阴极微凸起形状对热不稳定性的影响

Effect of cathode microprotrusion shape on its thermal instability

为了研究阴极微凸起形状对其热不稳定性的影响,采用数值模拟方法研究了不同外加电场条件下,圆柱、圆台和圆锥形等不同形状微凸起的热不稳定性发展过程。结果显示:对于不同形状的微凸起,当微凸起顶部温度达到阴极材料的熔点时,微凸起内部温度分布差异显著,随着微凸起形状由圆柱-圆台-圆锥形变化,微凸起内部温度接近材料熔点的部位越来越少;外加电场相同时,微凸起形状越接近圆锥形,爆炸电子发射延迟时间越长;在阴极表面电场强度高于11GV/m时,爆炸电子发射延迟时间随着微凸起顶底半径比值的减小或阴极表面电场强度的下降近似成指数规律增长。

In order to study the effect of the cathode microprotrusion shape on its thermal instability, the evolution process of the thermal instability has been numerically investigated with the microprotrusion shape chosen as column, truncated cone and cone under different applied electric field. There is an obvious difference in temperature distribution in the microprotrusion with different shapes when the temperature at the microprotrusion peak reaches inching point of the cathode material. While the shape of microprotrusion is changed from column, truncated cone to cone, the region where temperature is close to the melting point re- duces. At a given applied electric field, the smaller the ratio of top radius to bottom radius of the microprotrusion is, the larger the time delay of explosive electron emission is; the time delay of explosive electron emission increases exponentially with the de crease of the ratio of top radius to bottom radius of the microprotrusion or strength of the cathode surface electric field when the cathode surface electric field is larger than 11 GV/m.