Transcript GW-WWW
interferometric detector for GW: status and perspectives Giovanni Losurdo INFN Firenze-Urbino e-mail: [email protected] The ultimate goal GW astronomy: a new window on the universe GW ?? Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino Principle of Detection GW acting on a ring of freely falling masses Measure the space-time strain using light LIGO figures Target h ~ 10-21 1 L hL 2 Interference fringes (NS/NS @Virgo Cluster) Feasible L ~ 103 m Need to measure: L ~ 10-18 m Big challenge for experimentalists! Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino A simple detector Pout Pin cos2 (0 gw ) gw 4 l Lh Pout depends also on Pin , l, L. ITF sensitive to power and frequency fluctuations, displacement noises, … Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino Optical Readout Noise • Power fluctuations limit the phase sensitivity. Ultimate power fluctuations associated to the quantum nature of light • Shot noise (assuming P,l stable): shot • L = 100 km, P = 1 kW 2 1 cl hshot P L P hshot 3 1023 / Hz hshot 1021 Lengthen the detector to 100 km. Increase the light power to 1 kW. HOW? Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino 100 km ITF? • • Effective length: L' L Physics 2005 – Warwick, Apr. 13, 2005 2F • • Fabry-Perot cavities: amplify the length-to-phase transduction Higher finesse higher d/dL Drawback: works only at resonance G.Losurdo – INFN Firenze-Urbino 1 kW Power? Interferometer Ecology: recycle the wasted light! • • • Peff= Recycling factor ·Pin 20 W 1 Kwatt Shot noise reduced by a factor 7 One more cavity to be controlled Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino Thermal Noise • Fluctuation-dissipation theorem: ~ F 2 ( f ) 4k BT ( f ) • Thermal noise: mirrors, wires, pendulum • Possible cures: reduce dissipation or cool the mirrors by D.Crooks Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino Detector scheme Input Mode Cleaner 3 km long Fabry-Perot cavities: to lengthen the optical path to 100 km Laser 20 W Output Mode Cleaner Power recycling mirror: to increase the light power to 1 kW Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino Interferometers network • False alarm rejection will require coincidences • ITFs have little directionality: at least 3 detectors are necessary to reconstruct the source direction 600 m 3 km TAMA 4 & 2 km 300 m AIGO 4 km Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino FRANCE - CNRS ITALY - INFN • • • • • • • • • • • ESPCI – Paris IPN – Lyon LAL – Orsay LAPP – Annecy OCA - Nice Firenze-Urbino Frascati Napoli Perugia Pisa Roma Inaugurated July 2003 Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino Sensitivity Goal First attempt to extend the detection band down to a few Hz! seismic LIGO thermal shot Wideband detector! Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino HIGH SENSITIVITY REQUIRES SMART TECHNOLOGY Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino Vacuum • Requirements: – 10-9 mbar for H2 – 10-14 mbar for hydrocarbons Vacuum pipe: – 1.2 m diameter – Baked at 150 °C for 1 week or more • 1.00E-07 Residual Gases in tube 900m - 1500m N October 2001 partial pressure, mbar 1.00E-08 After bake Ptot=2E-10 mbar before bake Ptot=3E-8 mbar 1.00E-09 2: hydrogen 18: water 12,28: carbon monoxide 44: carbon dioxide 55, 57: hydrocarbon contamination 1.00E-10 1.00E-11 1.00E-12 1.00E-13 1.00E-14 0 10 20 30 40 50 mass/charge Physics 2005 – Warwick, Apr. 13, 2005 60 70 80 90 100 G.Losurdo – INFN Firenze-Urbino Laser • • • • 20 W, Nd:YVO4 laser, two pumping diodes Injection locked to a 0.7 W Nd:YAG laser Required power stability: dP/P~10-8 Hz-1/2 Required frequency stability: 10-6 Hz1/2 Laser cavity Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino Input Mode Cleaner • Input beam inbeam Mode cleaner cavity: filters laser noise, select TEM00 mode Transm. beam outbeam Input mode-cleaner: curved mirror Refl. beam refbeam Input mode-cleaner: dihedron Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino Mirrors • • • High quality fused silica mirrors 35 cm diameter, 10 cm thickness, 21 kg mass Figures: – Substrate losses: 1 ppm – Coating losses: <5 ppm – Surface deformation: l/100 Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino Output Optics • • • • Light filtering: output mode cleaner, 3.6 cm long monolithic cavity Light detection: InGaAs photodiodes, 3 mm diameter, 90% quantum efficiency Suppression of TEM01 by a factor of 10 Length control via temperature (Peltier cell) Physics 2005 – Warwick, Apr. 13, 2005 Detection bench G.LosurdoOutput – INFN Mode-Cleaner Firenze-Urbino Superattenuators • • • • Inverted pendulum