Rana Adhikari Caltech The Next Gravity Wave Interferometers.

Rana AdhikariCaltech

The Next Gravity Wave

Interferometers

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Gravitational Waves = “Ripples in space-time” Two transverse polarizations - quadrupolar: + and x

Gravitational Waves?

Example:

Ring of test masses

responding to wave

propagating along z

Amplitude parameterized by dimensionless strain h: L ~ h(t) x L

Need to measure strain of ~ 10-21-10-22

We want a very large ‘L’

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Compact binary inspirals: “chirp” NS-NS waveforms are well described. 1.4 Msolar NS/NS

inspiral is a standard candle.standard candle. BH-BH waveforms are rapidly improving

Supernovae / Mergers: “burst” Short signals. Waveforms not well known. Search in coincidence between two or more interferometers and

possibly with electromagnetic and/or neutrinos signals

Spinning NS: “continuous” search for signals from observed pulsars all-sky search computing challenging

Cosmic Background: “stochastic” Metric fluctuations amplified by inflation, phase transitions in

early universe, topological defects Unresolved foreground sources

GW Sources in LIGO Band 50-1000 Hz

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LIGO Observatories

Livingston, LA (L1 4km)

Hanford, WA (H1 4km, H2 2km) - Interferometers are aligned to be as close to parallel to each other as possible

- Observing signals in coincidence increases the detection confidence

- Determine source location on the sky, propagation speed and polarization of the gravity wave

LIGO GEO VirgoTAMA

AIGO (proposed)

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Michelson Interferometer

Anti-Symmetric (Dark) Port

Ly

LxReflected Port

PAS PBS x sin2()

dP/d PBS x

sin()cos()

= 2 (Ly - Lx) /

ddh L

Laser

Noise PAS

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End Test Mass

50/50 Beam Splitter

Photo detector

Laser

MichelsonInterferometer

MichelsonInterferometer 4 km Fabry-Perot

arm cavitywith Fabry-Perot Arm Cavities

Input Test Mass

6 W

Power Recycled

Power RecyclingMirror

300 W 20 kW

Interferometer Optical Layout

Signal Phase shift between the arms due to GW

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Science Requirements Doc:

The LIGO-I Sensitivity Goal

Seismic:Natural and anthropogenicground motions, filtered byactive/passive isolation systems.Depends strongly on in-vac seismic isolation.

Thermal:Brownian noise in the mirrors and in the mirrors’ steel suspension wires.Depends mostly on internal rubbing in the suspension wires.

Shot Noise:Photon counting statistics -- > 10 kW in the cavities ~ 200 mW detected power

- Goes down with increased laser power and better fringe contrast

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5 years of debuggin’ in Louisiana…

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What Is Inside1.2 m diameter - 3mm stainless 50 km of weld 10-9 torr vacuum and no leaks!

Seismic isolationStack of masses and springs

Coils and magnets to control the mirror

Fused silica mirror25 cm diameter10 kg mass

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Dark Port Optical Table

2 mm diameterInGaAs photodiode

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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

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]

2006

HEPI at LLO

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Caltech LIGO Laboratory MIT

LIGO Hanford Observatory LIGO Livingston Observatory

University of Adelaide ACIGA

Australian National University ACIGA

Balearic Islands University

Caltech LIGO

Caltech Experimental Gravitation CEGG

Caltech Theory CART

University of Cardiff GEO

Carleton College

Cornell University

Embry-Riddle Aeronautical University

University of Florida-Gainesville

Glasgow University GEO

NASA-Goddard Spaceflight Center

Hobart – Williams University

India-IUCAA

IAP Nizhny Novgorod

IUCCA India

Iowa State University

Loyola New OrleansLouisiana State University

Louisiana Tech University

MIT LIGO

Max Planck (Honnover) GEO

Max Planck (Potsdam) GEO

University of Michigan

Moscow State University

NAOJ - TAMA

Northwestern University

University of Oregon

Pennsylvania State University

Southeastern Louisiana University

Southern University

Stanford University

Syracuse University

University of Texas-Brownsville

Washington State University-Pullman

University of Western Australia ACIGA

University of Wisconsin-Milwaukee

LIGO Scientific Collaboration~40 institutions, ~550 scientists

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LIGO Science Run The fifth science run started in November 2005 S5 goal is to collect one year of triple coincidence data at the

design sensitivity Optimistic event rates: NS/NS ~3/year, BH/NS ~30/year Nakar,

Gal-Yam, Fox, astro-ph/0511254 Plan to reach the Crab pulsar spin down limit Expect to beat the Big-Bang Nucleosynthesis limit on

gravitational wave density in the LIGO band GEO interferometer joined the S5 run in January 2006. Virgo interferometer plans to join S5 later this year.

