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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 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
Toward a 3rd generation European
Gravitational Wave Observatory
M = 2.3 tL = 3m
Resonant bar detectors were designed in late 80’s
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:
Toward a 3rd generation European
Gravitational Wave Observatory
When applied to AURIGA:
Shh
• 1st run (97 - 99)
• 2th run (04 - ...)
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:
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)
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
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
Toward a 3rd generation European
Gravitational Wave Observatory
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)
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=2x108 K-1
M. Bonaldi et al. Phys. Rev. D 68 102004 (2003)
Evaluated sensitivity (SQL)
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 ( vs2-3 ) Al 5056 Mo, SiC, Sapph.
(50 x)
Readout system:
Test masses:
5x10 -20 m 5x10-22 (100x)
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
Toward a 3rd generation European
Gravitational Wave Observatory
Leverages for optical and capacitive readouts
Capacitive readout
Electric Field
Optical readout
3 Joints
Fabry-Perotmirrors
4 paired joints
Gain=10
90 mm
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=1.5 107 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
Toward a 3rd generation European
Gravitational Wave Observatory
Mechanical gain measurements
Direct Gain = Δy/ Δx
Frequency shift
Leverage
behavior
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=104, Al 7075, w0 =365 m
Leverage behavior: scaling with 1/α
1/α
Toward a 3rd generation European
Gravitational Wave Observatory
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
Toward a 3rd generation European
Gravitational Wave Observatory
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
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: 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
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
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
TimelineFeasibility study: 2005-2007Detailed design (?): 2008-2009