Historical research guide · 0302 · 2010
DIRD Pulsed High-Power Microwave Source Technology
DIA / AAWSAP contractor
In one minute
Defense Intelligence Reference Document DIA-08-0912-005 surveys pulsed high-power microwave sources and the engineering needed to build them. The author traces the chain from high-voltage insulation and sub-nanosecond switches through cathodes, electron beams, pulsed-power banks, tubes and antennas. It gives values from named systems: the Phoenix source radiated 45 kV/m at nine metres with a 90-picosecond rise time, and the fielded Active Denial System uses a 95-GHz gyrotron at 100 kW. The report also describes virtual cathode oscillators, cathode lifetime, gap closure, and the factors that set pulse repetition. Its closing section identifies higher-voltage, longer-lived photoconductive switches as a route toward phased-array microwave sources. It is a survey of existing hardware and design constraints, not a report of vacuum-field propulsion or a new propulsion experiment.
Connection
Chapter 8 asks what it would take to drive the vacuum with extreme electromagnetic flux, and this is the government’s own answer to the hardware half of that question: the switches, cathodes and insulation that set the real ceiling on how fast and how hard a field can be swung. It is also chapter 1’s evidence ladder in working order — every figure here is a measured figure from a named facility — and chapter 9’s plasma physics seen from the engineering side, since every one of these tubes runs on a deliberately created surface plasma.
From the source
High-power microwave sources built for electronic attack deliver peak powers in excess of 10 gigawatts, and the technology driving them has its roots in pulsed power and, for narrowband sources, in the tools developed by the plasma physics community.Summary, p. vii
The only directed-energy weapon system known to be fielded is built on a gyrotron: the Active Denial System operates continuously at 95 gigahertz, radiates 100 kilowatts through a flat parabolic surface antenna, reaches beyond 750 metres, and deposits its energy to a depth of about 0.4 millimetres of skin.Gyrotrons, p. 20; Figure 4
The virtual cathode oscillator has no conventional counterpart. It is tunable from 300 megahertz to 40 gigahertz, needs no magnetic field, delivers 200 megawatts to 15 gigawatts at 1 to 10 percent efficiency, and its free-running frequency is set by the relativistic beam plasma frequency and chirps upward through the pulse until plasma closure ends it.Virtual Cathode Oscillators, p. 18
Cathodes of caesium iodide over carbon microfibre emit below 3 kilovolts per centimetre, have exceeded 200,000 shots, and cut the anode-cathode gap-closure velocity to about a quarter of that for velvet or bare carbon; the programmes using them aim at hundreds of kiloamps for tens of microseconds, giving gigawatt narrowband sources at around 100 hertz and 100 megajoules of output energy per burst.Cesium Iodide Coated, p. 10; Table 3, p. 11
The textbook account of how a high-voltage switch closes — Townsend avalanching — is most likely incorrect, because it needs exaggerated ion densities to explain how switches reach full conduction in less than a billionth of a second; explanations built on runaway electron generation match the observations better.High-Voltage Switching, p. 11
If photoconductive solid-state switches capable of higher operating voltage and extended lifetime become available, variations of the phased array will become the high-power microwave source design of choice, given the inherent advantages.Conclusion, p. 29
The way in
https://documents2.theblackvault.com/documents/dia/AAWSAP-DIRDs/DIRD_03-DIRD_Pulsed_High-Power_Microwave_Source_Technology.pdfHow to cite it
DIA / AAWSAP contractor (2010) DIRD Pulsed High-Power Microwave Source Technology https://documents2.theblackvault.com/documents/dia/AAWSAP-DIRDs/DIRD_03-DIRD_Pulsed_High-Power_Microwave_Source_Technology.pdf