pre-isolation stage Cantilever blades+magnetic antisprings for vertical isolation 3 actuation points for hierarchical control of the mirror: inverted pendulum, marionette, recoil mass First and only attempt to extend the sensitivity bandwidth down to a few Hz Magnetic antisprings Blade springs Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino Passive Isolation performance • Expected seismic displacement of the mirror (red curve) compared with natural seismic noise • Thermal noise is dominant above 3 Hz • Isolation sufficient also for “advanced” interferometers • Active damping of the resonances at the top stage level Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino ITF Operation Conditions • Keep the FP cavities in resonance – Maximize the phase response • Keep the PR cavity in resonance – Minimize the shot noise • Keep the output on the “dark fringe” – Reduce the dependence on power fluctuations Keep the armlength constant within 10-12 m ! Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino Interferometer control • • Photodiodes Bx provide the error signals to control the 4 independent length of the interferometer Quadrant photodiodes provide the error signals to control the angular positions of the mirrors Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino Hierarchical Control • Force applied to the mirror (a.u.) without hierarchical control Limited dynamic range requires to split forces over more control stages 10 mN DC-0.01 Hz Force applied to the mirror with hierarchical control (same a.u.) 1 mN 0.01-8 Hz 8-50 Hz Physics 2005 – Warwick, Apr. 13, 2005 with tidal control with tidal control & re-allocation to G.Losurdo – INFNthe Firenze-Urbino marionette Towards the Target sensitivity • • Start of full VIRGO commissioning: July 2003 One cavity locked: autumn 2003 Extragalactic sensitivity to NS/NS coalescences 55 kpc Physics 2005 – Warwick, Apr. 13, 2005 • • Recombined ITF locked: Feb 2004 Power recycling locked: Oct 2004 >104 1 year G.Losurdo – INFN Firenze-Urbino Understanding the detector • Measure the sensitivity identify the noise sources try to reduce the noise Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino LIGO commissioning path • • Inaugurated at the end of 1999 Path to target sensitivity: more than 3 years May 01 More than 3 years… Physics 2005 – Warwick, Apr. 13, 2005 Aug 04 G.Losurdo – INFN Firenze-Urbino GW ASTRONOMY ?? Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino How Many Events? • COALESCING COMPACT BINARIES Expected rate of coalescences: 3/yr out of 40 200 Mpc [Grishchuk et al., astro-ph/0008481] • • Waveform accurately predicted: VIRGO/LIGO can detect a NS/NS event at ~ 20 Mpc Detection rate (best estimates): a few/yr [Burgay et al., Nature, 2003] Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino Expanding the Accessible Universe Where and how can we reduce the detector noise? Seismic No further suppression Thermal – New materials – Cryogenic interferometers Shot – High power laser – Better optics – QND techniques Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino Advanced LIGO (2009+) • • • • • Higher power laser (10 W180 W) New seismic isolation system (active) Fused silica suspension wires 40 kg sapphire mirrors Signal recycling from LIGO Initial LIGO Open up wider band ~ 15 in h ~3000 in rate Virgo/LIGO range Advanced Interferometers Adv. LIGO range by R.Powell Physics 2005 – Warwick, Apr. 13, 2005 LIGO figures G.Losurdo – INFN Firenze-Urbino Advanced Virgo • • • Virgo already has “advanced” vibration isolator: feasible with minor changes to the current detector New low dissipation suspension fibers and mirrors to reduce thermal noise New laser and optics to reduce shot noise Possible use of a new optical configuration (signal recycling) h(f) [1/sqrt(Hz)] • 10 -17 10 -18 10 -19 10 -20 10 -21 10 -22 10 -23 10 -24 Virgo Adv Virgo 1 10 100 1000 Frequency [Hz] • Also GEO600 and TAMA are thinking about 2nd generation detector Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino 10000 Towards a worldwide network The trans-Atlantic side: • • GEO is part of LIGO Science Community, full agreement for data exchange LIGO-Virgo MOU to be signed soon – Topic driven collaboration, initially focused on two defined subjects (inspirals and bursts) – Real joint analysis will start when comparable sensitivity will be reached The European side: • • A collaborative effort is starting in Europe (Virgo-GEO) Common working group have been set up in the ILIAS-GWA framework Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino GW-WWW 3 km TAMA Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino