1. LIGO-G050474-01-W The Status of Laser Interferometer Gravitational-Wave Detectors Fred Raab, LIGO Hanford Observatory On behalf of LIGO Scientific Collaboration and other laser interferometer groups

2. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors2 Laser-Interferometer Gravitational Wave Detectors Some background Kilometer-scale detectors are working An international network has conducted coordinated runs and science analyses Long-term, deep-sky, astrophysics searches begin this year Technology development for future detectors is well along

3. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors3 Different Frequency Bands of Laser- Based Detectors and Sources Planned laser-based Gravitational Wave detector coverage over ~8 orders of magnitude » (terrestrial + space) Audio band spaceterrestrial

4. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors4 A “Baseline” Source: Waves From Orbiting Black Holes and Neutron Stars Sketches courtesy of Kip Thorne Exercises most of the frequency range of the detector

5. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors5 Gravitational Waves known to exist, just hard to find Neutron Binary System – Hulse & Taylor PSR 1913 + 16 -- Timing of pulsars   17 / sec Neutron Binary System separated by 10 6 miles m 1 = 1.4m  ; m 2 = 1.36m  ;  = 0.617 Prediction from general relativity spiral in by 3 mm/orbit rate of change orbital period ~ 8 hr Emission of gravitational waves

6. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors6 Basic Signature of Gravitational Waves for All Detectors

7. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors7 Laser-Interferometer or “Free- Mass” Detectors 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.

8. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors8 GEO600 Optical Configuration 12W laser mode cleaner interferometer with „dual recycling“ mode cleaner photo detector Courtesy B. Willke signal recycling mirror power recycling mirror

9. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors9 The International Interferometer Network LIGO Simultaneously detect signal (within msec) detection confidence locate the sources decompose the polarization of gravitational waves GEO Virgo TAMA AIGO

10. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors10 LIGO (Washington) (4-km and 2km) LIGO (Louisiana) (4-km) North America: Laser Interferometer Gravitational-Wave Observatory Funded by the National Science Foundation; operated by Caltech and MIT; the research focus for ~ 500 LIGO Scientific Collaboration members worldwide.

11. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors11 GEO 600 (Germany) 600-m Virgo (Italy) 3-km Interferometers in Europe Operated by GEO, member of LIGO Scientific Collaboration CNRS/INFN collaboration

12. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors12 TAMA 300 (Japan) (300-m) AIGO (Australia) (80-m, but 3-km site) Interferometers in Asia, Australia Operated by ACIGA; part of LIGO Scientific Collaboration. Longest running detector: 9 data runs!

13. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors13 Gravitational waves are hard to find because spacetime is stiff! => Wave can carry huge energy with miniscule amplitude! h ~ (G/c 4 ) (E NS /r)

14. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors14 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 (1/1000 th 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

15. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors15 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

16. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors16 LIGO Commissioning Time Line First Science Data Inauguration 1999 3Q 4Q 2000 1Q 2Q 3Q 4Q 2001 1Q 2Q 3Q 4Q 2002 1Q 2Q 3Q 4Q 2003 1Q 2Q 3Q 4Q E1 Engineering E2E3E4E5E6E7E8E9 S1 Science S2S3 First Lock Full Lock all IFO's 10 -17 10 -18 10 -19 10 -20 strain noise density @ 200 Hz [Hz -1/2 ] 10 -21 Runs 10 -22 E10 TAUP2003

17. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors17 LIGO Vibration Isolation Systems »Reduce in-band seismic motion by 4 - 6 orders of magnitude above 40 Hz »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 BSC Chamber

18. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors18 LIGO Seismic Isolation – Springs and Masses damped spring cross section

19. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors19 LIGO Core Optics Suspension and Control Shadow sensors & voice-coil actuators provide damping and control forces Mirror is balanced on 30 micron diameter wire to 1/100 th degree of arc Optics suspended as simple pendulums

20. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors20 VIRGO Seismic Isolation and Suspensions “Long Suspensions” inverted pendulum five intermediate filters Suspension vertical transfer function measured and simulated (prototype) See E. Majorana talk on VIRGO progress this afternoon

21. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors21 GEO600 Seismic Isolation and Suspension

22. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors22 TAMA300 Upgrade to Seismic Isolation

23. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors23 Suspended Mirror Approximates a Free Mass Above Resonance LIGO data taken using shadow sensors & voice coil actuators Blue: suspended mirror XF Cyan: free mass XF

24. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors24 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 »3 points  (pit, yaw) = 6 loops

25. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors25 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

26. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors26 Interferometer Strain Sensitivity

27. LIGO-G050474-01-W 27 S4 Science Duty Cycle H1: 80.5% H2: 81.4% L1: 74.5%

28. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors28 LSC Search Papers (as of 5Sep05) 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)

29. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors29 S2 Search Papers (as of 5Sep05) 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”, Phys. Rev. D 72, 042002 (2005) “Upper limits on gravitational wave bursts from LIGO’s second science run”, gr-qc/0505029 “Search for gravitational waves from galactic and extra–galactic binary neutron stars”, gr-qc/0505041 “Search for gravitational waves from primordial black hole binary Coalescences in the Galactic Halo”, gr-qc/0505042 “Upper limits from the LIGO and TAMA detectors on the rate of gravitational-wave bursts”, gr-qc/0507081 “First all-sky upper limits from LIGO on the strength of periodic gravitational waves using the Hough transform”, gr-qc/0508065

30. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors30 S3 Search Papers (as of 5Sep05) S3: “Upper Limits on a Stochastic Background of Gravitational Waves”, astro-ph/0507254

31. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors31 S3/S4 Analyses Underway Einstein@Home “Screensaver” search for undiscovered neutron stars and strange quark stars Uses 40,000 host computers with capacity ~20 Tflops, 24x7 First-pass analysis for LIGO/GEO600 data

32. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors32 What to expect from S3/S4 analyses Pulsars (see Alicia Sintes’ talk): »Limits on GW emission from 93 known radio pulsars, coordinated with Jodrell-Bank Pulsar Group »expect best limits on neutron star ellipticities ~10 -6 »expect Crab sensitivity ~ 4  spindown limit »all-sky/all-frequency search underway Cosmic GW background limits expected to be near  GW ~10 -4 Sensitivity to neutron-star inspirals starting to include Virgo cluster First limits on cosmic strings

33. LIGO-G050474-01-W 33 LIGO S2 data Assumes H 0 = 72 km/s/Mpc, at design sensitivity LIGO S3 data Sensitivity to Isotropic Stochastic Background

34. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors34 It works! (see B. O’Reilly’s talk) Long-term search begins Nov05

35. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors35 Binary Neutron Stars: Initial LIGO Target Range Image: R. Powell S2 Range

36. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors36 Future Plans for Terrestrial Detectors Begin long-term search (~one integrated year) using initial LIGO GEO600, TAMA300 continue to run, striving for design sensitivity Virgo has made steady progress in commissioning, hope to begin science searches in near future (see Majorana’s talk) Increased networking of resonant bars with interferometers Advanced LIGO technology continues development, approved by US National Science Board, planning toward a detector construction start for FY2008: PPARC funding in place in UK; funding being worked in Germany For LCGT news, see Miyoki’s talk

37. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors37 What’s next? Advanced LIGO… Major technological differences between LIGO and Advanced LIGO Initial Interferometers Advanced Interferometers Open up wider band Reshape Noise Advanced interferometry Signal recycling Active vibration isolation systems High power laser (180W) 40kg Quadruple pendulum: Silica optics, welded to silica suspension fibers See S. Miyoki’s LCGT talk for another view of the future

38. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors38 Binary Neutron Stars: AdLIGO Range Image: R. Powell LIGO Range

39. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors39 …and opening a new channel with a detector in space. Planning underway for space-based detector, LISA, hoping to fly in next decade to open up a lower frequency band

40. LIGO-G050474-01-W Raab: Status of Laser Gravitational Wave Detectors40 Closing remarks… We are experiencing a rapid advance in the sensitivity of searches for gravitational waves The near future will see the confrontation of theory with many fine observational results