ligo-g050474-01-w the status of laser interferometer gravitational-wave detectors fred raab, ligo...
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LIGO-G050474-01-W
The Status of Laser Interferometer Gravitational-Wave Detectors
Fred Raab,
LIGO Hanford Observatory
On behalf of LIGO Scientific Collaboration and other laser interferometer groups
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Laser-Interferometer Gravitational Wave Detectors
•Some background
•Kilometer-scale detectors are working
•An international network has conducted coordinated runs and science analyses
•Long-term, deep-sky, astrophysics searches begin this year
•Technology development for future detectors is well along
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Different Frequency Bands of Laser-Based Detectors and Sources
Planned laser-based Gravitational Wave detector coverage over ~8 orders of magnitude» (terrestrial + space)
Audio band
space terrestrial
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A “Baseline” Source: Waves FromOrbiting Black Holes and Neutron Stars
Sketches courtesy of Kip Thorne
Exercises most of the frequency range of
the detector
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Gravitational Waves known to exist, just hard to find
Neutron Binary System – Hulse & TaylorPSR 1913 + 16 -- Timing of pulsars
17 / sec
Neutron Binary System• separated by 106 miles• m1 = 1.4m; m2 = 1.36m; = 0.617
Prediction from general relativity• spiral in by 3 mm/orbit• rate of change orbital period
~ 8 hr
Emission of gravitational waves
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Basic Signature of Gravitational Waves for All Detectors
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Laser-Interferometer or “Free-Mass” Detectors
suspended mirrors markinertial frames
antisymmetric portcarries GW signal
Symmetric port carriescommon-mode info
Intrinsically broad band and size-limited by speed of light.
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GEO600Optical Configuration
12W laser
mode cleaner
interferometer with „dual recycling“
mode cleaner
photo detectorCourtesy B. Willke
signal recycling mirror
power recycling
mirror
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The International Interferometer Network
LIGO
Simultaneously detect signal (within msec)
detection confidence locate the sources
decompose the polarization of gravitational waves
GEO VirgoTAMA
AIGO
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LIGO (Washington)(4-km and 2km)
LIGO (Louisiana)(4-km)
North America: Laser InterferometerGravitational-Wave Observatory
Funded by the National Science Foundation; operated by Caltech and MIT; the research focus for ~ 500 LIGO Scientific Collaboration members worldwide.
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GEO 600 (Germany)600-m
Virgo (Italy)3-km
Interferometers in Europe
Operated by GEO, member of LIGO Scientific Collaboration
CNRS/INFN collaboration
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TAMA 300 (Japan)(300-m)
AIGO (Australia)(80-m, but 3-km site)
Interferometers in Asia, Australia
Operated by ACIGA; part of LIGO Scientific Collaboration.
Longest running detector: 9 data runs!
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Gravitational waves are hard to find because 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
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 Sensitivityof 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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LIGO Commissioning Time Line
First Science Data
Inauguration
19993Q 4Q
20001Q 2Q 3Q 4Q
20011Q 2Q 3Q 4Q
20021Q 2Q 3Q 4Q
20031Q 2Q 3Q 4Q
E1Engineering
E2 E3 E4 E5 E6 E7 E8 E9
S1Science
S2 S3
First Lock Full Lock all IFO's
10-17 10-18 10-19 10-20strain noise density @ 200 Hz [Hz-1/2] 10-21
Runs
10-22
E10
TAUP2003
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LIGO Vibration Isolation Systems
» Reduce in-band seismic motion by 4 - 6 orders of magnitude above 40 Hz» 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 BSC Chamber
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LIGO Seismic Isolation – Springs and Masses
damped springcross section
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LIGO Core Optics Suspension and Control
Shadow sensors & voice-coil actuators provide
damping and control forces
Mirror is balanced on 30 microndiameter wire to 1/100th degree of arc
Optics suspended as simple pendulums
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VIRGO Seismic Isolation and Suspensions
“Long Suspensions”• inverted pendulum• five intermediate filters
Suspension vertical transfer function measured and simulated (prototype)See E. Majorana talk on VIRGO progress
this afternoon
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GEO600 Seismic Isolation and Suspension
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TAMA300 Upgrade to Seismic Isolation
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Suspended Mirror Approximates a Free Mass Above Resonance
LIGO data taken using
shadow sensors & voice coil actuators
Blue: suspended mirror XF
Cyan: free mass XF
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Feedback & Control for Mirrors and Light
