Gravity Waves

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

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Brief Outline

• Intro (astronomy gravity waves)
• Waves Gravity Waves
• GW Detectors (Bar, Ifo LIGO)
• Current State Future
• Demonstrations

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Intro

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

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Astronomy Gravity Waves

• Naked-eye observations

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Astronomy Gravity Waves (cont.)

• Electromagnetic (EM) observations
• (visible, microwave, IR, UV, X-ray, etc.)

Radio telescope array
Mauna Kea Observatories
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Astronomy Gravity Waves (cont.)

• Gravity Wave Observations (soon to come!)

Orbiting black holes
Albert Einstein
LIGO Hanford Observatory
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Waves Gravity Waves

• Wave phenomena throughout nature/everyday life
• Waves on a lake
• Light
• Sound

Familiar?
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Waves Gravity Waves (cont.)

• Picture of a Wave

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Waves Gravity Waves (cont.)

• Frequency is measured in Hz (cycles / wavelengths
  per sec)

-----------1 sec-----------
3 3/4Hz
5 3/4Hz
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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

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Waves Gravity Waves (cont.)

• VISIBLE LIGHT
• Small band of frequencies in EM spectrum
• These wiggling waves cause rods/cones in our eyes
  to wiggle

violet Wavelength 400nm
red Wavelength 700nm
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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

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Waves Gravity Waves (cont.)
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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

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Waves Gravity Waves (cont.)

• GRAVITY WAVES
• Einsteins Theory of General Relativity
• Concept of space-time---update on Newtons law of
  gravity
• Space and time tied together
• Instead of having gravitational forces, matter
  curves space time

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Waves Gravity Waves (cont.)

• Curved space-time
  Static example

This example shows a large object (big warp in
spacetime), w/ an object orbiting it.
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Waves Gravity Waves (cont.)

• GRAVITY WAVES
• 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)

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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)
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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!)

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Waves Gravity Waves (cont.)

• Gravity Wave passing through a person

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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

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Detectors LIGO

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

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Detectors LIGO (cont.)

• 1974Taylor 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

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Detectors LIGO (cont.)

• RESONANT BAR DETECTORS
• First Instrument designed for gravity wave
  detection (1960s)
• Developed by Joseph Weber (right)

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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

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Detectors LIGO (cont.)

• INTERFEROMETERS (a.k.a. ifo)
• Background
• How it works
• Current ifos LIGO
• Noise

Michelson Einstein Millikan
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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

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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

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Detectors LIGO (cont.)

• How An Ifo Works

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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)

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

• Hows LIGO Unique?
• Biggest Interferometers (one 2km and two 4km)
• Two observatories
• High power laser ( gt6W)
• Resonant arm cavities ( gt2500W)
• Seismic Isolation System
• One of the largest vacuum systems

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Detectors LIGO (cont.)
Hows LIGO Unique? 1) Three of the Biggest
Interferometers (one 2km and two 4km)
LIGO (Washington)
LIGO (Louisiana)
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Hows LIGO Unique? (cont.)

• Observatories at Hanford, WA (LHO) Livingston,
  LA (LLO)
• Support Facilities _at_ Caltech MIT campuses

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Hows LIGO Unique? (cont.)
High power (gt6W) laser and Mode Cleaning Cavity
Custom-built 10 W NdYAG Laser
Cavity for defining beam geometry
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Hows LIGO Unique? (cont.)

• Resonant arm cavities (resonating gt 2500W)

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Hows LIGO Unique? (cont.)
Seismic Isolation System
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Hows LIGO Unique? (cont.)
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Hows LIGO Unique? (cont.)

• Seismic noise over 40Hz attenuated
• Supports all internal components

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Hows LIGO Unique? (cont.)

• One of the largest vacuum systems
• Vacuum down to 10-9torr (vs. 7.6x102 torr )

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Hows LIGO Unique? (cont.)
Inside the Corner Station
Beam splitter chamber
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Hows LIGO Unique? (cont.)

• Specialized And Custom Optics
• Massive optics (to reduce thermal noise)
• Precisely polished surfaces
• Specially coated

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Hows LIGO Unique? (cont.)

• Layers of Isolation
• Damped Table
• Suspended Optic
• Electronically damped/
• controlled optic

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Noise Issues

• Seismic
• Microseism, tidal, cultural,
• logging, etc.
• Electrical
• Brownian/thermal

Hurricane in North Atlantic
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LIGOs Future

• LIGO will have overall upgrade around 2007
• Increased sensitivity
• Increased range

LIGO2
LIGO1
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Excitement at LIGO