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The Status of Gravitational-Wave Detectors Reported on behalf of LIGO colleagues by Fred Raab, LIGO Hanford Observatory LIGO-G050250-00-W Reach of Gravitational Wave Detectors is Rapidly Expanding Windows of opportunity GWs a known phenomenon, but undetected as yet Resonant-bar & laser detectors Worldwide networks of terrestrial detectors LIGO: the first generation of km-scale detectors Moving toward the future LIGO-G050250-00-W Raab: Status of Gravitational Wave Detectors 2 Different Frequency Bands of Detectors and Sources space EM waves are studied over ~20 orders of magnitude terrestrial Audio band » (ULF radio -> HE rays) Gravitational Wave coverage over ~8 orders of magnitude » (terrestrial + space) LIGO-G050250-00-W Raab: Status of Gravitational Wave Detectors 3 Catching Waves From Orbiting Black Holes and Neutron Stars Sketches courtesy of Kip Thorne LIGO-G050250-00-W Raab: Status of Gravitational Wave Detectors 4 Gravitational Waves the evidence Emission of gravitational waves Neutron Binary System – Hulse & Taylor PSR 1913 + 16 -- Timing of pulsars 17 / sec ~ 8 hr Neutron Binary System • separated by 106 miles • m1 = 1.4m; m2 = 1.36m; e = 0.617 Prediction from general relativity • spiral in by 3 mm/orbit • rate LIGO-G050250-00-W of change orbital period Raab: Status of Gravitational Wave Detectors 5 Basic Signature of Gravitational Waves for All Detectors LIGO-G050250-00-W Raab: Status of Gravitational Wave Detectors 6 Bar Network: Int’l Gravitational Event Collaboration Network of the 5 bar detectors almost parallel ALLEGRO NFS-LSU AURIGA INFN-LNL NIOBE ARC-UWA EXPLORER INFN-CERN NAUTILUS INFN-LNF LIGO-G050250-00-W http://gravity.phys.lsu.edu http://www.auriga.lnl.infn.it http://www.gravity.pd.uwa.edu.au http://www.roma1.infn.it/rog/rogmain.html Raab: Status of Gravitational Wave Detectors 7 CERN RE 5 MiniGrail LNF INFN Courtesy E. Coccia LIGO-G050250-00-W Raab: Status of Gravitational Wave Detectors 8 AURIGA 2nd run @ 4K: upgrades & results new mechanical suspensions: attenuation > 360 dB at 1 kHz FEM modelled new capacitive transducer: two-modes (1 mechanical+1 electrical) optimal mass new amplifier: double stage SQUID new data analysis: C++ object oriented code frame data format Bandwidth: noise floor below 5x10-21 Hz-1/2 on a 100 Hz band Stationary gaussian behaviour: few spurious event/h after anticoincidence veto with 20 ms all band electromagnetic glitches Courtesy M. Cerdonio LIGO-G050250-00-W Raab: Status of Gravitational Wave Detectors 9 New Generation of “FreeMass” Detectors Now Online suspended mirrors mark inertial frames antisymmetric port carries GW signal Symmetric port carries common-mode info Intrinsically broad band and size-limited by speed of light. LIGO-G050250-00-W Raab: Status of Gravitational Wave Detectors 10 The International Interferometer Network Simultaneously detect signal (within msec) LIGO GEO Virgo TAMA detection confidence locate the sources AIGO LIGO-G050250-00-W Raab: Status of Gravitational Wave Detectors decompose the polarization of gravitational waves 11 The Laser Interferometer Gravitational-Wave Observatory LIGO (Washington) (4-km and 2km) LIGO (Louisiana) (4-km) Funded by the National Science Foundation; operated by Caltech and MIT; the research focus for more than 500 LIGO Scientific Collaboration members worldwide. LIGO-G050250-00-W Raab: Status of Gravitational Wave Detectors 12 Interferometers in Europe GEO 600 (Germany) 600-m LIGO-G050250-00-W