1. LIGO-G030009-01-W "Colliding Black Holes" Credit: National Center for Supercomputing Applications (NCSA) Intro to LIGO Fred Raab, LIGO Hanford Observatory

2. LIGO-G030009-01-W LIGO: Portal to Spacetime2 Outline What LIGO is Relativity connection Terrestrial detector band How the detectors work LIGO searches

3. LIGO-G030009-01-W LIGO: Portal to Spacetime3 LIGO (Washington)LIGO (Louisiana) The Laser Interferometer Gravitational-Wave Observatory Funded by the National Science Foundation; operated by Caltech and MIT; the research focus for more than 500 LIGO Science Collaboration members worldwide.

4. The LIGO Observatories Adapted from “The Blue Marble: Land Surface, Ocean Color and Sea Ice” at visibleearth.nasa.gov NASA Goddard Space Flight Center Image by Reto Stöckli (land surface, shallow water, clouds). Enhancements by Robert Simmon (ocean color, compositing, 3D globes, animation). Data and technical support: MODIS Land Group; MODIS Science Data Support Team; MODIS Atmosphere Group; MODIS Ocean Group Additional data: USGS EROS Data Center (topography); USGS Terrestrial Remote Sensing Flagstaff Field Center (Antarctica); Defense Meteorological Satellite Program (city lights). LIGO Hanford Observatory (LHO) H1 : 4 km arms H2 : 2 km arms LIGO Livingston Observatory (LLO) L1 : 4 km arms 10 ms

5. LIGO-G030009-01-W LIGO: Portal to Spacetime5 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

6. LIGO-G030009-01-W LIGO: Portal to Spacetime6 John Wheeler’s Summary of General Relativity Theory

7. LIGO-G030009-01-W LIGO: Portal to Spacetime7 The New Wrinkle on Equivalence Not only the path of matter, but even the path of light is affected by gravity from massive objects Einstein Cross Photo credit: NASA and ESA A massive object shifts apparent position of a star

8. LIGO-G030009-01-W LIGO: Portal to Spacetime8 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:

9. LIGO-G030009-01-W LIGO: Portal to Spacetime9 Gravitational Collapse and Its Outcomes Present LIGO Opportunities f GW > few Hz accessible from earth f GW < several kHz interesting for compact objects

10. LIGO-G030009-01-W LIGO: Portal to Spacetime10 Catching Waves From Black Holes Sketches courtesy of Kip Thorne

11. LIGO-G030009-01-W LIGO: Portal to Spacetime11 Detection of Energy Loss Caused By Gravitational Radiation 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.

12. LIGO-G030009-01-W LIGO: Portal to Spacetime12 Potential sources Inspiral & merger of compact binaries Ringdown of newly formed black holes Supernovae (especially non-axisymmetric core collapse), Gamma-ray bursters Neutron-star (strange-quark-star ?) wobbles or quakes Accreting compact systems Stochastic signals or cosmological or astrophysical origin Cosmic string signals

13. LIGO-G030009-01-W How does LIGO detect spacetime vibrations?

14. LIGO-G030009-01-W LIGO: Portal to Spacetime14 Basic Signature of Gravitational Waves for All Detectors

15. LIGO-G030009-01-W LIGO: Portal to Spacetime15 Laser Beam Splitter End Mirror Screen Viewing Sketch of a Michelson Interferometer

16. LIGO-G030009-01-W LIGO: Portal to Spacetime16 Recycling Mirror Optical Cavity 4 km or 2-1/2 miles Beam Splitter Laser Photodetector Fabry-Perot-Michelson with Power Recycling

17. LIGO-G030009-01-W LIGO: Portal to Spacetime17 Spacetime is Stiff! => Wave can carry huge energy with miniscule amplitude! h ~ (G/c 4 ) (E NS /r)

