ET: Einstein Telescope Michele Punturo INFN Perugia On behalf of the ET design study team 1ILIAS General meeting, Jaca Feb 2008

ET: Einstein Telescope

Michele PunturoINFN Perugia

On behalf of the ET design study team

1ILIAS General meeting, Jaca Feb 2008

Evolution of the current GW detectors• Current Gravitational Wave interferometric

detectors have a well defined evolution line in the next 5-7 years– LIGO just completed its S5 scientific run– Virgo completed in October 07 its first long scientific run

in parallel with LIGO• Both the detectors are in upgrade/commissioning mode to

implement their 1.5 generation upgrade step (Virgo+, enhanced LIGO)

– GEO is covering (“astrowatch” mode) the down time of LIGO and Virgo in collaboration with the resonant bar detectors

• … see G.Losurdo Talk

2ILIAS General meeting, Jaca Feb 2008

1st generation GW detectors sensitivities

ILIAS General meeting, Jaca Feb 2008 3 ESO – May 2, 2006 G.Losurdo – INFN Firenze 310

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1 10 100 1000 104

h (

Hz-1

/2)

Virgo

LIGO

Resonantantennas

Hz

GEO

Core Collapse@ 10 Mpc

BH-BH MergerOscillations@ 100 Mpc

Pulsars hmax – 1 yr integration

BH-BH Inspiral,z = 0.4

BH-BH Inspiral, 100 Mpc

QNM from BH Collisions, 1000 - 100 Msun, z=1

NS, =10-6 , 10 kpc

QNM from BH Collisions, 100 - 10 Msun, 150 Mpc

NS-NS Inspiral, 300 Mpc

NS-NS MergerOscillations@ 100 Mpc

1st generation detectors

Credit: P.Rapagnani

ILIAS General meeting, Jaca Feb 2008 4

“1.5 generation” sensitivities

Laser amplifier

Higher finesse, lower mirror TNM

onolithic FS suspensions

Advanced detectors• Enhanced detectors are a step toward the realization of the 2nd

generation detectors (“advanced”)– Also GEO will participate to the network of enhanced detectors with an

upgraded version, “specialized” in the high frequency regime thanks (mainly) to the signal recycling technology

• GEO HF– They are based on “small” changes of the current detectors with

available technologies that anticipate the next step• Advanced detectors will be online in the >2013 timeslot

– They will be based on known technologies currently under preliminary engineering phase

• High power laser (~200W) and compliant optics• Lower thermal noise mirrors (substrates and coatings)• Lower thermal noise suspensions (FS monolithic suspensions)• Better seismic isolation

– Active filtering in LIGO– Focused improvements of the Virgo Super-Attenuator

• Signal recycling


Detectionprogresses

Credit:

Richard Powell,

Beverly Berger.

From LIGO presentation G050121

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h(f

) [1

/sq

rt(H

z)]

Frequency [Hz]

1st generation: Virgo LIGO

1.5 generation: Virgo+ eLIGO

2nd generation advVirgo advLIGO

NS-NS (1.4MS):13 15/50 120/170 Mpc

NS-NS

3rd generation detectors• Second generation detectors:

– Will permit the detection of Gravitational Waves (GW)– Will open the era of the GW astronomy– Will be the “core business” of the next decade in

experimental GW research• But can we look beyond?

– Precision GW astronomy needs high SNR to determine the parameters of the astrophysical process

– Interesting phenomena involves massive bodies that requires low frequency sensitivity in GW detectors

– We need to think to 3rd generation GW detectors


Objectives of a 3 rd generation GW detectorsFrom detection and initial GW astronomy to precision GW astronomy

• Fundamental Physics: Test general relativity in the strongly non-linear regime– Initial and advanced detectors won’t have the sensitivity required to test

strong field GR (too low SNR)• Most tests are currently quoted in the context of LISA, but in a different frequency range

– We need to have good enough SNR for rare BBH mergers which will enable strong-field test of GR

• Black hole physics:– What is the end state of a gravitational collapse?

• Astrophysics: Take a census of binary neutron stars in the high red-shift Universe– Adv VIRGO/LIGO might confirm BNS mergers, possibly provide links to -ray

bursts– 3rd generation GW detectors could do much more: see different classes of

sources (NS-NS, NS-BH) and contribute to resolve the enigma in the variety of -ray bursts


How to arrive to an European 3rd generation GW Observatory?

• Long preparatory path, already started:– ILIAS played a determinant role:

• ILIAS-GW-WP3 realized the correct environment where to discuss, at European level, the evolution of the current detectors and where to merge the efforts addressed to the proposition of a 3rd generation GW observatory

– It supported the meetings, the workshops and the preliminary studies– All the ET proposal writing meetings have been supported by WP3– WP3 has been also the core of the new WG6 (GW) in the ASPERA road-mapping

activity

• ILIAS-JRA3 (STREGA) partially supported R&D activities in thermal noise issues for 3rd generation GW detectors

– European Science Foundation supported an exploratory workshop (Perugia, Sept 2005) that has been a milestone in the definition of the strategy for the proposal of a new Observatory

– FP7 Design Study has been the perfect environment where to synthesize our ideas in a proposal and compete with other excellent proposals