Virgo (Italy) 3-km Raab: Status of Gravitational Wave Detectors 13 Interferometers in Asia, Australia TAMA 300 (Japan) (300-m) LIGO-G050250-00-W AIGO (Australia) (80-m, but 3-km site) Raab: Status of Gravitational Wave Detectors 14 Spacetime is Stiff! => Wave can carry huge energy with miniscule amplitude! h ~ (G/c4) (ENS/r) LIGO-G050250-00-W Raab: Status of Gravitational Wave Detectors 15 Some of the Technical Challenges Typical Strains < 10-21 at Earth ~ 1 hair’s width at 4 light years Understand displacement fluctuations of 4-km arms at the millifermi level (1/1000th of a proton diameter) Control arm lengths to 10-13 meters RMS Detect optical phase changes of ~ 10-10 radians Hold mirror alignments to 10-8 radians Engineer structures to mitigate recoil from atomic vibrations in suspended mirrors LIGO-G050250-00-W Raab: Status of Gravitational Wave Detectors 16 What Limits Sensitivity of Interferometers? • 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 LIGO-G050250-00-W Raab: Status of Gravitational Wave Detectors 17 Time Line 2000 1999 3Q 4Q 2Q 3Q 1Q Inauguration 2001 4Q 1Q Runs E1 Science 2Q 3Q E2 4Q 1Q 2Q 3Q 2003 4Q 1Q 2Q 3Q 4Q Full Lock all IFO's First Lock strain noise density @ 200 Hz [Hz-1/2] Engineering 2002 10-17 10-18 E3 E4 E5 E6 E7 10-19 10-20 E8 10-21 10-22 E9 S1 S2 E10 S3 First Science Data LIGO-G050250-00-W Raab: Status of Gravitational Wave Detectors 18 Vibration Isolation Systems » » » » Reduce in-band seismic motion by 4 - 6 orders of magnitude Little or no attenuation below 10Hz Large range actuation for initial alignment and drift compensation Quiet actuation to correct for Earth tides and microseism at 0.15 Hz during observation HAM Chamber LIGO-G050250-00-W Raab: Status of Gravitational Wave Detectors BSC Chamber 19 Seismic Isolation – Springs and Masses damped spring cross section LIGO-G050250-00-W Raab: Status of Gravitational Wave Detectors 20 Core Optics Suspension and Control Optics suspended as simple pendulums Shadow sensors & voice-coil actuators provide damping and control forces Mirror is balanced on 30 micron diameter wire to 1/100th degree of arc LIGO-G050250-00-W Raab: Status of Gravitational Wave Detectors 21 Feedback & Control for Mirrors and Light Damp suspended mirrors to vibration-isolated tables » 14 mirrors (pos, pit, yaw, side) = 56 loops Damp mirror angles to lab floor using optical levers » 7 mirrors (pit, yaw) = 14 loops Pre-stabilized laser » (frequency, intensity, pre-mode-cleaner) = 3 loops Cavity length control » (mode-cleaner, common-mode frequency, common-arm, differential arm, michelson, power-recycling) = 6 loops Wave-front sensing/control » 7 mirrors (pit, yaw) = 14 loops Beam-centering control » 2 arms (pit, yaw) = 4 loops LIGO-G050250-00-W Raab: Status of Gravitational Wave Detectors 22 Suspended Mirror Approximates a Free Mass Above Resonance Blue: suspended mirror XF Cyan: free mass XF Data taken using shadow sensors & voice coil actuators LIGO-G050250-00-W Raab: Status of Gravitational Wave Detectors 23 Despite a few difficulties, science runs started in 2002. LIGO-G050250-00-W Raab: Status of Gravitational Wave Detectors 24 LIGO Science Runs S1: 17 days in Aug-Sep 2002 » 3 LIGO interferometers in coincidence with GEO600 and ~2 days with TAMA300 S2: Feb 14 – Apr 14, 2003 » 3 LIGO interferometers in coincidence with TAMA300 S3: Oct 31, 2003 – Jan 9, 2004 » 3 LIGO interferometers in coincidence with periods of operation of TAMA300, GEO600 and Allegro S4: Feb 22 – Mar 23, 2005 » 3 LIGO