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Michele PunturoINFN Perugia and EGOOn behalf of the ET Design Study Teamhttp://www.et-gw.eu/
8th Amaldi Conference, New York, 2009 1
Why 3rd generation GW observatories? Science potentialities
Technologies for the 3rd generation GW detectors
The Einstein Telescope design study
8th Amaldi Conference, New York, 2009 2
8th Amaldi Conference, New York, 2009 3
Scie
ntif
ic R
un /
LIG
O -
Vir
go
Commis-sioning/ Upgrade
eLIG
O, V
irgo
+
Commis-sioning
Scie
ntif
ic r
un(s
)
2007 20092008
Same Infrastructures, improvements of the current technologies, some prototyping of the 2nd generation technologies
8th Amaldi Conference, New York, 2009 4
Scie
ntif
ic R
un /
LIG
O -
Vir
go
Commis-sioning/ Upgrade
eLIG
O, V
irgo
+
Commis-sioning
Scie
ntif
ic r
un(s
)
Upgrades & Runs
advL
IGO
, adv
Vir
go
Com-mis-
sioning
Scie
ntif
ic r
un(s
)
2007 2009 2011-12 20152008 2017 2022
Same Infrastructures, improvements of the current technologies, some prototyping of the 2nd generation technologies
Same Infrastructures, engineering of new technologies developed by currently advanced R&D
BNS
Either the detection is reached or there is
something fundamentally wrong
10 100 1000 1000010-24
10-23
10-22
10-21
10-20
Vela
Crab
BNS @ 100Mpc
Detector sensitivities
h(f
) [1
/sq
rt(H
z)]
Frequency [Hz]
Virgo iLIGO adVirgo/adLIGO
BNS @ 20Mpc
NS @ 10kpc, =10-6
1year integration
8th Amaldi Conference, New York, 2009 5
Scie
ntif
ic R
un /
LIG
O -
Vir
go
Commis-sioning/ Upgrade
eLIG
O, V
irgo
+
Commis-sioning
Scie
ntif
ic r
un(s
)
Upgrades & Runs
advL
IGO
, adv
Vir
go
Com-mis-
sioning
Scie
ntif
ic r
un(s
)
2007 2009 2011-12 20152008 2017 2022
Upgrades (High frequency
oriented?) and runs
Same Infrastructures, improvements of the current technologies, some prototyping of the 2nd generation technologies
Same Infrastructures, engineering of new technologies developed by currently advanced R&D
GW detection is expected to occur in the advanced detectors. The 3rd generation should focus on observational aspects:
Astrophysics: Measure in great detail the physical parameters of the stellar bodies composing the
binary systems NS-NS, NS-BH, BH-BH Constrain the Equation of State of NS through the measurement
of the merging phase of BNS of the NS stellar modes of the gravitational continuous wave emitted by a pulsar NS
Contribute to solve the GRB enigma Relativity
Compare the numerical relativity model describing the coalescence of intermediate mass black holes
Cosmology Measure few cosmological parameters using the GW signal from BNS emitting also an
e.m. signal (like GRB) Probe the first instant of the universe and its evolution through the measurement of the
GW stochastic background Astro-particle:
Contribute to the measure the neutrino mass 68th Amaldi Conference, New York, 2009
Advanced detectors will be able to determine BNS rates in the local Universe “Routine” detections at low to medium SNR But high precision fundamental physics, astrophysics and
cosmology may be limited would require good quality high-SNR events
Extremely rare in advanced detectors
8th Amaldi Conference, New York, 20097
Let suppose to gain about one order of magnitude in sensitivity in the full 1-10000Hz range It will permit to access a larger amount of information
embedded in the BS (BNS, BH-NS, BH-BH) chirp signal Higher harmonics Merging phase
The GW emission of the coalescence of a NS binary system is often computed through the Post-Newtonian approximation Amplitudes and phases of GWs are obtained as series expansions in
v/c. The current detection pipelines are based on the matched
filter algorithm: More sensitive to the phase than to the amplitude modulation The current “template” construction is essentially based on the
fundamental harmonic (fGW=2fOrb), with an higher approximation order in phase than in amplitude “Restricted PN approximation”
But, if the two star masses in the BS are unbalanced, higher multipole moments are associated to the source Higher harmonics Need of a full PN approximation
8th Amaldi Conference, New York, 2009 8
Higher harmonics could play an important role depending on the masses, mass asymmetry and the inclination angle
8th Amaldi Conference, New York, 2009 9
Harmonics PN corrections
McK
echa
n et
al (
2008
)
The first consequence of the higher harmonics is a richer spectrum of the signal detected by the ITF
