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Advanced Gravitational-wave Detectors and LIGO-India. Stan Whitcomb LIGO/Caltech 22 October 2011. Astrophysical Sources for Terrestrial GW Detectors. Compact binary inspiral: “chirps” NS-NS, NS-BH, BH-BH Supernovas or GRBs: “bursts”

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Advanced gravitational wave detectors and ligo india

Advanced Gravitational-wave Detectors and LIGO-India

Stan Whitcomb LIGO/Caltech

22 October 2011

Astrophysical sources for terrestrial gw detectors
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)

LIGO-India, October 2011

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 ~ 10-18 m

Useful bandwidth 10 Hz to 10 kHz,

determined by “unavoidable” noise (at low frequencies) and expected maximum source frequencies (high frequencies)

LIGO-India, October 2011

Laser interferometer gravitational wave observatory ligo
Laser Interferometer Gravitational-wave Observatory (LIGO)






















LIGO-India, October 2011

Optical configuration

Power Recycled

end test mass

with Fabry-Perot Arm Cavities

Light bounces back and forth along arms about 100 times

Light is “recycled” about 50 times

beam splitter


Optical Configuration



input test mass


LIGO-India, October 2011

Initial ligo sensitivity goal
Initial LIGO Sensitivity Goal

  • Strain sensitivity <3x10-23 1/Hz1/2at 200 Hz

  • Sensing Noise

    • Photon Shot Noise

    • Residual Gas

  • Displacement Noise

    • Seismic motion

    • Thermal Noise

    • Radiation Pressure

LIGO-India, October 2011

Ligo sensitivity
LIGO Sensitivity

LIGO-India, October 2011

What s next for ligo advanced ligo
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


 1 day of Advanced LIGO

» 1 year of Initial LIGO !

2008 fabrication start,installation began 2011

LIGO-India, October 2011

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


Initial LIGO



Advanced LIGO



10 Hz

100 Hz

1 kHz

LIGO-India, October 2011

Initial ligo laser
Initial LIGO Laser

Stabilization cavities

for frequency

and beam shape


10 W Nd:YAG


LIGO-India, October 2011

Advanced ligo laser
Advanced LIGO Laser

  • Designed and contributed by Albert Einstein Institute

  • Higher power

    • 10W -> 180W

  • Better stability

    • 10x improvement in intensity and frequency stability

LIGO-India, October 2011

Initial ligo mirrors
Initial LIGO Mirrors

  • Substrates: SiO2

    • 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

LIGO-India, October 2011

Advanced ligo mirrors
Advanced LIGO Mirrors

  • All substrates delivered

  • Polishing underway

  • Reflective Coating process starting up

  • Larger size

    • 11 kg -> 40 kg

  • Smaller figure error

    • 0.7 nm -> 0.35 nm

  • Lower absorption

    • 2 ppm -> 0.5 ppm

  • Lower coating thermal noise

LIGO-India, October 2011

Initial ligo vibration isolation











Initial LIGO Vibration Isolation

HAM stack

in air

BSC stackin vacuum

LIGO-India, October 2011

Advanced ligo seismic isolation
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

LIGO-India, October 2011

Initial ligo test mass suspension
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

LIGO-India, October 2011

Advanced ligo suspensions
Advanced LIGO Suspensions

four stages

40 kg silica test mass

  • 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

LIGO-India, October 2011


A global array of gw detectors source localization

DL = c dt




A Global Array of GW Detectors:Source Localization





Locate sources using multi-site arrival times (“aperture synthesis”)

LIGO-India, October 2011

Ligo and virgo alone
LIGO and Virgo Alone

Planned detector network has limited ability to locate sources, particularly near the celestial equator

LIGO-India, October 2011

Completing the Global Network






LIGO-India, October 2011

Ligo and virgo plus ligo india
LIGO and Virgo Plus LIGO-India

Adding LIGO-India to existing network gives nearly all-sky coverage

LIGO-India, October 2011

Ligo and virgo alone1
LIGO and Virgo Alone

LIGO-India, October 2011

Ligo india concept
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

LIGO-India, October 2011

What does india provide
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

    • LIGO provides requirements and its design

  • 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

LIGO-India, October 2011

Ligo livingston observatory
LIGO Livingston Observatory

LIGO-India, October 2011

India provides a facility with-

Vacuum system

Site, buildings

Ligo beam tube
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


LIGO-India, October 2011

Ligo vacuum equipment
LIGO Vacuum Equipment

LIGO-India, October 2011

Corner station chambers
Corner Station Chambers

  • Align, assemble, test under portable clean rooms

LIGO-India, October 2011

Beamtube gate valves
Beamtube Gate Valves

  • Large gate valves to isolatebeamtubes,LN2 traps

LIGO-India, October 2011

Detector installation using cleanrooms
Detector Installation using Cleanrooms

  • Chamber access through large doors

LIGO-India, October 2011

Ham chamber
HAM Chamber

LIGO-India, October 2011

Ligo lab concerns who does it
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

LIGO-India, October 2011

Ligo lab concerns site
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

LIGO-India, October 2011

Nsf review of ligo india
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.”

LIGO-India, October 2011

Where from here
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

LIGO-India, October 2011

Where from here continued
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

LIGO-India, October 2011