1. LIGO-G020518-00-W Status of the Laser Interferometer Gravitational-Wave Observatory Reported on behalf of LIGO colleagues by Fred Raab, LIGO Hanford Observatory

2. LIGO-G020518-00-W Status of LIGO2 Laser Interferometer Gravitational- wave Observatory LIGO Mission: To sense the distortions of spacetime, known as gravitational waves, created by cosmic cataclysms and to exploit this new sense for astrophysical studies Over nearly 400 years, astronomy has developed many clever ways to “see” and study the universe; LIGO hopes to add a “sound track” using interferometers that function like large terrestrial microphones, listening for vibrations of space.

3. LIGO-G020518-00-W Status of LIGO3 Gravitational Collapse and Its Outcomes Present LIGO Opportunities f GW > few Hz accessible from earth f GW < several kHz interesting for compact objects

4. LIGO-G020518-00-W Status of LIGO4 Potential LIGO Sources Supernovae, with strength depending on asymmetry of collapse Inspirals and mergers of compact stars, like black holes, neutron stars Starquakes and wobbles of neutron stars and black holes Stochastic waves from the early universe, cosmic strings, etc. Unknown phenomena

5. LIGO-G020518-00-W Status of LIGO5 Gravitational Waves Gravitational waves are ripples in space when it is stirred up by rapid motions of large concentrations of matter or energy Rendering of space stirred by two orbiting black holes:

6. LIGO-G020518-00-W Status of LIGO6 Catching Waves From Black Holes Sketches courtesy of Kip Thorne

7. LIGO-G020518-00-W Status of LIGO7 Energy Loss Caused By Gravitational Radiation Confirmed In 1974, J. Taylor and R. Hulse discovered a pulsar orbiting a companion neutron star. This “binary pulsar” provides some of the best tests of General Relativity. Theory predicts the orbital period of 8 hours should change as energy is carried away by gravitational waves. Taylor and Hulse were awarded the 1993 Nobel Prize for Physics for this work.

8. LIGO-G020518-00-W Status of LIGO8 Sounds of Compact Star Inspirals Neutron-star binary inspiral: Black-hole binary inspiral:

9. LIGO-G020518-00-W How does LIGO detect spacetime vibrations?

10. LIGO-G020518-00-W Status of LIGO10 Important Signature of Gravitational Waves Gravitational waves shrink space along one axis perpendicular to the wave direction as they stretch space along another axis perpendicular both to the shrink axis and to the wave direction.

11. LIGO-G020518-00-W Status of LIGO11 Laser Beam Splitter End Mirror Screen Viewing Sketch of a Michelson Interferometer

12. LIGO-G020518-00-W Status of LIGO12 LIGO (Washington)LIGO (Louisiana) The Laser Interferometer Gravitational-Wave Observatory Supported by the U.S. National Science Foundation; operated by Caltech and MIT; the research focus for more than 400 LIGO Scientific Collaboration members worldwide.

13. LIGO-G020518-00-W Status of LIGO13 The Four Corners of the LIGO Laboratory  Observatories at Hanford, WA (LHO) & Livingston, LA (LLO)  Support Facilities @ Caltech & MIT campuses LHO LLO

14. LIGO-G020518-00-W Status of LIGO14 Part of Future International Detector Network LIGO Simultaneously detect signal (within msec) detection confidence locate the sources decompose the polarization of gravitational waves GEO Virgo TAMA AIGO

15. LIGO-G020518-00-W Status of LIGO15 Spacetime is Stiff! => Wave can carry huge energy with miniscule amplitude! h ~ (G/c 4 ) (E NS /r)

16. LIGO-G020518-00-W Status of LIGO16 Some of the Technical Challenges Typical Strains less than ~ 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 Engineer structures to mitigate recoil from atomic vibrations in suspended mirrors Provide clear optical paths within 4-km UHV beam lines

