Dual R&D:

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

2. M = 2.3 t L = 3m Resonant bar detectors were designed in late 80’s

3. New devices and methods are now available Readout systems: • Superconductive amplifier sensitivity improved by a factor of 100 • Optical 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. When applied to AURIGA: • Shh • 1st run (97 - 99) • 2th run (04 - ...)

5. Readout systems: • 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

6. FEM analysis: • Suspension system design - M. Bignotto, Rev. Sci. Instrum. 76, 084502 (2005) • 3 - mode readout (100 Hz BW) • L.Baggio et al, Phys. Rev. Lett. 94, 241101 (2005)

7. 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) 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

8. 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

9. 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)

10. Evaluated sensitivity (SQL) M. Bonaldi et al. Phys. Rev. D 68 102004 (2003) Q/T=2x108 K-1 Mo Dual 16.4 ton height 3.0m 0.94m SiC Dual 62.2 ton height 3.0m 2.9m

11. Dual R&D : 3 main research topics Current technology DUAL requirements Readout system: • mechanical amplification resonant not resonant • 15 x 10x • 100 Hz BW 4 kHz BW • displacement sensitivity • and wide sensing area 5x10 -20 m 5x10-22 (100x) Test masses: • underground operation not necessary define requirements • high cross section ( vs2-3 ) Al 5056 Mo, SiC, Sapph. (50 x) Detector design • seismic noise control external passive + embedded active

12. Readout system for DUAL: mechanical amplification stage • Broadband amplification up to 5.0 kHz • Displacement gain factor about 10 • Negligible intrinsic thermal noise • Compliance H.J. Paik, proceedings First AMALDI Conference (1995) Leverage type amplifier

13. Leverages for optical and capacitive readouts Optical readout Capacitive readout Fabry-Perot mirrors Electric Field Gain=10 4 paired joints 3 Joints 90 mm

14. First experiment: leverage with optical readout A test-oscillator play the role of a GW detector test mass: Optimized by a parametric software • Test-Oscillator: • Material Al 7075 • First Longitudinal mode • at 1800 Hz • Stiffness K=3.5 108 N/m • Effective mass M=5.6 kg Rigid Lever • Material Al 7075 • Geometrical Gain factor 1/=10 • First Longitudinal mode at 2100 Hz • Stiffness K=1.5 107 N/m

15. Mechanical gain measurements Direct Gain = Δy/ Δx Leverage behavior Frequency shift

16. Next step: measure the thermal noise ANSYS Prediction by using Fluctuation Dissipation Theorem Leverage behavior: scaling with 1/α 1/α T=300 K, Q=104, Al 7075, w0 =365 m

17. M3 M1 M4 D M2 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 + spatial correlation effects

18. 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. 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 M. Bonaldi, F. Penasa, Trento Phys. Dept.

20. Test mass material characterization Low temperature measurements of the Q factor of ceramic materials J.P. Zendri, Laboratori Legnaro

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