8th Amaldi Conference, New York, 2009 10McKechan et al (2008)Plots normalized to LIGO I
Dominant harmonic 5 harmonics
Higher harmonics do not greatly increase overall power, but push power toward higher frequencies, which can make higher-mass systems detectable even if quadrupole signal is outside the observing band BBH improved identification
8th Amaldi Conference, New York, 2009 11
ET RestrictedET Full
Van Den Broeck and Sengupta (2007)
Harmonics increasing the structure, greatly enhance parameter determination, by breaking degeneracy between parameters
8th Amaldi Conference, New York, 2009 12
HAHAth )(
Antenna response is a linear combination of the two polarizations:
H+ and H× contain the “physics of the source” (masses and spins) and time and phase at coalescence
A+(, ,,DL,i) and A×(, ,,DL,i) contain the “geometry of the source-detector system” Right ascension Declination Polarization angle Luminosity distance Orientation of the binary wrt the line of sight
Credits: B.Sathyaprakash
To fully reconstruct the wave one would need to make five measurements:
(, ,,DL,i)
Restricted PN approximation can only measure the random phase of the signal at the coalescing time To fully determine a source are needed
either 5 co-located detectors (“a la sphere”) or 3 distant detectors (3 amplitudes, 2 time delays)
Detecting the harmonics one can measure the random phase of the signal with one harmonic, orientation of the binary with another and the ratio A+/A× with the third
Two detectors at the same site in principle allow the measurement of two amplitudes, the polarization, inclination angle and the ratio A+/A× – the source can be fully resolved
In practice, because of the limited accuracy, two ET observatories could fully resolve source: 4 amplitudes from two sites, one time delay
8th Amaldi Conference, New York, 2009 13Credits: B.Sathyaprakash
Networking is still a “must” !
In principle, the right model of the merging of a black holes binary should fully use the General Relativity (GR) Unable to analytically solve the Einstein Field Equation:
Use of the Numerical Relativity (NR) There is no fundamental obstacle to long-term (i.e. covering ~10+ orbits) NR
calculations of the three stages of the binary evolution: inspiral, merger and ringdown But NR simulations are computationally expensive and building a template bank out of
them is prohibitive Far from the merging phase it is still possible to use post-Newtonian
approximation Hybrid templates could be realized and carefully tested (in case of high SNR detection)
overlapping in the phenomenological template the PN and NR waveforms
8th Amaldi Conference, New York, 200914
Red – NR waveformBlack – PN 3.5 waveform
Green – phenomenological template
Credits: Bruno Giacomazzo
The late coalescence and the merging phase contain information about the GR models Test it through ET will permit to verify the NR modeling
This is true also for the NS-NS coalescence where the merging phase contains tidal deformation modeling and could constrain, through numerical simulations, of the Equation Of State (EOS)
8th Amaldi Conference, New York, 2009 15
EOS of the NS is still unknown Why it pulses? Is it really a NS or the core is made by
strange matter? Gravitational Wave detection from
NS will help to understand the composition of the NS: Trough asteroseismology, revealing
the internal modes of the star Trough its continuous wave emission
8th Amaldi Conference, New York, 2009 16
• Measuring the frequency and the decay time of the stellar mode Measuring the frequency and the decay time of the stellar mode it is possible to reconstruct the Mass and the Radius of the NSit is possible to reconstruct the Mass and the Radius of the NS
• Knowing the Mass and the Radius it is possible to constrain the Knowing the Mass and the Radius it is possible to constrain the equation of state (EOS) equation of state (EOS)
8th Amaldi Conference, New York, 2009 17Credits: B.Schutz
A fraction of the NS emits e.m. waves: Pulsars
These stars could emit also GW (at twice of the spinning rotation) if a quadrupolar moment is present in the star: ellipticity
The amount of ellipticity that a NS could support is related to the EOS through the composition of the star: i.e. high ellipticity solid quark
star? Crust could sustain only ~10-6-10-7
Solid cores sustains ~10-3
Role of the magnetic field?
