Overview Ground-based Interferometers
Barry BarishCaltechAmaldi-6
20-June-05
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InterferometerDetectors
LIGO Louisiana 4000mTAMA Japan
300m
Virgo Italy 3000m
GEO Germany 600mAIGO Australia
future
LIGO Washington 2000m & 4000m
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Network of Interferometers
LIGO
detection confidence
GEO VirgoTAMA
AIGOlocate the sources
decompose the polarization of gravitational waves
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Interferometer Concept
As a wave passes, the arm lengths change in different ways….
…causing the interference pattern
to change at the photodiode
SuspendedMasses
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Limiting Noise Sources
• Seismic noise & vibration limit at low frequencies
• Atomic vibrations (Thermal Noise) inside components limit at mid frequencies
• Quantum nature of light (Shot Noise) limits at high frequencies
• Myriad details of the lasers, electronics, etc., can make problems above these levels
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TAMA 300
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Automated Data Taking in DT9 -
Master-system (intelligent switching)PC + PCI boards + LabVIEW64ch digital I/O 16ch A/D + 24ch D/A
Lock acquisitionAuto adjustmentInterface with external system
Self-switching sub-systemLogic circuit + Embedded micro processor
Laser source controlMC controlLaser intensity stabilizationBeam axes control
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Sensitivity in DT9
Recycling gain: 4.5Extended control band width for the laser frequencyImproved strain sensitivity: h=1.7x10-21 /Hz1/2 @1kHz
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TAMA
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TAMA Ringdown Analysis
GEO600
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GEO 600 – Optical Layout
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GEO Sensitivity Evolution
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LIGO
LIGO HanfordLIGO Livingston
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Evolution of LIGO Sensitivity
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Active Seismic Isolation at LLO
Hydraulic external pre-isolator (HEPI)Signals from sensors on ground and cross-beam are blended and fed into hydraulic actuatorsStatus:» Installed on all 4 piers at
each of nine vacuum chambers
» System is operational
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Active Seismic Isolation at LLO
Can lock (and do commissioning work!) during daytimeAble to stay locked even when train passes nearby
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LIGO Livingston Sensitivity
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LIGO S4 – Best Performance
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Detection of Periodic Sources
Pulsars in our galaxy: “periodic”» search for observed neutron stars » all sky search (computing challenge)» r-modes
Frequency modulation of signal due to Earth’s motion relative to the Solar System Barycenter, intrinsic frequency changes.
Amplitude modulation due to the detector’s antenna pattern.
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LIGO – GEO Directed Pulsar Search
28 Radio Sources
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GEO-LIGO - Resultsh0 95% UL Pulsars
10-24 < h0 < 5 10-24 20
5 10-24 < h0 < 10-23 4
h0 > 10-23 4
ellipticity ε Pulsars
10-6 < ε < 10-5 4
10-5 < ε < 10-4 16
ε > 10-4 8
• Lowest 95% UL on h0 = 1.7 10-24 (J1910-5959D)
• Lowest bound on e = 4.5 10-6 (J2124-3358)
• Crab pulsar:
• h0 = 4.1 10-23
• ε = 2.1 10-2 (~30 times spin-down upper limit)
Crab pulsar
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Detection of Periodic Sources
Pulsars in our galaxy
Frequency modulation of signal due to Earth’s motion relative to the Solar System Barycenter, intrinsic frequency changes.
Amplitude modulation due to the detector’s antenna pattern.
NEW RESULT28 known pulsars
NO gravitational waves
ε < 10-5 – 10-6
(no mountains > 10 cm
ALL SKY SEARCHenormous computing challenge
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Einstein@Home
LIGO Pulsar Search using home pc’s
BRUCE ALLENProject Leader
Univ of Wisconsin Milwaukee
LIGO, UWM, AEI, APS
http://einstein.phys.uwm.edu
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Virgo
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Virgo Seismic Performance
Thermal noise
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Virgo - Sensitivity Goal
Designed to have good sensitivity at low frequencies
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Virgo Commissioning
Extragalactic sensitivity Extragalactic sensitivity toto NS/NS NS/NS coalescences coalescences
55 55 kpc kpc
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Advanced LIGO
Active Seismic
Multiple Suspensions
Improved Optics
Higher Power Laser
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Advanced LIGOEnhanced Systems
• laser• suspension• seismic isolation• test mass
RateImprovement
~ 104
+narrow band
optical configuration
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From Amaldi-6 Onwards
From Present Generation Advanced Detectors Next Generation Detectors (QND)
From 8 Mpc (NN inspiral) 200 Mpc and beyond
From Upper Limits Searches Detections
From Generic Waveforms Specified Waveforms
From Single Detectors Global Networks