ET – THE EINSTEIN TELESCOPEINSTRUMENTAL ASPECTS

Harald LückAEI Hannover

The goal

Frequency (Hz)

10-19

10-20

10-21

10-22

10-23

10-24

10-25

LIGO

Advanced LIGO/Virgo

Virgo

ETc

1 10 102 103 104

Stra

in [

1/(H

z)1/2 ]

ETb

3

1st Generation 2nd Generation

3rd Gen.

´06 ´07 ´08 ´09 ´10 ´11 ´12 ´13 ´14 ´15 ´16 ´17 ´18 ´19 ´20´21 ´22 ´23 ´24 ´25

Virgo

GEO

LIGO

LISA

E.T.

Hanford

Livingston

DS PCP Construction Comm. data Site Prep.

Virgo+

E-LIGO

Advanced Virgo

GEO 600

Advanced LIGO

Launch Transfer

You are here DetectionPhase

RareObservation

Routine Observation

GW Detection is a prerequisite for building ET

You are here

A LONG ROAD

The GWIC roadmap

The Einstein Telescope The Einstein Telescope project is currently in its conceptual

design study phase, supported by the European Union within FP7 with about 3M€ from May 2008 to July 2011.

Einstein Telescope 5

Participant Country

EGO ItalyFrance

INFN Italy

MPG Germany

CNRS France

University of Birmingham UK

University of Glasgow UK

Nikhef NL

Cardiff University UK

CNRS; 18

CU; 10

EGO; 13

INFN; 59MPG; 43

UNIBHAM; 12

UNI-GLAS-

GOW; 34

VU; 7

Participants per Bene-ficiary

Science team total: 249

TECHNIQUES FOR ET•Basic assumptions:•ET will be a long lasting (decades) infrastructure•Only mature techniques are foreseen as baseline design•Subsequent upgrades to novel techniques will follow•ET will be built underground, (see ‘seismic slides’) •Overall tunnel length will be 30km •ET will be built in a ‘triple Michelson’ arrangement (CQG 26 085012, 2009)

Antenna pattern

doi: 10.1088/0264-9381/26/8/085012

STARTING POINT: 2ND GENERATION

We consider:Michelson topology with

dual recycling.One detector covering the full frequency bandA single detector (no

network)Start from a 2nd Generation instrument.Each fundamental noise at least for some frequencies above the ET target.

=> OUR TASK: All fundamental noises have to be improved !!

2nd Generation design sensitivity

3G target sensitivity

(approximated)Courtesy:Stefan Hild

INCREASING THE ARM LENGTH

DRIVER: All displacement noisesACTION: Increase arm length from 3km to 10kmEFFECT: Decrease all displacement noises by a factor 3.3SIDE EFFECTS: Decrease in residual gas pressure

Change of effective Signal recycling tuning

ADV (3km)

ET (10km)

Courtesy:Stefan Hild

Credit: M. Beker, Nikhef

Gravity Gradient Noise

Credit: M. Beker, Nikhef

Seismic measurements

Credit: M. Beker, Nikhef

Seismic measurements

Credit: M. Beker, Nikhef

Seismic measurements

Credit: M. Beker, Nikhef

Seismic measurements

Credit: M. Beker, Nikhef

Courtesy:Stefan Hild

SIGNAL RECYCLING

DRIVER: Quantum noiseACTION: From detuned SR to tuned SR (with 10% transmittance) EFFECTS: Reduced shot noise by ~ factor 7 at high freqs

Reduced radiation pressure by ~ factor 2 at low freqs Reduced peak sensitivity by ~ factor sqrt(2) :(

MORE LASER POWER

DRIVER: Shot noise at high frequenciesACTION: Increase laser power (@ ifo input) from 125W to 500W EFFECT: Reduced shot noise by a factor of 2SIDE EFFECTS: Increased radiation pressure noise by a factor 2

Courtesy:Stefan Hild

QUANTUM NOISE REDUCTION

DRIVER: Shot noise at high frequenciesACTION: Introduced 10dB of squeezing (frequency depend angle)EFFECT: Decreases the shot noise by a factor 3SIDE EFFECTS: Decreases radiation pressure noise by a

factor 3

Courtesy:Stefan Hild Detuned Squeezing requires filter cavities

The effective squeezing level of lossy filter cavities for the low and high frequency ET Xylophone

FILTER CAVITIES

[paper in preparation]

FILTER CAVITIES

QND TECHNIQUESNOT FORESEEN FOR INITIAL TOPOLOGY

Detector topologies different than Michelson might offer even better quantum noise reduction, i.e. Dual Recycled Sagnac with arm cavities or Optical Bar / Optical Lever topologies.