8th Amaldi Conference, New York, 2009 18
Imagine.gsfc.nasa.gov
8th Amaldi Conference, New York, 2009 19
Upper limits placed on the ellipticity of known galactic pulsars on the basis of 1 year of AdVirgo observation time.
Credit: C.Palomba
Credits: B.Schutz
Improving the sensitivity of the advanced detectors by an order of magnitude will permit to access, for the BNS observation, cosmological distances in the universe
8th Amaldi Conference, New York, 2009 20
Cre
dits
: G. J
ones
Virgo
Coma
Observed mass
Intrinsicmass
Z=1
Z=3
BNS are considered “standard sirens” because, the amplitude depends only on the Chirp Mass and Effective distance Effective distance depends on the effective Luminosity Distance and the
antenna pattern Through the detection of the BNS gravitational signal (using three
detectors or through the higher harmonics) it is possible to reconstruct the luminosity distance DL:, but with an ambiguity due to the red-shift
8th Amaldi Conference, New York, 2009 21
In fact, the red-shift is entangled with the binary’s evolution: DL DL (1+z) (1+z)
The observer wrongly reconstruct the total mass of the binary system
Credits: B. Sathyaprakash, B. Schutz, C. van den Broeck
323
5
)( tD
Mth
L
tot
Mtot Mtot (1+z)
Hence, GWs, measuring the chirp mass and the waveform amplitude are able to determine the luminosity distance DL of the red-shifted BNS, but need an e.m. counterpart to measure the red-shift z. i.e. Short GRB are currently considered to be generated by coalescing BNS Coupling GW and e.m. measurements it is possible to determine the origin of
GRB Knowing (1+z) and DL it is possible to test the cosmological model
and parameters that relate these two quantities:
8th Amaldi Conference, New York, 2009 22
M: total mass density: Dark energy densityH0: Hubble parameterw: Dark energy equation of state parameter
B.Sathyprakash and co., show that, thanks to the huge number of BNS coalescences visible by a 3rd generation GW detector, the cosmological parameters can be determined with only a few percent of error (B. Sathyaprakash, B. Schutz, C. van den Broeck in prep).
8th Amaldi Conference, New York, 2009 23
Supernova Explosions generates visible light, huge neutrino emission and GW emission
Large t between light arrival and neutrino arrival times could occur, due to the interaction of the light in the outer layer of the collapsing star 3 hours according to the SNEWS (SuperNova Early Warning System) in the
SN1987A Small t expected for GW detectors: dettttt propSN Where tSN depends on the different models adopted to describe the
neutrinos and GW emission (tSN <1ms) tdet depends on the detectors reciprocal distance and on the source
direction tprop depends only on the mass of the neutrino and on the distance L of the
source:22222 10
11015.5
2
E
MeV
eV
cm
kpc
Lms
E
cm
c
Ltprop
N.Arnaud et al, Phys.Rev.D65,2002
248th Amaldi Conference, New York, 2009
A mass measurement accuracy lower than 1 eV could be reached But, the event rate?
