Post on 20-Jan-2016
description
LIGO-G000314-00-M
First Generation Interferometers
Barry Barish
30 Oct 2000
Workshop on Astrophysical Sources for Ground-Based
Gravitational Wave Detectors
Drexel University
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Detection of Gravitational Wavesprecision optical instrument
• detect a stretch (squash) of 10-18 m !! ( a small fraction of the size of a proton)
• first generation interferometers will have strain sensitivity h ~ 10-21 for 10Hz < f < 10KHz
• time frame 2001-2006, then upgrades to improve sensitivity (Fritschel)
LIGO interferometer
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Interferometers the noise floor
Interferometry is limited by three fundamental noise sources
seismic noise at the lowest frequencies thermal noise at intermediate frequencies shot noise at high frequencies
Many other noise sources lurk underneath and must be controlled as the instrument is improved
Sensitive region
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Interferomersinternational network
LIGO
Simultaneously detect signal (within msec)
detection confidence locate the sources
decompose the polarization of gravitational waves
GEO VirgoTAMA
AIGO
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LIGO (Washington) LIGO (Louisiana)
Interferometersinternational network
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GEO 600 (Germany) Virgo (Italy)
Interferometersinternational network
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TAMA 300 (Japan) AIGO (Australia)
Interferometersinternational network
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Interferometers the noise floor
Interferometry is limited by three fundamental noise sources
seismic noise at the lowest frequencies thermal noise at intermediate frequencies shot noise at high frequencies
Many other noise sources lurk underneath and must be controlled as the instrument is improved
Sensitive region
shot
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Phase Noisesplitting the fringe
• spectral sensitivity of MIT phase noise interferometer
• above 500 Hz shot noise limited near LIGO I goal
• additional features are from 60 Hz powerline harmonics, wire resonances (600 Hz), mount resonances, etc
shot noise
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Noise Floor40 m prototype
• displacement sensitivityin 40 m prototype. • comparison to predicted contributions from various noise sources
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Noise FloorTAMA 300
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Interferometers the noise floor
Interferometry is limited by three fundamental noise sources
seismic noise at the lowest frequencies thermal noise at intermediate frequencies shot noise at high frequencies
Many other noise sources lurk underneath and must be controlled as the instrument is improved
Sensitive region
vacuum
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Vacuum Systemsbeam tube enclosures
LIGO minimal enclosures
no services
Virgopreparing arms
GEOtube in the trench
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Beam Tubes
LIGO 4 km beam tube (1998)
TAMA 300 m beam pipe
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Beam Tube Bakeout
LIGO bakeout
standard quantum limit
phase noise
residual gas
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Vacuum Chamberstest masses, optics
TAMA chambers
LIGO chambers
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Interferometers the noise floor
Interferometry is limited by three fundamental noise sources
seismic noise at the lowest frequencies thermal noise at intermediate frequencies shot noise at high frequencies
Many other noise sources lurk underneath and must be controlled as the instrument is improved
Sensitive region
seismic
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Suspension vertical transfer function measured and simulated (prototype)
Seismic IsolationVirgo
“Long Suspensions”• inverted pendulum• five intermediate filters
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Long SuspensionsVirgo installation at the site
Beam Splitter and North Input mirror
All four long suspensions for the entire central interferometer
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Suspensions GEO triple pendulum
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Test Massesfibers and bonding - GEO
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Interferometers basic optical configuration
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Opticsmirrors, coating and polishing
All optics polished & coated» Microroughness within spec.
(<10 ppm scatter)» Radius of curvature within
spec. R/R 5%)» Coating defects within spec.
(pt. defects < 2 ppm, 10 optics tested)
» Coating absorption within spec. (<1 ppm, 40 optics tested)
LIGO
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LIGOmetrology
Caltech
CSIRO
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Interferometers lasers
Nd:YAG (1.064 m) Output power > 8W in
TEM00 mode
GEO Laser
LIGO Lasermaster oscillator power amplifier
Master-Slave configuration with 12W output power
Virgo Laser
residual frequency noise
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Prestabalized Laser performance
> 18,000 hours continuous operation
Frequency and lock very robust
TEM00 power > 8 watts
Non-TEM00 power < 10%
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1 10 100 100010
-23
10-22
10-21
10-20
10-19
10-18
C85 steel wire (total) Fused Silica wire (total) FS pendulum thermal noise Mirror thermal noise
h [1
/sqr
t(H
z)]
Frequency [Hz]
Virgo sensitivity curveInterferometerssensitivity curves
TAMA 300
GEO 600
Virgo
LIGO
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Interferometerstesting and commissioning
TAMA 300» interferometer locked; noise/robustness improved; successful two week data run (Aug 00)
LIGO» subsystems commissioned; » 2 km first lock (Nov 00)
Geo 600» commissioning tests
Virgo» testing isolation systems; commissioning input optics
AIGO» setting up central facility; short arm interferometer
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TAMA Performancenoise source analysis
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TAMA Performancenoise source analysis
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• best sensitivity: 5x10-21 Hz-1/2 (~ 1kHz)
• interferometer stability; longest lock > 12 hrs
• non-stationary noise significantly reduced • auxiliary signalsapprox 100 signals including feedback and error signals and environmental signals were recorded
• planstwo-month data run planned for Jan 2001; signal recycling added next year.
