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アウリガ. The AURIGA experiment: updates and prospects. バッジョ ルーチョ. BAGGIO Lucio ICRR on behalf of AURIGA collaboration. The AURIGA detector re-started data taking in Dec 2003, after 4 years of research and developement, in order to improve the sensitivity.

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The AURIGA experiment: updates and prospects

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The AURIGA experiment: updates and prospects

バッジョ ルーチョ



on behalf of AURIGA collaboration

The AURIGA detector re-started data taking in Dec 2003, after 4 years of research and developement, in order to improve the sensitivity.

A brief overview of the results during last year will be given.

Present international collaborations and future prospects will be reviewed.

[email protected]

Topics of this presentation

The AURIGA experiment: run 2

Characteristics and setup of the second run (after Dec 2003)

Burst analysis

Main issues with burst search: duty cycle, detection efficiency, background events


Memorandum of Understanding with LIGO, IGEC-2 agreement, contacts with VIRGO

Other activities

New cryogenic detector with optical transducer; the DUAL project

Next steps and Summary

New low-frequency suspensions, ultra-cryogenic cooling,

The AURIGA experiment: run 2

Old & New AURIGA detector


Cryogenic failure




Main upgrades for the 2nd run

  • New mechanical suspensions:

  • attenuation > 360 dB at 1 kHz

  • FEM modelled

  • 3 resonant modes operation:

  • two mechanical modes

  • one electrical mode

  • New data analysis and data acquisition:

  • C++ object oriented code

  • frame data format

  • Monte Carlo software injections (internal or MDC)

  • improved noise matching algorithm

  • selectable templates

“New suspension system for the gravitational wave bar detector AURIGA” (in preparation, to be submitted toRev. Sc. Inst.)

3-mode detection for widening the bandwidth of resonant gravitational wave detectors

L. Baggio,M. Bignotto, M. Bonaldi,M. Cerdonio,L. Conti,P. Falferi,N. Liguori,A. Marin,R. Mezzena,A. Ortolan,S. Poggi,G. A. Prodi,F. Salemi,G. Soranzo,L. Taffarello,G. Vedovato,A. Vinante,S. Vitale,and J. P. Zendri

(submitted toPhys. Rev D.)

The new suspension system (1)

Attenuation & Internal modes frequency (-240DB wide band  FEM)

(a,b,c,d,e,f) are resonances of the suspension predicted by FEM

Quality factor

Yield strength (no more than 25% to avoid creeps)

Ultracryogenic (0.1 K) compatibility (no thermal short-circuit with 4K container, good thermal link to diluition refrigerator)

Vacuum compatibility (10-6mb  no rubber)

The new suspension system (2)

New transducer & amplifier

■ Two-stage SQUID: Tn(h) = 97 + 78T(K)

● Single stage SQUID: Tn(h) = 1280 +300T(K)

Noise Temperature (h)

Temperature (K)

  • three resonant modes operation:

    • two mechanical modes

    • one electrical mode

  • transducer bias field 8 MV/m

  • new SQUID amplifier :

    • double stage SQUID

    • 650  energy resolution at 4.5 K in the detector

Raw data& calibration

Mechanical transfer function (response to force applied by a electromechanical actuator attached to the bar)

Fully-automatic adaptive noise matching algorithm enbedded in AURIGA data analysis




Frequency [Hz]

Fit of the psd with ARMA noise model

Temperature of normal modes

Monday morning

mode 1

mode 2

mode 3

T [ K ]

date13-15 Nov. 2004

Noise budget expected at 4.5K

Shh1/2 < 5·10-21Hz-1/2 over 90 Hz

single-sided Shh

Very good agreement with noise predictions

All these noise sources will scale with temperature

Burst analysis(matched filter)

Typical sensitivity to bursts



10-21 –

 [Hz-1]


2004, Nov 13-15 (weekend)

Time of arrival error estimate (Monte Carlo)

Unexpected non-linear, non stationary noise

unmodeled spurious noise peaks within the sensitivity bandwidth

  • not related to the dynamical linear response ofthe detector

  • non gaussian statistics

  • related to mechanical external disturbances

  • up-conversion of low frequency noise

Epoch vetoes and goodness-of-fit tests

with template information, further improvement comes from check of compliance

Epoch vetoes from out-of-band information


Time [day]

cumulative event rate above threshold

false alarm rate [hour-1]

after vetoing

epoch vetoes (50% of time)

vetoed glitches

Remaining events after vetoing

Background events: approaching the gaussian tail

Amplitude distribution of events

AURIGA Nov. 13-14, 2004

Duty cycle

low-frequency mechanical attenuators

Additional room-temperature vibration attenuators

Performances after the upgrade of suspensions

10 days of stationary gaussian operation:

< 2 outliers/day

~60% duty cycle for gaussian data

Experimental data

Simulated data (gaussian noise)

2004 Dec 03-13

(after vetoes)




International Gravitational Event Collaboration

AURIGA is member of the IGEC since its foundation in 1997. IGEC HP:

Main results in:

P. Astoneet al., “Methods and results of the IGEC search for burst gravitational waves in the years1997-2000”, Phys. Rev. D68 (2003) 022001

(also on astro-ph/0302482)

IGEC-2 Agreement, Jan 17th 2005

The groups running the four bar detectors ALLEGRO, AURIGA, EXPLORER, NAUTILUS have signed a Letter of Intent to perform a new joint observation starting from 2004 available data. The approach of this new joint observation, will be based on the previous IGEC experience. The observation times of the participating detectors will be coordinated. IGEC-2 is open to agreements with other projects sharing the same scientific objectives.


