LIGO-G050474-01-W The Status of Laser Interferometer Gravitational-Wave Detectors Fred Raab, LIGO...

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

Raab: Status of Laser Gravitational Wave Detectors

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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

LIGO-G050474-01-W The Status of Laser Interferometer Gravitational-Wave Detectors Fred Raab, LIGO...

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