Space charge limited current for bipolar flow in a crossed-field vacuum gap

• Published in: Vacuum Vol. 196; p. 110744
• Main Authors: Liao, Mei Yan, Yao, Ruo He, Zhu, Ying Bin
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.02.2022
• Subjects: Bipolar flow; Crossed-field vacuum device; Space charge effect; Crossed-field vacuum device; Bipolar flow; Space charge effect
• ISSN: 0042-207X; 1879-2715
• DOI: 10.1016/j.vacuum.2021.110744

In this paper, a numerical iteration approach is proposed to make an investigation of the influence of a transverse magnetic field on the space charge limited bipolar flow in a planar vacuum diode. By employing the method, the unknown limiting current density and potential distribution can be simultaneously determined. Considering a planar ion vacuum diode with a transverse magnetic field B parallel to the electrodes surface, we investigated the limiting current density as a function of B. Numerical calculations show that the limiting current density of the crossed-field vacuum diode may be approximately given by Je=JCL[a(B/BH)b+F], where JCL is the CL law and BH the Hull cutoff magnetic field, and a and b are the function of the ion current density, respectively. The physical meaning of F may be interpreted as the 1D current density enhancement factor due to the effect of ions for B=0. In the absence of ions, the limiting current solution is recovered in a crossed-field vacuum gap.