LIGO-G050589-00-W Searching for Distant Sources of Gravitational Waves with LIGO Fred Raab, LIGO Hanford Observatory November 15, 2005

LIGO-G050589-00-W

Searching for Distant Sources of Gravitational Waves with LIGO

Fred Raab,

LIGO Hanford Observatory

November 15, 2005

Raab: Searching for Distant Sources w/ LIGO

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highlights

Background on Gravity and its waves Initial LIGO detector Progress in commissioning and searching What have we learned from running S1 S4 Steps to S5; preparing for a long run Expectations

» Range/duty cycle goals

» Analysis goals


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John Wheeler’s Picture of General Relativity Theory


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General Relativity: A Picture Worth a Thousand Words


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The New Wrinkle on Equivalence

Not only the path of matter, but even the path of light is affected by gravity from massive objects

Einstein Cross

Photo credit: NASA and ESA

A massive object shifts apparent position of a star


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Gravitational Waves

Gravitational waves are ripples in space when it is stirred up by rapid motions of large concentrations of matter or energy

Rendering of space stirred by two orbiting black holes:


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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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Basic Signature of Gravitational Waves for All Detectors


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Initial LIGO: Power-recycled Fabry-Perot-Michelson

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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Core Optics Suspension and Control

Local sensors/actuators provide damping and control forces

Mirror is balanced on 1/100th inchdiameter wire to 1/100th degree of arc

Optics suspended as simple pendulums


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The LIGO Observatories

Adapted from “The Blue Marble: Land Surface, Ocean Color and Sea Ice” at visibleearth.nasa.govNASA Goddard Space Flight Center Image by Reto Stöckli (land surface, shallow water, clouds). Enhancements by Robert Simmon (ocean color, compositing, 3D globes, animation). Data and technical support: MODIS Land Group; MODIS Science Data Support Team; MODIS Atmosphere Group; MODIS Ocean Group Additional data: USGS EROS Data Center (topography); USGS Terrestrial Remote Sensing Flagstaff Field Center (Antarctica); Defense Meteorological Satellite Program (city lights).

LIGO Hanford Observatory (LHO)H1 : 4 km armsH2 : 2 km arms

LIGO Livingston Observatory (LLO)L1 : 4 km arms

10 ms


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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

DESIGN

COMMISSIONING


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Commissioning and Running Time Line

NowInauguration

1999 2000 2001 2002 20033 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4

E2Engineering

E3 E5 E9 E10E7 E8 E11

First Lock Full Lock all IFO

10-17 10-18 10-20 10-21

2004 20051 2 3 4 1 2 3 4 1 2 3 4

2006

First Science Data

S1 S4Science

S2 RunsS3 S5

10-224K strain noise at 150 Hz [Hz-1/2]4x10-23


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Some of the technical challenges for design and commissioning

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 Do all of the above 7x24x365

Now playing at an observatory near you…


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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 and what we learned from them…

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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After a lot of effort, it works!


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LSC Search Papers(as of 14Nov05)

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 14Nov05)

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”, Phys. Rev. D 72, 062001 (2005)

“Search for gravitational waves from galactic and extra–galactic binary neutron stars”, Phys. Rev. D 72, 082001 (2005)

“Search for gravitational waves from primordial black hole binary coalescences in the Galactic Halo”, Phys. Rev. D 72, 082001 (2005)


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S2 Search Papers (as of 14Nov05)

S2: “Upper limits from the LIGO and TAMA detectors on the rate of gravitational-wave bursts”, gr-qc/0507081, accepted by Phys. Rev. D

“First all-sky upper limits from LIGO on the strength of periodic gravitational waves using the Hough transform”, gr-qc/0508065 , accepted by Phys. Rev. D

“Search for gravitational waves from binary black hole inspirals in LIGO data”, gr-qc/0509129


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S3 Search Papers(as of 14Nov05)

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:» 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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Run S3

L1 21.8%

H1 69.3%

H2 63.4%

Triple 15.8%

S3 showed we could meet our RMS goal, but…

Needed to fix the duty cycle

Also wanted to improve high-frequency operation more laser

power


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Installation of HEPI at Livingstonhas improved the stability of L1


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S4 Science Duty Cycle

H1: 80.5% H2: 81.4%

L1: 74.5%HEPI delivers!