Speedmeter sensitivity.H. Mueller-Ebhardt et al:

https://pub3.ego-gw.it/itf/tds/file.php?callFile=ET-010-09.pdf

INCREASING THE BEAM SIZE

DRIVER: Coating Brownian noise ACTION: Increase of beam radius from 6 to 12cmEFFECT: Decrease of Coating Brownian by a factor 2SIDE EFFECTS: Decrease of Substrate Brownian noise (~factor 2)

Decrease of Thermo-optic noise (~factor 2) Decrease of residual gas pressure noise (~10-20%)

Courtesy:Stefan HildOR:

WAVEGUIDE COATINGS REDUCING MECHNICAL DISSIPATION

Waveguides may provide an elegant way to reduce coating Brownian noise.

Idea: replacing the dielectric (lossy, thick) multi-layer stack by a (low loss, thin) mono-crystalline silicon nano-structure or a (thin) single layer diffractive coating.

Brückner et al., Optics Express 17 (2009) 163 – 169

Si500 nm

Brückner et al., Optics Letters 33 (2008) 264 - 266 OR:

END MIRROR (KHALILI) CAVITIES

Using Khalili-cavities as end mirrors, we can reduce the total mirror thermal noise of the whole interferometer by about a factor 1.5.

With Khalili

No Khalili

“Khalili” cavities (F.Khalili Physics

Letters A, 2005, 334, 67 - 72) allow to reduce the influence of coating Brownian noise.

COOLING THE TEST MASSES

DRIVER: Coating Brownian noiseACTION: Reduce the test mass temperature from 290K to 20KEFFECT: Decrease Brownian by ~ factor of 4SIDE EFFECTS: Decrease of substrate Brownian

Decrease of thermo-optic noise Kuro

da 2

008

LIGO

-G08

0060

CLIO + LGCT

Courtesy:Stefan Hild Requires “cryogenic material” ->silicon

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 absorption

abso

rptio

n [c

m-1]

Wavelength [m]

M.A.Green and M.J. Keevers, Prog. in phot. res. and. appl. 3, 189 (1995)

Fused Silica unusable at cryo-temperatures Sapphire and Silicon best candidates Sapphire selected in LCGT Silicon under study in ET McGuigan 1978

Jena Group 2009

Silicon loss angle

10-8 1.5m

Floating zone high purity, up to 30 kOhms cm < 200mm diameter

Czochralski more impurities, <300 Ohms cm >300mm? ; bigger sizes in the ET era ?

Silicon

SUSPENSIONS

DRIVER: Seismic noiseACTION: Build a 17m Virgo-Style SuperattenuatorEFFECT: Decrease seismic noise by many orders of magnitudeor pushes the seismic wall from 10 Hz to about 1.5 Hz

S.Brachini: http://gw.icrr.u-tokyo.ac.jp/gwadw2010/program/2010_GWADW_Braccini.ppt

Courtesy:Stefan Hild

SUSPENSION TOWERS

Parameter ET- High Frequency

ET – Low Frequency

Arm length 10 km 10 kmInput power 500 W 3 WArm Power 3 MW 20 kWTemperature 290 K 10 KMirror material

Fused Silica Silicon

Mirror diameter x thickness

620 mm x 300 mm

450 mm x 300mm

Mirror masses 200 kg 110 kgLaser Wavelength

1064 nm 1550 nm

SR- Phase Tuned Detuned (0.6 rad)

SR Transmittance

10% 20 %

Beam shape LG33 TEM00Beam Radius 72 mm 120 mmSuspension Short SA SA 20m

‘Xylophone’: cool & hot

20K 300K

For more details please see S.Hild, S.Chelkowski, A.Freise, J.Franc, R.Flaminio, N.Morgado and R.DeSalvo: ‘A Xylophone Configuration for a third Generation Gravitational Wave Detector’, CQG 2010, 27, 015003

INSTALLATION OF ET

For efficiency reasons build a triangle.Start with a single xylophone detector.

For efficiency reasons build a triangle.Start with a single xylophone detector.

Add second Xylophone detector to fully resolve polarisation.

INSTALLATION OF ET

For efficiency reasons build a triangle.Start with a single xylophone detector.

Add second Xylophone detector to fully resolve polarisation.

Add third Xylophone detector for redundancy and null-streams.

INSTALLATION OF ET

Credit: Stefan Hild

Status and future of GW observatories

1st generation successfully completed: Long duration observations (~1yr)

in coincidence mode of 5 oberservatories.

Beat Spin-down upper limit of the Crab-Pulsar

2nd generation on the way: End of design phase, construction

started 10 times better sensitivity than

1st generation. => Scanning 1000 times larger volume of the Universe

3rd generation at the horizon: FP7 funded design study in Europe 100 times better sensitivity than

1st generation. => Scanning 1000000 times larger volume of the Universe

LCGT