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The US Laser Interferometer Gravitational-wave Observatory

The US Laser Interferometer Gravitational-wave Observatory. Status and Plans. Nergis Mavalvala Royal Astronomical Society, London February 14, 2003. Global network of detectors. GEO. VIRGO. LIGO. TAMA. AIGO. LIGO. Detection confidence Source polarization Sky location. LISA. 3. 0.

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The US Laser Interferometer Gravitational-wave Observatory

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  1. The US Laser Interferometer Gravitational-wave Observatory Status and Plans Nergis MavalvalaRoyal Astronomical Society, LondonFebruary 14, 2003

  2. Global network of detectors GEO VIRGO LIGO TAMA AIGO LIGO • Detection confidence • Source polarization • Sky location LISA

  3. 3 0 3 ( ± 0 1 k 0 m m s ) LIGO WA 4 km 2 km LA 4 km

  4. Coincidences between Sites • Two Sites – Three interferometers • Separation ~ 3020 km • Time window:    msec time of flight • Source triangulation: ~ arcminute directionality • Coincidence • Local coincidence - Hanford 2K and 4K ~ 1/day • Hanford / Livingston coincidence (uncorrelated) < 0.1/yr • GEO / TAMA coincidences further reduces the false signal rate • Amplitude discrimination with full- and half- length ifos at Hanford • Source polarization • Data (continuous time-frequency record) • Gravitational wave signal 0.2MB/sec • Total data recorded 9 MB/sec • Gravitational Wave Signal Extraction • Signal from noise (noise analysis, vetoes, coincidences, etc)

  5. Operations Principles • Interferometer performance • Integrate commissioning and data taking consistent with obtaining one year of integrated data at h = 10-21 by end of 2006 • Physics results from LIGO I • Initial upper limit results in early 2003 • First search results in 2004 • Reach LIGO I goals by 2007 • Advanced LIGO • Advanced LIGO proposal is about to be submitted • International collaboration and broad LSC participation • Advanced LIGO installation should begin by 2007

  6. DESIGN CONSTRUCTION OPERATION SCIENCE Detector R&D LIGO Laboratory MIT + Caltech ~140 people Director: Barry Barish LIGO Science Collaboration 44 member institutions > 400 individuals Spokesperson: Rai Weiss UK Germany Japan Russia India Spain Australia $ U.S. National Science Foundation LIGO Organization & Support

  7. Initial LIGO Sensitivity Goal • Strain sensitivity < 3x10-23 1/Hz1/2at 200 Hz • Displacement Noise • Seismic motion • Thermal Noise • Radiation Pressure • Sensing Noise • Photon Shot Noise • Residual Gas • Facilities limits much lower

  8. Limiting Noise Sources:Seismic Noise • Motion of the earth few mm rms at low frequencies • Passive seismic isolation ‘stacks’ • amplify at mechanical resonances • but get f-2 isolation per stage above 10 Hz

  9. FRICTION Limiting Noise Sources:Thermal Noise • Suspended mirror in equilibrium with 293 K heat bath akBT of energy per mode • Fluctuation-dissipation theorem: • Dissipative system will experience thermally driven fluctuations of its mechanical modes: Z(f) is impedance (loss) • Low mechanical loss (high Quality factor) • Suspension  no bends or ‘kinks’ in pendulum wire • Test mass  no material defects in fused silica

  10. Limiting Noise Sources:Quantum Noise • Shot Noise • Uncertainty in number of photons detected a • Higher input power Pbsa need low optical losses • (Tunable) interferometer response  Tifo depends on light storage time of GW signal in the interferometer • Radiation Pressure Noise • Photons impart momentum to cavity mirrorsFluctuations in the number of photons a • Lower input power, Pbs  Optimal input power for a chosen (fixed) Tifo

  11. Power-recycled Interferometer Optical resonance: requires test masses to be held in position to 10-10-10-13meter“Locking the interferometer” end test mass Light bounces back and forth along arms ~100 times 30 kW Light is “recycled” ~50 times 300 W input test mass Laser + optical field conditioning signal 6Wsingle mode

  12. Science Running Plan • Two “upper limit” runs S1 and S2 (at publishable early sensitivity) are interleaved with commissioning • S1 Aug-Sep 2002 duration: 2 weeks • S2 Feb-Apr 2003 duration: 8 weeks • Finish detector integration & design updates... • Engineering "shakedown" runs interspersed as needed • First “search” run S3 will begins late 2003 (duration: 6 months) Search for astrophysical signals at high strain sensitivity with high coincidence duty factor

  13. S1 Run Summary • 23 August – 9 September (17 days) • GEO and TAMA (part time) ran simultaneously • LIGO observation time ("science-mode" data) • L1 170 hours (42%) (limited by daytime seismic noise) • H1 235 hours (58%) • H2 298 hours (73%) • 3x 96 hours (23%) • Analyses near completion & preprints in preparation • Binary inspiral search • Burst search • Stochastic background search • Periodic/pulsar search

