GINGER An array of ring-lasers to test General Relativity
Local effects in Gravitational Physics: Theoretical and Experimental Effects LeCosPa, December 2015, NT Taiwan GINGER An array of ring-lasers to test General Relativity Angela Di Virgilio INFN-Pisa local effects in gravitational physics and measurement of the Length Of the Day (LOD) Angela Di Virgilio,December Angela Di Virgilio, December 15 2015
Local effects in Gravitational Physics: Theoretical and Experimental Effects OUTLINE General RelativityLense-Thirring one of the challenge Sagnac Effect and its applications Ring-Lasers and Lense-Thirring Present and future improvements GINGER, its roadmap and our prototypes: GINGERino, GP2 and GEMS CONCLUSIONS Angela Di Virgilio,December Angela Di Virgilio, December 15 2015
General Relativity Present Challenges (Cosmology) Celestial mechanics Lensing Gravitational waves Equivalence principle Rotation effects (gravitomagnetism) Angela Di Virgilio,December Angela Di Virgilio, December 15 2015
Satellite measurements Lares and Lageos require a very accurate knowledge of the Earth gravitational field (Grace) Angela Di Virgilio,December Angela Di Virgilio, December 15 2015
Expected detectable effect Torque on massive gyroscopes Asymmetric propagation along closed paths (in space) Ring laser Angela Di Virgilio,December Angela Di Virgilio, December 15 2015
Sagnac Effect and basic of ring laser Angela Di Virgilio,December Angela Di Virgilio, December 15 2015
RingLaser Ideal Gyroscope Angela Di Virgilio,December General relativity effect in a laser gyroscope on Earth
Angela Di Virgilio,December Angela Di Virgilio, December 15 2015
Local effects in Gravitational Physics: Theoretical and Experimental Effects Orders of magnitude, on the Earth surface Necessary to measure the Earth angular rotation Wbetter than 1 part 109 IERSprovides the Earth angular rotation done with VLBI, the comparison of the two independent measurements gives the GR terms Angela Di Virgilio,December Angela Di Virgilio, December 15 2015
RingLasers are used in navigation, a few very sensitive instruments have been developed GINGERino 14.4m Measuring rotations OFG Small ring laser GP2 5.4m G(Wettzell) 16m Aircraft Navigation SubmarineNavigation 10-4 10-6 10-8 10-10 10-12 10-14 rad/s General Seismics Earth Tides Relativity Earth Rotation Rate Fluctuations of Earth rotation Angela Di Virgilio,December Angela Di Virgilio, December 15 2015
The high sensitive RL technique has been developed in NewZealand (G. Stedman) A bunch of sensitive and largeRL are in NewZealand Angela Di Virgilio,December Angela Di Virgilio, December 15 2015
G Wettzell - Number One Current status: I. Backscatter correction II. Improvement of long term stability III.Geophysical Modelling Angela Di Virgilio,December II. Improvement of long term stability
Perimeter control based on Piezo closed loop locking, or Selfreferencing due to lock on FSR 633nm Courtesy of U. Schreiber and A. Gebauer Angela Di Virgilio,December Backscatter corrected raw data
Courtesy of U. Schreiber and A. Gebauer RLG Tilt Corrections: Polar Motion, Solid Earth Tides, Chandler Wobble, Annual Wobble Sensor/Environment: Backscatter, local Tilt Angela Di Virgilio,December 200 days of RLG observations
Local tilt effects are masking true RLG performance Top Soil disturbances Top soil wind, microseisms, variable hydrology effects reduce significantly with depth! GINGER Gyroscopes IN General Relativity
Octahedron with 8m side, Compatibility with Node B of LNGS is under test Angela Di Virgilio,December Necessary Improvements toward GINGER
3 axial system with redundancy (at least 4 independent rings) Heterolithis structure Heterolithic structure (G is monolithic) Active Control of the Geometry Necessary to monitor the relative angle between different rings with nrad accuracy External metrology (GEMS) Avoid top soil disturbances Underground (LNGS) ? Angela Di Virgilio,December Angela Di Virgilio, December 15 2015
