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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//EOR OEEICI0L Llili QI\IL¥ Coherent Versus Stochastic SOL The question under consideration in this paper is whether or not the Li-Baker detector, Figure 14, is quantum-limited when detecting relic HFGW. In other words, does the standard quantum limit (SQL) interfere with the sensitivity of the Li-Baker detector design? The answer will be negative if the SQL is less than 10-32 m/m. Grishchuk (1977, 2007) has calculated the SQL for GW detectors in general, which for a coherent GW is hdet = (1/Q)(nwJE/12 (5) and for a stochastic GW is: (6) where hdet is the metric (strain) detection limit in m/m, w is the frequency of sensed gravitational waves (typically around 10 GHz in the Li-Baker detector), Eis the effective energy contained within the detector cavity summed over the detection averaging time, and Q is the quality factor or selectivity of the signal over noise. The SQL depends on the values of these parameters. For the remainder of th is paper, we will consider the SQL of only the stochastic signal detection case. In the following subsections the best possible value of the SQL using current technology will be estimated to determine the fundamental limitations of the Li-Baker detector as now envisioned. Impact of Contained Energy Levels on SOL First attempt to estimate a realistic best case for the energy contained within the detection process, E. Typically it is expected that for a refrigerated microwave resonant cavity the best possible electrical quality factor will be around 2nx105. Assuming a "best efforts" value of 1000 W for the power of the Gaussian beam in a laboratory installation, the effective tota l RF energy stored in the microwave resonant cavity of the Li-Baker detector, summed over the system averaging time, is estimated to be given by (Grishchuk, 2007): ERF = (103 W) x (1000s) x (21tx105/21t) = 1011] (7) over a typical 1000 s averaging time. Both the Li-Baker detector and a detector using the Gertsenshtein effect use a large static magnetic field B. For the present suggested outline design for the Li-Baker detector, the nominal value of B = 3 T, so that the magnetic energy density is given by (8) The interaction volume in a practical laboratory-based detector is likely to be a maximum of around 1 m3 • So, the effective total stored energy from the Gaussian UNCLASSIFIED/ /FOR OEEICIJ.b HSI!! Dflti 18
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