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

1st generation GW detectors sensitivities 10 -24 -23 -22 -21 -20 -19 -18 1 100 1000 4 h (Hz-1/2) Virgo LIGO Resonant antennas Hz GEO Core Collapse @ 10 Mpc BH-BH Merger Oscillations @ 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, e =10 -6 , 10 kpc 100 - 10 Msun, 150 Mpc NS-NS Inspiral, 300 Mpc NS-NS Merger 1st generation detectors Credit: P.Rapagnani ILIAS General meeting, Jaca Feb 2008 ESO – May 2, 2006 G.Losurdo – INFN Firenze 3

“1.5 generation” sensitivities Monolithic FS suspensions Laser amplifier Higher finesse, lower mirror TN ILIAS General meeting, Jaca Feb 2008

ILIAS General meeting, Jaca Feb 2008 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 ILIAS General meeting, Jaca Feb 2008

Detection progresses NS-NS (1.4MS): 13  15/50  120/170 Mpc NS-NS Credit: Richard Powell, Beverly Berger. From LIGO presentation G050121 Detection progresses 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 ILIAS General meeting, Jaca Feb 2008

ILIAS General meeting, Jaca Feb 2008 Objectives of a 3 rd generation GW detectors From 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 g-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 g-ray bursts ILIAS General meeting, Jaca Feb 2008

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 ILIAS General meeting, Jaca Feb 2008

ILIAS General meeting, Jaca Feb 2008 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 ILIAS General meeting, Jaca Feb 2008

Participant organization name 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 7 NIKHEF The Netherlands 8 Cardiff University ILIAS General meeting, Jaca Feb 2008

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 ILIAS General meeting, Jaca Feb 2008

Project organization Project organization driven by the “Physics”: Project Coordinator Scientific Coordinator Secretary WP1 coordinator: Infrastructures Task responsible WP2 coordinator: suspensions Task reponsible WP3 coordinator: Topology WP4 coordinator: Astrophysics WP5: Management Executive board Governing Council Science Team Institutions Scientific community ET Project Information fluxes Project organization driven by the “Physics”: 4 working groups are devoted to the major technical and scientific issues Let see the main technical aspects: ILIAS General meeting, Jaca Feb 2008

ILIAS General meeting, Jaca Feb 2008 3 main noise sources 1st generation 2nd generation 3rd generation 1 10 100 1000 10000 -25 -24 -23 -22 -21 -20 -19 Seismic Shot Noise Thermal Noise ILIAS General meeting, Jaca Feb 2008

ILIAS General meeting, Jaca Feb 2008 Thermal Noise Long interferometer arms Cryogenic optics Large beams, large optics Non-gaussian beams Improved coatings 3 main noise sources 1st generation 2nd generation 3rd generation 1 10 100 1000 10000 -25 -24 -23 -22 -21 -20 -19 Thermal Noise Long interferometer arms Cryogenic optics Large beams, large optics Non-gaussian beams Improved coatings 2nd generation 10km ILIAS General meeting, Jaca Feb 2008

ILIAS General meeting, Jaca Feb 2008 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 a 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 General meeting, Jaca Feb 2008

ILIAS “supported” or related activities Silicon substrates R&D activities in many European Labs: Glasgow, INFN Florence & Perugia, Jena University, … Coatings studies R&D activities in many European Labs: Glasgow, INFN Perugia, LMA-Lyon, MPG Hannover, … Cryogenic Super attenuator R&D activities in INFN Rome & Pisa ILIAS General meeting, Jaca Feb 2008

ILIAS General meeting, Jaca Feb 2008 3 main noise sources Thermal Noise Long interferometer arms Cryogenic optics Large beams, large optics Non-gaussian beams Improved coatings Thermal Noise Long interferometer arms Cryogenic optics Large beams, large optics Non-gaussian beams Improved coatings 1st generation 2nd generation 3rd generation 1 10 100 1000 10000 -25 -24 -23 -22 -21 -20 -19 10km 10km, 20K ILIAS General meeting, Jaca Feb 2008

ILIAS General meeting, Jaca Feb 2008 3 main noise sources Thermal Noise Long interferometer arms Cryogenic optics Large beams, large optics Non-gaussian beams Improved coatings Thermal Noise Long interferometer arms Cryogenic optics Large beams, large optics Non-gaussian beams Improved coatings 1st generation 2nd generation 3rd generation 1 10 100 1000 10000 -25 -24 -23 -22 -21 -20 -19 10km, 20K 10km, 20K, 10cm ILIAS General meeting, Jaca Feb 2008

