2/9/2006Welcome to LIGO1 Welcome to LIGO!

2/9/2006Welcome to LIGO2 LIGO: A detector that measures very tiny displacements How tiny? m a meter a centimeter a millimeter a human hair one wavelength of light diameter of an atom LIGO displacement sensitivity diameter of a nucleus

2/9/2006Welcome to LIGO3 An ultra-sensitive device called an interferometer provides this precision Laser Beam Splitter End Mirror Screen

2/9/2006Welcome to LIGO4 Design enhancements are needed for full sensitivity Laser signal

2/9/2006Welcome to LIGO5 Why such extraordinary precision? Gravitational waves are ripples in the fabric of space when it is stirred up by rapid motions of large concentrations of matter or energy. LIGO uses large interferometers as it attempts to make the first direct detection of gravitational waves. Rendering of space stirred by two orbiting black holes: By the time gravitational waves pass the earth, their effects are vanishingly small

2/9/2006Welcome to LIGO6 LIGO science relies upon Einstein’s General Theory of Relativity John Wheeler’s view of Einstein’s description of space, time and gravity

2/9/2006Welcome to LIGO7 Large Mass Curves Space Gravity: The curvature of space (spacetime) caused by the presence of mass

2/9/2006Welcome to LIGO8 Curvature is real! 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

2/9/2006Welcome to LIGO9 LIGO listens for ripples in the curvature of space. These will produce vibrations of the interference pattern in the interferometer. Photosensors will record the vibrations. Inspiraling Neutron Stars Inspiraling Black Holes What might the “sound” of gravitational waves?

2/9/2006Welcome to LIGO10 “Can we order some extreme accelerations of large masses, please?

2/9/2006Welcome to LIGO11 A Pulsar Stirring Up Space

2/9/2006Welcome to LIGO12 How does the Interferometer sense the signal 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.

2/9/2006Welcome to LIGO13 LIGO’s suspended mirrors ride along in the space that shrinks and stretches as the gravitational wave passes by Laser signal Long arms increase the detector’s ability to sense gravitational waves Bouncing the light within the arms increases the time that the light, the mirrors and the gravitational wave interact

2/9/2006Welcome to LIGO14 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 Mirrors have freedom of movement in our frequency band thanks to their pendulum suspensions

2/9/2006Welcome to LIGO15 Vacuum chambers provide quiet homes for the mirrors View inside Corner Station Standing at vertex beam splitter

2/9/2006Welcome to LIGO16 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

2/9/2006Welcome to LIGO17 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

2/9/2006Welcome to LIGO18 LIGO now searches for gravitational waves at design sensitivity in the S5 science run