Transcript No Slide Title

The Status of Gravitational-Wave
Detectors
Reported on behalf of LIGO colleagues by
Fred Raab,
LIGO Hanford Observatory
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Reach of Gravitational Wave
Detectors is Rapidly Expanding
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Windows of opportunity
GWs a known phenomenon, but undetected as yet
Resonant-bar & laser detectors
Worldwide networks of terrestrial detectors
LIGO: the first generation of km-scale detectors
Moving toward the future
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Different Frequency Bands of
Detectors and Sources
space
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EM waves are
studied over ~20
orders of magnitude
terrestrial
Audio band
» (ULF radio -> HE  rays)
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Gravitational Wave
coverage over ~8
orders of magnitude
» (terrestrial + space)
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Catching Waves From
Orbiting Black Holes and Neutron Stars
Sketches courtesy
of Kip Thorne
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Gravitational Waves
the evidence
Emission of gravitational waves
Neutron Binary System – Hulse &
Taylor
PSR 1913 + 16 -- Timing of pulsars
17 / sec
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~ 8 hr
Neutron Binary System
• separated by 106 miles
• m1 = 1.4m; m2 = 1.36m; e = 0.617
Prediction from general relativity
• spiral in by 3 mm/orbit
• rate LIGO-G050250-00-W
of change orbital period
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Basic Signature of Gravitational
Waves for All Detectors
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Bar Network: Int’l Gravitational
Event Collaboration
Network of the 5 bar detectors
almost parallel
ALLEGRO NFS-LSU
AURIGA INFN-LNL
NIOBE ARC-UWA
EXPLORER INFN-CERN
NAUTILUS INFN-LNF
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http://gravity.phys.lsu.edu
http://www.auriga.lnl.infn.it
http://www.gravity.pd.uwa.edu.au
http://www.roma1.infn.it/rog/rogmain.html
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CERN RE 5
MiniGrail
LNF INFN
Courtesy E. Coccia
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AURIGA 2nd run @ 4K: upgrades & results
new mechanical suspensions:
attenuation > 360 dB at 1 kHz
FEM modelled
new capacitive transducer:
two-modes (1 mechanical+1 electrical)
optimal mass
new amplifier:
double stage SQUID
new data analysis:
C++ object oriented code
frame data format
Bandwidth: noise floor below 5x10-21 Hz-1/2
on a 100 Hz band
Stationary gaussian behaviour: few spurious
event/h after anticoincidence veto with 20 ms
all band electromagnetic glitches
Courtesy M. Cerdonio
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New Generation of “FreeMass” Detectors Now Online
suspended mirrors mark
inertial frames
antisymmetric port
carries GW signal
Symmetric port carries
common-mode info
Intrinsically broad band and size-limited by speed of light.
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The International Interferometer
Network
Simultaneously detect signal (within msec)
LIGO
GEO
Virgo
TAMA
detection
confidence
locate the
sources
AIGO
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decompose the
polarization of
gravitational
waves
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The Laser Interferometer
Gravitational-Wave Observatory
LIGO (Washington)
(4-km and 2km)
LIGO (Louisiana)
(4-km)
Funded by the National Science Foundation; operated by Caltech and MIT; the
research focus for more than 500 LIGO Scientific Collaboration members worldwide.
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Interferometers in Europe
GEO 600 (Germany)
600-m
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Virgo (Italy)
3-km
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Interferometers in Asia,
Australia
TAMA 300 (Japan)
(300-m)
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AIGO (Australia)
(80-m, but 3-km site)
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Spacetime is Stiff!
=> Wave can carry huge energy with miniscule amplitude!
h ~ (G/c4) (ENS/r)
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Some of the Technical Challenges
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Typical Strains < 10-21 at Earth ~ 1 hair’s width at 4
light years
Understand displacement fluctuations of 4-km arms
at the millifermi level (1/1000th of a proton diameter)
Control arm lengths to 10-13 meters RMS
Detect optical phase changes of ~ 10-10 radians
Hold mirror alignments to 10-8 radians
Engineer structures to mitigate recoil from atomic
vibrations in suspended mirrors
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What Limits Sensitivity
of Interferometers?
