Overview of Advanced LIGO March 2011 Rencontres de Moriond Sheila Rowan For the LIGO Scientific...
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Transcript of Overview of Advanced LIGO March 2011 Rencontres de Moriond Sheila Rowan For the LIGO Scientific...
Overview of Advanced LIGO
March 2011
Rencontres de Moriond
Sheila RowanFor the LIGO Scientific
Collaboration
LIGO sites (US)
LIGO Livingston Observatory• 1 interferometer
• 4 km arms
• 2 interferometers• 4 km, 2 km arms
LIGO Hanford Observatory
LIGO Observatories are operated by Caltech and MIT
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The LIGO Scientific Collaboration (LSC)
• 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.
Timeline of GW searches to 2011
We are here
Data analysis ongoing
1989
LIGO Proposal submitted to NSF
1995
Construction started
1999
Inauguration
Advanced LIGO construction funded
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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
100 million
light years
Advanced LIGO
Enhanced LIGO Initial 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
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
Three interferometers, as for Initial LIGO All three interferometers 4km in length
» For initial LIGO, one of the two instruments at Hanford is 2km
Advanced LIGO – path to improved sensitivity
Advanced LIG
O
(See Roman Schnabel’s talk on thoughts on how to improve on quantum
noise limited sensitivities..)
Design Outline
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Recombined Fabry-Perot Michelson with Signal recycling (increase sensitivity,
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)
Laser
Test Masses MArms of length LCavity finesse F
INITIAL LIGO LAYOUT
Power recycling mirror to increase circulating power
Michelson for sensing strain
Fabry-Perot arms to increase interaction time
GW signal
Signal Recycling Mirror to tune response
ADVANCED
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
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)
Prototype fused silica monolithic suspension successfully installed at MIT test facility
(See talk from Angus Bell)
Most test mass suspension components at both observatories are now cleaned, baked, and assembled into sub-assemblies
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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
Main mirrors (test masses)
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.
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
Current coatings in all detectors are made of alternating layers of ion-beam-sputtered 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
Coating thermal noise will limit
sensitivity between ~ 40 and 200 Hz
101
102
103
Frequency (Hz)
10-24
10-23
10-22
Str
ain
(1/
Hz
)
» Ta2O5 is the dominant source of dissipation in current SiO2/Ta2O5 coatings
» Doping the Ta2O5 with TiO2 can reduce the mechanical dissipation
= aLIGO baseline design
(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)
Projected Advanced LIGO sensitivity curve
The aLIGO laser
2W 35W 180W 165W
(for more info on high power laser development see talk by Patrick Kwee)
~$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
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)
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
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 LIGO-Australia.
Figure from: LIGO-DOC: T1000251
Status of project to date
Half way done! – excellent progress 20th October 2010 : Handoff of the LIGO Observatories
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!
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Advanced LIGO: Sensitivity
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