TAMA2 week data run
21 Aug to 4 Sept 00
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LIGOcommissioning
Mode cleaner and Pre-Stabilized Laser 2km one-arm cavity short Michelson interferometer studies
Lock entire Michelson Fabry-Perot interferometer
“FIRST LOCK”
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Detector Commissioning: 2-km Arm Test
12/99 – 3/00
Alignment “dead reckoning” worked
Digital controls, networks, and software all worked
Exercised fast analog laser frequency control
Verified that core optics meet specs
Long-term drifts consistent with earth tides
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LIGOlocking a 2km arm
12/1/99 Flashes of light
12/9/99 0.2 seconds lock 1/14/00 2 seconds lock 1/19/00 60 seconds lock 1/21/00 5 minutes lock
(on other arm) 2/12/00 18 minutes lock 3/4/00 90 minutes lock
(temperature stabilized laser reference cavity)
3/26/00 10 hours lock
First interference fringesfrom the 2-km arm
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2km Fabry-Perot cavity 15 minute locked stretch
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Near-Michelson interferometer
Interference fringes from thepower recycled near Michelsoninterferometer
• power recycled (short) Michelson Interferometer
• employs full mixed digital/analog servos
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LIGOfirst lock
signal
LaserX Arm
Y Arm
Composite Video
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LIGObrief locked stretch
X arm
Reflectedlight
Y arm
Anti-symmetricport
2 min
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Interferometerdata analysis
Compact binary inspiral: “chirps”» NS-NS waveforms are well described» BH-BH need better waveforms » search technique: matched templates
Supernovae / GRBs: “bursts” » burst signals in coincidence with signals in electromagnetic radiation » prompt alarm (~ one hour) with neutrino detectors
Pulsars in our galaxy: “periodic”» search for observed neutron stars (frequency, doppler shift)» all sky search (computing challenge)» r-modes
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Interferometer Data40 m
Real interferometer data is UGLY!!!(Gliches - known and unknown)
LOCKING
RINGING
NORMAL
ROCKING
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“Clean up” data stream
Effect of removing sinusoidal artifacts using multi-taper methods
Non stationary noise Non gaussian tails
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Inspiral ‘Chirp’ Signal
Template Waveforms
“matched filtering”687 filters
44.8 hrs of data39.9 hrs arms locked25.0 hrs good data
sensitivity to our galaxyh ~ 3.5 10-19 mHz-1/2
expected rate ~10-6/yr
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Detection Efficiency
• Simulated inspiral events provide end to end test of analysis and simulation code for reconstruction efficiency
• Errors in distance measurements from presence of noise are consistent with SNR fluctuations
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Setting a limit
Upper limit on event rate can be determined from SNR of ‘loudest’ event
Limit on rate:R < 0.5/hour with 90% CL = 0.33 = detection efficiency
An ideal detector would set a limit:R < 0.16/hour
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TAMA 300search for binary coalescence
• 2-step hierarchical method
• chirp masses (0.3-10)M0
• strain calibrated h/h ~ 1 %
Matched templates
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TAMA 300preliminary result
For signal/noise = 7.2
Expect: 2.5 eventsObserve: 2 events
Note: for a 1.4 M0 NS-NS inspiral this limit corresponds to a max distance = 6.2 kpc
Rate < 0.59 ev/hr 90% C.L.
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Conclusions First generation long baseline suspended mass
interferometers are being completed with h ~ 10-21
commissioning, testing and characterization of the interferometers is underway
data analysis schemes are being developed, including tests with real data from the 40 m prototype and TAMA
science data taking to begin soon – TAMA ; then LIGO (2002)
plans and agreements being made for exchange of data for coincidences between detectors (GWIC)
Second generation - significant improvements in sensitivity
(h ~ 10-22) are anticipated about 2007+