Interferometric length metrology for the dimensional control of ultra-stable ring laser gyroscopes

Belfi, Jacopo; Beverini, N.; Cuccato, Davide; Virgilio, A. Di; Maccioni, Enrico; Ortolan, A.; Santagata, Rosa

doi:10.1088/0264-9381/31/22/225003

Cited by 24 publications

(20 citation statements)

References 21 publications

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“…The relative variation of the scale factor is plotted for different values of the unbalance δD between the two diagonal absolute lengths. Note that even in the case of a systematic error in the difference between the two diagonal cavities lengths of 10 −6 m [18], the scale factor stability is compliant with the requirements of GINGER (∆k S /k S < 10 −10 ). The results of equation 14 and equation 15 provide a procedure in order to approach the regular square geometry, starting from a generic mirror configuration.…”

Section: Discussionmentioning

confidence: 69%

Optimization of the geometrical stability in square ring laser gyroscopes

Santagata

Beghi

Belfi

et al. 2015

Class. Quantum Grav.

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Abstract. Ultra sensitive ring laser gyroscopes are regarded as potential detectors of the general relativistic frame-dragging effect due to the rotation of the Earth: the project name is GINGER (Gyroscopes IN GEneral Relativity), a ground-based triaxial array of ring lasers aiming at measuring the Earth rotation rate with an accuracy of 10 −14 rad/s. Such ambitious goal is now within reach as large area ring lasers are very close to the necessary sensitivity and stability. However, demanding constraints on the geometrical stability of the laser optical path inside the ring cavity are required. Thus we have started a detailed study of the geometry of an optical cavity, in order to find a control strategy for its geometry which could meet the specifications of the GINGER project. As the cavity perimeter has a stationary point for the square configuration, we identify a set of transformations on the mirror positions which allows us to adjust the laser beam steering to the shape of a square. We show that the geometrical stability of a square cavity strongly increases by implementing a suitable system to measure the mirror distances, and that the geometry stabilization can be achieved by measuring the absolute lengths of the two diagonals and the perimeter of the ring.

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Section: Discussionmentioning

confidence: 69%

Optimization of the geometrical stability in square ring laser gyroscopes

Santagata

Beghi

Belfi

et al. 2015

Class. Quantum Grav.

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“…S depends basically on the geometry, the quality of the mirrors, the pressure and composition of the gas mixture, and the plasma. Suitable control strategy for the geometry of the square ring laser has been studied and it is at present under study [30,31], two colocated devices will have equal gas mixture and pressure, each mirror can be characterised and they can be interchanged, accordingly the realisation of two RLs with equal scale factors is feasible. In order to estimate the requirements for the Lense-Thirring test at ρ = 1%, we have studied the specifications for η ∼ 10 −10 and η ⊥ ∼ 3.510 −10 (LT test).…”

Section: Error Budget and Specifications Of The Experimental Apparatusmentioning

confidence: 99%

GINGER: A feasibility study

Virgilio

Belfi

et al. 2017

Eur. Phys. J. Plus

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Abstract. GINGER (Gyroscopes IN General Relativity) is a proposal for an Earth-based experiment to measure the Lense-Thirring (LT) and de Sitter effects. GINGER is based on ring lasers, which are the most sensitive inertial sensors to measure the rotation rate of the Earth. We show that two ring lasers, one at maximum signal and the other horizontal, would be the simplest configuration able to retrieve the GR effects. Here, we discuss this configuration in detail showing that it would have the capability to test LT effect at 1%, provided the accuracy of the scale factor of the instrument at the level of 1 part in 10 12 is reached. In principle, one single ring laser could do the test, but the combination of the two ring lasers gives the necessary redundancy and the possibility to verify that the systematics of the lasers are sufficiently small. The discussion can be generalised to seismology and geodesy and it is possible to say that signals 10-12 orders of magnitude below the Earth rotation rate can be studied; the proposed array can be seen as the basic element of multi-axial systems, and the generalisation to three dimensions is feasible adding one or two devices and monitoring the relative angles between different ring lasers. This simple array can be used to measure with very high precision the amplitude of angular rotation rate (the length of the day, LOD), its short term variations, and the angle between the angular rotation vector and the horizontal ring laser. Finally this experiment could be useful to probe gravity at fundamental level giving indications on violations of Einstein Equivalence Principle and Lorenz Invariance and possible chiral effects in the gravitational field.

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“…These resonators was mounted on an optical bench to simulate the cavities along the diagonals of a RL gyroscope. With this setup, we were able to demonstrate the capability of stabilizing the two lengths at the level of 1 part in 10 11 , and setting their difference equal to zero within the precision of 500 nm, with residual fluctuations only limited by the laser frequency noise 8 . Recently, this metrology technique has been partially implemented in GP2.…”

Section: The Gp2 Rl Gyroscopementioning

confidence: 99%

GINGER: An array of ring lasers for testing fundamental physics

Ortolan¹,

Belfi²,

Bosi³

et al. 2017

The Fourteenth Marcel Grossmann Meeting

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Ring laser (RL) gyroscopes are, at present, the most precise sensors of absolute angular velocity. In the near future, their application is foreseen to provide ground based tests of General Relativity. We have recently proposed a tri-axial array of RLs that can reach the sensitivity, accuracy, and long term stability required to measure the inertial frame dragging induced by the rotating Earth, as predicted by General Relativity. The effect, also known Lense-Thirring effect, amounts for the Earth to 1 part in 10 9 of its rotation rate, thus requiring an unprecedented sensitivity and accuracy of experimental apparatus. An array of at least 3 RLs 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, it would be possible to isolate the Geodetic and Lense-Thirring contributions. Our proposal GINGER (Gyroscopes IN GEneral Relativity) is intended to push the present knowledge of RL physics and technology to achieve an accuracy in the estimation of the Earth rotation rate of 1 part in 10 9 . In the experimental apparatus we have to account for systematic errors resulting from non linear dynamics of the active laser medium, and changes of the optical cavity geometry. The redundancy of the array, e.g. the addition of a ring almost parallel to the Earth rotation axis, should allow for the reduction of such errors at the level of the geometry control. In this contribution we describe the intermediate prototypes GP2 and GEMS (GINGER External Metrology System) devoted to control the geometrical fluctuations of a RL cavity and the 3D geometry of the RL array (dihedral angles among RLs), respectively.

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Interferometric length metrology for the dimensional control of ultra-stable ring laser gyroscopes

Cited by 24 publications

References 21 publications

Optimization of the geometrical stability in square ring laser gyroscopes

Optimization of the geometrical stability in square ring laser gyroscopes

GINGER: A feasibility study

GINGER: An array of ring lasers for testing fundamental physics

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