Transcript Gravitational Waves (Working group 6) resonant mass

Gravitational Waves
(Working group 6)
resonant mass detectors:
Visco
current generation terrestrial interferometers:
Frolov, Brady
next generation terrestrial interferometers:
Adhikari, Owen
“science fiction” terrestrial interferometers:
Mavalvala
Bruce Allen, UWM
Gravitational waves:
How are they different?
Gravitational waves
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Couple to mass 4-current
Produced by coherent motions
of high density or curvature
Wavelengths > source size, like
sound waves (no pictures)
Propagate through everything,
so you see dense centers
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Electromagnetic waves
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Couple to electric 4-current
Incoherent superposition of
many microscopic emitters
Wavelengths  source size,
can make pictures
Stopped by matter, so “beauty is
skin deep”
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Science Goals
• Direct verification of two dramatic predictions of Einstein’s
general relativity: gravitational waves & black holes
• Physics & Astronomy
– Detailed tests of properties of gravitational waves including
speed, polarization, graviton mass, .....
– Probe strong field gravity near black holes & in early universe
– Probe the neutron star equation of state
– Performing routine astronomical observations
• A new window on the Universe
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GW Sources 50-1000 Hz
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Compact binary inspiral:
“chirp”
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Supernovae / Mergers:
“burst”
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Spinning NS:
“continuous”
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Cosmic Background:
“stochastic”
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Present performance of resonant
mass detectors
Massimo Visco
INAF –IFSI Roma
INFN – Sez. Roma Tor Vergata
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International Gravitational Events Collaboration
ALLEGRO– AURIGA – ROG (EXPLORER-NAUTILUS)
• The “oldest” resonant detector EXPLORER started operations
about 16 years ago.
• This kind of detector has reached a high level of realibilty.
• The duty factor is greater than 90% .
A DIRECTIONAL 4-ANTENNAE
OBSERVATORY
• The four antennas are sensitive to the same region of the sky
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SENSITIVITY OF PRESENT DETECTORS
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TRIPLE COINCIDENCE DISTRIBUTION
AU-EX-NA (PRELIMINARY)
NO DETECTIONS
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2012 - 2018 NETWORK
WG6 summary, TEV II
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slide from INFN roadmap
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Status of LIGO
Valera Frolov
LIGO Lab
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LIGO Observatories
Hanford, WA (H1 4km, H2 2km)
- Interferometers are aligned to be as close
to parallel to each other as possible
- Observing signals in coincidence
increases the detection confidence
- Determine source location on the sky,
propagation speed and polarization of the
gravity wave
Livingston, LA (L1 4km)
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Time Line
1999
2000
2001
2002
2003
2004
2005
2006
3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4
Inauguration First Lock Full Lock all IFO
4K strain noise
Science
10-17 10-18
HEPI at LLO
10-20 10-21
S1
S2
at 150 Hz [Hz-1/2]
10-22
S3
Now
S4
S5
Runs
First
Science
Data
200
6
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NS-NS Inspiral Range
Improvement
Time progression since the start of S5
Design Goal
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Commissioning
breaks
Stuck ITMY optic
at LLO
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Triple Coincidence
Accumulation
~ 61%
100%
~ 45%
Expect to collect one year of triple
coincidence data by summer-fall 2007
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LIGO Observational Results
Patrick Brady
U. Wisconsin - Milwaukee
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Bursts
• Supernovae: Neutron star birth,
tumbling and/or convection
• Cosmic strings, black hole
mergers, .....
• Coincident EM observations
• Surprises!
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Detection Efficiency
• Evaluate efficiency by adding simulated GW bursts
to the data.
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Detection Efficiency
– Example waveform
S4
Central
Frequency
S5 sensitivity: minimum detectable in band energy in GW
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EGW > 1 M⊙ @ 75 Mpc
–
EGW > 0.05 M⊙ @ 15 Mpc (Virgo cluster)
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Upper Limits
• No GW bursts detected
through S4
– set limit on rate vs signal
strength.
Lower rate
limits from
longer
observation
times
Rate Limit (events/day)
S1
Lower amplitude limits from
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detector noise
S2
S4 projected
S5 projected
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Stochastic Background
• Big bang & early universe
• Background of gravitational
wave bursts
• Unresolved background of
contemporary sources
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
WMAP
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Predictions and Limits
LIGO S1: Ω0 < 44
0
PRD 69 122004 (2004)
Log
(0)
-4
LIGO S3: Ω0 < 8.4x10-4
H0 = 72 km/s/Mpc
-2
PRL 95 221101 (2005)
BB Nucleosynthesis
Pulsar
Timing
Cosmic strings
-6
Initial LIGO, 1 yr data
Expected Sensitivity
~ 4x10-6
-8
-10
Pre-big bang
model
CMB
-12
Inflation
-14
Slow-roll
-18
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-16
-14
-12
-10
Advanced LIGO, 1 yr data
EW or SUSY Expected Sensitivity
Phase transition
~ 1x10-9
Cyclic model
-8
-6
-4
-2
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Log (f [Hz])
0
2
4
6
8
10
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Compact Binaries
– Black holes & neutron stars
– Inspiral and merger
– Probe internal structure,
populations, & spacetime
geometry
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S5 Search
binary neutron star
horizon distance
• 3 months of S5
analyzed
• Horizon distance
over run
versus mass forAverage
BBH
130Mpc
1 sigma variation
binary black hole
horizon distance
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Image: R. Powell
Astrophysical sources of
gravitational waves
• Spinning neutron stars
– Isolated neutron stars with
mountains or wobbles
– Low-mass x-ray binaries
– Probe internal structure and
populations
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Known pulsars
S5 preliminary
Gravitational-wave amplitude
• 32 known isolated,
44 in binaries, 30 in
globular clusters
Lowest ellipticity upper limit:
PSR J2124-3358
(fgw = 405.6Hz, r = 0.25kpc)
ellipticity = 4.0x10-7
~2x10-25
Frequency (Hz)
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To participate, sign up at
http://www.physics2005.org
Einstein@Home
• Public distributed
computing project
• All-sky, all-frequency
search is
computationally limited
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S3 results:
– No evidence of pulsars
S4 search
– Post-processing underway
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Next Generation
Interferometers
Rana Adhikari
Caltech
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The next several years
4Q
‘06
4Q
‘05
4Q
‘07
4Q
‘08
4Q
‘09
4Q
‘10
Adv
S5
~2 years
S6
LIGO
 Between now and AdvLIGO, there is some
time to improve…
1)~Few years of hardware improvements +
1 ½ year of observations.
