1. Advanced Gravitational-wave Detectors and LIGO-India
Stan Whitcomb LIGO/Caltech
22 October 2011
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2. Astrophysical Sources for Terrestrial GW Detectors
Compact binary inspiral: “chirps”
NS-NS, NS-BH, BH-BH
Supernovas or GRBs: “bursts”
GW signals observed in coincidence with EM or neutrino detectors
Pulsars in our galaxy: “periodic waves”
Rapidly rotating neutron stars
Modes of NS vibration
Cosmological: “stochastic background”
Probe back to the Planck time (10-43 s)
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3. Detecting GWs with Interferometry
Suspended mirrors act as “freely-falling” test masses in horizontal plane for
frequencies f >> fpend
Terrestrial detector, L ~ 4 km
For h ~ 10–22 – 10–21 (Initial LIGO)
DL ~ m
Useful bandwidth 10 Hz to 10 kHz,
determined by “unavoidable” noise (at low frequencies) and expected maximum source frequencies (high frequencies)
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4. Laser Interferometer Gravitational-wave Observatory (LIGO)3 8 k m ( 1 s )
CALTECH
Pasadena
MIT
Boston
HANFORD
Washington
LIVINGSTON
Louisiana
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5. Optical Configuration
Light is “recycled” about 50 times
Power Recycled
Michelson
Interferometer
end test mass
beam splitter
signal
with Fabry-Perot Arm Cavities
Light bounces back and forth along arms about 100 times
input test mass
Laser
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6. Initial LIGO Sensitivity Goal
Strain sensitivity <3x /Hz1/2 at 200 Hz
Sensing Noise
Photon Shot Noise
Residual Gas
Displacement Noise
Seismic motion
Thermal Noise
Radiation Pressure
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7. LIGO Sensitivity
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8. What’s next for LIGO? Advanced LIGO
Take advantage of new technologies and on-going R&D
Active anti-seismic system operating to lower frequencies
Lower thermal noise suspensions and optics
Higher laser power
More sensitive and more flexible optical configuration
x10 better amplitude sensitivity
 x1000 rate=(reach)3
 1 day of Advanced LIGO
» 1 year of Initial LIGO !
2008 fabrication start, installation began 2011
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9. Advanced LIGO Performance
Newtonian background, estimate for LIGO sites
Seismic ‘cutoff’ at 10 Hz
Suspension thermal noise
Test mass thermal noise
Quantum noise dominates at most frequencies
10-21
Initial LIGO
10-22
Strain
10-23
Advanced LIGO
10-24
10 Hz
100 Hz
1 kHz
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10. Stabilization cavities
Initial LIGO Laser
Stabilization cavities
for frequency
and beam shape
Custom-built
10 W Nd:YAG
Laser
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11. Advanced LIGO Laser
Designed and contributed by Albert Einstein Institute
Higher power
10W -> 180W
Better stability
10x improvement in intensity and frequency stability
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12. Initial LIGO Mirrors Substrates: SiO2 Polishing Coating
25 cm Diameter, 10 cm thick
Homogeneity < 5 x 10-7
Internal mode Q’s > 2 x 106
Polishing
Surface uniformity < 1 nm rms (l / 1000)
Radii of curvature matched < 3%
Coating
Scatter < 50 ppm
Absorption < 2 ppm
Uniformity <10-3
Production involved 5 companies, CSIRO, NIST, and LIGO
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13. Advanced LIGO Mirrors Larger size Smaller figure error
11 kg -> 40 kg
Smaller figure error
0.7 nm -> 0.35 nm
Lower absorption
2 ppm -> 0.5 ppm
Lower coating thermal noise
All substrates delivered
Polishing underway
Reflective Coating process starting up
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14. Initial LIGO Vibration Isolation
HAM stack
in air
BSC stack in vacuum
102
100
10-2
10-4
10-6
10-8
10-10
Horizontal
Vertical
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15. Advanced LIGO Seismic Isolation
Two-stage six-degree-of-freedom active isolation
Low noise sensors, Low noise actuators
Digital control system to blend outputs of multiple sensors, tailor loop for maximum performance
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16. Initial LIGO Test Mass Suspension
Simple single-loop pendulum suspension
Low loss steel wire
Adequate thermal noise performance, but little margin
Magnetic actuators for control
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17. Advanced LIGO Suspensions
UK designed and contributed test mass suspensions
Silicate bonds create quasi-monolithic pendulums using ultra-low loss fused silica fibers to suspend interferometer optics
Pendulum Q ~105 -> ~108
40 kg silica test mass
four stages
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18. A Global Array of GW Detectors: Source Localization
GEO
Virgo
LIGO
LCGT
Locate sources using multi-site arrival times (“aperture synthesis”) 1 2 q
DL = c dt
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19. LIGO and Virgo Alone
Planned detector network has limited ability to locate sources, particularly near the celestial equator
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20. Completing the Global Network
GEO
Virgo
LIGO
TAMA/LCGT
LIGO-India
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21. LIGO and Virgo Plus LIGO-India
Adding LIGO-India to existing network gives nearly all-sky coverage
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22. LIGO and Virgo Alone
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23. LIGO-India Concept
A direct partnership between LIGO Laboratory and IndIGO to build an Indian interferometer
LIGO Lab (with its UK, German and Australian partners) provides components for one Advanced LIGO interferometer, unit #3, from the Advanced LIGO project
India provides the infrastructure (site, roads, building, vacuum system), “shipping & handling,” staff, installation & commissioning, operating costs
The interferometer, the third Advanced LIGO instrument, would be operated as part of LIGO to maximize the scientific impact of LIGO-India
Key deadline: LIGO needs a commitment from India by March 2012—otherwise, must begin installation of the LIGO-India detector at our US facility
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24. What Does India Provide?
