Workshop on Astrophysical Sources for Ground-Based Gravitational Wave Detectors Drexel University
First Generation Interferometers
Barry Barish 30 Oct 2000
LIGO-G000314-00-M Detection of Gravitational Waves precision optical instrument
LIGO interferometer • 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-G000314-00-M Interferometers the noise floor
§ Interferometry is limited by three fundamental noise sources Ø seismic noise at the Sensitive lowest frequencies region Ø thermal noise at intermediate frequencies Ø shot noise at high frequencies
§Many other noise sources lurk underneath and must be controlled as the instrument is improved
LIGO-G000314-00-M Interferomers international network
Simultaneously detect signal (within msec) GEO Virgo LIGO TAMA detection confidence
locate the sources
decompose the polarization of gravitational waves AIGO LIGO-G000314-00-M Interferometers international network
LIGO (Washington) LIGO (Louisiana)
LIGO-G000314-00-M Interferometers international network
GEO 600 (Germany) Virgo (Italy)
LIGO-G000314-00-M Interferometers international network
TAMA 300 (Japan) AIGO (Australia)
LIGO-G000314-00-M Interferometers the noise floor
§ Interferometry is limited by three fundamental noise sources Ø seismic noise at the Sensitive lowest frequencies region Ø thermal noise at intermediate frequencies Ø shot noise at high frequencies
§Many other noise sources lurk underneath and must be controlled as the instrument is improved
LIGO-G000314-00-M shot Phase Noise splitting the fringe
• spectral sensitivity of MIT shot noise 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
LIGO-G000314-00-M Noise Floor 40 m prototype
• displacement sensitivity in 40 m prototype.
• comparison to predicted contributions from various noise sources
LIGO-G000314-00-M Noise Floor TAMA 300
LIGO-G000314-00-M Interferometers the noise floor
§ Interferometry is limited by three fundamental noise sources Ø seismic noise at the Sensitive lowest frequencies region Ø thermal noise at intermediate frequencies Ø shot noise at high frequencies
§Many other noise sources lurk underneath and must be controlled as the instrument is improved
LIGO-G000314-00-M vacuum Vacuum Systems beam tube enclosures
LIGO minimal enclosures no services
Virgo preparing arms
GEO tube in the trench LIGO-G000314-00-M Beam Tubes
TAMA 300 m beam pipe
LIGO 4 km beam tube (1998)
LIGO-G000314-00-M Beam Tube Bakeout
phase noise
standard quantum limit
residual gas LIGO bakeout
LIGO-G000314-00-M Vacuum Chambers test masses, optics
LIGO chambers
TAMA chambers
LIGO-G000314-00-M Interferometers the noise floor
§ Interferometry is limited by three fundamental noise sources Ø seismic noise at the Sensitive lowest frequencies region Ø thermal noise at intermediate frequencies Ø shot noise at high frequencies
§Many other noise sources lurk underneath and must be controlled as the instrument is improved
LIGO-G000314-00-M seismic Seismic Isolation Virgo
“Long Suspensions” • inverted pendulum • five intermediate filters
Suspension vertical transfer function measured and simulated (prototype) LIGO-G000314-00-M Long Suspensions Virgo installation at the site
Beam Splitter and North Input mirror
All four long suspensions for the entire central interferometer
LIGO-G000314-00-M Suspensions GEO triple pendulum
LIGO-G000314-00-M Test Masses fibers and bonding - GEO
LIGO-G000314-00-M Interferometers basic optical configuration
LIGO-G000314-00-M Optics mirrors, coating and polishing
LIGO
§ All optics polished & coated » Microroughness within spec. (<10 ppm scatter) » Radius of curvature within spec. (dR/R < 5%) » Coating defects within spec. (pt. defects < 2 ppm, 10 optics tested) » Coating absorption within spec. (<1 ppm, 40 optics tested)
