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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/

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
interferometer principles
Interferometer: principles
  • Wide-band detectors (few Hz  kHz)
  • Description (see fig.)
  • Sensitivity
  • Noise (seismic, resonances, laser shot)
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

slide17
LIGO

Laser Interferometer Gravitational Wave Observatory

  • Will evolve into LIGOIII with a sensibility 10x better than LIGOI
slide18
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 sensitivity@1mHz ~ 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