脉冲等离子体超宽带微波辐射源的辐射机理研究

The structure, mechanism and especially sweeping frequency characteristics of pulsed plasma ultra-wide band mircowave radiator are obviously different from those of existing wide band mircowave radiator at home and abroad. The radiator is a new type of wide band mircowave radiator. The research on radiation mechanism of radiator is innovative. In this project, in order to master radiation mechanism of pulsed plasma ultra-wide band mircowave radiator and provide theoretical basis for more increasing radiation power, controlling range of radiation frequency and developing frequency band, characteristic of Cherenkov radiation by an accelerated motion electron bunch in poloidal magnetized plasma, instability and its growth rate of pulsed plasma, mechanism of beam-wave interaction and microwave amplification are researched. The research belongs to frontier field of technology of pulsed power and plasma and is a hot subject. It is complementary to the research of magnetically confined plasma. It has great significance for development of high-performance wide band mircowave radiator with Chinese independent intellectual property.

脉冲等离子体超宽带微波辐射源的结构、工作机理尤其是它的宽频带扫频辐射特性与目前国内外已有的宽频带辐射器件有着明显不同，是一种新型的宽频带辐射器件，属于创新性的研究。本项目通过对加速电子在角向磁化等离子体介质产生的辐射特性、脉冲等离子体的不稳定性及不稳定性增长率、束－波相互作用物理机制和微波放大机制的研究，以掌握脉冲等离子体辐射源的辐射机理，为进一步提高辐射功率、控制辐射频率范围及拓展辐射频带提供理论依据。此研究与磁约束等离子体的研究具有互补性，属于脉冲功率与等离子体科学技术中的前沿领域和热门课题，对于我国研制自主知识产权的高性能宽频带辐射器件具有重要意义。

通过对匀速和加速电子在角向磁化等离子体中切伦科夫辐射特性的研究，得到其辐射产生条件和各种参数的解析表达式，进而得出电子速度与其辐射特性各参数之间的关系，及在一定条件下，加速电子辐射更具方向性的结论，明确了脉冲等离子体超宽带微波辐射源的辐射激励机制。另外，研究了电子束电流大小对介质切伦科夫脉塞中束波相互作用色散关系的影响，得到了当等离子体返回电流能有效中和与不能有效中和电子束电流两种情形下色散关系和波的增长情况，得出：在各参数固定的情况下，电子束电流和器件效率之间存在最佳匹配关系。这些都为后续研究脉冲等离子体超宽带微波辐射源的辐射性能参数提升奠定了基础。与此同时，在研究中还发现，由于脉冲电子束是从阴极表面爆炸发射形成的阴极等离子体中提取而出，这种阴极爆炸发射方式致使间隙过早闭合，缩短了脉冲持续时间，从而限制了辐射时间的延长。此结论也为下一步研究与设计优质的阴极和电子束源提供了一定的理论基础。