X波段高增益高功率三轴相对论速调管放大器及两路空间相干合成研究

Spatial coherent combining (SCC) of high power microwaves (HPMs) can significantly enhance the equivalent radiation power of whole system, which is an important development direction of HPM technology. However, limited by the status of phase-locked high power devices, SCC of high-frequency HPMs has not yet been reported. In addition, the gain of high-frequency high power amplifier is difficult to improve due to the space charge effect of intense electron beam and the loss of input microwave. In this work, we therefore propose an X-band triaxial klystron amplifier (TKA) with high gain and high power, and furthermore investigate for the first time SCC of two-channel X-band HPMs in order to stimulate the development of SCC towards modularization and array. By investigating and solving the related physical issues of deep modulation of intense electron beam, suppression of parasitic modes, control of the maximum surface electric field strength, and plasma instability of electron beam, the proposed TKA would possess the features of high gain, high power, high efficiency, low magnetic field and long pulse. The typical simulation results will be that under the guiding magnetic field of 0.8 T, the output power is more than 2 GW in X-band with a gain higher than 50 dB. The efficiency is in excess of 40%, and the phase vibration is less than 15 degree. Moreover, in the two-channel SCC experiment, the expected combining pulse duration and efficiency are about 80 ns and higher than 90%, respectively.

高功率微波（HPM）空间相干合成能够显著提高系统的等效辐射功率，是HPM技术发展的重要方向，然而受到HPM锁相器件的发展制约，尚未有高频段HPM空间相干合成的研究报道。另外，由于强流电子束的空间电荷效应和注入微波损耗，高频段高功率放大器的增益较难提高。因此，本项目提出X波段高增益高功率三轴相对论速调管放大器，并首次开展两路X波段HPM模块的空间相干合成研究，促进高频段HPM空间相干合成技术的模块化、阵列化发展。通过研究和解决强流电子束深度调制、杂模自激振荡抑制、最大表面射频场强控制、电子束等离子体不稳定性等相关物理问题，使所研制的TKA具有高增益、高功率、高效率、低磁场和长脉冲等特点。预期模拟结果为：当磁场小于0.8 T时，在X波段输出微波功率大于2 GW，增益大于50 dB，效率大于40%，相位抖动小于15°；两路HPM模块空间相干合成实验达到合成脉宽约80 ns，合成效率大于90%。

空间相干合成是高功率微波器件突破单管物理机制限制，实现更高输出功率的重要途径。三轴相对论速调管放大器（简称TKA）具有高功率、频率稳定、相位可控等特点，是高频段高功率微波相干合成的优选器件。本项目开展了X波段高增益高功率三轴相对论速调管放大器及两路X波段HPM模块空间相干合成的理论和实验研究。首先，通过理论研究使强流带电粒子束在低注入功率条件下获得了高的调制深度，达到了高增益的要求；研究了杂模的自激振荡机制，实现了非旋转对称模式的自激振荡的有效抑制；开展了高功率输出腔研究，将电磁结构表面最大射频场强控制在击穿阈值以下，为TKA器件实现高频段高增益长脉冲高功率微波输出奠定了理论基础。其次，研究了一种X波段高增益高功率TKA 器件，通过电磁结构优化，PIC粒子模拟在电子束电压690kV、电流9.3kA、导引磁场0.8T的条件下，模拟输出微波功率2.42GW，增益49.8dB，效率38%。实验中，在电子束电压610kV、电流9.1kA，导引磁场0.77T，注入微波功率为40kW的条件下，实现输出功率约为1.77GW，效率为32%，增益为46.5dB，半高宽超过70ns的HPM输出。通过注入微波、导引磁场电子束参数对输出微波相位的优化控制，实现频率稳定、相位抖动小于10°的HPM微波输出。最后，在单管实验的基础上开展了两路X波段TKA模块的空间相干合成实验研究。通过模式转换和辐射系统的设计，使单路TKA实现了极化方向可控的定向HPM辐射，完成了两路TKA模块的同步触发和注入微波移相控制，实现合成等效辐射功率大于3GW、脉宽94ns、效率为98.4%的HPM输出，为大规模阵列化相干合成奠定了基础。