Transcript Caltech_Trustees

LIGO Update
-----------“The Search for Gravitational Waves”
Barry Barish
Caltech Trustees
10-Sept-02
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Laser Interferometer
Gravitational-wave Observatory

Goals
» First direct detection of gravitational waves
» Open new window on the universe – “gravitational wave astronomy”

NSF funded construction in 1994 for $296M
» Caltech has fiduciary responsibility
» Joint Caltech/MIT technical and scientific team
» Construction completed in both Louisiana and Washington in 2000

Commissioning, Operations and Scientific Programs
»
»
»
»

First Interferometer “locked” – (Oct 2000)
First coincidence running of both sites – (Dec 2001)
First scientific data run “upper limits” – (Sept 2002)
Search for gravitational waves – (2003 through 2006)
We propose to install “Advanced LIGO” in 2007
» Cost ~ $125M total -- international collaboration
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LIGO Scientific Collaboration
Member Institutions
LSC Membership
35 institutions > 350 collaborators
University of Adelaide ACIGA
Australian National University ACIGA
California State Dominquez Hills
Caltech LIGO
Caltech Experimental Gravitation CEGG
Caltech Theory CART
University of Cardiff GEO
Carleton College
Cornell University
University of Florida @ Gainesville
Glasgow University GEO
University of Hannover GEO
Harvard-Smithsonian
India-IUCAA
IAP Nizhny Novgorod
Iowa State University
Joint Institute of Laboratory Astrophysics
LIGO Livingston LIGOLA
LIGO Hanford LIGOWA
Louisiana State University
Louisiana Tech University
MIT LIGO
Max Planck (Garching) GEO
Max Planck (Potsdam) GEO
University of Michigan
Moscow State University
NAOJ - TAMA
University of Oregon
Pennsylvania State University Exp
Pennsylvania State University Theory
Southern University
Stanford University
University of Texas@Brownsville
University of Western Australia ACIGA
University of Wisconsin@Milwaukee
International
India, Russia,
Germany,
U.K, Japan
and
Australia.
The international
partners are
involved in all
aspects of the
LIGO research
program.
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Livingston Optical Telescope
broad outreach/education program
Telescope facts:
Draft building concept utilizes
surplus beam tube enclosures on
raised footings with roll-off roof
16 inch Richey Chretien telescope built
by Optical Guidance Systems
Proposed
telescope
location on
fire access
road gives
clear view to
south
Telescope provided by state funds via
LSU. LIGO provides site and internet
connection and incorporates telescope
use into outreach program.
Internet accessible to facilitate
classroom use
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Budget
LIGO Operations (2002 thru 2006)


Operations of LIGO funded beginning in 2002 for 5 years at a
total funding of $160M
We function as one distributed laboratory (LIGO Laboratory)
» Caltech (85 staff); MIT (25staff); Hanford (25 staff); Livingston (25 staff)

Advanced LIGO construction (not included) to be proposed
next year
FY
FY
FY
FY
FY
2002
2003
2004 2005 2006
($M)
($M)
($M)
($M) ($M)
Operations
$24
$29
$30
$30
$30
Advanced
R&D
$4
$4
$3
$3
$3
+ $5M
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LIGO at Caltech

Faculty
» Barish, Drever, Libbrecht, Prince and Weinstein (Exp) & Thorne(Th)

Scientists/Postdocs/Students
» PhD theses; talented junior and senior scientists

LIGO Management
» Directorate, Administration

LIGO Technical
» Engineering center – precision engineering; controls; electronics
» 40 meter prototype; Optical laboratories, etc

LIGO Data Analysis and Computing
» Simulations; Analysis infrastructure, Networking, Data Archive
» Scientific data analysis efforts

Source Simulations – Numerical Relativity
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Einstein’s Theory of Gravitation
gravitational waves
Newton’s Theory
“instantaneous action at a
distance”
Einstein’s Theory
information carried by gravitational
radiation at the speed of light
• A necessary consequence of
Special Relativity with its finite
speed for information transfer
• Time dependent gravitational
fields come from the acceleration of
masses and propagate away from
their sources as a space-time
warpage at the speed of light
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Direct Detection
astrophysical sources
Gravitational Wave
Astrophysical Source
Terrestrial detectors
LIGO, TAMA, Virgo,AIGO
Detectors
in space
LISA
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Interferometers
terrestrial
free
masses
free
masses
International network (LIGO, Virgo,
GEO, TAMA, AIGO) of suspended
mass Michelson-type interferometers
on earth’s surface detect distant
astrophysical sources
suspended test masses
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Suspended Mass Interferometer
the concept