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High laser power operation requires adaptive adjustments to optical figure

CO2

Laser

ITM

To ITM HRsurface

Thermal compensation system


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We now think Initial LIGO detector is ready for a long run

Run S4S5

TargetSRD

goal

L1 75% 85% 90%

H1 81% 85% 90%

H2 81% 85% 90%

3-way

57% 70% 75%

Sensitivity targets*:

•H1 inspiral range ~ 10 Mpc

•L1 inspiral range ~ 10 Mpc

•H2 inspiral range ~ 5 Mpc

* As measured by SenseMon

Duty Cycle targets:


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101

102

103

10-20

10-19

10-18

10-17

10-16

10-15

10-14

Frequency [Hz]

Dis

plac

emen

t [m

/H

z]H1: 11.1 Mpc, Predicted: 15.3, Oct 20 2005 06:43:50 UTC

DARMMICHPRCOscillatorOpticalLeversWFSOSEMSeismicETMITMBSSusThermIntThermShotDarkIntensityFrequencyTotalSRD

Automated Noise Budget


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Binary Inspiral Search: LIGO Ranges

Image: R. Powell

binary neutron star range

binary black hole range


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What to expect from S5 analyses

Sensitivity to bursts ~10-21 RMS Sensitivity to neutron-star inspirals at Virgo cluster Pulsars

» expect best limits on known neutron star ellipticities at few x10-7

» expect to beat spindown limit on Crab pulsar

» Hierarchical all-sky/all-frequency search

Cosmic GW background limits expected to be near GW~10-5

Perhaps a discovery?


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These are exciting times!

Pinning down origins of short GRBs will result in more solid

estimates of NS-NS and NS-BH mergers

Groups led by Burrows and Wheeler now have supernova models that explode! Expect to see action in re-computing GWB waveforms.


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On the more speculative front…

Graphic from KITP newsletter, heralding an observable string theory prediction: GWs from

cosmological strings may be verified by LIGO in its first

long science run.


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Closing remarks…

Progressive detector improvements have achieved design goals for Initial LIGO detector

Early implementation of Advanced LIGO techniques helped achieve goals» HEPI for duty-cycle boost

» Thermal compensation of mirrors for high-power operation

Some commissioning breaks expected during S5 to improve performance and/or reliability

Believe still room for post-S5 improvements before 2010 shutdown for Advanced LIGO upgrade


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The Beginning


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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


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Also: keep tragedy away


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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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Issues to resolve

At current sensitivity and duty cycle, it would be a shame not to start a long run, but some issues remain to be resolved during the run

Use monitors to identify sources of instrumental transients Identify low-frequency noise to extend range Upconversion is known to be important

» Need better vetoes» Identify and mitigate sources

Near “the wall” on high power operation» Protective shutters to handle loss of lock have a tough time» Steady state AS-port light is stressing photodiodes to limit» Need to design and implement an output mode cleaner to enable higher

power operation (probably post-S5)


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Low frequency noise not explained

102

10-19

10-18

10-17

10-16

10-15

Frequency (Hz)

Dis

pla

cem

ent

no

ise

(m/

Hz)

H1 noiseH1 predictedL1 noiseL1 predicted

40


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Possible source:upconversion from stack motion

Using HEPI, increase the suspension point motion at 1.5 Hz by a factor of 5 DARM noise increases

significantly over a wide band

Effect measured both at LHO & at LLO:

H1 exhibits a day-to-night variation in low frequency noise, with a ~10% reduction in inspiral range during the day


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Scattered light fringe wrapping?B

RT

ITM

ETMEsc~10 -6 E0

For 1% reflection from beam reducing optics & excitation of

ETMX only


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Stress at the antisymmetric port:

Loss-of-lock: full beamsplitter power can be dumped out the AS port, in a ~10 msec width pulse

PD damage due to» Too high trigger level» Shutter failure» Shutter too slow

Damaged PDs can be noisy and position-dependent

Working on shutter improvements

Steady-state stress (principally due to AS_I saturation) needs relief

~100 W

5 msec

Red: replaced damaged PDs

An example of photodiode stress

Documents

LIGO-G050589-00-W Searching for Distant Sources of Gravitational Waves with LIGO Fred Raab, LIGO Hanford Observatory November 15, 2005