1. Toward a 3rd generation European Gravitational Wave Observatory Dual R&D: presented by Massimo Cerdonio INFN Section and Department of Physics Padova how to obtain the best from acoustic detectors the DUAL R&D collaboration: Firenze, Legnaro, Padova, Trento, Urbino talk prepared by Michele Bonaldi IFN-CNR and INFN, Trento

2. Toward a 3rd generation European Gravitational Wave Observatory M = 2.3 t L = 3m Resonant bar detectors were designed in late 80’s

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

4. Toward a 3rd generation European Gravitational Wave Observatory When applied to AURIGA: Shh 1st run (97 - 99) 2th run (04 -...)

5. Toward a 3rd generation European Gravitational Wave Observatory Superconductive amplifier sensitivity improved by a factor of 100 P. Falferi et al., Appl. Phys. Lett. 82, 931 (2003) Optical readout available for acoustic detectors L. Conti et al., J. Appl. Phys. 93 (2003) 3589 Readout systems:

6. Toward a 3rd generation European Gravitational Wave Observatory Suspension system design - M. Bignotto, Rev. Sci. Instrum. 76, 084502 (2005) FEM analysis: 3 - mode readout (100 Hz BW) L.Baggio et al, Phys. Rev. Lett. 94, 241101 (2005)

7. Toward a 3rd generation European Gravitational Wave Observatory Technical improvement is not enough! 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) 2 - Selective readout: only GW sensitive normal modes must be measured - M. Bonaldi et al. Phys. Rev. D 68 102004 (2003) Avoid resonant bandwidh limit and thermal noise contribution by the resonant transducer Reduce overall thermal noise by rejecting the contribution of not useful modes

8. Toward a 3rd generation European Gravitational Wave Observatory Measurement of differential deformations of two nested resonators Intermediate GW broadband Dual: Main Concept 5.0 kHz π Phase difference The inner resonator is driven below frequency The outer resonator is driven above resonance

9. Toward a 3rd generation European Gravitational Wave Observatory Mode selection strategy 2-D Quadrupolar filter: X=X 1 +X 3 –X 2 –X 4 Capacitive transducer design Large interrogation regions Geometrically based mode selection Reject high frequency resonant modes which do not carry any GW signal Bandwidth free from acoustic modes not sensitive to GW Also FFP optical scheme F. Marin et.al, Phys. Lett. A 309, 15 (2003)

10. Toward a 3rd generation European Gravitational Wave Observatory Mo Dual 16.4 ton height 3.0m 0.94m SiC Dual 62.2 ton height 3.0m 2.9m Q/T=2x10 8 K -1 M. Bonaldi et al. Phys. Rev. D 68 102004 (2003) Evaluated sensitivity (SQL)

11. Toward a 3rd generation European Gravitational Wave Observatory Dual R&D : 3 main research topics Detector design seismic noise control external passive + embedded active displacement sensitivity and wide sensing area underground operation not necessary define requirements mechanical amplification resonant not resonant 15 x 10x 100 Hz BW 4 kHz BW Current technology DUAL requirements high cross section (  v s 2-3 ) Al 5056 Mo, SiC, Sapph. (50 x) Readout system: Test masses: 5x10 -20 m 5x10 -22 (100x)

12. Toward a 3rd generation European Gravitational Wave Observatory Broadband amplification up to 5.0 kHz Displacement gain factor about 10 Negligible intrinsic thermal noise Compliance Leverage type amplifier H.J. Paik, proceedings First AMALDI Conference (1995) Readout system for DUAL: mechanical amplification stage

13. Toward a 3rd generation European Gravitational Wave Observatory Leverages for optical and capacitive readouts Capacitive readout Electric Field Optical readout 3 Joints Fabry-Perot mirrors 4 paired joints Gain= 10 90 mm

14. Toward a 3rd generation European Gravitational Wave Observatory A test-oscillator play the role of a GW detector test mass: First experiment: leverage with optical readout Material Al 7075 Geometrical Gain factor 1/  =10 First Longitudinal mode at 2100 Hz Stiffness K=1.5  10 7 N/m Test-Oscillator: Material Al 7075 First Longitudinal mode at 1800 Hz Stiffness K=3.5  10 8 N/m Effective mass M=5.6 kg Rigid Lever Optimized by a parametric software

15. Toward a 3rd generation European Gravitational Wave Observatory Mechanical gain measurements Direct Gain = Δy/ Δx Frequency shift Leverage behavior

16. Toward a 3rd generation European Gravitational Wave Observatory Next step: measure the thermal noise ANSYS Prediction by using Fluctuation Dissipation Theorem T=300 K, Q=10 4, Al 7075, w 0 =365  m Leverage behavior: scaling with 1/ α 1/α

17. Toward a 3rd generation European Gravitational Wave Observatory 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 M1 M2 M3 M4 D Phys. Lett. A 309, 15 (2003) To average out the noise, we need a spot size > 10 cm !!!! Folded Fabry-Perot: FFP 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/N 2 + spatial correlation effects effective increase of spot size

18. Toward a 3rd generation European Gravitational Wave Observatory Progress towards an high sensitivity capacitive readout SQUID amplifiers with sensitivity approaching the quantum limit New SQUID chip design for: - improvement of the energy resolution - reduction of the 1/f noise contribution - suppression of the "hot electron effect" - reduction of the squid losses

19. Toward a 3rd generation European Gravitational Wave Observatory Apparatus for High voltage breakdown study Bias voltage in the 100 MV/m range M. Bonaldi, F. Penasa, Trento Phys. Dept. Goal: 10 8 V/m Achieved: 10 7 V/m Measurement of V.B. of aluminum polished surfaces of cylindrical samples Two axis adjustment - surface finishing effect - electrodes conditioning procedure - effect of dielectric films Linear vertical stage

20. Toward a 3rd generation European Gravitational Wave Observatory Test mass material characterization Low temperature measurements of the Q factor of ceramic materials J.P. Zendri, Laboratori Legnaro

21. Toward a 3rd generation European Gravitational Wave Observatory a deep revision of the resonant detector design The reserch is currently funded by: EGO (R&D program) CNR (QL-READOUT) INFN (DUAL R&D) EC (STREGA) DUAL is based on AND a challenging R&D on readout systems Timeline Feasibility study: 2005-2007 Detailed design (?): 2008-2009