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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/ /FOA OFFI€1Ak Wlilii ONkY rise time is the time required to heat the gas channel to full conductivity, and the inductive rise t ime is the delay caused by the addition of the switch into the circu it . There are two contributions to the inductive rise time, with Le being the spark channel inductance and Lh the housing inductance . A shorter switch gap reduces the inductive time by lowering the channel inductance but also increases the electric field in the gap, reducing the resistive time and resulting in a faster rise time. Even though the sw itch electrodes are usually designed for minimal cross-sectional area at a given current, the very short electrode separation required can still result in high interelectrode switch capacitance. As mentioned earlier, it is also preferable to charge the switch very quickly to achieve an overvolted switch ing cond ition, and, therefore, very fast switches always have some level of pre-pulse. Because the PRR is also of great importance, hydrogen has been chosen most often for high-speed gas switching in UWB HPM sources. Switches of this type have achieved rise times of just over 100 picoseconds (ps) and PRRs of 1,500 pulses per second. Another type of gas switch meriting mention for its util ity and ind ispensabil ity in the HPM pu lsed-power driver circuits is the hydrogen thyratron. The thyratron is a partial vacuum switch . Figure 1 shows what is known as the Paschen curve for air; however, all gases exhibit the same curve characteristics. At some product of pressure and electrode spacing, a minimum value of breakdown voltage is reached. While high pressure gas switches operate in the reg ion on the right side of the Paschen minimum, the hydrogen thyratron operates on the left side, beyond the Paschen minimum . The physics of voltage breakdown in this reg ion results in smaller electrode spacing holding off higher voltages and reduced pressure at the same spacing enabl ing greater voltage holdoff. The single-stage t hyratron operates at only tens of kilovolts, while high pressure gas switches may operate at several hundreds of kilovolts . When coupled with a good pulse transformer, a properly chosen thyratron forms the heart of an excellent driver for HPM sources. The thyratron also has the capability to initiate breakdown using modest trigger levels ( ~1 kilovolt) and with nanosecond timing, allow ing the use of multiple switches to share current. Breakdown Voltage vs. Pressure x Gap (Air) 100000 Ill 0- >I Q) 10000 C') «J -0 > C 3: 1000 0 "C ..:.:: «J Q) ....m 100 ' f¥ - -... ~ 1.00E-02 1.00E-01 1.00E-t-00 1.00E-t-01 1 .00E-+D2 1 .00E-t-03 1 .00E-t-04 Pl"essure x Gap - Torr Inches Figure 1. Paschen Curve for Air UNCLASSIFIED/ /fOll OfPl@IAL t:191!! er~t I 13
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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.