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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 OFFl@IAL l!ISl!!! 9Ht5i" thus, implies heightened safety concerns. Even low-volume vessels can contain hundreds of joules of energy in the compressed gas, and a housing failure can hurl fragments at deadly velocities. Highly compressed gases are used only in cases where some prized benefit is worth the increased cost and design trials to be exacted. One example of this is extremely fast switching where the electrode spacing is proportional to the added inductance during conduction-the smaller electrode spacing requires higher gas pressure for insulation. Almost every common gas has been used as insulation, and many have attributes making them desirable for certain applications. Sulfur hexafluoride, nitrogen, air, argon, helium, oxygen, and hydrogen are commonly used. Of these, only sulfur hexafluoride is an electronegative gas, meaning it has the ability to remove electrons from the volume through the formation of negative ions and thereby increase the dielectric strength. Electrical discharges in sulfur hexafluoride result in foul-smelling sulfur compounds that also deposit on the switch housing and electrodes and require frequent cleaning. These discharge compounds also tend to be highly corrosive, especially in the presence of water. Other gases with electronegative species, typica lly other halogens such as chlorine, also make good insulators. These gases are usual ly much denser than air, and breakdown voltage is roughly proportional to density, thus higher voltages can be supported even at low pressures. The halogenated hydrocarbon refrigerants, such as CCl4, CCl 2F2, CCb F, and C2Cl2f4, are also popular for insulation. The breakdown of air has been thoroughly researched, and in fact the breakdown voltage of a calibrated gap can be used to determ ine the magnitude of high voltages. Table 2 shows the breakdown voltages of severa l insulating gases relative to that of air. Table 2. Relative Spark Breakdown Strength of Gases Gaseous insulation as a switch medium limits the pulse repetition rate (PRR) to 500- 600 pulses per second because of the creation of numerous metastable states and elevated energy levels by the previous pulses. This is true for all gases listed here except hydrogen. Hydrogen can be used at a much higher PRR; however, its dielectric strength is only 65 percent that of air and, thus, almost twice as much pressure is required for the same operating voltage. When the pressure is doubled, the energy content increases by a factor of four, leading to elevated safety concerns. Using hydrogen for switch insulation poses no explosive danger provided the oxygen content in the gas is kept below about 5 percent. Other handling problems associated with hydrogen include hydrogen embrittlement-it will leak through even tiny holes, including the pores in metal tanks, eventually causing the metal to become brittle and fail. In addition, hydrogen is flammable when mixed with oxygen. A hydrogen flame is colorless but very hot, which can be dangerous if leaks develop in pressurized switches or gas lines. One class of hydrogen switches, hydrogen thyratrons, makes use of the low-pressure characteristics of gases to eliminate the safety concerns associated with high pressures (these are discussed in a later section dedicated exclusively to gas switches). UNCLASSIFIED/ /FOR OFFICIO! 1!SE ON! X 5
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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.