Toward a 3rd generation European Gravitational Wave Observatory Dual R&D: presented by Massimo Cerdonio INFN Section and Department of Physics Padova how

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



M = 2.3 tL = 3m

Resonant bar detectors were designed in late 80’s



• 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:



When applied to AURIGA:

Shh

• 1st run (97 - 99)

• 2th run (04 - ...)



• 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:



• 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)



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



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



Mode selection strategy

2-D Quadrupolar filter:X=X1 +X3 –X2 –X4

Capacitive transducer design

Large interrogation regions

Geometrically basedmode 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 schemeF. Marin et.al, Phys. Lett. A 309, 15 (2003)



Mo Dual 16.4 ton height 3.0m 0.94m

SiC Dual 62.2 ton height 3.0m 2.9m

Q/T=2x108 K-1

M. Bonaldi et al. Phys. Rev. D 68 102004 (2003)

Evaluated sensitivity (SQL)



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 ( vs2-3 ) Al 5056 Mo, SiC, Sapph.

(50 x)

Readout system:

Test masses:

5x10 -20 m 5x10-22 (100x)



• 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



Leverages for optical and capacitive readouts

Capacitive readout

Electric Field

Optical readout

3 Joints

Fabry-Perotmirrors

4 paired joints

Gain=10

90 mm



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=1.5 107 N/m

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

Optimized by a parametric software



Mechanical gain measurements

Direct Gain = Δy/ Δx

Frequency shift

Leverage

behavior



Next step: measure the thermal noise

ANSYS Prediction by using Fluctuation Dissipation Theorem

T=300 K, Q=104, Al 7075, w0 =365 m

Leverage behavior: scaling with 1/α

1/α



Progress towards a wide area optical readoutUsual cm-long cavities have small spot size (1mm)

→ higher order acoustic modes of the real system contribute to the noise

M1

M2

M3M4

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: constantrelative freq. noise due to Brownian noise 1/ Nrelative freq. noise due to rad pressure noise 1/N2

+ spatial correlation effects

effective increase of spot size



Progress towards an high sensitivity capacitive readout• SQUID amplifiers with sensitivity approaching the quantum

limitNew 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



Apparatus for High voltage breakdown study

• Bias voltage in the 100 MV/m range

M. Bonaldi, F. Penasa,

Trento Phys. Dept.

Goal: 108 V/m

Achieved: 107 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



Test mass material characterization

Low temperature measurements of the Q factor of ceramic materials

J.P. Zendri,

Laboratori Legnaro



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

TimelineFeasibility study: 2005-2007Detailed design (?): 2008-2009

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Toward a 3rd generation European Gravitational Wave Observatory Dual R&D: presented by Massimo Cerdonio INFN Section and Department of Physics Padova how