17. LIGO-G020518-00-W Status of LIGO17 Recycling Mirror Optical Cavity 4 km or 2-1/2 miles Beam Splitter Laser Photodetector Fabry-Perot-Michelson with Power Recycling

18. LIGO-G020518-00-W Status of LIGO18 Vacuum Chambers Provide Quiet Homes for Mirrors View inside Corner Station Standing at vertex beam splitter P < 10-6 Torr in chambers to reduce acoustics & molecular Brownian motion

19. LIGO-G020518-00-W Status of LIGO19 Beam Tube Provides Distortion- Free 4-km Pathway for Light  Requires P ~ 10 -9 Torr H 2 Equivalent  Baked out by insulating tube and driving ~2000 amps from end to end

20. LIGO-G020518-00-W Status of LIGO20 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

21. LIGO-G020518-00-W Status of LIGO21 Design for Low Background Spec’d From Prototype Operation For Example: Noise- Equivalent Displacement of 40-meter Interferometer (ca1994)

22. LIGO-G020518-00-W Status of LIGO22 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 BSC Chamber

23. LIGO-G020518-00-W Status of LIGO23 Seismic Isolation – Springs and Masses damped spring cross section

24. LIGO-G020518-00-W Status of LIGO24 Seismic System Performance 10 2 10 0 10 - 2 10 - 4 10 - 6 10 - 8 10 -10 Horizontal Vertical 10 -6 HAM stack in air BSC stack in vacuum

25. LIGO-G020518-00-W Status of LIGO25 Core Optics Suspension and Control Local sensors/actuators provide damping and control forces Mirror is balanced on 1/100 th inch diameter wire to 1/100 th degree of arc Optics suspended as simple pendulums

26. LIGO-G020518-00-W Status of LIGO26 Suspended Mirror Approximates a Free Mass Above Resonance

27. LIGO-G020518-00-W Status of LIGO27 IO Frequency Stabilization of the Light Employs Three Stages Pre-stabilized laser delivers light to the long mode cleaner Start with high-quality, custom-built Nd:YAG laser Improve frequency, amplitude and spatial purity of beam Actuator inputs provide for further laser stabilization Wideband Tidal 10-Watt Laser PSL Interferometer 15m 4 km

28. LIGO-G020518-00-W Status of LIGO28 Interferometer Control System Multiple Input / Multiple Output Three tightly coupled cavities Ill-conditioned (off-diagonal) plant matrix Highly nonlinear response over most of phase space Transition to stable, linear regime takes plant through singularity Employs adaptive control system that evaluates plant evolution and reconfigures feedback paths and gains during lock acquisition But it works!

29. LIGO-G020518-00-W Status of LIGO29 Steps to Locking an Interferometer signal Laser X Arm Y Arm Composite Video

30. LIGO-G020518-00-W Status of LIGO30 Watching the Interferometer Lock signal X Arm Y Arm Laser

31. LIGO-G020518-00-W Status of LIGO31 Why is Locking Difficult? One meter, about 40 inches Human hair, about 100 microns Wavelength of light, about 1 micron LIGO sensitivity, 10 -18 meter Nuclear diameter, 10 -15 meter Atomic diameter, 10 -10 meter Earthtides, about 100 microns Microseismic motion, about 1 micron Precision required to lock, about 10 -10 meter

32. LIGO-G020518-00-W Status of LIGO32 Tidal Compensation Data Tidal evaluation on 21-hour locked section of S1 data Residual signal on voice coils Predicted tides Residual signal on laser Feedforward Feedback

33. LIGO-G020518-00-W Status of LIGO33 Microseism Trended data (courtesy of Gladstone High School) shows large variability of microseism, on several-day- and annual- cycles Reduction by feed-forward derived from seismometers Microseism at 0.12 Hz dominates ground velocity

34. LIGO-G020518-00-W Status of LIGO34 Background Forces in GW Band = Thermal Noise ~ k B T/mode Strategy: Compress energy into narrow resonance outside band of interest  require high mechanical Q, low friction x rms  10 -11 m f < 1 Hz x rms  2  10 -17 m f ~ 350 Hz x rms  5  10 -16 m f  10 kHz

35. LIGO-G020518-00-W Status of LIGO35 Thermal Noise Checked in 1 st Violins on H2, L1 During S1 Almost good enough for tracking calibration.

