Viviana Fafone INFN - LNF

1. Future plans forresonant detectors Viviana Fafone INFN - LNF www.lnf.infn.it/esperimenti/rog

2. Leiden CERN RE 5 MiniGrail LNF INFN LNL INFN

3. New devices and methods are now available Readout systems: • Superconductive amplifier sensitivity improved by a factor of 100 • Optical and parametric readout for acoustic detectors FEM analysis: • Used to improve suspension system design • Wideband readout design Test masses: • Methods to develop large masses (100 ton) • New high cross section materials

4. 1998 2001 2003 AURIGA 10-20 2003 1999 EXPLORER WIDENING THE BAND… NAUTILUS 10-20 2001 880 950

5. The duty cycle is limited mainly by cryogenic operations and for most of the time is about 90% • The apparata show constant performances. • The data are not affected by human activity in the lab. 3·10-19 NAUTILUS DATA TAKING DURING 2005 No veto applied

6. Noise budget is well understood Present Status of EXPLORER reference signal • Present limit from amplifier noise Teff~ 2mK h ~ 3 10-19

7. Present Status of AURIGA one-sided Shh Very good agreement with noise predictions all these noise sources will scale with temperature

8. We need to improve the peak spectral sensitivity Increase M : large and/or multimode detectors Reduce T/Q : ultracryogenics. Low-loss materials We need to increase the bandwidth Increase the coupling of the e.m. transducer Reduce the noise temperature of the amplifier (double SQUIDs) To improve sensitivity:

9. M3 - R. Parodi INFN Genova Sh for AURIGA @ 0.2K, capacitive transducer Sh for NAUTILUS @ 0.1K, parametric transducer (m = 1 kg) Teff ≈ 6 mK, sensitivity < 1·10-21 /√Hz over about 50 Hz.

10. TOWARDS MORE POWERFUL AND SENSITIVE ACOUSTIC DETECTORS

11. GWIC Scenario for future detectors in the resonant-mass field • “…This paper suggests the following scenario for future detector development in this field: • In the medium-term, the realization of a spherical detector, to beproposed now to the funding agencies, • In the longer term, research toward wideband resonant detectors using Dual Detection techniques.

12. GWIC Scenario for future detectors in the resonant-mass field A spherical detector can make use of the state of the art readout technology, developed for the bars and for MiniGrail, profiting from a larger mass and from the omnidirectional nature of the spherical detectors.  Such a detector could have a sensitivity competitive with VIRGO and LIGO in the 1 kHz region. And since it allows full sky coverage during all observation time, and determination of the source direction, it can have an important role in a coordinated coincidence search. Since the principles of operation and technology are well understood, a funding proposal could be prepared soon. Research and development work on wideband resonant detectors using Dual Detection techniques is valuable because it offers the potential for a detector having unprecedented sensitivity in the band 1 to 7 kHz. …”

13. sensitivities in the 2006 - 2012 prospective The sphere has a quality factor due to the isotropy not shown in the plot GEO adv LIGO/adv VIRGO

14. Properties of spherical detectors: a summary… Thanks its five quadrupolar modes, equally sensitive to gravitational waves: • Reconstruction of the metric tensor (polarization states and arrival direction) • Omnidirectionality • Multi-frequency capability • Testing different metric theories of gravity

15. The experimental situation • MiniGRAIL • Fast cooling of large masses (60 mK already achieved) - Investigation of new material (CuAl 6%) - Q’s, effect of the suspension and trx fabrication - Coupling of transducers with the sphere

16. The experimental situation • 2. TIGA experiments • TIGA arrangements • TIGA experiments

17. To allow the detection and identification of GW signals it is useful to complement the IFO network with an advanced • resonant-mass observatory • Added value • Duty cycle • Sky coverage • Instruments based on different principles Strategy: Realization of a Resonant-mass GW Observatory Complementing the IFO Network VIRGO - SFERA 2m first hybrid observatory