Current SNe models estimates about 10-8M emitted in GW; in the past larger fractions were expected 1st generation were limited to our galaxy: Event rate: 1evt every 20 years
To reach an acceptable event rate (1evt/year) a sight sphere of 3-5Mpc should be considered (Christian D Ott, 2008) Events, optically detected, from 1/1/2002, to 31/8/2008 < 5MPc:
258th Amaldi Conference, New York, 2009
Upper limit SNR estimated
26
advLIGO
ET: ~ × 108th Amaldi Conference, New York, 2009
The target for the design of a 3rd generation GW detector is to gain roughly a factor 10 in sensitivity (broadband) with respect to the advanced detectors Driven by the “precision astronomy” objective Need of high SNR
What are the ideas under evaluation?
8th Amaldi Conference, New York, 2009 27
8th Amaldi Conference, New York, 2009 28
10-25
10-16
h(f)
[1/
sqrt
(Hz)
]
Frequency [Hz]1 Hz 10 kHz
Seismic
Thermal Quantum
Seismic
NewtonianSusp. Thermal
Quantum
Mirror thermal
3rd generation ideal target
Actions:Actions: Drawbacks/DifficultiesDrawbacks/Difficulties
Step 1: increase of the arm length: h=L/L0: 10 km arm, reduction
factor 3.3 respect to Virgo New infrastructure!!
Step 2: reduction and optimization of the quantum noise (HF): Increase of the laser power from
125W to 500W Optimization of the optical
parameters (signal recycling, …) Introduction of a 10dB squeezing
New site, new costs Angular noises …
Laser R&D difficulties Thermal lensing effects
Optical losses crucial
8th Amaldi Conference, New York, 2009 29
The power step requested for the 3rd generation GW detectors is linear with respect to the increase required for the advanced detectors
8th Amaldi Conference, New York, 2009 30
Las
er p
ower
[W
]Year
Key task: Dominate thermo-
optical effects
Virgo Virgo +
adV/adL
ET
Reduce deposited heat and thermal gradients
Compensate thermal aberrations
“New” possible technology under “initial” investigation Rare earth doped fiber amplifier
High power amplification available NUFERN 150W single frequency amplifier 50 kW multimode amplifier
Still noisy : learn how to stabilize
New (longer) wavelenght probably neededC
redi
ts: A
.Bri
llet
LZH is aiming to reach 1kW within 5 years (solid state laser @ 1064nm)
Squeezed light states injection in a GW detector does not seem anymore a 3rd generation technology, but it “risks” to become a noise reduction tool in the advanced detectors GEO is installing his squeezing bench now LIGO wants to make a test after S6
8th Amaldi Conference, New York, 2009 31
Driven by huge recent progresses Vahlbruch et al, PRL 97, 2006:
Demonstration of squeezing on a Michelson inteferometer down to audio bands
Vahlbruch et al, PRL 100, 2008:
10dB squeezing @5MHz:
22ndnd generation generation 10km+High Frequency10km+High Frequency
8th Amaldi Conference, New York, 2009 32Credits: S.Hild
10-26
10-19
8th Amaldi Conference, New York, 2009 33
10-25
10-16
h(f)
[1/
sqrt
(Hz)
]
Frequency [Hz]1 Hz 10 kHz
Seismic
Thermal Quantum
Seismic
NewtonianSusp. Thermal
Quantum
Mirror thermal
3rd generation ideal target
To improve the sensitivity in the medium-low frequency range the mirror and suspension thermal noise must be decreased.
Minimization of the mirror thermal noise Reduction of the mechanical dissipations and of the
thermo-elastic and thermo-refractive couplings New materials
Cryogenics New materials
Larger beams Larger test masses sizes or new beam geometries
8th Amaldi Conference, New York, 2009 34
8th Amaldi Conference, New York, 2009 35
Source Symbol Spectral density Crucial Parameters
Coating brownian T, 1/w, coat
Bulk brownianT, 1/w, sub
Coating Thermoelastic
T2, 1/w2, coat
Bulk Thermoelastic
T2, 1/w3, sub
Coating Thermorefractive
T2, 1/w2,
Bulk thermorefractive
T2, 1/w2,
)(. fS coatBrown
)(. fS bulkBrown
)(, fS coatT
)(, fS bulkT
)(, fS coatT
)(, fS bulkT
wfY
TkfS
s
subcoatbcoatbrown
23
212)(
wfY
TkfS
s
subsubbbulkbrown
23
212)(
G
wfC
dTkfS
sss
NsubcbcoatT
223
2222
,
18)(
2322
5
2222
,
14)(
fwC
TkfS
ss
ssbbulkT
fCw
TkfS
sss
effbcoatT
223
222
,
2)(
fCw
TkLS
sss
bssTR
223
22
8
Credits: J.Franc et al.
