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Virgo status

Virgo status. Marie-Anne Bizouard (LAL-Orsay) on behalf of the Virgo Collaboration. Outline. Ground based gravitational wave detectors Virgo detector commissioning – 2006 ( M. Barsuglia GW1) Virgo data analysis – searches and detector characterization (E. Cuoco GW4

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Virgo status

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  1. Virgo status Marie-Anne Bizouard (LAL-Orsay) on behalf of the Virgo Collaboration

  2. Outline • Ground based gravitational wave detectors • Virgo detector commissioning – 2006(M. Barsuglia GW1) • Virgo data analysis – searches and detector characterization (E. Cuoco GW4 C. Palomba GW4) • Preparation of Virgo future • Virgo+ (N. Man GW2) • Advanced Virgo • Short term planning MG 11 - Berlin

  3. The Virgo Collaboration as in 2006 • CNRS - LAPP - Annecy • INFN - Firenze/Urbino • CNRS - LMA/ESPCI – Lyon/Paris • INFN – Napoli • CNRS - OCA – Nice • CNRS - LAL - Orsay • INFN - Perugia • INFN - Pisa • INFN – Roma 2006: NIKHEF – Amsterdam (joining) Tor Vergata – Roma (just joining) • + EGO (European Gravitational Observatory) • 175 physicists / engineers MG 11 - Berlin

  4. 600 m 4 & 2 km GEO 3 km 300 m 4 km TAMA Growing ground based interferometers network MG 11 - Berlin

  5. Seismic noise Shot noise: quantum fluctuation in the number of detected photons Thermal noise: vibration of bulk due to non null temperature Interferometers at a glance How to detect the path of a GW?  measure the displacement of the mirrors induced by the GW  light phase shift measurement • But: • GW amplitude is small h~10-21L=3km  dL=10-18 m • The laser has fluctuations in phase and amplitude • External forces push the mirrors MG 11 - Berlin

  6. L=3km Input Mode Cleaner cavity Length = 144 m Recycling L=3km Laser Nd:YVO4 P=1kW P=20 W Virgo seismic attenuator Output Mode Cleaner cavity Length = 4 cm Virgo optical layout A Michelson with 3 partly-transparent mirrors to form optical cavities to increase the power inside the arms MG 11 - Berlin

  7. A L I G N M E N T Keep the arms’ length constant within 10-12 m Interferometer controls 1: longitudinal control 2: angular control ITF output port • Keep the Fabry Perot cavities in resonance • Keep the output on the “dark fringe” LOCKING ITF “locked” • Avoid high order mode generation (reduction of coupling dark fringe with frequency noise, power noise, input beam jitter, beam miscentering, ..) Reduction of the power fluctuation! Recycling cavity power Alignment ON MG 11 - Berlin

  8. Interferometer controls • Complicated scheme! • Controls introduce noise in • the dark fringe at low • frequency (<100Hz) MG 11 - Berlin

  9. Thermal noise Shot noise Seismic wall Foreseen sensitivity MG 11 - Berlin

  10. Virgo sensitivity curve progresses (as end of 2005) C7 run (sep. 2005): Best strain h ~ 6 10-22 / Hz1/2 NS/NS maximum range ~ 1.5 Mpc (optimal orientation) MG 11 - Berlin

  11. Noise budget MG 11 - Berlin

  12. Shutdown at end of 2005 – Why? • Increase the power 2005: need to operate with reduced power: 0.7 W instead of 10W because of backscattering light in the Mode Cleaner cavity  Increase a lot the frequency noise Solution: Faraday isolator on the injection bench to attenuate the backscattering light a new injection bench Backscattering MG 11 - Berlin

  13. 350 mm 350 mm 120 mm 120 mm R=4100 mm R=4100 mm Incident Beam Incident Beam Translations induce misalignment and jitter noise Shutdown at end of 2005 – Why? • Non-monolithic and curved Power Recycling mirror • Curved: because part of the output telescope to match the beam • Non-monolithic: lots of resonances  control problems and alignment drifts • Solution: • Monolithic mirror • Flat mirror need of a telescope on the injection bench a new injection bench … MG 11 - Berlin