Damp suspended mirrors to vibration-isolated tables» 14 mirrors (pos, pit, yaw, side) = 56 loops
Damp mirror angles to lab floor using optical levers» 7 mirrors (pit, yaw) = 14 loops
Pre-stabilized laser» (frequency, intensity, pre-mode-cleaner) = 3 loops
Cavity length control» (mode-cleaner, common-mode frequency, common-arm, differential
arm, michelson, power-recycling) = 6 loops
Wave-front sensing/control» 7 mirrors (pit, yaw) = 14 loops
Beam-centering control» 3 points (pit, yaw) = 6 loops
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LIGO Science Runs
S1: 17 days in Aug-Sep 2002» 3 LIGO interferometers in coincidence with GEO600 and ~2 days
with TAMA300
S2: Feb 14 – Apr 14, 2003» 3 LIGO interferometers in coincidence with TAMA300
S3: Oct 31, 2003 – Jan 9, 2004» 3 LIGO interferometers in coincidence with periods of operation of
TAMA300, GEO600 and Allegro
S4: Feb 22 – Mar 23, 2005» 3 LIGO interferometers in coincidence with GEO600, Allegro,
Auriga
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Interferometer Strain Sensitivity
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S4 Science Duty Cycle
H1: 80.5% H2: 81.4%
L1: 74.5%
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LSC Search Papers(as of 5Sep05)
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)
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S2 Search Papers (as of 5Sep05)
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”, Phys. Rev. D 72, 042002 (2005)
“Upper limits on gravitational wave bursts from LIGO’s second science run”, gr-qc/0505029
“Search for gravitational waves from galactic and extra–galactic binary neutron stars”, gr-qc/0505041
“Search for gravitational waves from primordial black hole binary Coalescences in the Galactic Halo”, gr-qc/0505042
“Upper limits from the LIGO and TAMA detectors on the rate of gravitational-wave bursts”, gr-qc/0507081
“First all-sky upper limits from LIGO on the strength of periodic gravitational waves using the Hough transform”, gr-qc/0508065
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S3 Search Papers(as of 5Sep05)
S3:“Upper Limits on a Stochastic Background of Gravitational Waves”, astro-ph/0507254
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S3/S4 Analyses Underway
Einstein@Home “Screensaver”
search for undiscovered neutron stars and strange quark stars
Uses 40,000 host computers with capacity ~20 Tflops, 24x7
First-pass analysis for LIGO/GEO600 data
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What to expect from S3/S4 analyses
Pulsars (see Alicia Sintes’ talk):» Limits on GW emission from 93 known radio pulsars, coordinated
with Jodrell-Bank Pulsar Group
» expect best limits on neutron star ellipticities ~10-6
» expect Crab sensitivity ~ 4 spindown limit
» all-sky/all-frequency search underway
Cosmic GW background limits expected to be near GW~10-4
Sensitivity to neutron-star inspirals starting to include Virgo cluster
First limits on cosmic strings
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-16 -14 -12 -10 -8 -6 -4 -2 0 2 4 6 8
-14
-12
-10
-8
-6
-4
-2
0
Log10
[ f (Hz) ]
Lo
g10
[
gw
]
CMBR
Pulsar timingNucleosynthesis
LIGO S1 data 2 Cryo Bars
LIGO, 1 yr data
LIGO S2 dataAssumes H0 = 72 km/s/Mpc
, at designsensitivity
LIGO S3 data
Sensitivity to Isotropic Stochastic Background
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It works! (see B. O’Reilly’s talk)Long-term search begins Nov05
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Binary Neutron Stars:Initial LIGO Target Range
Image: R. Powell
S2 Range
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Future Plans for Terrestrial Detectors
Begin long-term search (~one integrated year) using initial LIGO GEO600, TAMA300 continue to run, striving for design sensitivity Virgo has made steady progress in commissioning, hope to begin
science searches in near future (see Majorana’s talk) Increased networking of resonant bars with interferometers Advanced LIGO technology continues development, approved by
US National Science Board, planning toward a detector construction start for FY2008: PPARC funding in place in UK; funding being worked in Germany
For LCGT news, see Miyoki’s talk
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What’s next? Advanced LIGO…Major technological differences between LIGO and Advanced LIGO
Initial Interferometers
Advanced Interferometers
Open up wider band
ReshapeNoise
Advanced interferometry
Signal recycling
Active vibration isolation systems
High power laser (180W)
40kg
Quadruple pendulum:
Silica optics, welded to
silica suspension fibers
See S. Miyoki’s LCGT talk for another view of the future
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Binary Neutron Stars:AdLIGO Range
Image: R. Powell
LIGO Range
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…and opening a new channel with a detector in space.
Planning underway for space-based detector, LISA, hoping to fly in next decade to open up a lower frequency band
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Closing remarks…
We are experiencing a rapid advance in the sensitivity of searches for gravitational waves
The near future will see the confrontation of theory with many fine observational results