8th Amaldi Conference, New York, 2009 36
SiO2 Silicon Sapphire
300K CRYO 300 K CRYO 300 K CRYO
5 10-9 10-7 assumed
2 10-8 ~3 10-9 2 10-9 4 10-9
- W/(m.K) 1.38 0.13 @10K
130 297 @4K
2330 @10K
40 110 @4.2K
1500 @ 12.5K
C - J/(K.Kg)
746 1-7@10K 711 0.276 @10K 790 0.1 @ 10K
- 1/K 0.51 10-6 -0.25 10-6
@ 10K2.54 10-6 4.85 10-10
@10K5.1 10-6 5.7 10-10
@10K
- 1/K 8 10-6 1.01 10-6 @30K
2.5 10-6 5.8 10-6 @30K
1.3 10-5 9 10-8 @20K
Credits: J.Franc et al.
Material adopted in the LCGT designNew possible candidate
investigated in the ET Design Study
8th Amaldi Conference, New York, 2009 37
Christian Schwartz @ ET-WP2 workshopFriedrich-Schiller-University Jena
Institute of Solid State Physics – Low Temperature Physics
Christian Schwarz 27.02.2009 7
Dissipation peaks due to impurities in silicon bulk materials
impurities/defects
Silicon, Ø 3” x 12 mm
Φmin = 2.2 x 10-9 @ 5.8 K
P.Amico et al. CQG, 2004
8th Amaldi Conference, New York, 2009 38
0,6 0,7 0,8 0,9 1,0 1,1 1,2 1,3 1,4 1,510-8
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
101
102
103
104
Si room temperature Suprasil 3002 room temperature Sapphire (LCGT2001) cryo
Silicon optical absorptiona
bso
rptio
n [c
m-1]
Wavelength [m]
M.A.Green and M.J. Keevers, Prog. in phot. res. and. appl. 3, 189 (1995)
Mirror thermal noise will be dominated by the coating dissipation in the advanced detectors What about 3rd generation GW detectors?
8th Amaldi Conference, New York, 2009 39
The thermo-mechanical properties of the possible coating materials aren’t so well known at low temperature (and in film format) to permit a reliable simulation. What the experimental measurements say?