Develop the Active control of the geometry Check is underground location is good Relative angle between different rings: external metrology Angela Di Virgilio,December Prototypes GINGER: - LNGS rotational noise GINGERino @LNGS
- SENSITIVITY: rad/sec- STABILITY: 1 day - ACCURACY: 1 part in 1010 ERR -LNGS rotational noiseGINGERino@LNGS -Stability of geometry by active control GP @Pisa -Monitor of relative angle GEMS @Padova GINGER ExternalMetrological System GEMS Basedon the interferometric method developped for the NASA mission SIM light. Picometer accuracyrequired. GINGER(ino) LNGS GINGERino is a ring laser with 3.6 m side,installed inside the LNGS laboratory for Geodesy, Geophysics measurements and to test if LNGS is a suitable location for GINGER GP2: control geometry Pisa Inject the 2 Fabry-Perot cavities along diagonals with external laser andmeasure the 2 absolute lengths. Set them equal by controlling mirrorspositions by means of the 6 PZT andsearch for a saddle point of perimeter Angela Di Virgilio, December 15 2015
GINGERino Scale Factor (rad/s)/Hz Perimeter 14.4 m (Gross Ring: 16m) FSR 20.8MHz Sagnac Frequency 280Hz, compatible with Earth Rotation Rate and latitude of LNGS Ringdown time Ith Run ms, Q ~ 1012 Ringdown time IInd Run 140 ms, Q ~6 1011 Angela Di Virgilio,December Angela Di Virgilio, December 15 2015
GINGERino Xenon1T Angela Di Virgilio,December Angela Di Virgilio, December 15 2015
GINGERino, October 2014, the granite monument is in place, inside the box Angela Di Virgilio,December Sagnac Signal 280Hz has been observed
DECEMBER 2014 Several Improvements have been realizes and installed in order to stabilize mechanically the discharge and to isolate the instrument from the ground floor Let us take a look at the signals
Sensitivity of the ring-laser and Allan Deviation First Backscattering subtraction exercise Confrontation with G Wettzell Tiltmeter Seismometers and the problem of the pressure Angela Di Virgilio,December Angela Di Virgilio, December 15 2015
First Run 0.1 nrad/s/sqrt(Hz) Rasel Phys. Rev. Lett. 114, Published 9 February 2015, with cold atoms 120 nrad/s/sqrt(Hz) P.Bouyer et al. 3. nrad/s 800s integ. time no vibration control: 40 nrad/s 2000s integ. time ARXIV: v2 27 October 2015 1997: Gustavson et al PRL:2. nrad/s/sqrt(Hz) 2000: nrad/s/sqrt(Hz) Angela Di Virgilio,December Typical Allan Deviation
Selected data, low backscattering Typical, 8 hours Angela Di Virgilio,December The first backscattering subtraction
A first exercise for the off-line subtraction of the backscattering Data correlated to the backscattering channel for more than 95% 13% of the data have been used for the Allan deviation Angela Di Virgilio,December ~ rad/s Relative precision ~ rad/s Time (s) Improve: gain monitoring for the subtraction Short term stability The off-line subtraction will be repeated with more (new) calibrated data G-Pisa minimum of the Allan Deviation
GINGERino spring 2015 Angela Di Virgilio, December 15 2015
GINGERino 2016 plan Improve the mirrors: goal 1ms ringdown time(spring 2016) A new set of mirrors will be produced as soon as the substrates will beready Substrates with surfaces machined top of the art have been recentlyordered (roughness < 0.5A) Reflectivity > %, T > 0.5 ppm, losses ~ few ppm Improve the discharge support Perimeter control will be set up after the installation of thenew mirrors 1 month of duty cycle Angela Di Virgilio,December Heterolithic Ring Laser requires Geometry Control
G Wettzell cannot be extended 3D. Moreover itwould be very difficult to assemble undergrounda similar structure Active Control of the Geometry of the Ring 1 part requires: Suitable control strategy Enough error signals actuators Angela Di Virgilio,December Angela Di Virgilio, December 15 2015
