低脉冲磁场准单模GW级Ku波段高功率微波发生器研究

Ku-band high power microwave is very promising for applications in various military and civil fields such as high power radar, satellite communication, and so on, however there is no existing GW-class Ku-band high power microwave generator by far. In this program, we plan to carry out theoretical and experimental researches in order to design and realize a Ku-band overmoded slow wave Cerenkov-type high power microwave generator. The power handling capacity of a device can be significantly improved to GW-class by using overmoded slow wave structure with large transverse size. Higher order modes competition in overmoded slow wave structure will be analyzed so that mode control and selection method can be properly employed to ensure single-mode operation of the device, and moreover ensure high efficient beam-wave interaction. The condition of microwave absorption induced by electron cyclotron resonance will be analyzed, and normal operation of the device at low guiding magnetic field will be realized by optimizing the slow wave electromagnetic structure and electron beam parameters. If the guiding magnetic field is furthermore designed as a short pulse, Joule heating in the solenoid coils will be much lowered during repetitive operation, and weight and volume of the power supply system for charging solenoid will be considerably decreased. The expected typical simulation results are as follows. When the guiding magnetic field is as low as 0.6T, the generator will be capable of producing more than 1GW high power microwave with a frequency of around 14 GHz, corresponding to a power conversion efficiency of about 40%, and TM01 mode accounts for higher than 90% of the output microwave power. Furthermore, experimental researches will be performed.

Ku波段高功率微波在高功率雷达、卫星通讯以及其他诸多民用、军事领域具有广泛的应用前景，然而目前尚没有GW级Ku波段的高功率微波产生器件。本项目将开展相关的基础理论和实验研究，研制一台Ku波段过模慢波切伦科夫型高功率微波发生器。拟通过采用大横向尺寸的过模慢波结构，将器件的功率容量提高至GW量级，并分析过模慢波结构内部的高阶模式竞争，采取模式选择和控制方法使器件工作在单模状态，保证高效的束波相互作用。分析电子束对微波的回旋共振吸收条件，通过优化慢波电磁结构和电子束参数，实现过模器件在低导引磁场条件下的正常工作。进一步采用短脉冲式的磁场设计，减小重频运行时螺线管线圈中的焦耳发热和励磁供电系统的体积重量。器件的典型模拟结果预期为：在磁场强度约0.6T时，产生功率大于1GW、频率约14GHz的Ku波段高功率微波，功率转换效率约40%，输出微波中TM01模所占的功率比大于90%；并进一步开展实验研究。

民用和军事领域对Ku波段高功率微波（HPM）有着强烈的需求，然而目前尚没有GW级Ku波段高功率微波产生器件。切伦科夫型高功率微波振荡器具有功率效率高、频谱特性好、工作稳定等特点，是目前最有潜力的高功率微波产生器件之一。在此背景下，本项目研究了一种Ku波段低脉冲导引磁场过模慢波切伦科夫型HPM发生器，通过采用过模慢波结构，设置漂移腔和渐变慢波结构，以提高器件功率效率，并改善互作用区射频电场分布，减小最大表面电场强度，提高器件功率容量。该器件在较低的导引磁场条件下，实现了GW级准单模HPM输出。PIC粒子模拟结果为：在二极管电压540 kV、电子束流5.8 kA、导引磁场0.6 T的条件下，获得了功率为1.1 GW、频率为13.8 GHz、功率效率约35%的微波输出；输出微波主模为TM01模，占全部输出功率的95%；器件中最大表面电场强度为0.8 MV/cm。在Torch-01强流加速器平台上对器件开展了实验研究，在二极管电压为740 kV、电子束流为9.9 kA、脉冲导引磁场为0.8 T条件下，产生微波功率最高为1.1 GW、脉宽为24 ns，微波频率单一性良好，中心频率为13.76 GHz，模式为TM01模，功率效率为15%，并且器件具有稳定的运行能力。进一步在HEART强流加速器上开展了初步的长脉冲实验研究，然而实验中出现了严重的脉冲缩短现象，输出微波仅有320 MW，微波脉宽小于30 ns。分析了脉冲缩短的原因，对器件的电磁结构进行了优化改进，预期在Ku波段可实现GW的长脉冲微波输出。此外，项目组还在Ka波段过模HPM振荡器、碳纳米管强流电子束阴极、相对论速调管放大器等方面开展了拓展研究，取得了一些有意义的成果。该项目的研究工作能够促进高频段高功率微波技术的发展，结合项目组提出的脉冲磁场设计方案，可实现器件整体的紧凑模块化封装，具有良好的民用和军事应用前景。