Intro to LIGO

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

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

3. LIGO Observatories LIGO: Portal to Spacetime

4. Part of Future International Detector Network Simultaneously detect signal (within msec) Virgo GEO LIGO TAMA detection confidence locate the sources decompose the polarization of gravitational waves AIGO LIGO: Portal to Spacetime

5. A Slight Problem Regardless of what you see on Star Trek, the vacuum of interstellar space does not transmit conventional sound waves effectively. Don’t worry, we’ll work around that! LIGO: Portal to Spacetime

6. John Wheeler’s Summary of General Relativity Theory LIGO: Portal to Spacetime

7. 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 The New Wrinkle on Equivalence A massive object shifts apparent position of a star LIGO: Portal to Spacetime

8. 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: Gravitational Waves LIGO: Portal to Spacetime

9. What Phenomena Do We Expect to Study With LIGO?

10. Gravitational Collapse and Its Outcomes Present LIGO Opportunities fGW > few Hz accessible from earth fGW < several kHz interesting for compact objects LIGO: Portal to Spacetime

11. Do Supernovae Produce Gravitational Waves? Puppis A • Not if stellar core collapses symmetrically (like spiraling football) • Strong waves if end-over-end rotation in collapse • Increasing evidence for non-symmetry from speeding neutron stars • Gravitational wave amplitudes uncertain by factors of 1,000’s Credits: Steve Snowden (supernova remnant); Christopher Becker, Robert Petre and Frank Winkler (Neutron Star Image). LIGO: Portal to Spacetime

12. Gravitational-Wave Emission May be the “Regulator” for Accreting Neutron Stars • Neutron stars spin up when they accrete matter from a companion • Observed neutron star spins “max out” at ~700 Hz • Gravitational waves are suspected to balance angular momentum from accreting matter Credit: Dana Berry, NASA LIGO: Portal to Spacetime

13. Catching WavesFrom Black Holes Sketches courtesy of Kip Thorne LIGO: Portal to Spacetime

14. 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. Detection of Energy Loss Caused By Gravitational Radiation LIGO: Portal to Spacetime

15. Searching for Echoesfrom Very Early Universe Sketch courtesy of Kip Thorne LIGO: Portal to Spacetime

16. How does LIGO detect spacetime vibrations?

17. 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. LIGO: Portal to Spacetime

18. End Mirror End Mirror Beam Splitter Laser Screen Sketch of a Michelson Interferometer Viewing LIGO: Portal to Spacetime

19. Fabry-Perot-Michelson with Power Recycling 4 km or Optical Cavity 2-1/2 miles Beam Splitter Recycling Mirror Photodetector Laser LIGO: Portal to Spacetime

20. Spacetime is Stiff! => Wave can carry huge energy with miniscule amplitude! h ~ (G/c4) (ENS/r) LIGO: Portal to Spacetime

21. Vacuum Chambers Provide Quiet Homes for Mirrors View inside Corner Station Standing at vertex beam splitter LIGO: Portal to Spacetime

22. 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 BSC Chamber HAM Chamber LIGO: Portal to Spacetime

23. damped springcross section Seismic Isolation – Springs and Masses LIGO: Portal to Spacetime

24. 102 100 10-2 10-6 Horizontal 10-4 10-6 10-8 Vertical 10-10 Seismic System Performance HAM stack in air BSC stackin vacuum LIGO: Portal to Spacetime

25. Evacuated Beam Tubes Provide Clear Path for Light LIGO: Portal to Spacetime

26. All-Solid-State Nd:YAG Laser Custom-built 10 W Nd:YAG Laser, joint development with Lightwave Electronics (now commercial product) Cavity for defining beam geometry, joint development with Stanford Frequency reference cavity (inside oven) LIGO: Portal to Spacetime

27. Core Optics • Substrates: SiO2 • 25 cm Diameter, 10 cm thick • Homogeneity < 5 x 10-7 • Internal mode Q’s > 2 x 106 • 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 LIGO: Portal to Spacetime

28. Core Optics Suspension and Control Optics suspended as simple pendulums Local sensors/actuators provide damping and control forces Mirror is balanced on 1/100th inch diameter wire to 1/100th degree of arc LIGO: Portal to Spacetime

29. Suspended Mirror Approximates a Free Mass Above Resonance LIGO: Portal to Spacetime

30. Background Forces in GW Band = Thermal Noise ~ kBT/mode xrms  10-11 m f < 1 Hz xrms  210-17 m f ~ 350 Hz xrms  510-16 m f  10 kHz Strategy: Compress energy into narrow resonance outside band of interest  require high mechanical Q, low friction LIGO: Portal to Spacetime

31. Thermal Noise Observed in 1st Violins on H2, L1 During S1 Almost good enough for tracking calibration. LIGO: Portal to Spacetime

32. 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: Portal to Spacetime

33. Nuclear diameter, 10-15 meter Why is Locking Difficult? One meter, about 40 inches Human hair, about 100 microns Earthtides, about 100 microns Wavelength of light, about 1 micron Microseismic motion, about 1 micron Atomic diameter, 10-10 meter Precision required to lock, about 10-10 meter LIGO sensitivity, 10-18 meter LIGO: Portal to Spacetime

34. 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: Portal to Spacetime

35. 1999 2003 2000 2002 2001 4Q 3Q 2Q 2Q 2Q 2Q 4Q 4Q 4Q 4Q 1Q 1Q 1Q 1Q 3Q 3Q 3Q 3Q Full Lock all IFO's First Lock Inauguration 10-22 10-21 S1 S2 S3 Science Time Line Now strain noise density @ 200 Hz [Hz-1/2] 10-17 10-18 10-19 10-20 E1 E2 E3 E4 E5 E6 E7 E8 E9 E10 Engineering Runs First Science Data LIGO: Portal to Spacetime

36. 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 LIGO: Portal to Spacetime

37. And despite a few difficulties, science runs started in 2002… LIGO: Portal to Spacetime

38. Binary Neutron Stars:S1 Range LIGO: Portal to Spacetime Image: R. Powell

39. Binary Neutron Stars:S2 Range S1 Range LIGO: Portal to Spacetime Image: R. Powell

40. Binary Neutron Stars:Initial LIGO Target Range S2 Range LIGO: Portal to Spacetime Image: R. Powell

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

42. Binary Neutron Stars:AdLIGO Range LIGO Range LIGO: Portal to Spacetime Image: R. Powell