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This Defense Intelligence Reference Document was prepared by the Defense Intelligence Agency under its Advanced Aerospace Weapon System Applications (AAWSA) program, is dated 6 April 2010 and is part of a series of advanced technology reports produced in FY 2009. It reviews proposed laboratory generators and detectors of high-frequency gravitational waves for communications. It favors an infrared-excited molecules transmitter and the Li-Baker detector, estimating about 1.9 million bits per second over 7,000 km through the Earth. It also discusses timing standards and interplanetary navigation uses.
UNCLASSIFIED/ ,'1"1!11'- l!ll"l"U!llltt l!l!ii! 8Hlo1.C 2.2.4 Li-Baker HFGW Detector The detector, shown in Figure 14, has five major components: 1. A Gaussian (focused, with minimal side lobes) microwave beam (GB) is aimed along the +z-axis at the same frequency as the intended HFGW signal to be detected (Yariv, 1975), typically in the GHz band, and also aligned in the same direction as the HFGW to be detected. The microwave transmitter's horn antenna is not shown, but would be located on the -z-axis. 2. A static magnetic field B, generated by two powerful magnets, typically using powerful superconductor magnets such as those found in a conventional MRI medical body scanner, is directed along the y-axis. 3. Two paraboloid-shaped reflectors, which are formed from "fractal membranes" (Wen et al., 2002; Zhou et al., 2003; Hou et al., 2005), are located in the y-z plane at the origin of the coordinate system to aim and focus the detection photons at diffraction- limited spot antennas connected to two microwave receivers. These reflectors, shown in planer form in Figure 15, are segmented (similar to a Fresnel lens) and located back-to- back in the y-z plane. They are thin enough (less than a centimeter thick in the x- direction) to not block the z-directed Gaussian beam. These microwave reflectors reflect the x-directed detection photons (PPF) and reject the z-directed Gaussian-beam photons, which move parallel to the surface of the reflectors in the y-z plane. 4. High-sensitivity shielded microwave receivers are located at each end of the x-axis each about one meter distant from the origin. 5. Interior noise from thermal photon generation is eliminated by cooling the Li-Baker detection apparatus to below~ 48 mK (0.048 Kelvin). Thus there are effectively no thermal photons at 10 GHz. Noise from the interior background photon flux (BPF) from the EM Gaussian beam is reduced to a negligible level by moving the receivers out to the side about a meter away from the EM beam and by a series of superconductor or microwave absorbent baffles to "shade" the receivers. Stray EM resulting from scattering of particulate matter near the apparatus and possible dielectric dissipation can be effectively suppressed by evacuating the apparatus to about 7.5x 10-7 Torr (a rather high vacuum). External noise is eliminated by the use of a steel and titanium cryogenic containment vessel surrounding the low-temperature Li-Baker detection apparatus. In summary, several different HFGW receivers can be utilized for communication; but the proposed Li-Baker detector (plans & specification development in Appendix B) shows the most promise (detailed underlying concept is derived in the paper included as Appendix C). 20 UNCLASSIFIED/ ,«re~ 8FFHiil11J.k W&liii Ollk¥
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Report, from the dia collection. The PDF is mirrored here; the original link is above. 57 pages are in the text index: search them above, or from the library's search.