36. LIGO-G020518-00-W Status of LIGO36 Chronology of Detector Installation & Commissioning 7/98Begin detector installation 6/99Lock first mode cleaner 11/99Laser spot on first end mirror 12/99First lock of a 2-km Fabry-Perot arm 4/00Engineering Run 1 (E1) 10/00Recombined LHO-2km interferometer in E2 run 10/00First lock of LHO-2km power-recycled interferometer 2/01Nisqually earthquake damages LHO interferometers 4/01Recombined 4-km interferometer at LLO 5/01Earthquake repairs completed at LHO 6/01Last LIGO-1 mirror installed 12/01Power recycling achieved for LLO-4km 1/02E7: First triple coincidence run; first on-site data analysis 1/02Power recycling achieved for LHO-4km 9/02First Science Run (S1) completed 2/03Second Science Run (S2) begun

37. LIGO-G020518-00-W Status of LIGO37 LIGO Sensitivity Livingston 4km Interferometer May 01 Jan 03

38. LIGO-G020518-00-W Status of LIGO38 S1 Analysis Working Groups Data from S1 is being analyzed by LSC working groups for: »Detector Characterization – monitors of data quality, instrument diagnostics, tuning displays »Binary Inspirals – modeled chirps from BH’s, NS’s, MACHO’s »Bursts – unmodeled deviations from stationarity; independent searches; searches triggered on GRB’s, SN’s »Periodic Sources – known pulsar search; work toward all-sky search for unknown pulsars »Stochastic Background – early universe

39. LIGO-G020518-00-W Status of LIGO39 Summary  First triple coincidence run completed (17 days with ~23% triple coincidence duty factor)  On-line data analysis systems (Beowulf parallel supercomputer) functional at LHO and LLO  S1 coincidence analyses with GEO & TAMA are first science analyses with international laser-GW network  First science data analysis ongoing  Interferometer control system still being commissioned and tuned  Working to increase immunity to high seismic noise periods (especially important at LLO)  S2 running 14Feb03 – 14Apr03

40. LIGO-G020518-00-W Status of LIGO40 Future Plans Improve reach of initial LIGO to run 1 yr at design sensitivity Advanced LIGO technology under development with intent to install by 2008 Planning underway for space-based detector, LISA, to open up a lower frequency band ~ 2015

41. LIGO-G020518-00-W Status of LIGO41 Despite a few difficulties, science runs started in 2002.

42. LIGO-G020518-00-W Status of LIGO42 Stochastic Background sensitivities and theory E7 S1 S2 LIGO Adv LIGO results projected

43. LIGO-G020518-00-W Status of LIGO43 We Have Continued to Progress…

44. LIGO-G020518-00-W Status of LIGO44

45. LIGO-G020518-00-W Status of LIGO45 Pre-stabilized Laser (PSL) Custom-built 10 W Nd:YAG Laser, joint development with Lightwave Electronics (now commercial product) Frequency reference cavity (inside oven) Cavity for defining beam geometry, joint development with Stanford

46. LIGO-G020518-00-W Status of LIGO46 Digital Interferometer Sensing & Control System

47. LIGO-G020518-00-W Status of LIGO47 Core Optics Substrates: SiO 2 »25 cm Diameter, 10 cm thick »Homogeneity < 5 x 10 -7 »Internal mode Q’s > 2 x 10 6 Polishing »Surface uniformity < 1 nm rms »Radii of curvature matched < 3% Coating »Scatter < 50 ppm »Absorption < 2 ppm »Uniformity <10 -3 Production involved 6 companies, NIST, and LIGO