Transcript transparencies - Rencontres de Moriond

Overview of Advanced LIGO
March 2011
Rencontres de Moriond
Sheila Rowan
For the LIGO Scientific Collaboration
The Global Network
of Gravitational Wave Detectors
LIGO
GEO600
Germany
LIGO
TAMA
Japan
VIRGO
Italy
LIGO sites (US)
LIGO Observatories are operated
by Caltech and MIT
• 2 interferometers
• 4 km, 2 km arms
LIGO Hanford Observatory
LIGO Livingston Observatory
• 1 interferometer
• 4 km arms
The LIGO Scientific Collaboration (LSC)
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The LSC carries out the scientific program of
LIGO – instrument science, data analysis.
The 3 LIGO interferometers and the GEO600
instrument are analyzed as one data set
(also share our data with French-Italian Virgo)
Approximately 800 members
~ 50 institutions including the LIGO Laboratory
Participation from (at least) Australia,
Germany, India, China, Korea, Italy, Hungary
Japan, Russia, Spain, the U.K. and the U.S.A.
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Timeline of GW searches to 2011
1989
1995
1999
LIGO Proposal
submitted to NSF
Construction
started
Inauguration
Advanced LIGO
construction funded
We are here
Data analysis ongoing
The worldwide GW roadmap for the future
We are here
Advanced LIGO
 Factor of 10 greater sensitivity than initial
LIGO
 Factor 4 lower start to sensitive frequency
range
» ~10 Hz instead of ~40 Hz
» More massive astrophysical systems,
greater reach, longer observation of
inspirals
 Intended to start gravitational-wave
astronomy
 Frequent detections expected – exact rates
to be determined, of course
» Most likely rate for NS-NS inspirals
observed: ~40/year
Enhanced LIGO
Initial LIGO
100
million
light years
Advanced LIGO
(See J. Abadie et al “Predictions for the Rates
of Compact Binary Coalescences Observable
by Ground-based Gravitational-wave
Detectors”,arXiv:1003.2480; submitted to CQG)
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Advanced LIGO
Scope
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Re-use of vacuum system,
buildings, technical infrastructure
 Replacement of virtually all initial
LIGO detector components
» Re-use of a small quantity of
components where possible
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Three interferometers, as for Initial LIGO
 All three interferometers 4km in length
» For initial LIGO, one of the two
instruments at Hanford is 2km
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Advanced LIGO – path to improved sensitivity
(See Roman Schnabel’s talk on
thoughts on how to improve on quantum
noise limited sensitivities..)
Design Outline
 Recombined Fabry-Perot Michelson with
 Signal recycling (increase sensitivity,
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add tunability)
Active seismic isolation, quadruple
pendulum suspensions
(seismic noise wall moves from 40Hz 
10 Hz)
Fused Silica Suspension
(decreased low-frequency thermal noise)
40 kg test masses
(lower photon pressure noise)
Larger test mass surfaces,
low-mechanical-loss optical coatings
(decreased mid-band thermal noise)
~20x higher input power (lower shot noise)
ADVANCED
INITIAL LIGO LAYOUT
Test Masses M
Arms of length L
Cavity finesse F
Michelson for
sensing strain
Laser
GW
signal
Power recycling
mirror to increase
circulating power
Fabry-Perot
arms to increase
interaction time
Signal Recycling
Mirror to tune
response
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aLIGO – seismic Isolation – outside and inside the tanks
aLIGO Suspension Systems – What They Need to Do
 Support the optics to minimise the effects of
» seismic noise acting at the support point
» thermal noise in the suspension
Test mass noise requirement: 10-19 m/√Hz at 10 Hz
 Provide damping of low frequency suspension resonances (local
control), and
 Provide means to maintain interferometer arm lengths (global control)
» while not compromising low thermal noise of mirror
» and not introducing noise through control loops
 Provide interface with seismic isolation system and core optics system
 Support optic so that it is constrained against damage from earthquakes
Main suspensions
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40kg fused silica mirror
suspended on 4 fused silica fibres
to give low-thermal-noise
suspension
 ~£8.2M contribution from
GEO UK (Science and
Technology Facilities Council)
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Prototype fused silica monolithic
suspension successfully installed
at MIT test facility
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(See talk from Angus Bell)
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Most test mass suspension
components at both observatories
are now cleaned, baked, and
assembled into sub-assemblies
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Main mirrors (test masses)
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40 kg substrates of high optical quality fused silica
» Available in suitably large sizes
» Low optical absorption at 1064nm
» Can be suitably polished and coated
» Low mechanical loss
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For mirrors with spatially
inhomogeneous mechanical loss we
should not simply add incoherently
the noise from the thermally excited
modes of a mirror – loss from a
volume close to the laser beam
dominates.
