Michele Punturo INFN Perugia and EGO On behalf of the ET design team.

Transcription

1 Michele Punturo INFN Perugia and EGO On behalf of the ET design team 58th Fujihara Seminar, May

2 ET is a design study of a 3 rd generation GW detector supported by the European Commission under the Framework Programme 7 (FP7) Capacities Research Infrastructures Design studies Identification of the future European research infrastructures It is a ~3 years project supported by EC with about 3 M It started in the middle of 2008 and will end in th Fujihara Seminar, May

3 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 58th Fujihara Seminar, May

4 The ET design study aim is to deliver, at the end of the 3 years, a conceptual design study of a 3 rd generation gravitational wave (GW) observatory: Science potentialities New infrastructures New site New detection and analysis technologies 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 58th Fujihara Seminar, May

5 To understand the role and the interest about the ET physics, we should insert it in our evolution path of the GW detectors 58th Fujihara Seminar, May

6 Same Infrastructures, improvements of the current technologies, some prototyping of the 2 nd generation technologies Same Infrastructures, engineering of new technologies developed by currently advanced R&D Scientific Run / LIGO - Virgo Commis -sioning/ Upgrade eligo, Virgo+ Scientific run(s) Upgra des & Runs advligo, advvirgo Commissioning LCGT Commissioning Construction LCGT Scientific run(s) Commissioning Upgrades (High frequency oriented?) and runs ET Conceptual Design ET Preparatory Phase and Technical Design Preliminary site preparation 2017 ET Construction th Fujihara Seminar, May

7 Site and infrastructure Thermal noise of mirrors and suspensions / cryogenics Optical configuration Astrophysics issues Management J. v.d. Brand F. Ricci A. Freise B. S. Sathyaprakash J. Colas M. Punturo H. Lück 58th Fujihara Seminar, May

8 Since GW detection is expected to occur in the advanced detectors, the ET science targets are mainly addressed to 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 58th Fujihara Seminar, May

9 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 not be possible would require good quality high-snr events ET sensitivity target aims to decrease the noise level of about one order of magnitude in the full Hz 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 58th Fujihara Seminar, May

10 Credits: B. Sathyaprakash A coalescing binary emits most of its GW radiation at twice of the orbital frequency Current (an partially advanced) interferometers, basing the detection upon the matched filtering technique, far more sensitive to phasing than amplitude modulation, privilege the correct phase reconstruction of the signal (PN approximations) rather than the amplitude modulation PN approximation is currently known to 3.5 PN in phase and 3 PN in amplitude and up to eight harmonics of the orbital frequency Harmonics PN corrections The so-called restricted waveform uses only the dominant harmonic The full waveform includes radiation emitted at other frequencies These higher harmonics are due to higher multipole moments associated with the source 58th Fujihara Seminar, May

11 The first consequence of the higher harmonics is a richer spectrum of the signal detected by the ITF Dominant harmonic 5 harmonics McKechan et al (2008) Plots normalized to LIGO I Higher harmonics do not greatly increase overall power, but move power toward higher frequencies, which can make higher-mass systems detectable even if quadrupole signal is outside the observing band BBH improved identification 58th Fujihara Seminar, May

12 Harmonics do increase structure, greatly enhance parameter determination, by breaking degeneracy between parameters Antenna response is a linear combination of the two polarizations: h ( t) = A A H + H + + H + and H contain the physics of the source (masses and spins) and time and phase at coalescence A + (α, δ,ψ,d L,i) and A (α, δ,ψ,d L,i) contain the geometry of the sourcedetector system Right ascension Declination Polarization angle Luminosity distance Orientation of the binary wrt the line of sight 58th Fujihara Seminar, May Credits: B.Sathyaprakash

13 To fully reconstruct the wave one would need to make five measurements: (α, δ,ψ,d L,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 58th Fujihara Seminar, May 2009 Credits: B.Sathyaprakash 13

14 EOS of the NS is still unknown Why it pulses? Is it really a NS or the core is made by strange matter? Like in the ordinary stars, the study of the stellar internal modes (asteroseismology) could help to understand the composition of the NS Credits: B.Schutz 58th Fujihara Seminar, May

15 Measuring the frequency and the decay time of the stellar mode it is possible to reconstruct the Mass and the Radius of the NS Knowing the Mass and the Radius it is possible to constrain the equation of state (EOS) Credits: B.Schutz 58th Fujihara Seminar, May

