The earliest prediction of the Sagnac effect, and of the possibility of detecting the Earth’s rotation with an interferometer of square kilometer area, is by Lodge (1893, 1897). We illustrate the extraordinary range of theoretical motivations for the experimental study of the Sagnac effect, starting with previously unpublished correspondence between Lodge and Larmor, and ending with present (and planned) ring interferometer experiments whose sensitivity to the Earth’s rotation is of the order of parts per million (billion, respectively).
The possibility of detecting the Lense–Thirring field generated by the rotating earth (also rotating laboratory masses) is reassessed in view of recent dramatic advances in the technology of ring laser gyroscopes. This possibility is very much less remote than it was a decade ago. The effect may contribute significantly to the Sagnac frequency of planned instruments. Its discrimination and detection will require an improved metrology, linking the ring to the celestial reference frame, and a fuller study of dispersion- and backscatter-induced frequency pulling. Both these requirements have been the subject of recent major progress, and our goal looks feasible.
Aring laser unlocked by the Earth's Sagnac effect has attained a frequency resolution of 1 part in 3 × 10(21) and a rotational resolution of 300 prad. We discuss both theoretically and experimentally the sideband structure of the Earth rotation-induced spectral line induced in the microhertz-hertz region by frequency modulation associated with extra mechanical motion, such as seismic events. The relative sideband height is an absolute measure of the rotational amplitude of that Fourier component. An initial analysis is given of the ring laser record from the Arthur's Pass-Coleridge seismic event of 18 June 1994.
The Fano factor in germanium at liquid-nitrogen temperature has been found to be F = 0.129±0.003 using 7 rays at energies from 0.122 to 4.8 MeV. F appears to be independent of the primary energy in the investigated energy range. Care has been exercised to eliminate the influence of ballistic deficit, recombination, and trapping in planar lithium-drifted structures as well as noise, drift, and pile-up in the apparatus. Measurements with crystals having volumes from 0.8 to 13 cm gave consistent results. We examined the line shift and the linewidth dependence up to and into electric field strengths where saturation of electron and hole velocities occurs.
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