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Design study for 3rd generation interferometers Work Package 1 Site Identification Jo van den Brand e-mail: [email protected] Third generation detector Two order of magnitude compared to initial Virgo Underground site Multiple interferometers: – 3 Interferometers; triangular configuration? – 10 km long – 2 polarization + redundancy Design study part of ILIAS & FP7 Construction: 2010-16 ? LISA Rüdiger, ‘85 Scientific Production: fundamental physics in the early universe - Inflation, phasefor transitions, topological defects justification 3rd generation ITF - String-inspired cosmology, brane-world scenarios Spectrum slope, peaks give masses of key particles & energies of transitions A TeV phase transition would have left radiation in 3G band Primordial gravitational waves LISA Introduction Features of 3rd generation ITF • Sensitivity below 10-24 m/sqrt(Hz) • Ultra-low frequency cut-off • Vibration isolation • Sensitive in range 0.1 – 10 Hz • Multiple sites for signal correlation • Advanced optical schemes (squeezed light) • Cryogenic optics • Underground sites • LISA 10 kilometer arms Ultra Low Frequency: 1Hz 1st - 2nd generation 10 Hz cutoff 3rd generation 1 Hz cutoff One more decade at low frequency LISA Isolation requirements Required isolation @1 Hz: at least 1010 with ground noise. LISA Ultra soft vibration isolation – Long pendulums (50, 100 m) – Very good thermal stabilization Active platforms – Very low noise sensors – Very good thermal stabilization – Very low tilt noise Very quiet site Site identification process Even pressure fluctuations due to weather are a relevant source of gravity gradient noise [11]. acceleration ( g / sqrt ( Hz ) ) 10 10 10 10 10 10 component 2 component 1 -4 -5 -6 -7 -8 -9 10 -5 -4 10 10 frequency ( Hz ) Seismic measurements at LNGS LISA -3 10 -2 V. N. Rudenko, A. V. Serdobolski, K. Tsubono, “Atmospheric gravity perturbations measured by a ground-based interferometer with suspended mirrors”, Class. And Quant. Grav., vol. 20, pp. 317-329. LIGO Site selection criteria LISA LIGO Site evaluation criteria LISA LIGO Site evaluation criteria LISA Seismic noise attenuation LISA Not only seismic noise… Direct action of wind on buildings Strong correlation between mirror motion and wind speed at f < 0.1 Hz Detector operation more difficult in windy days, duty cycle affected Even more difficult in the future, with high finesse cavities LISA Underground interferometers LISM: 20 m Fabry-Perot interferometer, R&D for LCGT, moved from Mitaka (ground based) to Kamioka (underground) Seismic noise much lower: LISA 102 overall gain 103 at 4 Hz Interferometer operation becomes much easier underground. Noise reduced by orders of magnitude Displacement spectrum m/RHz S.Kawamura, ‘02 LISA LISM at Mitaka LISM at Kamioka limit by isolation system Hz Large-scale Cryogenic Gravitational-wave Telescope: LCGT LISA CLIO – Prototype for LCGT LISA LISM in Kamioka LISA ILC, NLC, Tesla, VLHC, Muon Source – Site requirements LISA ILC, NLC, Tesla, VLHC, Muon Source – Site requirements LISA Isolation shortcircuit Newtonian noise h ( f ) const. G0 x0 ( f ) H( f ) SEISMIC NOISE Figure: M.Lorenzini LISA Seismically generated Newtonian noise LISA Newtonian noise estimate Cella-Cuoco, 98 LISA NN reduction Courtesy: G.Cella Surface waves Compression waves Surface waves give the main contribution to newtonian noise Surface movement dominates the bulk compression effect Surface waves die exponentially with depth: GO UNDERGROUND! LISA NN reduction in caves 102 less seismic noise x 104 geometrical reduction 106 overall reduction (far from surface) Reduction factor (Compression waves not included) Spherical Cave G.Cella NN reduction of 104 @5 Hz with a 20 m radius cave 5 Hz 10 Hz 20 Hz 40 Hz Cave radius [m] LISA 1st generation (a) 3 Generation nd 2 generation (b) LCGT (c) advanced LIGO rd 3 generation (d) advanced Virgo -19 10 rd -20 10 h(f) [1/sqrt(Hz)] -21 10 (g) (e) LIGO (f) Virgo (g) GEO600 (f) -22 10 (e) -23 10 (a) (d) (b) Ground surface (c) -24 10 Underground -25 10 1 10 100 Frequency [Hz] LISA 1000 10000 NN from compression waves In a spherical cave NN is reduced as 1/R3 MAKE LARGE CAVERN Beam direction is more important. ELLIPSOIDAL? Credit: R. De Salvo LISA A possible design Upper experimental hall 50-100 m well to accomodate long suspension for low frequency goal Ellipsoidal/spherical cave for newtonian noise reduction 10 km tunnel LISA Credit: R.De Salvo Site identification process Gran Sasso Salt mines LISA Complementarity with LIGO, VIRGO and LISA Vast range in wavelength (8 orders of magnitude) Rotating Neutron Stars LISA 3rd ITF LIGO/VIRGO Frequency [Hz] LISA Summary LISA Expected features of 3rd generation ITF – Triangular configuration – Advanced optical schemes – Low-frequency isolation and suspension – Cryogenic optics – Multiple underground sites Design study – Develop preliminary ideas – Define site identification process