ET

• ET: Einstein Telescope– An European 3rd Generation Gravitational Wave

Observatory• Conceptual design study proposed at the May

2007 FP7 call– Capacities

• Research Infrastructures– Collaborative projects


ET: Participants


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

ET: Status of the project• The proposal passed the first selection and now

we are in an advanced negotiation phase• We agreed a budget reduction to 3M€ for

38Months of activity – Main costs: man power and travels

• Description of Work document accepted by the European Officer– We are submitting the signed documents to prepare

the Grant Agreement– Consortium Agreement under final definition


Project organization

• Project organization driven by the “Physics”:– 4 working groups are devoted to the major

technical and scientific issues– Let see the main technical aspects:


Executive board

GoverningCouncil

Science Team

Institutions Scientific community

ET Project

Information fluxes

3 main noise sources


1st generation2nd generation3rd generation

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Thermal Noise




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2nd generation

10km

Thermal Noise

•Long interferometer arms

• Cryogenic optics

•Large beams, large optics

• Non-gaussian beams

• Improved coatings

Thermal Noise • Long interferometer arms


• Large beams, large optics



Cryogenic Optics


• Test masses and suspensions thermal noise reduces at low temperature: <X2> ~ T

• Thermoelastic noise of the mirror substrates and coatings decrease: <X2> ~ α T2

– Thermal expansion rate decreases at low temperature;

• Mechanical Q of some materials increases at low temperature

• Thermal lensing:– Thermal conductivity increases and consequently reduces thermal gradients on the

coating;– Refraction index variation with temperature is very small at low temperature;

(Sapphire @ 20K β = 9 × 10−8, Fused Silica @ 300K β ~ 10−6)

ILIAS “supported” or related activities


Silicon substrates

R&D activities in many European Labs:Glasgow, INFN Florence & Perugia, Jena University, …

Cryogenic Super attenuator

R&D activities in INFN Rome & Pisa

0 50 100 150 200 250 300

1.0x10-5

1.5x10-5

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3.5x10-5 4th mode undoped Ta

2O

5

4th mode, TiO2 doped Ta

2O

5

Mec

hani

cal l

oss

of c

oate

d si

licon

can

tilev

er

Temperature (K)

Coatings studies

R&D activities in many European Labs:Glasgow, INFN Perugia, LMA-Lyon, MPG Hannover, …




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Non Gaussian Beams• Thermal noise in a GW interferometric detector

could be further reduced by using “flatter” beams:





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10km, 20K, 10cm














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800kW

3MWShot Noise

Shot Noise

• High laser power

Shot Noise


• Squeezing

• Long interferometer arms

Shot Noise


(maybe 1550nm for silicon;

less thermal lensing @ 25K)




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3MW, 6dB3MW, 6dB, 10km

3MW, 6dB, 10km, 3ifos

Shot Noise


Shot Noise


• Squeezing

Shot Noise


• Squeezing


Shot Noise


• Squeezing


• Multiple colocated interferometers

Co-located interferometers• “Old” idea still under debate

– Possible implementation: 3 detectors in a triangle configuration


Rüdiger, ‘85

Angular response of a standard ITF

Angular responseof the triangle configurationCredit: Cella, Vicerè

Antenna Patterns:




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• Underground operation

• Homogeneous ‚soil‘Seismic

Underground operations


• LISM: 20 m Fabry-Perot interferometer, R&D for LCGT, moved from Mitaka (ground based) to Kamioka (underground)• Seismic noise strongly reduced

Credit: K.Kuroda

102 overall gain103 at 4 Hz

Seismic Isolation Shortcut

ILIAS General meeting, Jaca Feb 2008 27Figure: M.Lorenzini

Newtonian Noise!

NewtonianNoisecredit: G.Cella


• Surface waves give the main contribution to newtonian noise

Credit: G.Cella

Surface waves die

exponentially with depth

Compression wavesSurface waves

Credit: G. CellaCredit: G. Cella

NN reduction of 104 @5 Hz

with a 20 m radius cave

Cave radius [m]

Redu

ction

fact

or

(Compression waves not included)

106 overall reduction (far from surface)102 less seismic noise x 104 geometrical reduction




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Ground surface

Underground

Conclusions• The target of the four Working Groups in the ET project is to try to

transform these (and many other) ideas in a coherent conceptual design

• It is an huge job for a restricted set of persons• ET is an emerging facility for the whole Europe and we don’t want

to limit the contribution to the founding team/institutions• The proposal writers created in the project structure a special body

that permits the exchange with a larger Scientific Community


Executive board

GoverningCouncil

Science Team

Institutions Scientific community

ET Project• The Science Team has been considered extremely important by the project referee and already promoted the interest of European and extra-European Scientists

• If you are interested, please, contact us

Comments

• ILIAS-N5 played a fundamental role in building-up the framework where ET project is born

• ILIAS-JRA3 partially supported the technological development needed to “think” to ET

• ET is a conceptual design, with any R&D support:– It needs a further support from the ILIAS (-next)

community


Conclusions: Planning


´06´06 ´07´07 ´08´08 ´09´09 ´10´10 ´11´11 ´12´12 ´13´13 ´14´14 ´15´15 ´16´16 ´17´17 ´18´18 ´19´19 ´20´20 ´21´21 ´22´22

VirgoVirgo

GEOGEO

LIGOLIGO

LISALISA

E.T.E.T.

Virgo+

LIGO+

Advanced Virgo

GEO HF

Advanced LIGO

DS PCP Construction Commissioning

HanfordHanford

LivingstonLivingston

Launch Transfer data

data

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ET: Einstein Telescope Michele Punturo INFN Perugia On behalf of the ET design study team 1ILIAS General meeting, Jaca Feb 2008