An interferometric gravitational
wave detector
» A laser is used to measure the relative
lengths of two orthogonal cavities (or
arms)
• Arms in LIGO are 4km
» Current technology then allows one
to measure h = dL/L ~ 10-21 which
turns out to be an interesting target
…causing the
interference pattern
to change at the
photodiode
As a wave
passes, the arm
lengths change
in different
ways….
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How Small is 10-18 Meter?
One meter, about 40 inches
 10,000
100
Human hair, about 100 microns
Wavelength of light, about 1 micron
 10,000
Atomic diameter, 10-10 meter
 100,000
Nuclear diameter, 10-15 meter
 1,000
LIGO sensitivity, 10-18 meter
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What Limits Sensitivity
of Interferometers?
•
Seismic noise & vibration
limit at low frequencies
•
Atomic vibrations (Thermal
Noise) inside components
limit at mid frequencies
•
Quantum nature of light
(Shot Noise) limits at high
frequencies
•
Myriad details of the lasers,
electronics, etc., can make
problems above these levels
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Noise Floor
40 m prototype
sensitivity demonstration
• displacement sensitivity
in 40 m prototype.
• comparison to predicted
contributions from
various noise sources
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LIGO
long baseline interferometers (4 km)
Laser Interferometer Gravitational-wave Observatory (LIGO)
Hanford
Observatory
Livingston
Observatory
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LIGO
Livingston Observatory
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LIGO
Hanford Observatory
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LIGO
beam tube
1.2 m diameter - 3mm stainless
50 km of weld

LIGO beam tube under
construction in January
1998

65 ft spiral welded sections

girth welded in portable
clean room in the field
NO LEAKS !!
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LIGO
vacuum equipment
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Core Optics
fused silica
LIGO requirements





Surface uniformity < 1 nm rms
Scatter < 50 ppm
Absorption < 2 ppm
ROC matched < 3%
Internal mode Q’s > 2 x 106
LIGO measurements
• central 80 mm of 4ITM06
(Hanford 4K)
• rms = 0.16 nm
• optic far exceeds specification.
Surface figure = / 6000
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Core Optics
installation and alignment
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Interferometer
locking
end test mass
Requires test masses to
be held in position to
10-10-10-13 meter:
“Locking the
interferometer”
Light bounces back
and forth along
arms about 150
times
Light is “recycled”
about 50 times
input test mass
Laser
signal
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Lock Acquisition
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LIGO
watching the interferometer lock
Composite Video
Y Arm
Laser
X Arm
signal
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LIGO
watching the interferometer lock
Y arm
X arm
2
min
Y Arm
Reflected
light
Anti-symmetric
port
Laser
X Arm
signal
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Engineering Run
detecting earthquakes
From electronic logbook 2-Jan-02
An earthquake occurred, starting
at UTC 17:38.
The plot shows the band limited
rms output in counts over the 0.10.3Hz band for four seismometer
channels. We turned off lock
acquisition and are waiting for the
ground motion to calm down.
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17:03:03
01/02/2002
=========================================================================
Seismo-Watch
Earthquake Alert Bulletin No. 02-64441
=========================================================================
Preliminary data indicates a significant earthquake has occurred:
Regional Location: VANUATU ISLANDS
Magnitude: 7.3M
Greenwich Mean Date: 2002/01/02
Greenwich Mean Time: 17:22:50
Latitude: 17.78S
Longitude: 167.83E
Focal depth: 33.0km
Analysis Quality: A
Source: National Earthquake Information Center (USGS-NEIC)
Seismo-Watch, Your Source for Earthquake News and Information.
Visit http://www.seismo-watch.com
=========================================================================
All data are preliminary and subject to change.
Analysis Quality: A (good), B (fair), C (poor), D (bad)
Magnitude: Ml
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Detecting the Earth Tides
Sun and Moon
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LIGO Goals and Priorities

Interferometer performance
» Integrate commissioning and data taking consistent with
obtaining one year of integrated data at h = 10-21 by end of
2006

Physics results from LIGO I
» Initial upper limit results by early 2003
» First search results in 2004
» Reach LIGO I goals by 2007

Advanced LIGO
» Prepare advanced LIGO proposal this fall
» International collaboration and broad LSC participation
» Advanced LIGO installation beginning by 2007
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Preliminary
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Astrophysical Sources
the search for gravitational waves

Compact binary inspiral:
“chirps”
» NS-NS waveforms are well described
» BH-BH need better waveforms
» search technique: matched templates

Supernovae / GRBs:
“bursts”
» burst signals in coincidence with signals in
electromagnetic radiation
» prompt alarm (~ one hour) with neutrino detectors

Pulsars in our galaxy:
“periodic”
» search for observed neutron stars (frequency,
doppler shift)
» all sky search (computing challenge)
» r-modes

Cosmological Signals
background”
“stochastic
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“Stochastic Background”
cosmological signals
‘Murmurs’ from the Big Bang
signals from the early universe
Cosmic
microwave background
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Stochastic Background
coherence plot LHO 2K & LLO 4K
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Stochastic Background
projected sensitivities
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Advanced LIGO
Multiple Suspension
Active Seismic
Saphire Optics
Higher Power Laser
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Advanced LIGO
Enhanced Systems
•
•
•
•
improved laser
suspension
seismic isolation
test mass material
• narrow band optics
Improvement factor
~ 104
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Gravitational-wave Astronomy
frequency range

Audio band
EM waves are studied
over ~20 orders of
magnitude
» (ULF radio -> HE -rays)

Gravitational Waves over
~10 orders of magnitude
»
(terrestrial + space)
LISA 2011-
LIGO I (2003-06)
Adv LIGO (2008 -)
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