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Virgo status Marie-Anne Bizouard (LAL-Orsay) on behalf of the Virgo Collaboration MG 11 - Berlin Outline • Ground based gravitational wave detectors • Virgo detector commissioning – 2006 • Virgo data taking – 2005 • Virgo data analysis – searches and detector characterization ( M. Barsuglia’s talk) (E. Cuoco’s and C. Palomba’s talk) • Virgo future preparation – Virgo++ – Advanced Virgo (N. Man talk) • Short term planning MG 11 - Berlin 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) + EGO (European Gravitational Observatory) 175 physicists / engineers MG 11 - Berlin Growing ground based interferometers network 4 & 2 km 600 m 3 km TAMA 300 m + LCGT 3 km planned 4 km AIGO MG 11 - Berlin ? km proposed 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~10-21 L=3km dL=10-18 m • The laser has fluctuations in phase and amplitude • External forces push the mirrors h dL L 2 Seismic noise h L / L Shot noise: quantum fluctuation in the number of detected photons Thermal noise: vibration of bulk due to non null temperature MG 11 - Berlin Virgo optical layout L=3km Finesse=50 Input Mode Cleaner Length = 144 m Laser Nd:YAG Recycling P=1kW P=20 W L=3km Finesse=50 Output Mode Cleaner Length = 4 cm A Michelson with 3 semi-transparent mirrors to form optical cavities to increase the power inside the arms MG 11 - Berlin Interferometer controls 1: longitudinal control • Keep the FP cavities in resonance (maximization of the phase response) • Keep the PR cavity in resonance (minimization of the shot noise) • Keep the output on the “dark fringe” (reduction of the dependence on power fluctuations) Keep the arms’ length constant within 10-12 m MG 11 - Berlin Interferometer controls 2: angular control • Avoid high order mode generation (reduction of coupling dark fringe with frequency noise, power noise, input beam jitter, beam miscentering, ..) ITF power (a.u.) Auto-alignment ON Reduction of the power fluctuation! • Needs to control 12 degrees of freedom MG 11 - Berlin Interferometer controls MG 11 - Berlin • Complicated scheme! • Controls introduce noise in the dark fringe at low frequency (<100Hz) MG 11 - Berlin Free falling test masses … • Multi stage pendulum - pre-isolator: inverted pendulum - cantilever springs for vertical isolation - cascade of six stages - height ~ 10 m MG 11 - Berlin Foreseen sensitivity Thermal noise Seismic wall MG 11 - Berlin Outline • Ground based gravitational wave detectors • Virgo detector commissioning – 2006 • Virgo data taking – 2005 • Virgo data analysis – searches and detector characterization • Virgo future preparation – Virgo++ – Advanced Virgo • Short term planning MG 11 - Berlin 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 MG 11 - Berlin (optimal orientation) Noise budget MG 11 - Berlin Shutdown at end of 2005 – Why? • Fringes due to backscattering in the Mode Cleaner Increase a lot the frequency noise Need to operate with reduced power 0.7 W instead of 7W ! Solution: Faraday isolator on the injection bench to attenuate the backscattering light a new injection bench MG 11 - Berlin Backscattering 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 350 mm 120 mm R=4100 mm Incident Beam • Solution: – Monolithic mirror – Flat mirror Translations induce misalignment and jitter noise flat mirror No more lens effect: larger beam coming from the injection bench need of a telescope on the injection bench a new injection bench MG 11 - Berlin New injection bench Faraday isolator MG 11 - Berlin New parabolic telescope Virgo commissioning – new input bench Sep 2005 – April 2006 • • • • • New scheme of the alignment wrt to the ITF Parabolic telescope alignment done Locking of the Mode Cleaner cavity Beam matching: 95% reached Faraday isolator tuned July 2004: before beam attenuation (.7W) 7 W entering in the ITF 280 W on the BS (sep. 2005: 25W! March 2006: Mode Cleaner transmitted power Mode Cleaner transmitted power Concern: the Faraday isolator attenuation factor is only 100 instead of 10000. Under investigation while not yet a problem in the sensitivity curve! MG 11 - Berlin Virgo commissioning – full power recycled interferometer Feb 2006 – until now We had few problems/difficulties: • • • • • Improvement of the beam matching and centering Beam matching increase the power inside the ITF by a factor 2 Beam astigmatism no more wire heating Beam clipping on detection bench Oscillations in signals used for control lock losses! Thermal effect in substrate (25W 280W on Beam Splitter mirror) ? Work done on: - demodulation phase tuning - more