LIGO-G000314-00-M LIGO metrology
§ Caltech
§ CSIRO
LIGO-G000314-00-M Interferometers lasers
§ Nd:YAG (1.064 mm) § Output power > 8W in TEM00 mode LIGO Laser master oscillator power amplifier GEO Laser Virgo Laser
residual frequency noise
Master-Slave configuration with 12W outputLIGO-G000314 power-00-M Prestabalized Laser performance
§ > 18,000 hours continuous operation
§ Frequency and lock very robust
§ TEM00 power > 8 watts
§ Non-TEM00 power < 10%
LIGO-G000314-00-M Interferometers Virgo sensitivity curve sensitivity curves 10-18
10-19 C85 steel wire (total) Fused Silica wire (total) FS pendulum thermal noise TAMA 300 -20 10 Mirror thermal noise
10-21 h [1/sqrt(Hz)]
10-22 Virgo
10-23 1 10 100 1000 Frequency [Hz]
LIGO GEO 600
LIGO-G000314-00-M Interferometers testing 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 LIGO-G000314-00-M TAMA Performance noise source analysis
LIGO-G000314-00-M TAMA Performance noise source analysis
LIGO-G000314-00-M TAMA 2 week data run
• best sensitivity: 21 Aug to 4 Sept 00 5x10-21 Hz-1/2 (~ 1kHz)
• interferometer stability; longest lock > 12 hrs
• non-stationary noise significantly reduced
• auxiliary signals approx 100 signals including feedback and error signals and environmental signals were recorded
• plans two-month data run planned for Jan 2001; signal recycling added next year. LIGO-G000314-00-M LIGO commissioning
§ Mode cleaner and Pre-Stabilized Laser § 2km one-arm cavity § short Michelson interferometer studies
§ Lock entire Michelson Fabry-Perot interferometer “FIRST LOCK”
LIGO-G000314-00-M 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
LIGO-G000314-00-M LIGO locking 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 First interference fringes § 3/4/00 90 minutes lock (temperature stabilized laser from the 2-km arm reference cavity) § 3/26/00 10 hours lock
LIGO-G000314-00-M 2km Fabry-Perot cavity 15 minute locked stretch
LIGO-G000314-00-M Near-Michelson interferometer
• power recycled (short) Michelson Interferometer
• employs full mixed digital/analog servos
Interference fringes from the power recycled near Michelson interferometer
LIGO-G000314-00-M LIGO first lock Composite Video
Y Arm
Laser X Arm signal
LIGO-G000314-00-M LIGO brief locked stretch
Y arm X arm
Reflected light Anti-symmetric port
2 min
LIGO-G000314-00-M Interferometer data 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
LIGO-G000314-00-M Interferometer Data 40 m
Real interferometer data is UGLY!!! (Gliches - known and unknown)
LOCKING NORMAL
RINGING ROCKING
LIGO-G000314-00-M “Clean up” data stream
Effect of removing sinusoidal artifacts using multi-taper methods
Non stationary noise Non gaussian tails
LIGO-G000314-00-M Inspiral ‘Chirp’ Signal
Template Waveforms
“matched filtering” 687 filters
44.8 hrs of data 39.9 hrs arms locked 25.0 hrs good data sensitivity to our galaxy h ~ 3.5 10-19 mHz-1/2 expected rate ~10-6/yr
LIGO-G000314-00-M 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
LIGO-G000314-00-M 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 e = 0.33 = detection efficiency
An ideal detector would set a limit: R < 0.16/hour
LIGO-G000314-00-M TAMA 300 search for binary coalescence
Matched templates
• 2-step hierarchical method
• chirp masses (0.3-10)M0
• strain calibrated dh/h ~ 1 %
LIGO-G000314-00-M TAMA 300 preliminary result
For signal/noise = 7.2
Expect: 2.5 events Observe: 2 events
Rate < 0.59 ev/hr 90% C.L.
Note: for a 1.4 M0 NS-NS inspiral this limit corresponds to a max distance = 6.2 kpc LIGO-G000314-00-M 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+
LIGO-G000314-00-M