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interferometric detector for GW: status and perspectives

interferometric detector for GW: status and perspectives. Giovanni Losurdo INFN Firenze-Urbino e-mail: losurdo@fi.infn.it. GW ??. The ultimate goal. GW astronomy: a new window on the universe. Interference fringes. Principle of Detection. GW acting on a ring of freely falling masses.

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interferometric detector for GW: status and perspectives

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  1. interferometric detector for GW:status and perspectives Giovanni Losurdo INFN Firenze-Urbino e-mail: losurdo@fi.infn.it

  2. GW ?? The ultimate goal GW astronomy: a new window on the universe Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino

  3. Interference fringes 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 (NS/NS @Virgo Cluster) Feasible L ~ 103 m Need to measure:DL ~ 10-18 m Big challenge for experimentalists! Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino

  4. A simple detector 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

  5. 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): • L = 100 km, P = 1 kW  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

  6. 100 km ITF? • Effective length: • Fabry-Perot cavities: amplify the length-to-phase transduction • Higher finesse  higher df/dL • Drawback: works only at resonance Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino

  7. 1 kW Power? Interferometer Ecology: recycle the wasted light! • Peff= Recycling factor ·Pin20 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

  8. by D.Crooks Thermal Noise • Fluctuation-dissipation theorem: • Thermal noise: mirrors, wires, pendulum • Possible cures: reduce dissipation or cool the mirrors Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino

  9. Input Mode Cleaner 3 km long Fabry-Perot cavities: to lengthen the optical path to 100 km Output Mode Cleaner Detector scheme Laser 20 W Power recycling mirror: to increase the light power to 1 kW Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino

  10. 3 km 600 m TAMA 4 & 2 km 300 m AIGO 4 km Interferometers network • False alarm rejection will require coincidences • ITFs have little directionality: at least 3 detectors are necessary to reconstruct the source direction Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino

  11. FRANCE - CNRS • ESPCI – Paris • IPN – Lyon • LAL – Orsay • LAPP – Annecy • OCA - Nice • ITALY - INFN • Firenze-Urbino • Frascati • Napoli • Perugia • Pisa • Roma Inaugurated July 2003 Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino

  12. seismic LIGO thermal shot Sensitivity Goal First attempt to extend the detection band down to a few Hz! Wideband detector! Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino

  13. HIGH SENSITIVITY REQUIRES SMART TECHNOLOGY Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino

  14. 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 Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino

  15. Laser cavity 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 Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino

  16. Input beam Transm. beam Refl. beam Input Mode Cleaner • Mode cleaner cavity: filters laser noise, select TEM00 mode Input mode-cleaner: curved mirror Input mode-cleaner: dihedron Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino

  17. 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

  18. 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) Detection bench Output Mode-Cleaner Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino

  19. 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

  20. Thermal noise 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

  21. LOCKING Keep the armlength constant within 10-12 m ! 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 Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino

  22. 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

  23. DC-0.01 Hz Force applied to the mirror with hierarchical control (same a.u.) Force applied to the mirror (a.u.) without hierarchical control 1 mN 0.01-8 Hz 10 mN 8-50 Hz with tidal control & re-allocation to the marionette with tidal control Hierarchical Control • Limited dynamic range requires to split forces over more control stages Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino

  24. Start of full VIRGO commissioning: July 2003 One cavity locked: autumn 2003 Recombined ITF locked: Feb 2004 Power recycling locked: Oct 2004 >104 1 year Extragalactic sensitivity to NS/NS coalescences 55 kpc Towards the Target sensitivity Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino

  25. 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

  26. May 01 More than 3 years… Aug 04 LIGO commissioning path • Inaugurated at the end of 1999 • Path to target sensitivity: more than 3 years Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino

  27. GW ASTRONOMY ?? Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino

  28. 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

  29. Seismic Thermal Shot Expanding the Accessible Universe Where and how can we reduce the detector noise? • No further suppression • New materials • Cryogenic interferometers • High power laser • Better optics • QND techniques Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino

  30. Initial LIGO Open up wider band ~ 15 in h ~3000 in rate Advanced Interferometers Advanced LIGO (2009+) • Higher power laser (10 W180 W) • New seismic isolation system (active) • Fused silica suspension wires • 40 kg sapphire mirrors • Signal recycling NS/NS detectable @300 Mpc from LIGO Virgo/LIGO range LIGO figures Adv. LIGO range by R.Powell Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino

  31. 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) • Also GEO600 and TAMA are thinking about 2nd generation detector Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino

  32. 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

  33. 3 km GW-WWW TAMA Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino

  34. Physics 2005 – Warwick, Apr. 13, 2005 G.Losurdo – INFN Firenze-Urbino

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