Michele Punturo INFN Perugia and EGO On behalf of the ET Design Study Team 8th Amaldi Conference,...

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



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Same Infrastructures, improvements of the current technologies, some prototyping of the 2nd generation technologies


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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


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Upgrades (High frequency

oriented?) and runs


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


Higher harmonics could play an important role depending on the masses, mass asymmetry and the inclination angle


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


ET RestrictedET Full

Van Den Broeck and Sengupta (2007)

Harmonics increasing the structure, greatly enhance parameter determination, by breaking degeneracy between parameters


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


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)


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


• 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?


Imagine.gsfc.nasa.gov


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


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


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:


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).

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


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:


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?



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


The power step requested for the 3rd generation GW detectors is linear with respect to the increase required for the advanced detectors


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


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


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



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.


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


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


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?


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


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


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


* 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


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


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


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)


Low Frequency optimized detector: Underground, Long suspensions, Cryogenic, Low

Laser power High Frequency detector High laser power, room temperature, “standard

suspensions”



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?



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

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


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


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


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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


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.


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:


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


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

Michele Punturo INFN Perugia and EGO On behalf of the ET Design Study Team 8th Amaldi Conference,...

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Transcript of Michele Punturo INFN Perugia and EGO On behalf of the ET Design Study Team 8th Amaldi Conference,...