16 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 ε 10-7 Solid cores sustains ε~10-3 Role of the magnetic field? Imagine.gsfc.nasa.gov 58th Fujihara Seminar, May

17 LIGO limited the fraction of energy emitted by the Crab pulsar through GW to ~6% (ε< ) 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 58th Fujihara Seminar, May

18 Credits: B.Schutz Upper limits placed on the ellipticity of known galactic pulsars on the basis of 1 year of AdVirgo observation time. Credit: C.Palomba 58th Fujihara Seminar, May

19 The aim of ET is to design a GW detector with roughly a factor 10 lower noise (broadband) respect to advanced detectors What are the ideas under evaluations? 58th Fujihara Seminar, May

20 10-16 Seismic h(f) [1/sqrt(Hz)] Hz Frequency [Hz] 10 khz 58th Fujihara Seminar, May

21 Actions: Drawbacks/Difficulties Step 1: increase of the arm length: New site, new costs h=δl/l 0 : 10 km arm, reduction factor 3.3 respect to Virgo New infrastructure!! Angular noises Step 2: reduction and optimization of the quantum noise: Increase of the laser power from 125W to 500W Optimization of the optical parameters (signal recycling, ) Laser R&D difficulties Thermal lensing effects Introduction of a 10dB squeezing Optical losses crucial 58th Fujihara Seminar, May

22 2 nd generation 10km+High Frequency Credits: S.Hild 58th Fujihara Seminar, May

23 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 58th Fujihara Seminar, May

24 Source Symbol Spectral density Crucial Parameters Coating brownian Bulk brownian Coating Thermoelastic Bulk Thermoelastic Coating Thermorefractive S coat Brown S bulk Brown S coat α T S bulk α T S coat β T.( f.( f, ( f, ( f, ( f ) ) ) ) ) S coat α, T S S coat brown bulk brown ( f ) = ( f ) = 2k b T Φ 2k T Φ b coat 3 2 s π Y wf sub 3 2 s π Y wf ( 1+ σ ) 2 ( 1 σ ) sub 2 ( 1 σ ) 2 2 8kbT αc sub d ( f ) = π κ C ρ f w S bulk α, T S 2 4kbT α ( f ) = 5 2 π coat β, T ( f ) = π s s 2 s s 2 2 N 2 ( 1+ σ ) sub ( C ρ ) w f s 2k 3 2 w b 2 s T 2 β s 2 eff G 2 κ κ ρ C s 2 λ s s f ( ) ω T, 1/w, Φ coat T, 1/w, Φ sub T 2, 1/w 2, α coat T 2, 1/w 3, α sub T 2, 1/w 2, β Bulk thermorefractive S bulk β T, ( f ) S s TR β s L = 8ζ 2 π 3 2 w 2 k b T κ ρ C s 2 s s f T 2, 1/w 2, β Credits: J.Franc et al. 58th Fujihara Seminar, May

25 SiO2 Silicon Sapphire 300K CRYO 300 K CRYO 300 K CRYO Φ assumed κ - W/(m.K) 1.38 C - J/(K.Kg) ~ K @10K K α -1/K K β -1/K Credits: J.Franc et al. 58th Fujihara Seminar, May

26 Friedrich-Schiller-University Jena Institute of Solid State Physics Low Temperature Physics Dissipation peaks due to impurities in silicon bulk materials impurities/ defects Φ min = 2.2 x 5.8 K Silicon, Ø 3 x 12 mm Christian Schwarz th Fujihara Seminar, May

27 Credits: J.Franc et al. 58th Fujihara Seminar, May

28 SiO 2 Al 2 O 3 Ta 2 O 5 TiO 2 HfO 2 Φ Density κ - W/(m.K) 5@10K C - J/(K.Kg) 0.1@10K 3.17@50K α -1/K β -1/K 1.01 A lot of missing parameters Y σ same 0.2 values taken 0.21 at cryo and K n Credits: J.Franc et al. 58th Fujihara Seminar, May

29 SiO 2 -Ta 2 O 5 coatings : 17 doublets Some parameters of Ta2O5 are at 300K (unkown at low temperature) Credits: J.Franc et al. 58th Fujihara Seminar, May

