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This Defense Intelligence Reference Document (DIA-08-0912-005) is dated 28 January 2010. The Defense Intelligence Agency's Defense Warning Office prepared it under the Advanced Aerospace Weapon System Applications Program. It gives an overview of pulsed high-power microwave sources and the technologies needed to build them, including insulation, cathode materials, high-voltage switching, pulse generators and antennas. The paper concludes that progress requires better cathodes, switching and insulation, and that compact ultrawideband antennas will remain difficult to build.
From the source: Release of 2026-09-18 Incident: 1/28/10, Las Vegas, Nevada. Released with redactions. This document is a Defense Intelligence Reference Document (DIRD), a technical reference format used by the Defense Intelligence Agency (DIA) to capture baseline knowledge on a specific topic for later analytic use. DIRDs are best understood as reference and synthesis products rather than as original research. It is one of 38 DIRDs produced under the Advanced Aerospace Weapon System Applications Program (AAWSAP) between 2009 and 2011. Because AAWSAP’s scope permitted a broad range of supporting topics, not every DIRD in the series directly concerns aerospace systems or future threat assessment. The following summary reflects the DIRD’s scope and framing at the time of writing and should not be read as implying current validation of the concepts discussed. This DIRD surveys pulsed high-power microwave (HPM) source technology and argues that such systems remain of military interest because they can disrupt or damage electronic systems with short, intense electromagnetic pulses. The report reviews the main source types and the supporting technologies they depend on, including high-voltage insulation, switching, cathode materials, antennas, and pulse-power generation. It emphasizes the difficulty of building systems that are compact, efficient, and practical to field, since short pulse durations, antenna size, heating, detectability, and beam or signal quality all impose hard engineering limits. Its overall conclusion is that the technology has significant potential military value, but that further progress depends on advances in cathodes, predictive modeling, high-speed high-voltage switching, and low-loss insulation, while compact ultrawideband systems will remain difficult because of basic physical constraints on antenna design.
UNCLASSIFIED/ /FOR OFFI@IAl W&liii 9PU.Y has resulted in an average dielectric strength of more than 3 kV/mil for the volumes mentioned . Adapting this scheme to the manufacture of high-voltage capacitors could result in significant improvement over the current state of the art of 1 joule per cubic centimeter. DIELECTRIC TAPERING This insulation scheme is little known but has been used with much success in many high-voltage systems, especially where compact high voltage is required. The basic scheme is to first design the system while minimizing the peak electric field stress. Th is involves hours of small but well-chosen changes to a design in order to shape the field lines and achieve the least range from minimum to maximum field stress. We then find the surfaces, which have the highest electric field stresses and therefore the highest probability of breakdown. In evaluating these parameters, it must be remembered that dielectric media are much less likely to initiate breakdown than are conducting surfaces under the same electric field stress. The conductor surfaces under highest field stress are then layered with high-voltage coatings (usually acrylics, polyurethanes, silicones, or engineered coatings) with dielectric constants chosen to reduce the electric field strength at the conductor surface. This technique works because the conductor is the source of electrons, without which breakdown will not occur. Since the electric field is excluded from regions of relatively higher dielectric constant, if the insulating volume is filled with mineral oil (relative dielectric constant of 2.2), then a conducting surface coated with 10 mils of polyurethane (relative dielectric constant of 3.6) will have a lower electric field stress than it would without the coating, and the increase in field stress in the mineral oil will be minimal. Dialectic tapering can be applied using several layers of coatings with progressively lower relative dielectric constant from the conducting surface and dramatically reduces the conducting surface electric field stress. Using finite element electric field solving codes and several hours of iteration, th is technique can often reduce peak electric field stress for a system by 50 percent. The technique works best when the volume dielectric fluid has a low relative dielectric constant, such as mineral oil has (E r =2.2), since coatings are readily available for Er = ~3 to 5. In practice, care must be taken in choosing and applying the coatings to ensure that no voids or bubbles are introduced at the conductor surface. Careful inspection and repair of any flaws is relatively simple with this techn ique. Another, more recent use of this concept is what is termed continually varying dielectrics in ultrawideband (UWB) guiding structures, such as transmission lines with greatly reduced dispersion at bends. CATHODE MATERIALS This area of research is vitally important to any HPM source requiring electron beam generation. All high-power microwave tubes, including virtual cathode oscillators and cavity resonators, rely on a bunched flow of free electrons to set up oscillating electric fields and thereby generate a radiofrequency (RF) output. The electron flow is usually initiated by applying a high-voltage pulse to a vacuum diode. For high -power operation, the cathode must be capable of emitting a very high electron current density using one of several emission mechanisms. UNCLASSIFIED/ /FOR OFFI@IAL Y!JIE OHL¥ 7
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Official release, from the pursue collection. The PDF is mirrored here; the original link is above. 37 pages are in the text index: search them above, or from the library's search.