 Factor of ~2.5 in noise, factor of ~10 in event rate.
1)3-6
interferometers
running in coincidence ! 28
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Lower Thermal
Noise Estimate
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Increased Power +
Enhanced Readout
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Advanced LIGO Design Features
40 KG FUSED
SILICA TEST
MASSES
ACTIVE
SEISMIC
ISOLATION
FUSED SILICA, MULTIPLE
PENDULUM SUSPENSION
180 W LASER,
MODULATION SYSTEM
PRM
BS
ITM
ETM
SRM
PD
Power Recycling Mirror
Beam Splitter
Input Test Mass
End Test Mass
Signal Recycling Mirror
Photodiode
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Advanced LIGO
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What can gravitational waves
tell us about neutron stars?
Ben Owen
PSU
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Periodic signals:
Pulsar emission mechanism
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Pulse profiles in different EM
bands illuminate mechanism
Profiles show (phase) timing
noise, mostly in young pulsars
GW won’t show interesting
pulse profiles (only lowest
harmonic detectable)
Will be able to test if GW signal
has timing noise or not
Tells us how magnetosphere is
coupled to dense interior (Does
B-field structure go all the way
in? Just crust? …)
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Periodic signals:
How solid is a neutron star?
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NS definitely have (thin) solid crust
(known from pulsar glitches)
Normal nuclear crusts can only
produce ellipticity  < few  10-7
If “?” is solid quark matter, whole
star could be solid,  < few  10-4
If “?” is quark-baryon mixture or
meson condensate, half of core
could be solid,  < 10-5
High ellipticity measurement
means exotic state of matter
Low ellipticity is inconclusive:
strain, buried B-field…
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Burst signals:
Supernova core collapse
• Burst from collapse and
bounce
• Poorly modeled: different
groups predict different
waveforms, agree that there
is no supernova explosion….
• Long GRBs: knowing time &
location helps GW searches
• GRB/GW/neutrino relative
delays could shed light on
explosion mechanism
• If GW &  signals are both
short, result is a black hole
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Path to sub-quantum-noise
limited gravitational wave
interferometers
Nergis Mavalvala
MIT
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Optical Noise
• Shot Noise
– Uncertainty in number of photons
detected a
h( f
– Higher circulating power Pbs
a low optical losses
– Frequency dependence a light (GW signal) storage
time in the interferometer
)
1
Pbs
• Radiation Pressure Noise
– Photons impart momentum to cavity mirrors
Fluctuations in number of photons a
– Lower power, Pbs
– Frequency dependence
a response of mass to forces
Optimal input power depends
on frequency
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h( f ) 
Pbs
M2 f 4
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A Quantum Limited
Interferometer
Input laser
power
> 100 W
LIGO I
Circulating
power
> 0.5 MW
Ad LIGO
Mirror mass
40 kg
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Squeezed input vacuum state
in Michelson Interferometer
• Consider GW signal in
the phase quadrature
– Not true for all
interferometer
configurations
– Detuned signal recycled
interferometer 
GW signal in both
quadratures
Laser
X-X++
X-
X+
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• Orient squeezed state
to reduce noise in
phase quadrature
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Squeezed vacuum states
for GW detectors
• Requirements
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Squeezing at low frequencies (within GW band)
Frequency-dependent squeeze angle
Increased levels of squeezing
Long-term stable operation
• Generation methods
– Non-linear optical media (c(2) and c(3) non-linearites)
crystal-based squeezing
– Radiation pressure effects in interferometers
ponderomotive squeezing
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Squeezed Vacuum
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Noise budget
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Conclusions
• Resonant bar detectors are operating in a stable mode but at low
sensitivity compared with…
• LIGO is currently carrying out a science run at design sensitivity.
• Searches for all major categories of sources are underway and will
at least set upper limits.
• Detections are possible!
• Enhancements in ~ 3 years will increase the reach by a factor of 3
• An upgrade (Advanced LIGO) is planned early next decade
• Detections are ‘guaranteed’
• Quantum non-demolition techniques needed to beat quantum limits
(squeezed light)
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