Pulsed High-Power Microwave Source Technology

This Defense Intelligence Reference Document, dated January 28, 2010, provides a comprehensive technical overview of Pulsed High-Power Microwave (HPM) source technology. Produced under the Advanced Aerospace Weapon System Applications (AAWSA) Program, the report details the evolution of HPM technology from its origins in studying high-altitude electromagnetic pulse (HEMP) effects to its modern application as a directed-energy weapon. The document outlines the critical technologies required to build functional HPM sources, specifically focusing on insulation, cathode materials, high-voltage switching, and pulse sources. It discusses various insulating materials, including solids, liquids, and gases, noting the trade-offs between dielectric strength, maintenance, and safety. A significant portion of the report is dedicated to cathode materials, which are vital for electron beam generation. The author evaluates different emission mechanisms—thermionic, secondary, field, and explosive—and compares materials like velvet, carbon, and cesium iodide-coated structures. The report also examines high-voltage switching technologies, highlighting the challenges of achieving fast rise times and high repetition rates, and discusses the potential of photoconductive solid-state (PCSS) switches. Furthermore, the document describes various HPM source types, including pulsed electron beam sources (such as magnetrons, gyrotrons, and virtual cathode oscillators) and impulse HPM sources (such as SNIIPER, EMBL, and the H-series). It concludes by emphasizing that while HPM technology is increasingly accessible and attractive for various applications, including potential use by terrorist groups, the physics of radiation and the need for compact, high-gain antenna designs remain significant challenges for future development.