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The loss of the dielectric multilayer
coatings used to form highly reflective
mirrors at 1064nm could be expected
to be an important parameter
Thermal noise from optical mirror coatings
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Current coatings in all detectors are made of alternating layers of ion-beamsputtered SiO2 (low refractive index) and Ta2O5 (high index)
Experiments suggest:
» Thermal noise from mechanical loss of the dielectric mirror coatings will limit
sensitivity of 2nd generation interferometric gravitational wave detectors
» Ta2O5 is the dominant source of
dissipation in current SiO2/Ta2O5
coatings
» Doping the Ta2O5 with TiO2 can reduce
Coating thermal
the mechanical dissipation
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noise will limit
= aLIGO baseline design
sensitivity between
~ 40 and 200 Hz
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(Just one example of impact of experimental
GW research on other fields:
» Coating noise limits performance of
laser stabilisation cavities; frequency
combs; other precision physics expts
» Very active research area both for
‘beyond advanced’ GW detectors and
other apps)
Strain (1/Hz)
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-23
10
-24
10
1
10
2
10
3
Frequency (Hz)
Projected Advanced LIGO sensitivity curve
The aLIGO laser
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~$14M contribution from GEO
Germany (Max Planck Society)
 3 complete laser systems, including
lasers, servos, reference cavities, etc.
 Installation of first article laser at
Livingston Observatory has started
2W
35W
180W
(for more info on
high power laser
development see
talk by Patrick
Kwee)
165W
aLIGO thermal compensation
• Wavefront sensors for Thermal
Compensation System (Adelaide)
• Cavity pre-lock length stabilization system,
and ‘tip-tilt’ in-vacuum steering mirrors, for
Interferometer Sensing and Control (ANU)
• ~$1.7M from Australian Research Council
‘LIGO-Australia’ (see talk from David Blair)
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Goal–
a southern hemisphere interferometer early in the Advanced LIGO & Advanced
Virgo operating era
Install one of the Advanced LIGO interferometers planned for Hanford into
infrastructure in Australia provided by Australia for possible detector operation in
2017
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In-principle approval
from NSF
 Australian proposal for
construction funds
submitted March 2011
 IndIGO is preparing
proposal for significant
funding to participate in
and contribute to LIGOAustralia.
Figure from:
LIGO-DOC: T1000251
Status of project to date
 Half way done! – excellent progress
 20th October 2010 : Handoff of the LIGO Observatories
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to the aLIGO project
First new parts going in NOW
System upgrades staggered
Last IFO should realistically be back online in 2015.
Tuning and optimizing to reach design sensitivity
Conclusions
 Initial LIGO attained its design sensitivity and has produced
astronomically important upper limits on gravitational wave
production.
 Advanced LIGO should increase our sensitivity by more than 10. At
that sensitivity, GW detection should be a frequent occurrence.
 Advanced LIGO is scheduled to be online by 2015.
 Collaboration in the worldwide GW community is growing. The LIGO-
Virgo Collaboration (LIGO, GEO, and Virgo) share data, analysis
efforts, and technical knowledge.
 Exciting (and unexpected?) physics awaits us!
Extra slides follow
Advanced LIGO: Sensitivity
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As for Initial LIGO, we
specify the sensitivity of
Advanced LIGO by an
RMS sensitivity:
10-22 hRMS in a 100 Hz band
» A factor of 10
improvement
over Initial LIGO
 Flexibility of tuning will
allow a range of responses
 Anticipated performance is
better than above – roughly
3x10-23 hRMS in a 100 Hz
band, around 250 Hz,
tuned for NS -NS inspirals
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