Surface breakdown and plasma formation in cross-field high power microwave sources
Abstract
Approved for Public Release Plasma dynamics in high power microwave (HPM) sources are considered a detriment to the operation of vacuum electronic devices to generate electromagnetic signals. The formation and existence of the plasma flows due to outgassing and evaporation of materials become more and more critical, particularly when operating the compact HPM sources at a high-frequency range, which is of great interest to the U.S. naval missions. While electromagnetic particle-in-cell (PIC) simulations have been widely used for design and optimization tools of HPM devices, many simulations focus on the cases where only electrons exist in HPM tubes. The knowledge gap in the HPM community, therefore, lies in the high-fidelity plasma simulations of surface breakdown and plasma formation, namely, the effects of ions near the plasma-immersing materials on the electromagnetic field propagation.The goal of this proposed research project is to advance the understanding of surface breakdown and plasma formation in cross-field HPM devices. Specificresearch objectives include: (i) to develop and test relativistic, electromagnetic plasma fluid and kinetic models; (ii) to characterize the space charge limited sheath due to the plasma formation near explosive emission cathodes; and (iii) to investigate the anode plasma formation and radiofrequency wave-driven surface breakdown mechanisms. One of the innovative technical approaches in this proposed project is the development of a high-order (five- and ten-moment) fluid models for the plasma formation, providing an efficient model for the dense plasma formation around the anode, cathode, and window surfaces, such as the antenna. The fluid and hybrid fluid-kinetic models will be benchmarked against particle simulation results to assess whether reduced-order description can be constructed to model the beam-plasma interactions in the HPM devices. The expected outcome is the high-fidelity characterization of the ionized gases that form in the HPM sources. The computational and theoretical modeling is particularly important for actual HPM devices, because the experimental characterization can be challenging. The reduced-order description obtained from the plasma modeling will serve as new boundary conditions to state-of-the-art PIC simulations. Additionally, the plasma simulation tools developed in this proposed project can be directly integrated in the state-of-the-art models in a self-consistent manner. The most direct impact of this proposed research on DoD capabilities is for directed energy weapons. The research outcomes can help (i) address existing issues in the HPM sources developed and deployed by the U.S. Navy, and (ii) improve the optimization and design processes of the future HPM sources using the predictive modeling capabilities developed through this proposed project. Training of the next-generation scientists and engineers in HPMs and plasma physics, through collaborations with researchers in national laboratories, industry, and other academic institutions, is one of the most enduring effects of this proposed project. In addition, advancing the fundamental understanding of the interaction between plasma flows, electromagnetic waves, and plasma-immerse materials possesses further immense impacts to other DoD applications and missions, including space propulsion, fusion energy, space weather, aerodynamics, combustion, and material processing.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 05, 2021
- Source ID
- N000142112698
Entities
People
- Ken Hara
Organizations
- Office of Naval Research
- Stanford University
- United States Navy