1. Design study for 3rd generation interferometers Work Package 1 Site Identification Jo van den Brand e-mail: jo@nikhef.nl

2. 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: 2010-16 ?

3. 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

4. LISA Introduction Features of 3 rd 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 10 kilometer arms

5. 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

6. LISA Isolation requirements Required isolation @1 Hz: at least 10 10 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

7. 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. 317-329. Seismic measurements at LNGS

8. LISA LIGO Site selection criteria

9. LISA LIGO Site evaluation criteria

10. LISA LIGO Site evaluation criteria

11. LISA Seismic noise attenuation

12. 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

13. 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

14. 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

15. LISA Large-scale Cryogenic Gravitational-wave Telescope: LCGT

16. LISA CLIO – Prototype for LCGT

17. LISA LISM in Kamioka

18. LISA ILC, NLC, Tesla, VLHC, Muon Source – Site requirements

19. LISA ILC, NLC, Tesla, VLHC, Muon Source – Site requirements

20. LISA Isolation shortcircuit Newtonian noise Figure: M.Lorenzini SEISMIC NOISE

21. LISA Seismically generated Newtonian noise

22. LISA Newtonian noise estimate Cella-Cuoco, 98

23. 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!

24. 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 4 @5 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

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

26. 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

27. LISA A possible design Upper experimental hall Credit: R.De Salvo 50-100 m well to accomodate long suspension for low frequency goal Ellipsoidal/spherical cave for newtonian noise reduction 10 km tunnel

28. LISA Site identification process Gran Sasso Salt mines

29. 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

30. 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