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NS-NS Inspiral Range Improvement

Time progression since the start of S5

HistogramDesign Goal

Commissioningbreaks

Stuck ITMY opticat LLO

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S5 Duty Factor

S5 Goal is 85% for single

interferometer and 70% for

triple coincidence

One week running average

Commissioningbreaks

Stuck ITMY opticat LLO

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H1H1 H2H2 L1L1

UptimeUptime 72% 79% 60%

Wind, Storms, Earthquakes 4.5% 9%

Nearby Logging, Construction, Trains - - 10%

Maintenance, Commissioning, Calibration

10% 9%

Hardware and Software Failures 3.5% 7%

Lock Acquisition, Other 10% 5%

S5 Duty Factor

H1&H2&L1 = 45% H1||H2||L1||G1 close to 100%H1&H2&L1 = 45% H1||H2||L1||G1 close to 100%

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Triple Coincidence Accumulation

100%

~ 45%

~ 61%

Expect to collect one year of triple coincidence data by summer-fall 2007

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Sometimes You Get Lucky Large mirror (ITMY) was wedged into the earth quake stops Vented the vacuum and released it. Adjusted EQ stop. Noise improved!? 12->14 Mpc

Earth quake stop

before

after

ChargeDissipation

on the optic?

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Advanced LIGO LIGO mission: detect

gravitational waves and initiate GW astronomy

Next detector Should have assured detectability

of known sources Should be at the limits of

reasonable extrapolations of detector physics and technologies

Must be a realizable, practical, reliable instrument

Daily gravitational wave detections R&D is mature, prototypes exist Installation start in 2011

Advanced LIGO

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101

102

103

10-24

10-23

10-22

Frequency (Hz)

Str

ain

No

ise,

h(f

) /H

z1/2

10 Hz 100 Hz 1 kHz

10-22

10-23

10-24

10-21

Anatomy of the projected Adv LIGO detector performance

Newtonian background,estimate for LIGO sites

Seismic ‘cutoff’ at 10 Hz

Suspension thermal noise

Test mass thermal noise

Unified quantum noise dominates at most frequencies for fullpower, broadband tuning

Initial LIGO

Advanced LIGONS-NS Tuning

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End Test Mass

50/50 beam splitter

GW signal

Optical Configuration

Laser

MichelsonInterferometer

MichelsonInterferometer 4 km Fabry-Perot

arm cavitywith Fabry-Perot Arm Cavities

Input Test Mass

125 W

Power Recycled

Power Recyclingmirror

2 kW 500 kW

Signal Recycling mirror

Dual recycled

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Detuned Signal Recycling

frequency offset from carrier [Hz]

•Responses of GW USB and GW LSB are different due to the detuning of the signal recycling cavity.

•IFO Differential Arm mode is detuned from resonance at operating point

00

SRC DARM0

Car

rier

fre

quen

cy

-10000 -5000 0 5000 10000

50

100

200

500

1000

Sid

eban

d am

plit

ude

[a.u

.]

FWHM

USBLSB

fsig

IFO DARM/CARM

from R. Ward

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Opto-mechanical Spring

Optical Spring stiffness ~ 107 N/m

Angular spring resonance ~ 2 Hz

• ½ MW in the arms ->

• ‘Optical Bar’ detector

• ~75 Hz unstable opto-mechanical resonance

• High Bandwidth servos

Measured Transfer Functions from the 40m prototype

BMW Z4 ~ 104 N/m

Radiation pressure: F = 2 P / cDetuned Cavity -> dF/dx

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The next several years

Between now and AdvLIGO, there is some time to improve…

1) ~Few years of hardware improvements + 1 ½ year of observations.1) Factor of ~2.5 in noise, factor of ~10 in event rate.2) 3-6 interferometers running in coincidence !

