PT3 - Experimental Gravitation |
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Speaker |
Ortolan, Antonello |
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Coauthors |
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| Talk Title |
GINGER: an array of ring lasers for testing fundamental physics |
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Abstract |
Ring laser gyroscopes, laser-gyros are, at the present, the most precise sensors of absolute angular velocity. They are essential in estimating rotation rates relative to the local inertial frame in many contexts ranging from inertial guidance to angle metrology, from geodesy to geophysics, as well to fundamental physics [1]. In the near future, their application is foreseen to provide ground based tests of General Relativity [2]. In particular, we have recently proposed [3] a tri-axial array of ring lasers that can reach the sensitivity, accuracy, and long term stability required to measure the inertial frame dragging predicted by General Relativity, and induced by the rotating Earth. The effect, also known Lense-Thirring effect, is the general relativistic term coming from a rotating mass. For the Earth, it amounts to 1 part in a billion of its rotation rate thus requiring an unprecedented sensitivity of the entire apparatus. An array of at least three ring lasers would allow us to measure not only the rotation rate, i.e. the angular velocity modulus, but also the angular velocity vector. In this way, having at disposal the time series of the daily estimate of Earth rotation vector from the International Earth Rotation and Reference System Service (http://www.iers.org), it would be possible to isolate the Geodetic and Lense-Thirring contributions. Our experiment, named GINGER (Gyroscopes IN GEneral Relativity), is intended to push the present knowledge of ring laser physics and technology to achieve an accuracy in the estimation of the Earth rotation rate of 1 part in 10^9. In the real apparatus this conceptual measurement come to different bottlenecks due to the systematic errors which affect the rotation rate estimate: mainly the non linear dynamics of the active laser medium and changes of the optical cavity geometry. They should be carefully estimated and kept under control. In this contribution we describe also the intermediate prototypes GP2 and GINGERino and the related experimental efforts of the GINGER collaboration to get rid of systematics (GP2) and to qualify the underground site of the Gran Sasso INFN Laboratory (GINGERino), where the GINGER apparatus should be possibly operated. References [1] N. Barbour and G. Schmidt, Sensors Journal, IEEE, 1, 4, 332 - 339 (2001); Yu. V. Filatov et al Metrologia 34, 343 (1997); K. U. Schreiber, et al., J. Geophys. Res. 109, B06405 (2004); K. U. Schreiber, et al., Phys. Rev. Lett. 107, 173904 (2011); G. E. Stedman, Rep. Prog. Phys., 60, 615-688 (1997); J. Belfi, et al., Applied Physics B106, 2 , 271-281 (2011);A. Di Virgilio et al. Class. Quantum Grav. 27, 084033 (2010); [2] F. Bosi et al., “Measuring Gravito-magnetic Effects by Multi Ring-Laser Gyroscope,” Phys. Rev. D84, 122002 (2011). [3] A. Di Virgilio et al., Int. J. Mod. Phys. D19, 2331 (2010). |
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