脉冲条件下电极镀膜对沿面闪络性能的影响研究

The design and running of many pulsed power devices are affected by surface flashover of insulator, resulting in reduction of voltage and current output, so the research of physical problem under the corresponding parameter condition is limited. Based on the results of previous studies about surface flashover and the understanding of its mechanism, this project proposes to inhibit the primary electron emission with electrode coating, thereby improving the surface flashover performance. The method of stainless steel coated with alumina film has been explored in advance, indicating that the pulse breakdown strength in vacuum is much higher with the coated electrode. Based on these preliminary results, the applicants plan to further research the effect of electrode coating on surface flashover performance, investigating the influence of different coating conditions on surface flashover performance, exploring the mechanism of how electrode coating affects surface flashover, and optimizing the coating process. The purpose of this project is to increase surface flashover voltage substantially and provide technical support for the design of pulsed power device with higher output capability.

许多脉冲功率装置在设计与运行时都受到绝缘堆处沿面闪络的影响，导致装置的电压、电流输出等级降低，使得相应参数条件下的物理问题研究受限。本课题基于以往沿面闪络的研究结果及对其机理的认识，提出通过电极表面镀膜来抑制初始电子发射从而提高沿面闪络性能。前期已经开展了不锈钢基体材料表面镀氧化铝膜的工艺探索，镀膜后电极真空表面脉冲击穿场强有较大程度的提高。基于这些前期研究，申请人计划进一步研究电极镀膜对沿面闪络性能的影响，通过考察不同镀膜条件对沿面闪络性能的影响规律，探索电极镀膜抑制沿面闪络的作用机制，总结电极镀膜抑制沿面闪络的最优方法。以期通过电极镀膜有效提高沿面闪络电压，为设计更高输出能力的大型脉冲功率装置提供技术支撑。

已有的真空沿面闪络性能提升主要是从绝缘材料改性方面着手，而结构优化和外加磁场等方式会增加装置的设计加工难度。前期开展的真空沿面闪络研究结果表明，初始电子发射相比闪络通道发展维持所需的电压等级更高，因此，沿面闪络电压主要取决于初始电子发射阈值。本项目采用电极表面镀膜的方式来提升电子发射阈值，从而抑制真空沿面闪络的源头，提升沿面闪络性能。主要研究内容和取得的重要结果概括如下：通过研究不同电极表面粗糙度和膜厚对镀膜电极真空沿面闪络性能的影响，结合镀膜工艺的限制，给出了镀膜电极提升真空沿面闪络性能的参数优选，镀膜电极（电极粗糙度Ra0.8，膜厚1μm）相比未镀膜电极在首次闪络电压、老练电压和耐受电压上均有一定程度的提升，分别提高了39.3%、26.5%以及39.1%。通过电极表面电场畸变情况的模拟以及绝缘膜对电子发射的阻挡作用估算，结合镀膜电极与未镀膜电极闪络后的微观形貌分析，表明电极镀膜能够有效阻挡初始电子发射，从而提升电子发射阈值和真空沿面闪络性能。这一电极处理方法有望提升脉冲功率装置中绝缘结构的真空沿面闪络水平，为充分利用现有装置的驱动能力以及建造更高等级的脉冲功率装置提供技术支撑。