Computational Modeling of Plasma-induced Secondary Electron Emission from Micro-architected Surfaces
Advances in electrode, chamber, and structural materials will enable breakthroughs in future generations of electric propulsion and pulsed power (EP & PP) technologies. Although wide ranges of EP & PP technologies have witnessed rapid advances during the past few decades, much of the progress was based on empirical development of materials through experimentation and trial-and- error approaches. To enable future technologies and to furnish the foundations for quantum leaps in performance metrics of these systems, a science-based materials development effort is required. The present study aims to develop computational models to simulate, analyze, and predict the sec- ondary electron emission of plasma devices in order to aid the design of materials architectures for EP & PP technologies through an integrated research approach that combines multi-scale modeling of plasma-material interactions, experimental validation, and material characterization. The range of materials of interest in EP & PP technologies include refractory metals, such as tungsten (W) and its alloys (W-Re) and molybdenum (Mo), ceramic composites, such as boron nitride (BN) and alumina (Al2O3), high-strength copper alloys, and carbon-carbon composites. These classes of materials serve various design functions; primarily in cathode and anode applications, in accelerator grids, and in beam dumps of high power (∼ a few GW) microwave (HPM) sources. We first give an overview of our fundamental understanding for the limits of using these materials in EP & PP technologies, and the opportunity to design material architectures that may dramatically improve their performance. Next, we introduce the computational framework to model secondary electron emission from micro-architected surfaces. A detailed description of the underlying physics, computational models and methods are then provided, followed by simulation results, respectively. Finally, discussions and conclusions of our major findings as well as suggested future work are given.