LIGO Hanford Observatory Gravity Waves And LIGO Corey Gray LIGO Hanford Observatory LIGO Laboratory

Brief Outline Intro (astronomy & gravity waves) Waves & Gravity Waves GW Detectors (Bar, Ifo = LIGO) Current State & Future Demonstrations LIGO Laboratory

The Laser Interferometer Gravitational-Wave Observatory Intro LIGO = The Laser Interferometer Gravitational-Wave Observatory Laser = type of light used for our interferometer Interferometer = Instrument/measuring device Gravitational Wave = signal LIGO Laboratory

Astronomy & Gravity Waves Naked-eye observations LIGO Laboratory

Astronomy & Gravity Waves (cont.) Electromagnetic (EM) observations (visible, microwave, IR, UV, X-ray, etc.) Radio telescope array Mauna Kea Observatories LIGO Laboratory

Astronomy & Gravity Waves (cont.) Gravity Wave Observations (soon to come!) Orbiting black holes Albert Einstein LIGO Hanford Observatory LIGO Laboratory

Waves & Gravity Waves Wave phenomena throughout nature/everyday life Waves on a lake Light Sound Familiar? LIGO Laboratory

Waves & Gravity Waves (cont.) Picture of a Wave LIGO Laboratory

Waves & Gravity Waves (cont.) Frequency is measured in Hz (cycles / wavelengths per sec) |-----------1 sec-----------| ~3 3/4Hz ~5 3/4Hz LIGO Laboratory

Waves & Gravity Waves (cont.) SOUND Movement of a medium (i.e. air particles) by vibrating matter (piano, drum, book dropping) Our ears have range of ~20-20,000Hz Wiggling of air vibrates our ear drum so we can detect sound LIGO Laboratory

Waves & Gravity Waves (cont.) VISIBLE LIGHT Small band of frequencies in EM spectrum These wiggling waves cause rods/cones in our eyes to wiggle red Wavelength = 700nm violet Wavelength = 400nm LIGO Laboratory

Waves & Gravity Waves (cont.) ELECTROMAGNETIC SPECTRUM Waves composed of coupled electric and magnetic fields Includes large family of waves: radio, microwaves, IR, visible, UV, X-rays, gamma rays All travel at “c”  c = speed of light = 3 x 10 ^8 m/s LIGO Laboratory

Waves & Gravity Waves (cont.) LIGO Laboratory

Waves & Gravity Waves (cont.) Examples of different signals/waves: Distant earthquake = 0.03 - 0.09 Hz Microseism (ocean weather) = 0.15 Hz Truck & car traffic = 3 - 15 Hz Computer monitor (fan?) = 60 - 80Hz Human voice range = 100 – 1200Hz LIGO Laboratory

Waves & Gravity Waves (cont.) Einstein’s Theory of General Relativity Concept of space-time---update on Newton’s law of gravity Space and time tied together Instead of having gravitational forces, matter curves space time LIGO Laboratory

Waves & Gravity Waves (cont.) Curved space-time Static example This example shows a large object (big warp in spacetime), w/ an object orbiting it. LIGO Laboratory

Waves & Gravity Waves (cont.) Generated by accelerating matter/energy, but matter must be HUGE, because…. Signals are extremely weak Only catastrophic events generate signals big enough to detect Possible sources: Binary systems (NS, BH,pulsar) NS/NS Supernova---------------------------------------- Stochastic background (Big Bang remnants) LIGO Laboratory

Waves & Gravity Waves (cont.) 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: BH/BH (no noise) BH/BH (noise) LIGO Laboratory

Waves & Gravity Waves (cont.) Gravity Wave Characteristics: Velocity = speed of light, c Gravity waves shrink space along one axis as they stretch space along another axis (this is convenient for ifos!) LIGO Laboratory

Waves & Gravity Waves (cont.) Gravity Wave passing through a person: LIGO Laboratory

Waves & Gravity Waves (cont.) Gravity waves are completely different from EM waves(macro vs. nuclear level) Will offer a completely different way to look at the cosmos Gravity waves will hold completely different types of information to current EM signals LIGO Laboratory

Detectors = LIGO How Will We Detect Gravity Waves?? Indirectly have already been discovered Resonant Bar Detectors Interferometers LIGO Laboratory