  14. Strain Sensitivities During S1 H2 &H1 L1 3*10-21 Hz -1/2@ f ~300 Hz

  15. Displacement Sensitivity(Science Run 1, Sept. 2002)

  16. Expected upper limits for S1 • Preliminary “upper limit” sensitivities as projected in October 2002 • Stochastic backgrounds • Upper limit 0 < 30 • Neutron star binary inspiral • Upper limit distance < 200 kpc • Periodic sources PSR J1939+2134 at 1283 Hz • Upper limit h < 5 10-22 90% CL • Actual refined analysis results to be presentation at AAAS meeting, 2003 • S2 should be at least 10x more sensitive than S1

  17. Three targets: Neutron star binaries (1-3 Msun) Black hole binaries (> 3 Msun) MACHO binaries (0.5-1 Msun) Search method template based matched filtering Status Neutron star search complete MACHO search under way Black hole search in S2 Neutron star search 2.0 post-Newtonian template waveforms for non-spinning binaries Discrete set of 2110 templates designed for at most 3% loss in SNR Sensitivity measured in distance to 2 x 1.4 Msun optimally oriented inspiral at SNR = 8 40 kpc < D < 200 kpc Sensitive to inspirals in Milky Way, LMC & SMC Search for gravitational waves from coalescing binaries

  18. IFO 2 GW Channel Auxiliary Data Matched Filter DMT Veto Analysis Pipeline • Matched filter trigger: • If SNR > 6.5, compute a2 : small values indicate that SNR accumulates in manner consistent with an inspiral signal. • If a2 < 5.0, record trigger • Triggers are clustered within duration of each template • Auxiliary data triggers • Vetoes eliminate noisy data IFO 1 GW Channel Auxiliary Data Matched Filter DMT Veto • Event Candidates • Coincident in time, binary mass, and distance when H1, L1 clean • Single IFO trigger when only H1 or L1 operate Event Candidates

  19. Strain Sensitivity coming into S2 L1 S1 6 Jan

  20. The next-generation detectorAdvanced LIGO (aka LIGO II) • Now being designed by the LIGO Scientific Collaboration • Goal: • Quantum-noise-limited interferometer • Factor of ten increase in sensitivity • Factor of 1000 in event rate. One day > entire2-year initial data run • Schedule: • Begin installation: 2007 • Begin data run: 2009

  21. Quantum LIGO I LIGO II Test mass thermal Suspension thermal Seismic A Quantum Limited Interferometer • Facility limits • Gravity gradients • Residual gas • (scattered light) • Advanced LIGO • Seismic noise 4010 Hz • Thermal noise 1/15 • Optical noise 1/10 • Beyond Adv LIGO • Thermal noise: cooling of test masses • Quantum noise: quantum non-demolition

  22. f i (l) r(l).e Power Recycling l Signal Recycling Optimizing the optical response: Signal Tuning Cavity forms compound output coupler with complex reflectivity. Peak response tuned by changing position of SRM Reflects GW photons back into interferometer to accrue more phase

  23. Thorne… Advance LIGO Sensitivity:Improved and Tunable

  24. Conclusion • LIGO construction is complete, and the worldwide GW community is actively exploiting its scientific capabilities along with sister detectors GEO and TAMA • Despite setbacks, sensitivity has improved 4 decades in 2 years(though still another decade to go...) • We are analyzing S1 coincidence science data more sensitive than any prior search • S2 and S3 promise significantly better sensitivity and uptime • We are moving forward with our proposal for advanced next-generation detectors to increase search volume by a further factor of 1,000+ within this decade

  25. Sensitivity to Stochastic Background S1

  26. ~10 min 20 Mpc ~3 sec 300 Mpc Implications for source detection • NS-NS Inpiral • Optimized detector response • NS-BH Merger • NS can be tidally disrupted by BH • Frequency of onset of tidal disruption depends on its radius and equation of state a broadband detector • BH-BH binaries • Merger phase  non-linear dynamics of highly curved space time a broadband detector • Supernovae • Stellar core collapse  neutron star birth • If NS born with slow spin period (< 10 msec) hydrodynamic instabilities a GWs

  27. Sco X-1 Signal strengths for 20 days of integration Source detection • Spinning neutron stars • Galactic pulsars: non-axisymmetry uncertain • Low mass X-ray binaries:If accretion spin-up balanced by GW spin-down, then X-ray luminosity  GW strengthDoes accretion induce non-axisymmetry? • Stochastic background • Can cross-correlate detectors (but antenna separation between WA, LA, Europe a dead band) • W(f ~ 100 Hz) = 3 x 10-9 (standard inflation  10-15) (primordial nucleosynthesis d 10-5) (exotic string theories  10-5) Thorne GW energy / closure energy

  28. GWs neutrinos photons now Astrophysical sources of GWs • Coalescing compact binaries • Classes of objects: NS-NS, NS-BH, BH-BH • Physics regimes: Inspiral, merger, ringdown • Other periodic sources • Spinning neutron stars  numerically hard problem • Burst events • Supernovae  asymmetric collapse • Stochastic background • Primordial Big Bang (t = 10-43 sec) • Continuum of sources • The Unexpected

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