Transcript Searching for GW with LIGO

Advanced Gravitational-wave Detectors
and LIGO-India
Stan Whitcomb
LIGO/Caltech
22 October 2011
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Astrophysical Sources for
Terrestrial GW Detectors
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Compact binary inspiral: “chirps”
» NS-NS, NS-BH, BH-BH
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Supernovas or GRBs:
“bursts”
» GW signals observed in coincidence
with EM or neutrino detectors
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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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Detecting GWs with Interferometry
Suspended mirrors act as
“freely-falling” test masses
in horizontal plane for
frequencies f >> fpend
h  DL / L
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)
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Laser Interferometer Gravitational-wave
Observatory (LIGO)
HANFORD
Washington
MIT
Boston
CALTECH
Pasadena
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LIVINGSTON
Louisiana
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Optical Configuration
Power Recycled
Michelson
Interferometer
with Fabry-Perot
Arm Cavities
end test mass
Light bounces back
and forth along arms
about 100 times
Light is “recycled”
about 50 times
input test mass
Laser
signal
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beam splitter
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Initial LIGO Sensitivity Goal
•

Strain sensitivity
<3x10-23 1/Hz1/2
at 200 Hz
Sensing Noise
» Photon Shot Noise
» Residual Gas

Displacement Noise
» Seismic motion
» Thermal Noise
» Radiation Pressure
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LIGO Sensitivity
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What’s next for LIGO?
Advanced LIGO
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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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Advanced LIGO Performance
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Newtonian background,
estimate for LIGO sites
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Seismic ‘cutoff’ at 10 Hz
10-21
Initial LIGO
-22
Suspension thermal noise
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Test mass thermal noise
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Strain
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Strain Noise, h(f) /Hz1/2
10
10-22
-23
10
10-23
Advanced LIGO
Quantum noise
dominates at most
frequencies
-24
10-2410
1
10
10 Hz
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10
Frequency (Hz)
100 Hz
3
10
1 kHz
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Initial LIGO Laser
Stabilization
cavities
for frequency
and beam shape
Custom-built
10 W
Nd:YAG
Laser
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Advanced LIGO Laser
•
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Designed and contributed by Albert Einstein Institute
Higher power
» 10W -> 180W
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Better stability
» 10x improvement in intensity and frequency stability
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Initial LIGO Mirrors
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•
•
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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
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Advanced LIGO Mirrors
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Larger size
» 11 kg -> 40 kg
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Smaller figure error
» 0.7 nm -> 0.35 nm
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Lower absorption
» 2 ppm -> 0.5 ppm
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•
•
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Lower coating thermal noise
All substrates delivered
Polishing underway
Reflective Coating process starting up
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Initial LIGO Vibration Isolation
HAM stack
in air
BSC stack
in vacuum
102
100
102
10-
10-6
Horizontal
4
106
108
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Vertical
10-10
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Advanced LIGO Seismic Isolation
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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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Initial LIGO Test Mass Suspension
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Simple single-loop pendulum suspension
Low loss steel wire
» Adequate thermal noise performance,
but little margin
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Magnetic actuators for control
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Advanced LIGO Suspensions
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four stages
40 kg silica
test mass
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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
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A Global Array of GW Detectors:
Source Localization
LIGO
GEO
Virgo
LCGT
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Locate sources
using multi-site
arrival times
(“aperture
synthesis”)
q
1
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LIGO and Virgo Alone
Planned detector network
has limited ability to locate
sources, particularly
near the
celestial
equator
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Completing the Global Network
LIGO
GEO
Virgo
TAMA/LCGT
LIGO-India
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LIGO and Virgo Plus LIGO-India
Adding LIGO-India to existing network
gives nearly all-sky coverage
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LIGO and Virgo Alone
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LIGO-India Concept
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•
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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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What Does India Provide?
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Participation in Advanced LIGO installation and
commissioning in US
» Training, but also early participation in detector development
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Site
» LIGO provides requirements and its design
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Buildings
» LIGO provides requirements and its design
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Vacuum system
» LIGO provides detailed drawings for up-dating, assistance for
achieving low out-gassing performance
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Staff to install, commission and operate
» LIGO provides training for Indian staff, collaboration and support
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All data are shared throughout the collaboration
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LIGO
Livingston Observatory
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India provides a
facility withVacuum system
Site, buildings
LIGO Beam Tube
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LIGO beam tube under
construction in January 1998
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16 m spiral welded sections
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girth welded in portable
clean room in the field
1.2 m diameter - 3mm stainless
50 km of weld
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NO LEAKS !!
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LIGO Vacuum Equipment
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Corner Station Chambers
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Align, assemble, test under portable clean rooms
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Beamtube Gate Valves
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Large gate
valves to isolate
beamtubes,
LN2 traps
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Detector Installation using Cleanrooms
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Chamber access
through large doors
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HAM Chamber
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Optics Installation Under
Cleanroom Conditions
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LIGO Lab Concerns:
Who Does it?
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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
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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)
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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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LIGO Lab Concerns :
Site
•
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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.
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Site selection guidance given to IndIGO
» Data collection could take some months
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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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NSF Review of LIGO-India
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•
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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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Where from Here?
•
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Intense evaluation by LIGO Lab over next six months
Group of senior LIGO Lab scientists to India in midOctober (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
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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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Where from Here?(continued)
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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
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Stay engaged in planning process in India
» Assist with Detailed Project Report (proposal)
» Provide information, as needed
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Consult people with experience in collaborating with
India to assess export control issues
» Fermilab, TMT, others?
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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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