Los
s an
gle
Martin et al, ET-WP2 meetingYamamoto et al, CQG. 21 (2004) S1075–S1081
The reduction of the coating dissipation could be obtained reducing the Tantala layer thickness using the waveguide coatings
8th Amaldi Conference, New York, 2009 40
SIO2 / Ta2O5: 99.1% reflectivityBrückner et al., Opt.Expr., 17,2009
Si500 nm
R>99.8%Brückner via Schnabel
Credits: H.Lueck @ GWADW ‘09
It is possible to gain even more increasing also the beam size Laguerre-Gauss higher order modes could help:
lower thermal noise & lensing
8th Amaldi Conference, New York, 2009 41
Coatings Standard : SiO2-Ta2O5
(HL)19HLL : Transmission 4 ppm
Substrate Silicon
Temperature 10K
Mirror dimension
Diameter : 62 cm
Thickness : 30 cm
Beam dimensions
Ratio insuring 1 ppm diffraction losses versus order of the LG mode
LG33 : w = a/4.3 = 7.2 cm
LG00 : w=a/2.6 = 11.9 cm
410
2 endinput SxSxh
T : 300KArm length : 3 kmBeam radius : 6 cm
10-27
10-22
J.Franc et al @ ET-WP3 meeting
TTN LG00
TTN LG33
Adopting some* of the solutions listed in the previous slides it is possible to approach the “ideal” 3rd generation sensitivity Still many unresolved technical questions
42
Credits: S.Hild
10-26
10-19
8th Amaldi Conference, New York, 2009
* Large LG00, Silicon test mass, cryogenics
• Reduction of the seismic excitation:Reduction of the seismic excitation:• Learning from the LISM lesson in Kamioka (Japan)
• New underground facility
• ~1 Hz seismic filtering system
8th Amaldi Conference, New York, 2009 43
Tre
xEnt
erpr
ises
• Reduction of the gravity gradient noise (NN)Reduction of the gravity gradient noise (NN)• New underground facility
• Suppression of the NN through correlation measurements?• Clever design of the cave doesn’t help (G. Cella)
• Reduction of the radiation pressure noiseReduction of the radiation pressure noise• Heavier mirrors
• 400mm maximum dimension of Si bulk by wafer producers
• Large SiC Mirror used in Astronomy• But optical quality (in transmission) poorer
Going underground we could gain 2-3 orders in seismic excitation, but we still need to filter
8th Amaldi Conference, New York, 2009 44
Moscow June 2008
Credit: K.Kuroda
LISM
A 50 m tall Virgo-like Super-Attenuator?
Optimized at 1HzCourtesy G. Cella
Horizontal
Violin modes to be considered
Noise requirements could be matched with a 7m long stage
8th Amaldi Conference, New York, 2009 45
Site requirements? Geological properties? Human activities in the surface? The depth? Seismic noise decreases exponentially going underground But analytical models foresee a minor Newtonian Noise
reduction Possibility to subtract the
residual noise measuring related auxiliary quantities Network of sensors
around the test masses Modeling in progress R
educ
tion
fac
tor
Frequency [Hz]
G.C
ella
, Fuj
ihar
a se
min
ar ‘
09
High power on the main cavities is a requirement conflicting with the design options devoted to reduce the low frequency noises: Cryogenics Long suspensions
A single broadband detector is probably too difficult to be realized
Possible solution: Realize a GW observatory composed by two (or more)
detectors Xylophone design (R. De Salvo, 2003)
8th Amaldi Conference, New York, 2009 46
Low Frequency optimized detector: Underground, Long suspensions, Cryogenic, Low
Laser power High Frequency detector High laser power, room temperature, “standard
suspensions”
8th Amaldi Conference, New York, 2009 47
8th Amaldi Conference, New York, 2009 48
Credits: S.Hild
The infrastructure (tunnels, deep underground cavities, …) are by far the dominant component of a 3rd generation GW observatory cost It will be difficult to realize more than one observatory per
continent Is it possible to find a geometry that optimizes the
costs and presents some additional benefit?