18. The short term proposed detector: SFERA 2 m dia, CuAl M = 33 tons f1 = 1.0 kHz f2 = 1.9 kHz The Collaboration INFN (I) University of Geneva (CH) University of Leiden (NL) Cost ~ 3 MEURO

19. Pulse tubes 3He pumping tube 80 K radiation shield 4 K radiation shield Joule-Thomson heat exchanger 700 mK radiation shield 50 mK radiation shield still Continuous heat exchanger 50 mK plate Sintered heat exchanger Mixing chamber C2 - G. Frossati, Leiden

20. M6 - G. Mazzitelli, INFN - LNF At the final sensitivity an underground location will be probably necessary, to avoid cosmic ray noise

21. SFERA If funded in January 2006 Assembling and tests during 2006-2007 Commissioning at the beginning of 2008 Science Run at the beginning of 2009

22. Dual R&D: a full open bandwidth acoustic detector INFN and Dept of Physics: Firenze – Legnaro - Padova – Trento - Urbino DUAL detector is based on new ideas 1 – Wideband transducer:read displacement signal between two massive resonator - M. Cerdonio et al. Phys. Rev. Lett. 87 031101 (2001) Avoid resonant bandwidh limit and thermal noise contribution by the resonant transducer 2 - Selective readout:only GW sensitive normal modes must be measured - M. Bonaldi et al. Phys. Rev. D 68 102004 (2003) Reduce overall thermal noise by rejecting the contribution of not useful modes

23. Dual: Main Concept The outer resonator is driven above resonance The inner resonator is driven below frequency πPhase difference Measurement of differential deformations of two nested resonators 5.0 kHz Intermediate GW broadband

24. Mode selection strategy Geometrically based mode selection Large interrogation regions Capacitive transducer design Reject high frequency resonant modes which do not carry any GW signal Bandwidth free from acoustic modes not sensitive to GW 2-D Quadrupolar filter: X=X1 +X3 –X2 –X4 Also FFP optical scheme F. Marin et.al, Phys. Lett. A 309, 15 (2003)

25. Evaluated sensitivity (SQL) M. Bonaldi et al. Phys. Rev. D 68 102004 (2003) Mo Dual 16.4 ton height 3.0m 0.94m SiC Dual 62.2 ton height 3.0m 2.9m Antenna pattern: like 2 IFOs colocated and rotated by 45° Q/T=2x108 K-1

26. DUAL is based on a deep revision of the resonant detector design AND a challenging R&D on readout systems (Some topics are tackled within STREGA) Timeline R&D: 2005-2008 Detailed design: 2008-2009

27. T3 - P. Falferi, IFN Trento Selective readout system for DUAL: mechanical amplification stage • Broadband amplification (5.0 kHz) • Displacement gain factor about 10 • Negligible intrinsic thermal noise • Compliance Leverage type amplifier Optic readout Capacitive readout Fabry-Perot mirrors Electric Field

28. M3 M1 M4 D M2 T3 - P. Falferi INFN Firenze Progress towards a wide area optical readout Usual cm-long cavities have small spot size (1mm) →higher order acoustic modes of the real system contribute to the noise To average out the noise, we need a spot size > 10cm !!!! Folded Fabry-Perot: FFP Phys. Lett. A 309, 15 (2003) effective increase of spot size relative shot noise limited displacement sensitivity: constant relative freq. noise due to Brownian noise 1/ N relative freq. noise due to rad pressure noise  1/N2

29. Bias voltage in the 100 MV/m range Goal: 108 V/m Achieved: 107 V/m - surface finishing effect - electrodes conditioning procedure - effect of dielectric films Apparatus for High voltage breakdown study Two axis adjustment Measurement of V.B. of aluminum polished surfaces of cylindrical samples Linear vertical stage M2 - J.P. Zendri, IFN Trento

30. Test mass material characterization Low temperature measurements of the Q factor of ceramic materials M2 - J.P. Zendri, INFN Legnaro

31. The End