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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.
“BEAMS”17 pages
UNCLASSIFIED/ ,'l"e" Cl"l"!e!•t tl9E CHE I beam is much greater than the stored magnetic field energy, and it follows that E ::::ERF = 10 11 J to a reasonable approximation. Sources of Quality Factor and Effect on SQL To calculate the SQL, hdet, we also need the value of the detector quality factor Q (not the same as the cavity quality factor). Anything that concentrates or enhances the signal preferentially over noise, in any measurement dimension, can be considered a contributor to the quality factor Q. The quality factor can therefore be understood as the "signal selectivity" in each dimension, so that Qtot = ( Qspatia/) (Qt) = QrQsolid angieQt . (9) The temporal quality factor in the Li-Baker detector arises from averaging the signal over time, so that at 10 GHz, Qt= fltint = (10x10 9 Hz) x 1000s = 1013 . There is a contribution to Q arising from the fractal membranes that focus and concentrate the signal photon energy - but not the background photons - along the radial dimension. The radial selectivity arising from the general relativity solution, in conjunction with fractal membranes, is calculated by Li et al. (2008). Their table III gives Qr= SNRrr~37cmJ/5NRrr~3.scmJ = 3.4x10 21 . This is mostly due to the effective Q contribution arising from the synchro-resonance solution to the Einstein field equations that limit the PPF signal to a radiation pattern in certain directions, whereas noise is distributed uniformly. By utilizing directional antennas, the Li-Baker detector can capitalize upon this gain due to the focusing power of fractal membranes as a contribution to Q in angular space as well. This is calculated in detail, octant by octant, by Li et al. (2008). Page 24 of Li et al. summarizes this in terms of angular concentration onto the detector. A non-directional antenna corresponds roughly to solid angle 2ff steradians ( one hemisphere), so that the effective antenna gain is estimated as (Qso1idang1e) = 2rr sr/10. 4sr = 6.3x10 4 . Therefore, the predicted maximum quality factor will be Qtotat = QrQsotidangteQt = 2.1x1039 . This finally gives the Standard Quantum Limit (SQL) for stochastic GW detection at 10 GHz: hdet = (1/Q) 112 (floJ/E) 112 = 1.8x10- 37 m/m . ( 10) Comparison of SOL With Predicted Sensitivity As noted in the previous section, hdet = 1.8x10- 37 m/m represents the lowest possible GW amplitude detectable by each RF receiver in the Li-Baker HFGW detector, limited by quantum back-action. An additional ( 1;-,/2) factor applies if the separate outputs from the two RF receivers are averaged, rather than used independently for false alarm reduction, resulting in a minimum hdet = l.2x10-37 . Since the predicted best sensitivity of the Li-Baker detector in its currently proposed configuration is A= 10-32 m/m, these results confirm that the Li-Baker Detector is photon-signal limited, not quantum noise limited; that is, the Standard Quantum Limit is so low that a properly designed Li-Baker detector can have sufficient sensitivity to observe HFRGW of amplitude A== 10-32 m/m. 19 UNCLASSIFIED//r;Oll oi;i;1,;;1•k llili O•lk¥
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Report, from the dia collection. The PDF is mirrored here; the original link is under it. 57 pages are in the text index: search them above, or from the library's search.