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

LIGO-G W LIGO: Portal to Spacetime2 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.

LIGO-G W LIGO: Portal to Spacetime3 LIGO Observatories

LIGO-G W LIGO: Portal to Spacetime4 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

LIGO-G W LIGO: Portal to Spacetime5 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-G W LIGO: Portal to Spacetime6 John Wheeler’s Summary of General Relativity Theory

LIGO-G 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

LIGO-G 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:

LIGO-G W What Phenomena Do We Expect to Study With LIGO?

LIGO-G W LIGO: Portal to Spacetime10 Gravitational Collapse and Its Outcomes Present LIGO Opportunities f GW > few Hz accessible from earth f GW < several kHz interesting for compact objects

LIGO-G W LIGO: Portal to Spacetime11 Do Supernovae Produce Gravitational Waves? 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). Puppis A

LIGO-G W LIGO: Portal to Spacetime12 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-G W LIGO: Portal to Spacetime13 Catching Waves From Black Holes Sketches courtesy of Kip Thorne

LIGO-G W LIGO: Portal to Spacetime14 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.

LIGO-G W LIGO: Portal to Spacetime15 Searching for Echoes from Very Early Universe Sketch courtesy of Kip Thorne

LIGO-G W How does LIGO detect spacetime vibrations?

LIGO-G W LIGO: Portal to Spacetime17 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-G W LIGO: Portal to Spacetime18 Laser Beam Splitter End Mirror Screen Viewing Sketch of a Michelson Interferometer

LIGO-G W LIGO: Portal to Spacetime19 Recycling Mirror Optical Cavity 4 km or 2-1/2 miles Beam Splitter Laser Photodetector Fabry-Perot-Michelson with Power Recycling

LIGO-G W LIGO: Portal to Spacetime20 Spacetime is Stiff! => Wave can carry huge energy with miniscule amplitude! h ~ (G/c 4 ) (E NS /r)

LIGO-G W LIGO: Portal to Spacetime21 Vacuum Chambers Provide Quiet Homes for Mirrors View inside Corner Station Standing at vertex beam splitter

LIGO-G W LIGO: Portal to Spacetime22 Vibration Isolation Systems »Reduce in-band seismic motion by 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

LIGO-G W LIGO: Portal to Spacetime23 Seismic Isolation – Springs and Masses damped spring cross section

LIGO-G W LIGO: Portal to Spacetime24 Seismic System Performance Horizontal Vertical HAM stack in air BSC stack in vacuum

LIGO-G W LIGO: Portal to Spacetime25 Evacuated Beam Tubes Provide Clear Path for Light

LIGO-G W LIGO: Portal to Spacetime26 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

LIGO-G W LIGO: Portal to Spacetime27 Core Optics Substrates: SiO 2 »25 cm Diameter, 10 cm thick »Homogeneity < 5 x »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

LIGO-G W LIGO: Portal to Spacetime28 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

LIGO-G W LIGO: Portal to Spacetime29 Suspended Mirror Approximates a Free Mass Above Resonance

LIGO-G W LIGO: Portal to Spacetime30 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  m f < 1 Hz x rms  2  m f ~ 350 Hz x rms  5  m f  10 kHz

LIGO-G W LIGO: Portal to Spacetime31 Thermal Noise Observed in 1 st Violins on H2, L1 During S1 Almost good enough for tracking calibration.

LIGO-G W LIGO: Portal to Spacetime32 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-G W LIGO: Portal to Spacetime33 Why is Locking Difficult? One meter, about 40 inches Human hair, about 100 microns Wavelength of light, about 1 micron LIGO sensitivity, meter Nuclear diameter, meter Atomic diameter, meter Earthtides, about 100 microns Microseismic motion, about 1 micron Precision required to lock, about meter

LIGO-G W LIGO: Portal to Spacetime34 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-G W LIGO: Portal to Spacetime35 Time Line Now First Science Data Inauguration Q 4Q Q 2Q 3Q 4Q Q 2Q 3Q 4Q Q 2Q 3Q 4Q Q 2Q 3Q 4Q E1 Engineering E2E3E4E5E6E7E8E9 S1 Science S2S3 First LockFull Lock all IFO's strain noise 200 Hz [Hz -1/2 ] Runs E10

LIGO-G W LIGO: Portal to Spacetime36 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-G W LIGO: Portal to Spacetime37 And despite a few difficulties, science runs started in 2002…

LIGO-G W LIGO: Portal to Spacetime38 Binary Neutron Stars: S1 Range Image: R. Powell

LIGO-G W LIGO: Portal to Spacetime39 Binary Neutron Stars: S2 Range Image: R. Powell S1 Range

LIGO-G W LIGO: Portal to Spacetime40 Binary Neutron Stars: Initial LIGO Target Range Image: R. Powell S2 Range

LIGO-G W LIGO: Portal to Spacetime41 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

LIGO-G W LIGO: Portal to Spacetime42 Binary Neutron Stars: AdLIGO Range Image: R. Powell LIGO Range