current density are designed for a 200GHz dual-mode ribbon-beam traveling-wave tube and a 263GHz band-beam traveling-wave tube. by adjusting the distance of the transverse focusing electrode, the 200GHz adjustable electron gun can emit a low-current band-shaped beam of 0.86A to drive a 200GHz band-shaped beam traveling wave tube with a low gain and a continuous wave working mode; a high current band beam of 0. 2126a can also be produced to drive a 200ghz band-beam traveling wave tube to generate high gain pulsed electromagnetic radiation. At the same time, under the focus of a uniform magnetic field of 1. 2T, a good electron flow rate is achieved for both the low current ribbon beam and the high current ribbon beam. The 263GHz band beam electron gun uses a complex curved cathode to compress the electron beam to produce a high-quality ribbon beam and improve the flow rate of the ribbon beam. At the same time, the transmission theory of the ribbon beam is analyzed, the circulation of the ribbon beam and its influencing factors are studied. 鍦ㄧ悊璁哄垎鏋愮殑鍩虹涓，

本文編號：2351728