无箔二极管电磁PIC模拟空间电荷限制发射模型比较

 为了在无箔二极管电磁PIC模拟中采用与电磁场自洽的空间电荷限制发射模型,对查尔特定律模型、高斯定律模型和一维二极管模型进行了理论分析和实例模拟比较。模拟结果表明,三种模型都能与电磁场自洽并反映外加磁场对发射电流的影响,但高斯定律模型受网格剖分粗细程度的影响较大且容易产生振荡,一维二极管模型在网格参数合理的情况下结果与查尔特定律模型基本接近,但需要求解超越方程,花费时间多。通过对模拟结果进行分析和比较,认为外加磁场对电子发射模型本身的影响很小,在电磁PIC数值模拟中可以不考虑,因此,查尔特定律模型更适合用于无箔二极管的电磁PIC模拟。

Comparison of space charge limited emission models in electromagnetic particle-in-cell simulation of foilless diode

In order to obtain self-consistent space charge limited electron emission model in electromagnetic PIC(particle in cell) simulation of foilless diode, Child law model, Gauss law model and 1 D diode model have been analyzed and compared. The simulation results show that the three models are all self consistent with electromagnetic field. Gauss law model tends to be affected by the width of the first cell and yield nonphysical oscillation. 1 D diode model with reasonable discrete grid gets almost the same results as Child law model, but it needs to solve a transcendental equation, which would cost much time. And it is demonstrated that the external applied magnetic field has little influence on the emission model and can be neglected in the electromagnetic PIC simulations. Child law model is more suitable for the electromagnetic PIC simulation of foilless diode.