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 from the 2-km arm (temperature stabilized laser 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.