S5 S6

4Q‘05

4Q‘06

4Q‘07

4Q‘08

4Q‘10

4Q‘09

Adv

LIGO~2 years

Other interferometers in operation (GEO, Virgo)NOW 4 yrs

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NS/NS Binary

Most of the sensitivity comes from a band around 50 Hz

50 Hz

Area proportional to SNR

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30/30 M BH/BH

Most of the sensitivity comes from a band around 30 Hz

Area proportional to SNR

30 Hz

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Astrophysical Motivation

How does the number of surveyed galaxies increase as the sensitivity is improved?

From astro-ph/0402091, Nutzman et al.

Power law: 2.7For NS-NS binaries

Prop. to inspiral range

Factor of 2.5 reduction in strain noise,

factor of 10 increase in # of sources

S4

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Baseline Goals

1. Dark Port Filter Cavity (Caltech/MIT)1. Reduce amount of junk light, reduce shot noise

2. Reducing detected light power allows higher laser power

3. Upgrade the detection system to the Advanced LIGO style.

2. Higher power laser (Hannover)1. Our (10 W) laser company was bought out by JDS Uniphase.

2. Collaborators at AEI/LZH are offering us 35 W lasers (for free!)

3. High Power Input Optics (UF, Gainesville)

4. Miscellaneous …

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Seismic:No modification in seismic isolation systems

Thermal:Good wires, good mirrors, and control of “technical” noises

Shot Noise:- New in-vac filter cavity-- 4-5x more laser power-- Advanced readout technique

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Increased Power + Enhanced ReadoutLower Thermal

Noise Estimate

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The Plan

Improvements on the 4km IFOs starting in Sep07Do Louisiana first (pathfinder). Start Hanford in Jan08.Some modest Suspension electronics fixesThen some more science running.

Not enough time/manpower to do all 3 IFOs.

A factor of 2.5 on H1/L1 is better than a factor of 2 on all three.

We don’t gain more AdvLIGO knowledge by doing 3 IFOs.

After the pumpdown, H2 can join Virgo in a science run.

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Conclusions

1 more year of R&D to support the upgrade Starting installation in Sep ’07 Next Science Run (w/ improved sensitivity) starts

in Sep ’09.

Reduces much technical risk for Advanced LIGO Its time to make the first gravitational wave

detection.

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Short, Hard GRBs Several Short Hard Gamma-Ray Bursts

since last year Detected by Swift, HETE-2, then Hubble,

Chandra, and BATSE SHGRBs (< 2 s) different from ‘Long Soft

GRBs’ (supernova explosions) Candidates for progenitors of SHGRBs:

double neutron star (NS/NS) or neutron star-black hole (NS/BH 1.4/10) coalescences

Optimistic rates for Initial LIGO (S5) could be as high as a few/year

Nakar, Gal-Yam, Fox, astro-ph/0511254

Double Neutron Star MergerDana Berry / NASA

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Suspension wire re-working Change the clamp to reduce excess noise (no evidence so far) Change the wire to reduce the intrinsic noise Needs some serious coil driver redesigns capitalize on lower noise. Need to know more about the excess noise first.

Squeezed Light Implement on one IFO instead of the laser upgrade; more

speculative, but doesn’t require new IO equipment. An opportunity to commission another AdvLIGO system

Signal Recycling No real sensitivity improvement; lots of work.

Double Suspension Not directly applicable to AdvLIGO. Substantial reworking req. Not clear if we can get the technical noises out of the way.

Beyond ‘Fixes’

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Cross-correlation estimator

Theoretical variance

Optimal Filter

Strain Power:

Choose N such that: HY

)100/()( HzfHfH )()(

)(),(1),(

21

point~

fPfP

fHft

NftQ

,,2,1

)(2

point

^

),(A

At

At

c

txfi

FFeft

Detection Strategy, point source

Point Spread Function

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S4 Upper Limit map , H(f)=const

148%90 10)1.685.0( HzH