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Seismic noise & vibration
limit at low frequencies
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Atomic vibrations (Thermal
Noise) inside components
limit at mid frequencies
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Quantum nature of light
(Shot Noise) limits at high
frequencies
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Myriad details of the lasers,
electronics, etc., can make
problems above these levels
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Time Line
2000
1999
3Q
4Q
2Q 3Q
1Q
Inauguration
2001
4Q
1Q
Runs
E1
Science
2Q 3Q
E2
4Q
1Q
2Q 3Q
2003
4Q
1Q
2Q 3Q
4Q
Full Lock all IFO's
First Lock
strain noise density @ 200 Hz [Hz-1/2]
Engineering
2002
10-17
10-18
E3 E4 E5 E6 E7
10-19 10-20
E8
10-21
10-22
E9
S1
S2
E10
S3
First
Science
Data
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Vibration Isolation Systems
»
»
»
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Reduce in-band seismic motion by 4 - 6 orders of magnitude
Little or no attenuation below 10Hz
Large range actuation for initial alignment and drift compensation
Quiet actuation to correct for Earth tides and microseism at 0.15 Hz during
observation
HAM Chamber
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BSC Chamber
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Seismic Isolation – Springs and
Masses
damped spring
cross section
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Core Optics Suspension and
Control
Optics
suspended
as simple
pendulums
Shadow sensors & voice-coil
actuators provide
damping and control forces
Mirror is balanced on 30 micron
diameter wire to 1/100th degree of arc
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Feedback & Control for Mirrors
and Light
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Damp suspended mirrors to vibration-isolated tables
» 14 mirrors  (pos, pit, yaw, side) = 56 loops
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Damp mirror angles to lab floor using optical levers
» 7 mirrors  (pit, yaw) = 14 loops
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Pre-stabilized laser
» (frequency, intensity, pre-mode-cleaner) = 3 loops
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Cavity length control
» (mode-cleaner, common-mode frequency, common-arm, differential
arm, michelson, power-recycling) = 6 loops
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Wave-front sensing/control
» 7 mirrors  (pit, yaw) = 14 loops
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Beam-centering control
» 2 arms  (pit, yaw) = 4 loops
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Suspended Mirror Approximates a
Free Mass Above Resonance
Blue: suspended
mirror XF
Cyan: free mass XF
Data taken
using shadow
sensors &
voice coil
actuators
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Despite a few difficulties, science
runs started in 2002.
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LIGO Science Runs
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S1: 17 days in Aug-Sep 2002
» 3 LIGO interferometers in coincidence with GEO600 and ~2 days
with TAMA300
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S2: Feb 14 – Apr 14, 2003
» 3 LIGO interferometers in coincidence with TAMA300
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S3: Oct 31, 2003 – Jan 9, 2004
» 3 LIGO interferometers in coincidence with periods of operation of
TAMA300, GEO600 and Allegro
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S4: Feb 22 – Mar 23, 2005
» 3 LIGO interferometers in coincidence with GEO600, Allegro,
Auriga
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Binary Neutron Stars:
S1 Range
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Image: R. Powell
Binary Neutron Stars:
S2 Range
S1
Range
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Image: R. Powell
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Interferometer Strain Sensitivity
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Science Analysis
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Searches for periodic sources, such as neutron stars
Searches for compact-binary inspirals, e.g., neutron
stars, black holes, MACHOs
Searches for burst sources
» Waveforms may be unknown or poorly known
» Non-triggered search
» Triggered search(e.g., supernova or GRB triggers)
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Stochastic waves of cosmological or astrophysical
origin
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LIGO Search Papers
(as of 9May05)
S1:
“Setting upper limits on the strength of periodic gravitational waves
using the first science data from the GEO600 and LIGO detectors”,
Phys. Rev. D 69, 082004 (2004)
“First upper limits from LIGO on gravitational wave bursts”,
Phys. Rev. D 69, 102001 (2004)
“Analysis of LIGO data for gravitational waves from binary neutron
stars”, Phys. Rev. D 69, 122001 (2004)
“Analysis of first LIGO science data for stochastic gravitational
waves”, Phys. Rev. D 69, 122004 (2004)
S2:
“Limits on gravitational wave emission from selected pulsars using
LIGO data”, Phys. Rev. Lett. 94, 181103 (2005).
“A search for gravitational waves associated with the gamma ray
burst GRB030329 using the LIGO detectors”, gr-qc/0501068
“Upper limits on gravitational wave bursts from LIGO’s second
science run”, gr-qc/0505029
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Binary Neutron Stars:
Initial LIGO Target Range
S2 Range
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Image: R. Powell
Future Plans for Terrestrial
Detectors
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Improve reach of initial LIGO to run 1 integrated triple-coincidence
year at design sensitivity
Virgo has made steady progress in commissioning, due to come on
line in ~ 1 year
GEO600, TAMA300, striving for design sensitivity
Resonant bars networking with interferometers for future runs
Advanced LIGO technology under development, planning toward a
detector construction start for FY2008
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What’s next? Advanced LIGO…
Major technological differences between LIGO and Advanced LIGO
40kg
Quadruple pendulum:
Silica optics, welded to
silica suspension fibers
Initial Interferometers
Active vibration
isolation systems
Open up wider band
Reshape
Noise
Advanced Interferometers
High power laser
(180W)
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Advanced interferometry
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Signal recycling
Binary Neutron Stars:
AdLIGO Range
LIGO Range
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Image: R. Powell
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…and opening a new channel with
a detector in space.
Planning underway for space-based detector, LISA, to open up a
lower frequency band ~ 2013-ish
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Summary
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We are currently experiencing a rapid advance in the
sensitivity of searches for gravitational waves
Elements of world-wide networks of interferometers
and bars are operating
The near future will see the confrontation of theory
with many fine observational results
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