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