  14. New injection bench Faraday isolator MG 11 - Berlin New parabolic telescope

  15. Virgo commissioning – new input benchSep 2005 – April 2006 Lots of work: • New scheme of the alignment wrt to the ITF • Parabolic telescope alignment done • Beam matching: 95% reached • Faraday isolator tuned No more backscattering light problem! M. Barsuglia GW1 7 W entering in the ITF 280 W on the BS (sep. 2005: 25W! ) MG 11 - Berlin

  16. 10 hours Virgo commissioning – full power recycled ITFFeb 2006 – until now We had few problems/difficulties: • Beam matching • Beam astigmatism • Beam clipping on detection bench • Oscillations in signals used for control  lock losses! • Thermal effect in substrate (25W  280W on Beam Splitter mirror) ? See M. Barsuglia in GW1 Work done on: - demodulation phase tuning - more angular degrees of freedom controlled Lock stability improved a lot ! • Where are we now? • f>200 Hz: better than one year ago • f<200 Hz: a lot of work to be done! • (dominated by control noise) • … • but the noise hunting period just restarted! MG 11 - Berlin

  17. The last data taking periods - 2005 C6 July 2005 Maximal distance for SNR=8, optimally oriented 1.4/1.4 M NS-NS binary 14 days duty cycle: 86% in Science Mode Maximal distance (Mpc) Sensitivity improvement C7 Sep. 2005 5 days duty cycle: 65% in Science Mode Shorter but better sensitivity best NS-NS distance range: 1.5 Mpc ! Beyond Andromeda reached! MG 11 - Berlin

  18. Data analysis in Virgo at a glance NS EOS, Strong field gravity, GRB models, Binary population … lots of astronomy! • Virgo search groups • Burst (SN, neutron star and black hole birth, ..) • Binary inspiral (neutron star + black hole) • Continuous waves (spinning neutron stars) • Stochastic background (big bang + background of “standard” GW) But we don’t have yet the sensitivity to set competitive upper limits … So C6 & C7 data taking analysis …. more dealing with • pipeline development / tuning • detector characterization than with “physics” search or competitive upper limits More details in E. Cuoco and C. Palomba’s talks MG 11 - Berlin

  19. Events Dark fringe (whiten) SNR Time (s) Frequency (Hz) Events without veto with veto SNR Burst events search • Burst studies on a single detector: hard! • Events distribution dramatically different from Gaussian • Vetoes based on auxiliary channels  understand the machine • Identification of the main source of excess noise for the burst search: • Vetoes strategy: • Vetoes definition: • excess frequency noise • environmental glitches • (air conditioning, air plane, …) • Nice reduction of the burst fake events … • but huge dead time: >20% • Excess noise above 100 Hz due to GW channel coupling • with the frequency noise when the North End mirror is tilted • problem of mirror angular control (too loose during C6 &C7) MG 11 - Berlin

  20. Before 2 After 2 Inspiral search • C6/C7 analysis focus: NS-NS search • 2 pipelines developed in Virgo • Veto studies – Virgo data understanding • Fake events rejection: • Veto against “identified” noisy data periods • Use of “2” methodsto reject fake events (the 2checks the compatibility between the signal waveform and the recorded strain) Hardware GW injections • Fake event rejection safety test? • Hardware event injection (force applied on the mirrors) ( + signal recovery accuracy estimation) vetoes are safe for the hardware injections, while strongly reducing the event distribution tails ! Hardware GW injections MG 11 - Berlin

  21. Continuous sources search • All-sky search pipeline: hierarchical + coincidence • C6 & C7 work goal: • 1kHz band considered (50Hz 1050 Hz) • Production of bank of candidates for C6 and C7 and perform coincidence • Detection of detector related noise that could bias the analysis C. Palomba GW4 Example: 10 Hz disturbance : pulses caused by a video camera C6: number of candidates before coincidence Number of candidates : excess for some frequencies! Sensitivity obtained : h~10-23 [200-1000 Hz] (Virgo design: h~10-25 @ 200 Hz) MG 11 - Berlin Frequency (Hz)

