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This Defense Intelligence Reference Document, DIA-08-1004-005, is dated 6 April 2010. The Defense Intelligence Agency's Defense Warning Office prepared it under the Advanced Aerospace Weapon System Applications program. It reviews proposed laboratory generators and detectors for high-frequency gravitational waves. It favors a piezoelectric approach for proof-of-concept tests, IR-excited molecules for an operational transmitter and the Li-Baker detector as the receiver. It estimates about 1.9 million bits per second over 7,000 km through the Earth and discusses timing standards and interplanetary navigation uses.
From the source:Release of 2026-09-18 Incident: 4/6/10, 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 examines whether high-frequency gravitational waves could serve as a communications medium while avoiding the attenuation that limits radio-frequency systems. The report surveys proposed transmitter and detector concepts, argues that gravitational-wave communications could support secure point-to-point links, timing standards, and interplanetary navigation, and gives particular attention to laboratory generator concepts and the Li-Baker detector as possible building blocks for such a system. The document makes clear, however, that the entire concept depends on capabilities that had not been demonstrated in practice, including laboratory-scale generation and reliable detection of usable high-frequency gravitational-wave signals. It is an exploratory systems-oriented review built around a future communications concept.
UNCLASSIFIED//iiOlil OiiiilCI0L Llili QPIL¥ 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 signa l 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 eta/., 2002; Zhou eta/., 2003; Hou eta/., 2005), are located in the y-z pla ne 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 t han 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 sh ielded 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 elim inated 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 7.5x10-7 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 Append ix B) shows the most promise (detailed underlying concept is derived in the paper included as Appendix C). UNCLASSIFIED/ /FOR OiiiilCl.t.k HSI!! eflti 20
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