Design study for 3rd generation interferometers Work Package 1 Site Identification Jo van den Brand

LISA Third generation detector Rüdiger, ‘85  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: ?

LISA Scientific justification for 3 rd generation ITF Primordial gravitational waves Production: fundamental physics in the early universe - Inflation, phase transitions, topological defects - 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

LISA Introduction Features of 3 rd generation ITF Sensitivity below 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 10 kilometer arms

LISA Ultra Low Frequency: 1Hz 3 rd generation 1 Hz cutoff 1 st - 2 nd generation 10 Hz cutoff One more decade at low frequency

LISA Isolation requirements Required Hz: at least with ground noise.  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

LISA Site identification process Even pressure fluctuations due to weather are a relevant source of gravity gradient noise [11]. 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 Seismic measurements at LNGS

LISA 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: 10 2 overall gain 10 3 at 4 Hz

LISA LISM at Mitaka LISM at Kamioka limit by isolation system Interferometer operation becomes much easier underground. Noise reduced by orders of magnitude S.Kawamura, ‘02 Hz Displacement spectrum m/RHz

LISA 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 Figure: M.Lorenzini SEISMIC NOISE

LISA Seismically generated Newtonian noise

LISA Newtonian noise estimate Cella-Cuoco, 98

LISA NN reduction  Surface waves give the main contribution to newtonian noise  Surface movement dominates the bulk compression effect Surface waves Compression waves Courtesy: G.Cella Surface waves die exponentially with depth: GO UNDERGROUND!

LISA NN reduction in caves Reduction factor Cave radius [m] Spherical Cave G.Cella 5 Hz 10 Hz 20 Hz 40 Hz NN reduction of 10 Hz with a 20 m radius cave 10 6 overall reduction (far from surface) (Compression waves not included) 10 2 less seismic noise x 10 4 geometrical reduction

LISA 1 st generation 2 nd generation 3 rd generation Newtonian noise Ground surface Underground

LISA NN from compression waves  In a spherical cave NN is reduced as  1/R 3  Beam direction is more important. Credit: R. De Salvo ELLIPSOIDAL? MAKE LARGE CAVERN

LISA A possible design Upper experimental hall Credit: R.De Salvo m well to accomodate long suspension for low frequency goal Ellipsoidal/spherical cave for newtonian noise reduction 10 km tunnel

LISA Site identification process Gran Sasso Salt mines

LISA Complementarity with LIGO, VIRGO and LISA Rotating Neutron Stars Vast range in wavelength (8 orders of magnitude) LIGO/VIRGO LISA Frequency [Hz] 3 rd ITF

LISA Summary  Expected features of 3 rd 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