the ligo project ( l aser i nterferometer g ravitational-wave o bservatory )
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The LIGO Project ( L aser I nterferometer G ravitational-Wave O bservatory ). Rick Savage – Scientist LIGO Hanford Observatory. New kind of astronomical observatory. Looking for Gravitational waves , not Electromagnetic waves. General relativity – gravitational waves. - PowerPoint PPT PresentationTRANSCRIPT
The LIGO Project
(Laser Interferometer Gravitational-Wave Observatory)
Rick Savage – Scientist
LIGO Hanford Observatory
Looking for Gravitational waves, not Electromagnetic waves
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New kind of astronomical observatory
General relativity – gravitational waves
Laser Interferometer
GW: oscillating quadrupolar strain in spacetime
“Matter tells spacetime how to curve.Spacetime tells matter how to move.”
J. A Wheeler
Albert Einstein1916
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LIGO: Laser Interferometer Gravitational-wave Observatory
3002 km(L/c = 10 ms)
Caltech
MIT
• Managed and operated by Caltech & MIT with funding from NSF
• Goal: Direct observation ofgravitational waves
•Open a new observationalwindow on the Universe
Livingston, LA
Hanford, WA
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Movie
http://www.einsteinsmessengers.org/
Detection of gravitational waves
Michelson interferometer- differential length change sensor
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LIGO detectors
Laser
4 km-long Fabry-Perotarm cavity
recyclingmirror test masses
beam splitter
Power recycledMichelsoninterferometerwith Fabry-Perotarm cavities
signal
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Even the most energetic sourceswill generate oscillating length changes in LIGOof about ~10-18 meters
i.e. 0.000000000000000001 meters
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The Challenge for LIGO
How Small is 10-18 Meter?
Wavelength of light, about 1 micron100
One meter, about 40 inches
Human hair, about 100 microns000,10
LIGO sensitivity, 10-18 meter000,1
Nuclear diameter, 10-15 meter000,100
Atomic diameter, 10-10 meter000,10
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H1 detector sensitivity – July 10, 2010
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10-19 meters
S6 science run – July 2009 to October 2010
H1 detector range – July 10, 2010
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Sketch:Kip Thorne
1 Mpc = 1 million parsecs1 parsec ~ 3 light years
How Far is 20 MegaParsecs?
Speed of light is 300,000,000 meters/second
One parsec = 3.26256 light years
One year = 365 x 24 x 60 x 60 = 31,536,000 seconds
LIGO trying to sense motions of 0.0000000000000000001 meters caused by cosmic events 600,000,000,000,000,000 meters away (36 orders of magnitude in distance)
20 parsec x 3.26256 LY/parsec x 31,536,000 seconds/ LY x 300,000,000 meters/ sec = 617,328,552,960,000,000 meters
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No detections - data still being analyzed
Astrophysical results – upper limits» “If LIGO didn’t see it, then it can’t be bigger than …”
» CRAB pulsar – “no more than 4 percent of the energy loss of the pulsar is caused by the emission of gravitational waves.” (Caltech press release)
» Gamma ray burst GRB070201 – LIGO “results give an independent wayto reject hypothesis of a compact binaryprogenitor in M31”(Isabel Leonor for the LIGO Scientific Collaboration)
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What have we learned so far?
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What’s next? Advanced LIGO
Quantum noise limited interferometer
Factor of 10 increase in sensitivity
Factor of 1000 increase in event rate
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Laser source: 10 W to 200 W
Diode-pumpedYAG lasers
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Vibration isolation: passive to active
• Geophones and accelerometers on payload• Active feedback control – 6 deg. of freedom
• Masses anddamped springs
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Test mass suspensions
• Quadruple pendulumwith reaction masses
• 40 kg test masses
• Single pendulum
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Advanced LIGO ~2014
Hubble telescope WFPC2 image (NASA - JPL)
Searching (listening) for gravitational waves from cosmic events located 10 times farther away (~500 million light years)