A Memorandum of understanding between the experiment AURIGA and the LIGO project has been recently signed, for the purposes of joint data analysis and dissemination of results

2004/07/12 LIGO-M040010-00-M (MoU)

2004/07/12 LIGO-M040191-00-M (Attachment 1)

2004/07/12 LIGO-M040198-00-M (Membership list)

Joint LIGO-AURIGA working group activity


Outline of the most interesting analysis to be performed based on preliminary study of sensitivity and efficiency of the detectors

Document Type LIGO-T040202-00 2004/10/13

Proposal for the First AURIGA-LIGO Joint Analysis

L. Baggio, L Cadonati, S. Heng, W. Johnson, A. Mion, S. Poggi, G.A. Prodi, A. Ortolan, F. Salemi, P. Sutton, G.Vedovato, M. Zanolin

1st STEP

Cross-correlation between LIGOs (L1, H1 & H2) around the times of AURIGA triggers  Analysis of S3 data in progress

2nd STEP

Implementation of IGEC-like analysis (self adapting directional coincidence search between candidate event lists from each detector) <in preparation >


A working group for the joint burst search in LIGO and AURIGA has been formed, with the purpose to:

  • develop methodologies for bar/interferometer searches, to be tested on real data

  • time coincidence, triggered based search on a 2-week coincidence period (Dec 24, 2003 – Jan 9, 2004)

  • explore coherent methods

‘best’ single-sided PSD

Simulations and methodological studies are in progress.

White paper on joint analysis

Two methods will be explored in parallel:

  • Method 1:

  • IGEC style, but with a new definition of consistent amplitude estimator in order to face the radically different spectral densities of the two kind of detectors (interferometers and bars).

  • To fully exploit IGEC philosophy, as the detectors are not parallel, polarization effects should be taken into account (multiple trials on polarization grid).

  • Method 2:

  • No assumptions are made on direction or waveform.

  • A CorrPower search (see poster) is applied to the LIGO interferometers around the time of the AURIGA triggers.

  • Efficiency for classes of waveforms and source population is performed through Monte Carlo simulation, LIGO-style (see talks by Zweizig, Yakushin, Klimenko).

  • The accidental rate (background) is obtained with unphysical time-shifts between data streams.

Other activities

Optical readout for a bar detector


Transducer cavity: a Fabry-Perot cavity between the bar and the resonant

Reference cavity: a stable Fabry-Perot cavity acting as length reference

Laser frequency locked to the reference cavity

Working principle:

Variations of the transducer cavity length are measured by the stabilized laser


Room temperature prototype (2001)

The readout mechanics

The reference cavity

L = 110 mm, FSR = 1.36 GHz, F = 44000

Sensitivity of the room temperature prototype

New detector with cryogenic optical transducer (1)

Sensitivity predicted at T=4K with already developed technology

Goal: acquire data from a cryogenic bar equipped with the optical readout

  • New transducer mechanics

  • New bench on top of the bar with cryogenic-compliant motorized mounts for optics

  • New cryogenic-compliant bar suspension

  • New clean vacuum system

  • New anechoic housing for the laser optical bench

  • Higher finesse cavity

The new reference cavity


New cryogenic bar housing (in progress)

Transducer with optimized mass (after first tests)

New detector with cryogenic optical transducer (2)

cables and optical phiber thermalization

Lhe vessel

adaptater & pre-attenuation

single-column cryogenic suspension

Direct thermal links from the Lhe vessel


April: delivery of the cryogenic container

Summer: assembling and testing

Autumn: commissioning of the complete detector

2006: first measures

Two possible configurations:

DUAL: concept

Measurement of differential deformations of two nested bodies, resonating at different frequencies and both sensitive to the gw signal

Dual sphere

PRL 87 (2001) 031101

antenna pattern:


Dual cylinder

PRD 68 (2003) 102004

antenna pattern:

identical to that of 2 interferometers at 45 degrees with respect to each other

  • In the intermediate frequency range:

  • the outer resonator is driven above resonance,

  • the inner resonator is driven below resonance

  • → phase difference of 

In the differential measurement:

→ the signals sum up

→ the readout back action noise subtracts

DUAL: predicted sensitivity

Q/T > 2 108 K-1 , Standard Quantum Limit

  • Current activity:

  • Detector design

  • seismic noise control (pre-filtering)

  • high frequency (in band) mechanical

  • vibration filtering

  • underground operation

  • Readout system

  • Requirement: ~ 5x10-23 m/√Hz

  • Two concurrent studies: capacitive (+SQUID) and optical (folded Fabry-Perot, Phys. Lett. A 309, 15 (2003) ) readout

Mo Dual16.4 ton height 2.3 m Ø 0.94m

SiC Dual 62.2 ton height 3 m Ø 2.9m

Next steps

New low frequency vibrational damping

New external suspensions: “fast” assembling in April-June

Air springs: effective above1-2 Hz

Past, present and future sensitivity

Further steps to increase the bandwidth

T = 0.1K

T = 0.1K and bias field x2.5

Detector sensitivity comparison

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