The Basic original Idea: Control the two diagonals Angela Di Virgilio,December Angela Di Virgilio, December 15 2015
.if the ring is a regular poligon Angela Di Virgilio,December Angela Di Virgilio, December 15 2015
GP2 Geometry Active Control Angela Di Virgilio,December Angela Di Virgilio, December 15 2015
Optical setup Angela Di Virgilio,December Angela Di Virgilio, December 15 2015
Diagonal cavities injection Angela Di Virgilio,December Angela Di Virgilio, December 15 2015
Summary of GP2 Fabry-Perot along the diagonals are resonating RingLaser ON Technique to stabilize the diagonals (absolutemeasurement) already tested on table topexperiment improvements on the laboratory are necessary(improve thermal stabilization) test of the geometry control of GP2 Angela Di Virgilio,December Angela Di Virgilio, December 15 2015
GEMSGINGER External Metrology A prototype similar to the laser gage developed for SIM Light JPL is under development in Padua Angela Di Virgilio,December Italian and International Collaboration
J. Belfi, F. Bosi,A. Di Virgilio INFN Sez. di Pisa, Pisa, Italy A. Ortolan Laboratori Nazionali di Legnaro, INFN Legnaro (Padova), Italy A. Porzio, C. Altucci,G. Velotta University of Naples, and INFN, Naples, Italy A. Beghi, D. Cuccato, A. Donazzan, G. Naletto, M. Pelizzo University of Padova and INFN, Padua Italy M. Allegrini, N. Beverini, G. Carelli, E. Maccioni, A. Simonelli University of Pisa, Pisa, Italy M. L. Ruggiero, A. Tartaglia Polit. of Torino and INFN, Turin, Italy G. Saccorotti, G. De Luca, INGV, Italy K. U. Schreiber Technische Universitaet Muenchen H. Igel Department of Earth Science of LMU J-P. R. Wells, Department of Physics and Astronomy, University of Canterbury, New Zealand MOU The participants of the collaboration are listed in this slide, together with the institutions involved. The financial support for the R&D comes from the commission II of INFN. There is an MOU signed between INFN and the tree non italianinstitutions Angela Di Virgilio,December Angela Di Virgilio, December 15 2015
CONCLUSIONS Very High sensitivity RingLasers are finally reliableinstruments. Duty cycle and bandwidth are extremely high, and theycan be efficiently used as Observatory for geophysicsand geodesy Sensitivity is so high that with a factor 10 improvement thegravitomagnetism of the Earth (LenseThirring effect) canbe measure directly and locally in an Earth Basedexperiment GINGER has been designed for this purpose The basic pieces of GINGER are already in place An international collaboration is growing around GINGER Angela Di Virgilio,December GINGER ESSENTIAL BIBLIOGRAPHY
Bosi, F.; Cella, G.; Di Virgilio, A.; Ortolan, A.; Porzio, A.; Solimeno, S.; Cerdonio, M.; Zendri, J.P.; Allegrini, M.; Belfi, J.; Beverini, N.; Bouhadef, B.; Carelli, G.; Ferrante, I.; Maccioni, E.;Passaquieti, R.; Stefani, F.; Ruggiero, M. L.; Tartaglia, A.; Schreiber, K. U.; Gebauer, A.; Wells,J-P. R.Measuring gravitomagnetic effects by a multi-ring-laser gyroscopePHYSICALREVIEW D Di Virgilio, Angela;et al.A ring lasers array for fundamental physicsCOMPTES RENDUSPHYSIQUE Santagata, R.et al. Optimization of the geometrical stability in square ring laser gyroscopesCLASSICAL AND QUANTUM GRAVITY Belfi, J. et al. Interferometric length metrology for the dimensional control of ultra-stable ring lasergyroscopes CLASSICAL AND QUANTUM GRAVITY Cuccato, D. et al. Controlling the non-linear intracavity dynamics of large He-Ne laser gyroscopesMETROLOGIA Belfi, Jacopo et al. Horizontal rotation signals detected by "G-Pisa" ring laser for the M-w=9.0, March2011, Japan earthquakeJOURNAL OF SEISMOLOGY 16 4 SI GINGER is interdisciplinary GR + Geodesy (G data are part of IERS) + Geophysics (ROMY) Angela Di Virgilio,December