Parametric Study of Cavity IEMP Responses in a Cylinder by Coupling Monte Carlo Method and 3-D Electromagnetic Particle-in-Cell Method

Internal electromagnetic pulse generated inside a cavity, known as Cavity IEMP, would disturb or damage sensitive electronic systems inside a spacecraft when illuminated by transient X-rays. To ensure their normal operations, accurate prediction and analysis of Cavity IEMP responses are required. In this article, the physical phenomena involved in three-dimensional (3-D) Cavity IEMP problems are numerically studied, including the interaction process between X-rays and the cavity wall material and the self-consistent process involving the motion of electrons and the evolution of electromagnetic fields. The interaction process is simulated with the Monte Carlo method to obtain the actual emission characteristics of forward electrons emitted into a cavity, including their yields, energy, and angular spectra, while the self-consistent process is simulated with a proposed 3-D electromagnetic particle-in-cell method to solve electromagnetic fields generated inside a cavity, whose driving forces are forward electrons with the calculated emission characteristics. This method fully considers electrons with different energies and directions and their impacts on the generated electromagnetic fields. With such method, the electromagnetic field distribution inside a cylinder exposed to transient X-rays is discovered based on the actual emission characteristics of X-ray-induced forward electrons. Furthermore, as forward electron emission characteristics are determined by properties of X-rays and cavities, the impacts of the blackbody temperature in X-ray energy spectrum, the cylinder wall thickness, and the cylinder wall material on the intensity of generated electric fields are fully explored. Based on the results, several suggestions are given to protect electronic systems in cavities against the electromagnetic coupling from Cavity IEMP. The study would guide radiation hardening design of electronic systems in spacecraft.