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31 Sapphire Silicon Transparent at the standard wavelenght (1064nm) New wavelenght nm New laser Upgrade of the 2 nd generation lasers Upgrade of the 2 nd generation coatings Adv LIGO and LCGT studies available Bonding technique to be evaluated New coatings? Minimization of the thermal lensing issues High thermal conductivity Very low optical absorption Standard bonding technology 58th Fujihara Seminar, May

32 Silicon is a favorable material to realize the suspension fibres of a 3 rd generation GW detector: High thermal conductivity High mechanical strength (>7GPa) Linear expansion coefficient vanishes at low temperature Thermo-elastic noise reduction Possibility to realize a monolithic suspension through silicate bonding Spoiling of the thermal conductivity? thermal noise [m/sqrt(hz)] Brownian Thermoelastic total temperature [K] 58th Fujihara Seminar, May

33 Reduction of the thermal noise Reduction of the thermal lensing problems Increase of the anthropogenic seismic noise Increase of the complexity of the infrastructures P.Puppo et al. Prototype cooled down to 24K: 58th Fujihara Seminar, May

34 Adopting all the solutions listed in the previous slides it is possible to approach the ideal 3 rd generation sensitivity Many unresolved technical questions th Fujihara Seminar, May 2009 Credits: S.Hild 34

35 Reduction of the seismic excitation: Learning from the LISM lesson in Kamioka (Japan) New underground facility ~1 Hz seismic filtering system? 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 studies) Reduction of the radiation pressure noise Heavier mirrors Limitation to 400mm of the substrate diameter if in Silicon 58th Fujihara Seminar, May

36 Under discussion the location In Europe? Verification with geologists The deepness Measurement of seismic noise in the undeground laboratories in Europe and USA Analytical and finite element modeling of the seismic and newtonian noise underground The Geometry Triangular, L-shaped? Costs? 58th Fujihara Seminar, May

37 Going underground we could gain 2-3 orders in seismic excitation, but we still need to filter A 50 m tall Virgo-like Super- Attenuator? Credit: K.Kuroda Horizontal LISM Courtesy G. Cella Optimized at 1Hz Moscow June 2008 Violin modes to be considered 58th Fujihara Seminar, May

38 Integrate the requirements to improve the high frequency regime (high power, high finesse, heavy test masses, squeezing, ) with the requirements to reduce the low frequency noises (cryogenics, long suspension system, underground installation, ) in a single detector is probably too difficult. But we could integrate them in a single observatory if we use the Xylophone principle (R.De Salvo 2003) Integrate more than one detector in a single observatory Each detector is devoted to a reduced frequency range 58th Fujihara Seminar, May

39 HF detector: high power (3MW), room temperature, normal suspensions, LG33 mode, no gravity gradient noise subtraction LF detector: low power (18kW), cryogenic, underground location, 50m suspensions, TEM00 mode, gravity gradient subtraction Credits: S.Hild 58th Fujihara Seminar, May

40 The ET design study aim is to verify the feasibility of a new 3 rd generation GW observatory, having a factor 10 improved sensitivity respect to the advanced detectors The science potentiality of this observatory are under evaluation, but ET could permit to realize precision astronomy and cosmology measurements A new underground facility is needed to improve the sensitivity at low frequency, but technical difficulties are suggesting to evaluate a Xylophone option A worldwide effort and collaboration is required to elaborate the new design concepts of such as detector Networking is still a necessity with the 3 rd generation GW detectors 58th Fujihara Seminar, May

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43 Higher harmonics could have an important role depending on the masses, mass asymmetry and the inclination angle McKechan et al (2008) 58th Fujihara Seminar, May

44 In principle, the correct way to model the merging of a black holes binary is to 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 with ET overlapping in the phenomenological template the PN and NR waveforms Credits: Bruno Giacomazzo (ILIAS meeting) Red NR waveform Black PN 3.5 waveform Green phenomenological template 58th Fujihara Seminar, May

45 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) 58th Fujihara Seminar, May

46 The beam size could be used to reduce the thermal noise (and lensing) both of the substrate and of the coating More clever ideas needed for the coatings New material? New design? High order modes? strain noise [1/ Hz] ET addet Credits: R. Nawrodt et al. assuming advdet. aspect ratio w [mm] m [kg] frequency [Hz] ROC m~ w 3 58th Fujihara Seminar, May