ILIAS General meeting, Jaca Feb 2008 Non Gaussian Beams Thermal noise in a GW interferometric detector could be further reduced by using “flatter” beams: ILIAS General meeting, Jaca Feb 2008

ILIAS General meeting, Jaca Feb 2008 3 main noise sources Thermal Noise Long interferometer arms Cryogenic optics Large beams, large optics Non-gaussian beams Improved coatings Thermal Noise Long interferometer arms Cryogenic optics Large beams, large optics Non-gaussian beams Improved coatings 1st generation 2nd generation 3rd generation 1 10 100 1000 10000 -25 -24 -23 -22 -21 -20 -19 10km, 20K, 10cm 10km, 20K, 10cm, non gauss ILIAS General meeting, Jaca Feb 2008

ILIAS General meeting, Jaca Feb 2008 3 main noise sources Shot Noise High laser power Squeezing Long interferometer arms Shot Noise High laser power (maybe 1550nm for silicon; less thermal lensing @ 25K) Shot Noise High laser power 1st generation 2nd generation 3rd generation 1 10 100 1000 10000 -25 -24 -23 -22 -21 -20 -19 800kW 3MW Shot Noise ILIAS General meeting, Jaca Feb 2008

ILIAS General meeting, Jaca Feb 2008 3 main noise sources Shot Noise High laser power Squeezing Shot Noise High laser power Shot Noise High laser power Squeezing Long interferometer arms Shot Noise High laser power Squeezing Long interferometer arms Multiple colocated interferometers 1st generation 2nd generation 3rd generation 1 10 100 1000 10000 -25 -24 -23 -22 -21 -20 -19 800kW 3MW 3MW, 6dB 3MW, 6dB, 10km 3MW, 6dB, 10km, 3ifos ILIAS General meeting, Jaca Feb 2008

Co-located interferometers “Old” idea still under debate Possible implementation: 3 detectors in a triangle configuration Rüdiger, ‘85 Antenna Patterns: Angular response of a standard ITF Angular response of the triangle configuration Credit: Cella, Vicerè ILIAS General meeting, Jaca Feb 2008

ILIAS General meeting, Jaca Feb 2008 3 main noise sources 1st generation 2nd generation 3rd generation 1 10 100 1000 10000 -25 -24 -23 -22 -21 -20 -19 Underground operation Homogeneous ‚soil‘ Seismic ILIAS General meeting, Jaca Feb 2008

Underground operations LISM: 20 m Fabry-Perot interferometer, R&D for LCGT, moved from Mitaka (ground based) to Kamioka (underground) Seismic noise strongly reduced 102 overall gain 103 at 4 Hz Credit: K.Kuroda ILIAS General meeting, Jaca Feb 2008

Seismic Isolation Shortcut Newtonian Noise! ILIAS General meeting, Jaca Feb 2008 Figure: M.Lorenzini

Newtonian Noise credit: G.Cella Compression waves Surface waves Surface waves give the main contribution to newtonian noise (Compression waves not included) Reduction factor NN reduction of 104 @5 Hz with a 20 m radius cave Surface waves die exponentially with depth Cave radius [m] 102 less seismic noise x 104 geometrical reduction 106 overall reduction (far from surface) ILIAS General meeting, Jaca Feb 2008 Credit: G.Cella

ILIAS General meeting, Jaca Feb 2008 3 main noise sources 1st generation 2nd generation 3rd generation 1 10 100 1000 10000 -25 -24 -23 -22 -21 -20 -19 1st generation 2nd generation 3rd generation Newtonian noise Underground Ground surface ILIAS General meeting, Jaca Feb 2008

ILIAS General meeting, Jaca Feb 2008 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 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 Executive board Governing Council Science Team Institutions Scientific community ET Project ILIAS General meeting, Jaca Feb 2008

ILIAS General meeting, Jaca Feb 2008 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 ILIAS General meeting, Jaca Feb 2008

Conclusions: Planning You are here ´06 ´07 ´08 ´09 ´10 ´11 ´12 ´13 ´14 ´15 ´16 ´17 ´18 ´19 ´20 ´21 ´22 Virgo GEO LIGO LISA E.T. Virgo+ Advanced Virgo GEO HF Hanford LIGO+ Advanced LIGO Livingston Launch Transfer data DS PCP Construction Commissioning data ILIAS General meeting, Jaca Feb 2008