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This Defense Intelligence Reference Document from the Defense Intelligence Agency, dated 28 January 2010, surveys pulsed high-power microwave (HPM) source technology. It was produced under the Advanced Aerospace Weapon System Applications (AAWSA) program. It covers insulation, cathode materials, high-voltage switching, pulse generators, microwave sources such as magnetrons, gyrotrons and the Phoenix and Jolt sources, and antennas. The document concludes that progress depends on advances in cathodes, switching and insulation. It says compact ultrawideband antennas will remain difficult to build.
UNCLASSIFIED//FQA. QFFllil*L 1!1!11! t,llt I The Orion system, first fielded in 1995, is a self-contained, transportable HPM test facility housed in five standard shipping containers. It is computer controlled via fiberoptic links. The system is based on four continuously tunable magnetrons with a tunable frequency range of 1 to 3.3 GHz. The thyratron-switched modulator pulse charges an 11-section pulse-forming network through a step-up transformer and a triggered gas output switch. This provides a 100- to 500-ns pulse at 200 to 500 kV and up to 100 PRR that drives the magnetrons. The magnetrons are tuned by stepper-motors and use Figure 3. Orion HPM Testing Facility explosive emission cathodes. The vacuum of 10-6 to 10-7 is provided by cryopumps. The magnetic field of about 10 kG is provided by cryomagnets. The system includes an entire shipping container housing a combiner/attenuator network to provide continuously variable power over five orders of magnitude. The antenna is formed by two offset, shaped parabolic reflectors, each fed by two pyramidal horns. The antenna produces a 7 x 15 meter elliptical beam spot at a distance of 100 meters. Figure 3 shows the Orion test facility with its antenna. GYROTRONS Gyrotrons tap the energy associated with electrons gyrating about strong magnetic field lines. The main purpose for gyrotron development thus far has been magnetic confinement fusion research, in which megawatt-power, long-pulse gyrotron sources operating at more than 100 GHz provide resonant heating, current drive, and instability suppression. These devices use an electron gun to launch an electron beam into a region of slowly increasing magnetic field, where it is compressed. Compression raises the current density and produces a perpendicular component to the beam velocity. After compression, electron-guiding structures are placed at the peak electric field position for the TE01 mode. The beam and guiding center structure then enter a resonant cavity. Inside the cavity, the electron motion decomposes into three components: a drift along the magnetic field lines, a slow rotation of the beam about - -the magnetic axis owing to the Ex B drift involving the beam self-electric field, and the Larmor rotation of individual electrons about the guiding centers. Resonant cavity fields oscillating faster than the rotational cyclotron frequency of electrons cause the electrons to bunch on one side of their common guiding centers. This bunching causes net electron energy to be given up to the cavity fields, which is then extracted. 19 UNCLASSIFIED//F811. QFFUiil,tik Wili Q•ik¥
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Report, from the dia 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.