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Gravitational Wave DetectorsPowerPoint Presentation

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
- Examples

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

- Origin
- Characteristics: isotropic, stationary, unpolarized
- Main property: frequency spectrum
- 3 useful characterizations:
- Energy density:
- Spectral density
- Characteristic amplitude

GW Background (ex.)

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

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

- 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

- 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

- Wide-band detectors (few Hz kHz)
- Description (see fig.)
- Sensitivity
- Noise (seismic, resonances, laser shot)

Two-interferometer correlation

- Dramatic increase in sensitivity
- Interf-interf
- Interf-res. mass
- Not applicable to LISA

5x10-11

Advanced LIGO

VIRGO

- Pisa (Italy)
- Arm length: 3km
- Large collaboration: 11 laboratories (I,F) ~200 people
- Sensitivity:

http://www.virgo.infn.it

VIRGO

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

LIGO

Laser Interferometer Gravitational Wave Observatory

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

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)

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)

Laser Interferometer Space Antenna

- Frequency range: 10-4 Hz 1 Hz
- Best sensitivity: 330 mHz
- f>30mHz: GW<2L
- f<3mHz: spurious forces on test masses
- Low f: expected bg from white-dwarfs binaries

LISA (sensitivity)

Laser Interferometer Space Antenna

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