Boundary value problem of magnetically insulated diode: existence of solutions and complex bifurcation

TL;DR

This paper investigates the existence and bifurcation of solutions in a magnetically insulated vacuum diode modeled by a singular Vlasov-Maxwell system, introducing new analytical and numerical insights into complex solution behaviors.

Contribution

It introduces a novel analysis of the bifurcation phenomena in magnetically insulated diodes, including the first numerical bifurcation analysis for the case where the effective potential is negative.

Findings

Existence of solutions for the nonlinear ODE system in certain intervals.

Identification of complex bifurcation structures depending on parameters.

Determination of the insulated diode spacing.

Abstract

The paper focuses on the stationary self-consistent problem of magnetic insulation for a vacuum diode with space-charge limitation, described by a singularly perturbed Vlasov-Maxwell system of dimension 1.5. The case of insulated diode when the electrons are deflected back towards the cathode at the point $x^{*}$ is considered. First, the initial VM system is reduced to the nonlinear singular limit system of ODEs for the potentials of electric and magnetic fields. The second step deals with the limit system's reduction to the new nonlinear singular ODE equation for effective potential $\theta(x)$. The existence of non-negative solutions is proved for the last equation on the interval $[0, x^{*})$ where $\theta(x)>0$. The most interesting and unexplored case is when $\theta(x)<0$ on the interval $(x^{*}, 1]$ and corresponds to the case of an insulated diode. For the first time, a numerical analysis of complex bifurcation of solutions in insulated diode is considered for $\theta(x)<0$ depending on parameters and boundary conditions. Bifurcation diagrams of the dependence of solution $\theta(x)$ on a free point (free boundary) $x^{*}$ were constructed. Insulated diode spacing is found.