Gravitational wave detectors
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Gravitational Wave Detectors. Course in Inflation, Structure formation and CMB 7 November 2002 Silvio Orsi. GW: My presentation. GW production Upper bounds on GW background Frequency range Detectors for GW: Under construction & future detectors Frequency range & sensitivity Noise

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Gravitational wave detectors

Gravitational Wave Detectors

Course in Inflation, Structure formation and CMB

7 November 2002

Silvio Orsi


Gw my presentation

GW: My presentation

  • GW production

  • Upper bounds on GW background

  • Frequency range

  • Detectors for GW:

    • Under construction & future detectors

    • Frequency range & sensitivity

    • Noise

    • Examples


Gw production

GW Production

  • GW background from amplification of vacuum fluctuations

    • Standard inflation

    • Pre-Big Bang cosmology

    • Other models

  • Known astrophysical sources

  • Noise (unresolved astrophysical sources)

  • On Earth: Seismic noise


Gw background

GW Background

  • Origin

  • Characteristics: isotropic, stationary, unpolarized

  • Main property: frequency spectrum

    • 3 useful characterizations:

    • Energy density:

    • Spectral density

    • Characteristic amplitude


Gw background ex

GW Background (ex.)

http://www.ba.infn.it/~gasperin/


Upper bounds on energy density

Upper bounds on Energy Density


Gw detectors

GW Detectors

  • Existing detectors give upper bounds

  • Resonant mass experiments: EXPLORER (CERN), NAUTILUS (I), AURIGA (I), ALLEGRO (Louisiana), NIOBE (Aus)

  • Interferometers

    • Large-scale (under construction): LIGO, VIRGO (I,F), GEO600 (D), TAMA300 (Jap), AIGO (Aus)

    • Second generation (planned): LISA (space interf.), Advanced LIGO

    • Two-interferometer correlation

  • (Pulsars)


Resonant mass experiments

Resonant mass experiments

  • Bars are narrow-band detectors and work at two resonances

  • f ~ 1kHz

  • Half-heigth bandwiths ~ 1Hz

  • Strain sensitivity ~ 5x interferometers

  • Optimization = (Quality factor x Mass)/Temperature

  • AURIGA


Auriga

AURIGA

  • Ultracryogenic Resonant Antenna for the Gravitational Astronomical Investigation

  • Resonant acoustic detector

  • Resonator: Aluminium bar (length=3m, diameter=60cm, mass=2.3t, T~100mK, Teff~mK, quality factor Q=106)

  • Signals @ ~1kHz


Auriga1

AURIGA


Interferometer principles

Interferometer: principles

  • Wide-band detectors (few Hz  kHz)

  • Description (see fig.)

  • Sensitivity

  • Noise (seismic, resonances, laser shot)


Typical sensitivity curve

Typical sensitivity curve

RESONANCE

REGION


Two interferometer correlation

Two-interferometer correlation

  • Dramatic increase in sensitivity

  • Interf-interf

  • Interf-res. mass

  • Not applicable to LISA

5x10-11

Advanced LIGO


Virgo

VIRGO

  • Pisa (Italy)

  • Arm length: 3km

  • Large collaboration: 11 laboratories (I,F) ~200 people

  • Sensitivity:

http://www.virgo.infn.it


Virgo1

VIRGO

http://wwwlapp.in2p3.fr/virgo/gwf.html


Virgo sensitivity

VIRGO Sensitivity


Gravitational wave detectors

LIGO

Laser Interferometer Gravitational Wave Observatory

  • Will evolve into LIGOIII with a sensibility 10x better than LIGOI


Gravitational wave detectors

LISA

Laser Interferometer Space Antenna

  • Proposed by ESA (1993)

  • NASA/ESA collaboration

  • Launch estimated 2010-2020

  • Mission: 2yrs (up to 10)

  • 3 arms (redundancy)

  • Common noise (3 non-indep. interf.)

  • NSR (noise to signal ratio) negligible

  • Info on GW polarization & direction


Lisa 2

LISA (2)

Laser Interferometer Space Antenna

  • Better discrimination of GW stochastic bg, binaries, cosmological effects & instrumental noise

  • No seismic & gravity-gradient noise

  • Frequency range: 10-4 Hz  1 Hz

  • Very long length (L~5x106 km)

  • Strain [email protected] ~ 4x10-21 Hz –1/2


Lisa 3

LISA (3)

Laser Interferometer Space Antenna

  • Frequency range: 10-4 Hz  1 Hz

  • Best sensitivity: 330 mHz

  • f>30mHz: GW<2L

  • f<3mHz: spurious forces on test masses

  • Low f: expected bg from white-dwarfs binaries


Lisa sensitivity

LISA (sensitivity)

Laser Interferometer Space Antenna


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