Light and/or atomic beams to detect ultraweak gravitational effects (original) (raw)
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Experimental determination of gravitomagnetic effects by means of ring lasers
2013
A new experiment aimed to the detection of the gravito-magnetic Lense-Thirring effect at the surface of the Earth will be presented; the name of the experiment is GINGER. The proposed technique is based on the behavior of light beams in ring lasers, also known as gyrolasers. A three-dimensional array of ringlasers will be attached to a rigid monument; each ring will have a different orientation in space. Within the space-time of a rotating mass the propagation of light is indeed anisotropic; part of the anisotropy is purely kinematical (Sagnac effect), part is due to the interaction between the gravito-electric field of the source and the kinematical motion of the observer (de Sitter effect), finally there is a contribution from the gravito-magnetic component of the Earth (gravito-magnetic frame dragging or Lense-Thirring effect). In a ring laser a light beam traveling counterclockwise is superposed to another beam traveling in the opposite sense. The anisotropy in the propagation leads to standing waves with slightly different frequencies in the two directions; the final effect is a beat frequency proportional to the size of the instrument and its effective rotation rate in space, including the gravito-magnetic drag. Current laser techniques and the performances of the best existing ring lasers allow at the moment a sensitivity within one order of magnitude of the required accuracy for the detection of gravito-magnetic effects, so that the objective of GINGER is in the range of feasibility and aims to improve the sensitivity of a couple of orders of magnitude with respect to present. The experiment will be underground, probably in the Gran Sasso National Laboratories in Italy, and is based on an international collaboration among four Italian groups, the Technische Universität München and the University of Canterbury in Christchurch (NZ).
Measuring gravitomagnetic effects by a multi-ring-laser gyroscope
Physical Review D, 2011
We propose an under-ground experiment to detect the general relativistic effects due to the curvature of space-time around the Earth (de Sitter effect) and to rotation of the planet (dragging of the inertial frames or Lense-Thirring effect). It is based on the comparison between the IERS value of the Earth rotation vector and corresponding measurements obtained by a tri-axial laser detector of rotation. The proposed detector consists of six large ring-lasers arranged along three orthogonal axes. In about two years of data taking, the 1% sensitivity required for the measurement of the Lense-Thirring drag can be reached with square rings of 6 m side, assuming a shot noise limited sensitivity (20prad/s/ √ Hz). The multi-gyros system, composed of rings whose planes are perpendicular to one or the other of three orthogonal axes, can be built in several ways. Here, we consider cubic and octahedron structures. The symmetries of the proposed configurations provide mathematical relations that can be used to study the stability of the scale factors, the relative orientations or the ring-laser planes, very important to get rid of systematics in long-term measurements, which are required in order to determine the relativistic effects.
Measuring gravito-magnetic effects by multi ring-laser gyroscope
We propose an under-ground experiment to detect the general relativistic effects due to the curvature of space-time around the Earth (de Sitter effect) and to the rotation of the planet (dragging of the inertial frames or Lense-Thirring effect). It is based on the comparison between the IERS value of the Earth rotation vector and corresponding measurements obtained by a tri-axial laser detector of rotation. The proposed detector consists of six large ring-lasers arranged along three orthogonal axes. In about two years of data taking, the 1% sensitivity required for the measurement of the Lense-Thirring drag can be reached with square rings of 6 m side, assuming a shot noise limited sensitivity (20prad/s/sqrt(Hz). The multi-gyros system, composed of rings whose planes are perpendicular to one or the other of three orthogonal axes, can be built in several ways. Here, we consider cubic and octahedral structures. It is shown that the symmetries of the proposed configurations provide mathematical relations that can be used to ensure the long term stability of the apparatus.
GINGER - Toward an experimental test of General Relativity
Proceedings of Corfu Summer Institute 2017 "Schools and Workshops on Elementary Particle Physics and Gravity" — PoS(CORFU2017)
GINGER (Gyroscopes IN General Relativity) is a proposal for measuring the Lense-Thirring effect using an array of ring laser-gyroscopes. Those are, nowadays, the most sensitive inertial sensors to measure the rotation rate of the Earth. The Lense-Thirring contribution to the Earth gravitational field marks itself as a tiny DC perturbation onto Ω, the Earth rotation rate. Its magnitude is 10 −9 × Ω so that to be able to discriminate it a very high sensitivity and long measurement times in order to move toward low frequency are required. For such an experiment, an underground location guarantees further isolation from anthropic as well as environmental disturbances. GINGERINO is a single axis ring laser located inside the the INFN Gran Sasso laboratory. It has demonstrated that the very high thermal stability of the cave allows continuous operation, and sensitivity well below fractions of nrad/s are feasible with duty cycle above 90% even without stabilisation of the scale factor of the ring laser. Here we show the GINGER experiment concept together with the first evaluation of the GINGERINO sensitiviy that shows how such a device can be of use also in earth science and related phenomena.
A ring lasers array for fundamental physics
Comptes Rendus Physique, 2014
After reviewing the importance of light as a probe for testing the structure of space-time, we describe the GINGER project. GINGER will be a three-dimensional array of large size ring-lasers able to measure the de Sitter and Lense-Thirring effects. The instrument will be located at the underground laboratory of GranSasso, in Italy. We describe the preliminary actions and measurements already under way and present the full road map to GINGER. The intermediate apparatuses GP2 and GINGERino are described. GINGER is expected to be fully operating in few years.
2015
After reviewing the signal to be expected from a ring laser of convenient size, located on earth, the project of a three-dimensional array of ring lasers named GINGER is presented. The sensitivity analysis is discussed, stressing that the available techniques for research lasers do allow for the detection of general relativistic effects originated by the mass and the angular momentum of the earth. The project is under development at the Gran Sasso National Laboratories of the INFN in Italy. Two intermediate instruments in the road towards the full GINGER have been built, one in Pisa (GP2) and one at the Gran Sasso (GINGERino). They are being used to validate the dynamical control of the geometry and to characterize the site allotted to the experiment.
2006
Using the linearized Einstein gravitational field equations and the Maxwell field equations it is shown that the plane of polarization of an electromagnetic wave is rotated by the gravitational field created by the electromagnetic radiation of a ring laser. It is further shown that this gravitational Faraday effect shares many of the properties of the standard electromagnetic Faraday effect. An experimental arrangement is then suggested for the observation of this gravitational Faraday effect induced by the ring laser. KEY WORDS: general relativity; gravitation; lasers; Maxwell’s equations; Faraday effect.