  22. f> 300 Hz: Virgo-GEO performs good! S. Ballmer gr-qc/0510096 Stochastic background GW search with Virgo • This search requires cross-correlation between 2 detectors’ output (GW background sensitivity depends on distance and orientation) • Auriga/Nautilus/Explorer/Virgo Scope limited by the bars sensitivity curve • LHO, LLO, GEO, Virgo • Isotropic background search • Directional search (sky map luminosity) (background could be dominated by individual sources!) • First detectors generation sensitivity: WGW ~ 4 x 10-6advanced detectors needed! Virgo at design sensitivity : WGW < 2 x 10-2 MG 11 - Berlin

  23. International collaborations • Auriga-RoG-Virgo • Burst search + Stochastic background search • LSC-Virgo: • Burst + Inspiral : working effort for 2 years (simulated data) + SB just joins “Physics gain” to add a (non aligned) ITF to LIGO network: - reconstruction of the source location (need of at least 3 ITF!) - signal parameters estimation - detection efficiency enhanced by 50% (burst) or 30% (inspiral) • Now: discussions about • data exchange agreement (MOU to be signed) • how to work as a joint data analysis group • Sketching a tentative joint run planning VERY TENTATIVE MG 11 - Berlin

  24. Outline • Ground based gravitational wave detectors • Virgo detector commissioning – 2006 • Virgo data analysis – searches and detector characterization • Preparation of Virgo future • Virgo+ • Advanced Virgo (second generation ITF) • Short term planning MG 11 - Berlin

  25. LIGO - Virgo LIGO+ - Virgo+ AdvLIGO - AdvVirgo Credit: R.Powell Virgo future preparation • Virgo+ • Advanced Virgo (second generation ITF) • A factor 10 in distance • to hit sources in a volume 1000 times larger MG 11 - Berlin

  26. Now 2007 2008 2009 Virgo upgrades planning • Short term • Acoustic isolation • Pre-Mode Cleaner • Upgrade of the quadrant diode front-end electronics • New coil drivers (R&D) • Intermediate term • Eddy current dissipation mitigation • New MC mirror payload • New DSP electronics (R&D) • Thermal compensation • Virgo+ upgrades • Short • Acoustic isolation • Pre-Mode Cleaner • Upgrade of the quadrant diode front-end electronics • New coil drivers (R&D) • Intermediate • Eddy current dissipation mitigation • New MC mirror payload • New DSP electronics (R&D) • Thermal compensation • Virgo+ upgrades “Standard” upgrades dedicated to reach the Virgo design sensitivity MG 11 - Berlin

  27. What is Virgo+ project? Last stage of the suspension thermal noise (pendulum mode excited) friction metallic wires clamping wire dissipation  Monolithic suspension! shot noise  higher power laser! mirror thermal noise (bulk + coating)  higher Q new material + coating R&D MG 11 - Berlin

  28. Virgo+ • Virgo+ upgrades • High power laser amplifier 20W 50W • Replace all Virgo mirrors with Suprasil 311 fused silica (low losses) • Improved coatings R&D • Fused silica monolithic payload • New DAQ electronics (R&D) • Compatible with current Virgo optical configuration • Require a relative short shutdown N. Man (GW2) MG 11 - Berlin

  29. Monolithic payload on going activities 2 machines for producing and welding fused silica fibers in Cascina: H2-O2 (Perugia) CO2 (Glasgow) (different technology) Fused silica fiber Fused silicate fiber H2-O2 pulling machine on site Dummy mirror to test the monolithic suspension MG 11 - Berlin

  30. Shot noise decrease Virgo+ scientific outreach Thermal noise decrease NS-NS signal detection benefits of the sensitivity improvement at intermediate frequency MG 11 - Berlin

  31. Short term planning - Conclusions • Commissioning: • Noise hunting phase • Reduction of control noise sources  In the next weeks: reach LIGO sensitivity at high frequency Start collecting “Science” data this fall Soft transition towards long data taking periods for GW searches • Huge campaign of upgrades : Virgo+ foreseen in 2008 inspiral event rate: gain more than a factor 10! • Advanced Virgo: design choice by end of 2007 MG 11 - Berlin

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