8th Amaldi Conference, New York, 2009 49
8th Amaldi Conference, New York, 200950
LL
45°
Fully resolve polarizations
5 end caverns
4×L long tunnels
45° stream generated by virtual interferometry
Null stream
Redundancy
7 end caverns
6×L long tunnels
60°
L’=L/sin(60°)=1.15×L
Fully resolve polarizations by virtual interferometry
Null stream
Redundancy
3 end caverns
3.45×L long tunnels L
Equivalent to
A Freise et al 2009 Class. Quantum Grav. 26
8th Amaldi Conference, New York, 2009 51
ET is a “design study” of a 3rd generation GW detector supported (3M€ in 3 years: 2008-2011) by the European Commission under the Framework Programme 7 FP7 - Identification of the future European research infrastructures
The aim is to deliver a conceptual design study of a 3rd generation gravitational wave (GW) observatory Feasibility study
Identification of the needed infrastructures Identification of the crucial technologies Identification of the fundamental elements of the design Science case development Technical details to be defined in a future phase
8th Amaldi Conference, New York, 2009 52
http://www.et-gw.eu/
Next ET general meeting: 14-16 October 2009, Erice, Sicily
ET design study team is composed by all the major groups leading the experimental Gravitational wave search in Europe: Virgo & GEO
8th Amaldi Conference, New York, 2009 53
Participant no. Participant organization name Country
1 European Gravitational Observatory Italy-France
2 Istituto Nazionale di Fisica Nucleare Italy
3 Max-Planck-Gesellschaft zur Förderung der Wissenschaften e.V., acting through Max-
Planck-Institut für Gravitationsphysik
Germany
4 Centre National de la Recherche Scientifique France
5 University of Birmingham United Kingdom
6 University of Glasgow United Kingdom
7 NIKHEF The Netherlands
8 Cardiff University United Kingdom
8th Amaldi Conference, New York, 2009 54
Scie
ntif
ic R
un /
LIG
O -
Vir
go
Commis-sioning/ Upgrade
eLIG
O, V
irgo
+
Commis-sioning
Scie
ntif
ic r
un(s
)
Upgrades & Runs
advL
IGO
, adv
Vir
go
Com-mis-
sioning
Scie
ntif
ic r
un(s
)
2007 2009 2011-12 20152008
ET Conceptual Design
ET Preparatory Phase and Technical
Design
Prel
imin
ary
site
pr
epar
atio
n
2017
ETConstruction
2022
Upgrades (High frequency
oriented?) and runs
2010 call for
Preparatory phase
INFRA-2010-1.1.30: Research Infrastructures for dark matter search,
neutrinos,gravitational waves
Third generation gravitational wave observatories will open, together with the future space detectors (LISA), the window of the precision gravitational wave astronomy Many contributions in Astrophysics, cosmology and fundamental
physics The technologies to realize these infrastructures are under
identification, but an intense R&D programme is necessary for their development Even if the success of the advanced detectors is mandatory, we
need to think now about these infrastructures, since the path is very long
A Worldwide collaboration is necessary to design, develop and realize a network of 3rd generation GW detectors
8th Amaldi Conference, New York, 2009 55
8th Amaldi Conference, New York, 2009 56
LIGO limited the fraction of energy emitted by the Crab pulsar through GW to ~6% (<1.8×10-4)
Virgo, at the start of the next science run could in few weeks set the upper limit for the Vela.
8th Amaldi Conference, New York, 2009 57
Spin down limits (1 year of integration)
Credit: B. Krishnan
BNS are considered “standard sirens” because, the amplitude depends only on the Chirp Mass and Effective distance Effective distance depends on the Luminosity Distance, Source
Location (pointing!!) and polarization The amplitude of a BNS signal is:
8th Amaldi Conference, New York, 2009 58
where the chirp mass is:
Cre
dits
: D. E
. Hol
z, S
.A.H
ughe
s
The Redshift is entangled with the binary’s evolution: The coalescing evolution has timescales (Gmi/c3) and these timescales
redshift Since also DL scales with (1+z), a coalescing binary with masses
[(1+z)m1, (1+z)m2] at redshift z is indistinguishable from a local binary with masses [m1, m2]
tD
nLtfMh
tD
nLtfMh
L
L
sin4
cos1
2
32
35
32
35
2
5
1
53
21
21
mm
mmM
Credits: B.Schutz
8th Amaldi Conference, New York, 2009 59
Sign
al s
tren
gth
and
nois
e am
plit
ude
[1/s
qrt(
Hz)
]
Credits: B.Sathyaprakash
If n=0, the Big-Bang-Nucleosynthesis limit is 0<1.1×10-5.
The SGWB is characterized by the dimensionless energy density GW(f):
n
fGW
cGW f
f
df
dff
00
n=0 for standard inflationary theoryn>1 for other theories (strings,..)
In principle, co-located ITF could measure the correlation needed to detect the SGWB, but local (low frequency) noises could spoil the measurement