Identification and correction of Sagnac frequency variations: an implementation for the GINGERINO data analysis
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Regular Article - Experimental Physics
Identification and correction of Sagnac frequency variations: an implementation for the GINGERINO data analysis Angela D. V. Di Virgilio1,a , Nicolò Beverini2 , Giorgio Carelli2 , Donatella Ciampini2 , Francesco Fuso2 , Umberto Giacomelli1, Enrico Maccioni1,2 , Antonello Ortolan3 1
INFN Pisa, Largo B Pontecorvo 3, 56127 Pisa, Italy Università di Pisa, Dipartimento di Fisica “E. Fermi”, Largo B Pontecorvo 3, 56127 Pisa, Italy 3 INFN-National Lab. of Legnaro, viale dell’Università 2, 35020 Legnaro, PD, Italy
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Received: 27 June 2019 / Accepted: 18 January 2020 / Published online: 21 February 2020 © The Author(s) 2020
Abstract Ring laser gyroscopes are top sensitivity inertial sensors used in the measurement of angular rotation. It is well known that the response of such remarkable instruments can in principle access the very low frequency band, but the occurrence of nonlinear effects in the laser dynamics imposes severe limitations in terms of sensitivity and stability. We report here general relationships aimed at evaluating corrections able to effectively account for nonlinear laser dynamics. The so-derived corrections are applied to analyse thirty days of continuous operation of the large area ring laser gyroscope GINGERINO leading to duly reconstruct the Sagnac frequency ωs . The analysis shows that the evaluated corrections affect the measurement of the Earth rotation rate Ω⊕ at the level of 1 part in 1.5 × 103 . The null shift term ωns plays a non negligible role. It turns out proportional to the optical losses μ of the ring cavity, which are changing in time at the level of 10% within the considered period of thirty days. The Allan deviation of estimated Ω⊕ shows a remarkable long term stability, leading to a sensitivity better than 10−10 rad/s with more than 10 s of integration time, and approaching (8.5 ± 0.5) × 10−12 rad/s with 4.5 × 105 s of integration time.
1 Introduction Ring laser gyroscopes (RLGs) are inertial sensors based on the Sagnac effect [1–3]. They are largely used for inertial navigation, and applications in geodesy, geophysics and even for General Relativity, where tests are foreseen [4]. Since 2011 we are studying the feasibility of the test of Lense– Thirring dragging of the rotating Earth at the level of 1% with an array of large frame RLGs [5–7]. For that purpose it a e-mail:
[email protected] (corresponding author)
is necessary to push the relative accuracy of the Earth rotation rate Ω⊕ measurement in the range from 1 part in 109 up to 1 part in 1012 . RLG consists of a laser with a cavity comprising of three or four mirrors, rigidly attached to a frame; large frame RLGs are utilised to measure the Earth rotation rate, being attached to the Earth crust. Because of the Sagnac effect, the two counter-propagating cavity beams have slightly different frequency, and the beat note of the two beams is proportional to the angular rotation rate of the ring cavity. Large frame RLGs are the most sensitive instruments for inertial angular ro
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