High-Accuracy Ring Laser Gyroscopes: Earth Rotation Rate and Relativistic Effects

摘要

TheGrossRingGisasquareringlasergyroscope,builtasamonolithicZerodurstructurewith4mlengthonallsides.IthasdemonstratedthatalargeringlaserprovidesasensitivityhighenoughtomeasuretherotationalrateoftheEarthwithahighprecisionofΔΩE10-8.Itispossibletoshowthatfurtherimprovementinaccuracycouldallowtheobservationofthemetricframedragging,producedbytheEarthrotatingmass(Lense-Thirringeffect),aspredictedbyGeneralRelativity.Furthermore,itcanprovidealocalmeasurementoftheEarthrotationalratewithasensitivityneartothatprovidedbytheinternationalsystemIERS.TheGINGERprojectisintendingtotakethislevelofsensitivityfurtherandtoimprovetheaccuracyandthelong-termstability.AmonolithicstructuresimilartotheGringlaserisnotavailableforGINGER.Thereforethepreliminarygoalisthedemonstrationofthefeasibilityofalargergyroscopestructure,wherethemechanicalstabilityisobtainedthroughanactivecontrolofthegeometry.Aprototypemoderatesizegyroscope(GP-2)hasbeensetupinPisainordertotestthisactivecontroloftheringgeometry,whileasecondstructure(GINGERino)hasbeeninstalledinsidetheGranSassoundergroundlaboratoryinordertoinvestigatethepropertiesofadeepundergroundlaboratoryinviewofaninstallationofafutureGINGERapparatus.Thepreliminarydataonthesetwolatterinstrumentsarepresented...