LIGO-G050250-00-W The Status of Gravitational-Wave Detectors Reported on behalf of LIGO colleagues by Fred Raab, LIGO Hanford Observatory

LIGO-G050250-00-W

The Status of Gravitational-Wave Detectors

Reported on behalf of LIGO colleagues by

Fred Raab,

LIGO Hanford Observatory

Raab: Status of Gravitational Wave Detectors

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Reach of Gravitational Wave Detectors is Rapidly Expanding

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

EM waves are studied over ~20 orders of magnitude» (ULF radio HE rays)

Gravitational Wave coverage over ~8 orders of magnitude» (terrestrial + space)

Audio band

space terrestrial


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Catching Waves FromOrbiting Black Holes and Neutron Stars

Sketches courtesy of Kip Thorne


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Gravitational Waves the evidence

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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Bar Network: Int’l Gravitational Event Collaboration

Network of the 5 bar detectors almost parallel

ALLEGRO NFS-LSU http://gravity.phys.lsu.eduAURIGA INFN-LNL http://www.auriga.lnl.infn.itNIOBE ARC-UWA http://www.gravity.pd.uwa.edu.auEXPLORER INFN-CERN http://www.roma1.infn.it/rog/rogmain.htmlNAUTILUS INFN-LNF


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CERN RE 5

LNF INFNMiniGrail

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 “Free-Mass” Detectors Now Online

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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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)

The Laser InterferometerGravitational-Wave Observatory

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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GEO 600 (Germany)600-m

Virgo (Italy)3-km

Interferometers in Europe


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TAMA 300 (Japan)(300-m)

AIGO (Australia)(80-m, but 3-km site)

Interferometers in Asia, Australia


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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

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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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


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Vibration Isolation Systems

» 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 BSC Chamber


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Seismic Isolation – Springs and Masses

damped springcross section


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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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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» 2 arms (pit, yaw) = 4 loops


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Suspended Mirror Approximates a Free Mass Above Resonance

Data taken using shadow

sensors & voice coil actuators

Blue: suspended mirror XF

Cyan: free mass XF


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Despite a few difficulties, science runs started in 2002.


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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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Binary Neutron Stars:S1 Range

Image: R. Powell


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Binary Neutron Stars:S2 Range

Image: R. Powell

S1 Range


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Interferometer Strain Sensitivity


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Science Analysis

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)

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

Image: R. Powell

S2 Range


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Future Plans for Terrestrial Detectors

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

Initial Interferometers

Advanced Interferometers

Open up wider band

ReshapeNoise

Quadruple pendulum:

Silica optics, welded to

silica suspension fibers

Advanced interferometry

Signal recycling

Active vibration isolation systems

High power laser (180W)

40kg


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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, to open up a lower frequency band ~ 2013-ish


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Summary

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

Documents

LIGO-G050250-00-W The Status of Gravitational-Wave Detectors Reported on behalf of LIGO colleagues by Fred Raab, LIGO Hanford Observatory