Detectors = LIGO (cont.) 1974—Taylor & Hulse Indirectly discover existence of gravity waves emitted from pulsar/neutron star system. Energy seeping away from binary system directly correlated to emission of gravity waves Nobel Prize in 1993 LIGO Laboratory

Detectors = LIGO (cont.) RESONANT BAR DETECTORS First Instrument designed for gravity wave detection (1960s) Developed by Joseph Weber (right) LIGO Laboratory

Detectors = LIGO (cont.) Bar is basically a bell Designed to resonate at one frequency by a gravity wave Consist of Al bar (hundreds of lbs) Seismic isolation Motion detectors (piezos) Limitations Only one frequency Hard to improve sensitivity LIGO Laboratory

Detectors = LIGO (cont.) INTERFEROMETERS (a.k.a. “ifo”) Background How it works Current ifos = LIGO Noise Michelson Einstein Millikan LIGO Laboratory

Detectors = LIGO (cont.) IFO BACKGROUND Interferometers were born from Michelson-Morley experiment of the late 1800s High precision instrument used in many fields of science Uses wave nature of light to detect small changes in lengths interferes light w/ itself LIGO Laboratory

Detectors = LIGO (cont.) Rai Weiss (MIT) began work w/ use of an ifo as a gravity wave detector (‘70s) Resonating the arms of an ifo was developed by Ron Drever (’70s); this is birth of current LIGO set up In the 80s Caltech developed a 40m experimental ifo & VIRGO begins Mid 80s – present, Caltech/MIT join for current LIGO project LIGO Laboratory

Detectors = LIGO (cont.) How An Ifo Works LIGO Laboratory

Detectors = LIGO (cont.) LIGO Interferometer: Ideal GW Instrument Technology improvements of last 30+ years Geometry of an ifo is perfect for the orthogonal (90 deg) nature of gravity waves Ifos can detect signals over a wide range of frequencies (tens to thousands of Hz) Able to improve on sensitivity in many different ways (consists of several sub-systems) LIGO Laboratory

Detectors = LIGO (cont.) Locked on dark fringe Acquiring w/ 1-arm locks Locked LIGO Laboratory

Detectors = LIGO (cont.) How’s LIGO Unique? Biggest Interferometers (one 2km and two 4km) Two observatories High power laser ( >6W) Resonant arm cavities ( >2500W) Seismic Isolation System One of the largest vacuum systems LIGO Laboratory

Detectors = LIGO (cont.) How’s LIGO Unique? 1) Three of the Biggest Interferometers (one 2km and two 4km) LIGO (Washington) LIGO (Louisiana) LIGO Laboratory

How’s LIGO Unique? (cont.) Observatories at Hanford, WA (LHO) & Livingston, LA (LLO) Support Facilities @ Caltech & MIT campuses LIGO Laboratory

How’s LIGO Unique? (cont.) High power (>6W) laser and Mode Cleaning Cavity Custom-built 10 W Nd:YAG Laser Cavity for defining beam geometry LIGO Laboratory

How’s LIGO Unique? (cont.) Resonant arm cavities (resonating > 2500W) LIGO Laboratory

How’s LIGO Unique? (cont.) Seismic Isolation System LIGO Laboratory

How’s LIGO Unique? (cont.) damped spring cross section LIGO Laboratory

How’s LIGO Unique? (cont.) Seismic noise over ~40Hz attenuated Supports all internal components LIGO Laboratory

How’s LIGO Unique? (cont.) One of the largest vacuum systems Vacuum down to 10^-9torr (vs. ~7.6x10^2 torr ) LIGO Laboratory

How’s LIGO Unique? (cont.) Inside the Corner Station Beam splitter chamber LIGO Laboratory

How’s LIGO Unique? (cont.) Specialized And Custom Optics Massive optics (to reduce thermal noise) Precisely polished surfaces Specially coated LIGO Laboratory

How’s LIGO Unique? (cont.) Layers of Isolation: Damped Table Suspended Optic Electronically damped/ controlled optic LIGO Laboratory

Noise Issues Seismic Electrical Brownian/thermal Microseism, tidal, cultural, logging, etc. Electrical Brownian/thermal Hurricane in North Atlantic LIGO Laboratory

LIGO’s Future LIGO will have overall upgrade around 2007 Increased sensitivity Increased range LIGO2 LIGO1 LIGO Laboratory

Excitement at LIGO LIGO Laboratory