18. LIGO-G030009-01-W LIGO: Portal to Spacetime18 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

19. LIGO-G030009-01-W LIGO: Portal to Spacetime19 Vacuum Chambers Provide Quiet Homes for Mirrors View inside Corner Station Standing at vertex beam splitter

20. LIGO-G030009-01-W LIGO: Portal to Spacetime20 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

21. LIGO-G030009-01-W LIGO: Portal to Spacetime21 Seismic Isolation – Springs and Masses damped spring cross section

22. LIGO-G030009-01-W LIGO: Portal to Spacetime22 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

23. LIGO-G030009-01-W LIGO: Portal to Spacetime23 Evacuated Beam Tubes Provide Clear Path for Light

24. LIGO-G030009-01-W LIGO: Portal to Spacetime24 All-Solid-State Nd:YAG Laser 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

25. LIGO-G030009-01-W LIGO: Portal to Spacetime25 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

26. LIGO-G030009-01-W LIGO: Portal to Spacetime26 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

27. LIGO-G030009-01-W LIGO: Portal to Spacetime27 Suspended Mirror Approximates a Free Mass Above Resonance

28. LIGO-G030009-01-W LIGO: Portal to Spacetime28 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

29. LIGO-G030009-01-W LIGO: Portal to Spacetime29 Thermal Noise Observed in 1 st Violins on H2, L1 During S1 Almost good enough for tracking calibration.

30. LIGO-G030009-01-W LIGO: Portal to Spacetime30 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

31. LIGO-G030009-01-W LIGO: Portal to Spacetime31 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 LockFull 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

32. LIGO-G030009-01-W LIGO: Portal to Spacetime32 And despite a few difficulties, science runs started in 2002…

33. LIGO-G030009-01-W LIGO: Portal to Spacetime33

34. LIGO-G030009-01-W LIGO: Portal to Spacetime34 LIGO Science Run S1 17 days in Aug-Sep 2002 3 LIGO interferometers in coincidence with GEO600 and ~2 days with TAMA300 “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)

35. LIGO-G030009-01-W LIGO: Portal to Spacetime35 Binary Neutron Stars: S1 Range Image: R. Powell

36. LIGO-G030009-01-W LIGO: Portal to Spacetime36 LIGO Science Run S2 Feb 14 – Apr 14, 2003 3 LIGO interferometers in coincidence with TAMA300; GEO600 not available for science running A Search for Gravitational Waves Associated with the Gamma Ray Burst GRB030329 Using the LIGO Detectors Limits on gravitational wave emission from selected pulsars using LIGO data

37. LIGO-G030009-01-W LIGO: Portal to Spacetime37 Binary Neutron Stars: Initial LIGO Target Range Image: R. Powell S2 Range

38. LIGO-G030009-01-W LIGO: Portal to Spacetime38 What’s next? Advanced LIGO… Major technological differences between LIGO and Advanced LIGO Initial Interferometers Advanced Interferometers Open up wider band Reshape Noise Quadruple pendulum Sapphire optics Silica suspension fibers Advanced interferometry Signal recycling Active vibration isolation systems High power laser (180W) 40kg

39. LIGO-G030009-01-W LIGO: Portal to Spacetime39 Binary Neutron Stars: AdLIGO Range Image: R. Powell LIGO Range

40. LIGO-G030009-01-W LIGO: Portal to Spacetime40 A Sampling of PhD Theses on LIGO Giaime – Signal Analysis & Control of Power-Recycled Fabry- Perot-Michelson Interferometer Regehr – Signal Analysis & Control of Power-Recycled Fabry- Perot-Michelson Interferometer Gillespie – Thermal Noise in Suspended Mirrors Bochner – Optical Modeling of LIGO Malvalvala – Angular Control by Wave-Front Sensing Lyons – Noise Processes in a Recombined Suspended Mirror Interferometer Evans – Automated Lock Acquisition for LIGO Adhikari – Noise & Sensitivity for Initial LIGO Sylvestre – Detection of GW Bursts by Cluster Analysis