interferometers in coincidence with GEO600, Allegro, Auriga LIGO-G050250-00-W Raab: Status of Gravitational Wave Detectors 25 Binary Neutron Stars: S1 Range LIGO-G050250-00-W Raab: Status of Gravitational Wave Detectors 26 Image: R. Powell Binary Neutron Stars: S2 Range S1 Range LIGO-G050250-00-W Raab: Status of Gravitational Wave Detectors Image: R. Powell 27 Interferometer Strain Sensitivity LIGO-G050250-00-W Raab: Status of Gravitational Wave Detectors 28 Science Analysis Searches for periodic sources, such as neutron stars Searches for compact-binary inspirals, e.g., neutron stars, black holes, MACHOs Searches for burst sources » Waveforms may be unknown or poorly known » Non-triggered search » Triggered search(e.g., supernova or GRB triggers) Stochastic waves of cosmological or astrophysical origin LIGO-G050250-00-W Raab: Status of Gravitational Wave Detectors 29 LIGO Search Papers (as of 9May05) S1: “Setting upper limits on the strength of periodic gravitational waves using the first science data from the GEO600 and LIGO detectors”, Phys. Rev. D 69, 082004 (2004) “First upper limits from LIGO on gravitational wave bursts”, Phys. Rev. D 69, 102001 (2004) “Analysis of LIGO data for gravitational waves from binary neutron stars”, Phys. Rev. D 69, 122001 (2004) “Analysis of first LIGO science data for stochastic gravitational waves”, Phys. Rev. D 69, 122004 (2004) S2: “Limits on gravitational wave emission from selected pulsars using LIGO data”, Phys. Rev. Lett. 94, 181103 (2005). “A search for gravitational waves associated with the gamma ray burst GRB030329 using the LIGO detectors”, gr-qc/0501068 “Upper limits on gravitational wave bursts from LIGO’s second science run”, gr-qc/0505029 LIGO-G050250-00-W Raab: Status of Gravitational Wave Detectors 30 Binary Neutron Stars: Initial LIGO Target Range S2 Range LIGO-G050250-00-W Raab: Status of Gravitational Wave Detectors 31 Image: R. Powell Future Plans for Terrestrial Detectors Improve reach of initial LIGO to run 1 integrated triple-coincidence year at design sensitivity Virgo has made steady progress in commissioning, due to come on line in ~ 1 year GEO600, TAMA300, striving for design sensitivity Resonant bars networking with interferometers for future runs Advanced LIGO technology under development, planning toward a detector construction start for FY2008 LIGO-G050250-00-W Raab: Status of Gravitational Wave Detectors 32 What’s next? Advanced LIGO… Major technological differences between LIGO and Advanced LIGO 40kg Quadruple pendulum: Silica optics, welded to silica suspension fibers Initial Interferometers Active vibration isolation systems Open up wider band Reshape Noise Advanced Interferometers High power laser (180W) LIGO-G050250-00-W Raab: Status of Gravitational Wave Detectors Advanced interferometry 33 Signal recycling Binary Neutron Stars: AdLIGO Range LIGO Range LIGO-G050250-00-W Raab: Status of Gravitational Wave Detectors Image: R. Powell 34 …and opening a new channel with a detector in space. Planning underway for space-based detector, LISA, to open up a lower frequency band ~ 2013-ish LIGO-G050250-00-W Raab: Status of Gravitational Wave Detectors 35 Summary We are currently experiencing a rapid advance in the sensitivity of searches for gravitational waves Elements of world-wide networks of interferometers and bars are operating The near future will see the confrontation of theory with many fine observational results LIGO-G050250-00-W Raab: Status of Gravitational Wave Detectors 36