Participation in Advanced LIGO installation and commissioning in US
Training, but also early participation in detector development
Site
LIGO provides requirements and its design
Buildings
Vacuum system
LIGO provides detailed drawings for up-dating, assistance for achieving low out-gassing performance
Staff to install, commission and operate
LIGO provides training for Indian staff, collaboration and support
All data are shared throughout the collaboration
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25. LIGO Livingston Observatory
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26. India provides a facility with-
Vacuum system
Site, buildings

27. LIGO Beam Tube
LIGO beam tube under construction in January 1998
16 m spiral welded sections
girth welded in portable clean room in the field
1.2 m diameter - 3mm stainless
50 km of weld
NO LEAKS !!
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28. LIGO Vacuum Equipment
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29. Corner Station Chambers
Align, assemble, test under portable clean rooms
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30. Beamtube Gate Valves Large gate valves to isolate beamtubes, LN2 traps
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31. Detector Installation using Cleanrooms
Chamber access through large doors
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32. HAM Chamber
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33. Optics Installation Under Cleanroom Conditions
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34. LIGO Lab Concerns: Who Does it?
Number of experienced interferometer experts is small
Initially, IndIGO mostly theorists or data analysts
Growing interest from experimental community, but still new to GWs
August: Rana Adhikari visit to India to assess capability and to recruit
Expect to have a training program in LIGO for interferometer specialists
Started last year in anticipation of LIGO-Australia
Working to recruit postdocs to work with LIGO (2 so far)
Need to identify Project team
Most likely source from National Labs or Centres
Requires official standing with government departments for commitments, but some expressions of support
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35. LIGO Lab Concerns : Site
So far, no definite site identified and characterized
In terms of ‘Science’, specific location with in India (including orientation) is not critical
Result of simulation studies by Sathya et al.
Site selection guidance given to IndIGO
Data collection could take some months
My opinion: I expect that finding a suitable site is possible (requirements are not that extreme)
Difficult issues will be ability to secure it and timescale
Discussions about possible site hampered initially by lack of approved project status
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36. NSF Review of LIGO-India
Blue-ribbon panel to judge science case and to advise on possible implementation issues
Provided with background documents and met Oct 7 (via internet) for ~6 hours of presentation/ discussion
Summary finding:
“The panel believes that the science case for LIGO-India is compelling, and reason enough to move forward in the near term with the understanding that there are a number of outstanding issues with funding, site selection, and the selection of institutional leadership, top management and technical expertise that must be resolved before making a deeper commitment. “We note that LIGO-India is the only option actively under consideration by the LIGO Laboratory.”
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37. Where from Here? Intense evaluation by LIGO Lab over next six months
Group of senior LIGO Lab scientists to India in mid-October (this visit)
Meet potential participants and laboratory directors to assess capabilities and interest (follow-up to Rana’s visit, ‘measure first derivative’)
Understand project capabilities in national labs
Visit potential site
Attempt to arrange visit from vacuum system company representatives to LIGO facility
Continuing “training program”
Second Indian postdoc starts at Caltech
Applications for next year now open
Measure of momentum in forming core team
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38. Where from Here?(continued)
IGC2011 conference in Goa, Workshop in Pune in December--next opportunity for face-to-face meetings
Number of LIGO Lab and LSC attendees
NSF Assistant Director Ed Seidel also planning to go
Stay engaged in planning process in India
Assist with Detailed Project Report (proposal)
Provide information, as needed
Consult people with experience in collaborating with India to assess export control issues
Fermilab, TMT, others?
Planning for a final “go/no-go” visit to India in February
Best assessment of how far have we gotten
Funding status, likely lead lab, perhaps some key personnel
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