angular degrees of freedom controlled Lock stability improved a lot ! MG 11 - Berlin 10 hours Virgo sensitivity – July 2006! High frequency: better than one year ago Low frequency: a lot of work to be done! The noise hunting period just restarted Power Recycling mirror control noise MG 11 - Berlin More details in M. Barsuglia’s talk Outline • Ground based gravitational wave detectors • Virgo detector commissioning – 2006 • Virgo data taking – 2005 • Virgo data analysis – searches and detector characterization • Virgo future preparation – Virgo++ – Advanced Virgo • Short term planning MG 11 - Berlin The last data taking periods - 2005 Horizon for SNR=8, optimally oriented 1.4/1.4 M NS-NS binary 14 days C6 July 2005 duty cycle: 86% in Science Mode Horizon for SNR=8, optimally oriented 1.4/1.4 M NS-NS binary C7 Sep. 2005 Andromeda 5 days duty cycle: 65% in Science Mode 11 - Berlin bestMG NS-NS distance range: 1.5 Mpc Outline • Ground based gravitational wave detectors • Virgo detector commissioning – 2006 • Virgo data taking – 2005 • Virgo data analysis – searches and detector characterization • Virgo future preparation – Virgo++ – Advanced Virgo • Short term planning MG 11 - Berlin Data analysis in Virgo at a glance • Group activities – – – – – Noise Burst (SN, unmodelled short signal) Binary inspiral Pulsar Stochastic background Data taking: C6 & C7 More dealing with • pipeline development • detector characterization than with “physics” search or competitive upper limits • Collaborations – Auriga-RoG-Virgo – LIGO-Virgo More details in E. Cuoco and C. Palomba’s talks MG 11 - Berlin Burst events search • Burst studies on a single detector: hard! – Event distribution dramatically different from Gaussian – Vetoes based on auxiliary channels • Understand the machine! • Hardware injections to test veto safety • Identification of the main source of excess noise for the burst search Excess noise above 100 Hz due to dark fringe coupling with the frequency noise when the North End is tilted problem of mirror angular control (too loose during C6 &C7) Vetos definition: • excess frequency noise • environmental glitches (air conditioning for instance) • air plane Nice reduction of the burst fake events … MG 11 - Berlin but huge dead time: >20% without veto with veto Inspiral search • Up to now focus only on NS-NS search (2 pipelines developed in Virgo) • C6 & C7 analysis main concern: veto strategies set up fake events • The 2 checks the compatibility between the signal waveform and the recorded strain 22 bands < 40 Samples above threshold < 30 Samples above threshold < 30 22 bands< 40 MG 11 - Berlin use of “2” methods to reject “hardware” injected events (equivalent force applied on mirror) Continuous sources search • All-sky search pipeline • C6 & C7 work goal: For more details: C. Palomba’s talk – 1kHz band considered – Production of bank of candidates for C6 and C7 and performance coincidence – Detection of detector related noise that could bias the analysis Example: 10 Hz disturbance : pulses caused by a video camera C6 Number of candidates : excess for some frequencies! Sensitivity obtained : h~10-23 300-1000 Hz MG 11 - Berlin Frequency (Hz) Stochastic background search • • Search done by cross- correlated the output of 2 detectors The closer the detectors, the lower the frequencies that can be searched Virgo Ligo Hanford Virgo Ligo Livingston Virgo GEO Ligo Hanford Ligo Livingston Ligo Hanford GEO Ligo Livingston GEO Virgo does not have yet the sensitivity to constrain the SB but got prepared. Two collaborations: • Auriga/Nautilus/Explorer/Virgo Limited by the bars sensitivity curve WGW< 2 x 10-2 (Virgo design sensitivity) • LSC-Virgo – Just starting project – Standard cosmological background (isotropic) search – Targeted search (sky map of gw) MG 11 - Berlin International collaborations • Auriga-RoG-Virgo – Burst search – Stochastic background search • LSC-Virgo: joint GEO, LIGO and Virgo data analysis effort – Burst, inspiral : start working for 2 years! “Physics gain” to add a non aligned ITF to LIGO network: - reconstruction of the source location - detection efficiency enhanced by 50% (burst) or 30% (inspiral) – SB just joins – We are in the process of defining the data exchange agreement and how to work as a joint data analysis group. – Sketching a possible joint run planning (VERY PRELIMINARY) S5 MG 11 - Berlin Outline • Ground based gravitational wave detectors • Virgo detector commissioning – 2006 • Virgo data taking – 2005 • Virgo data analysis – searches and detector characterization • Virgo future preparation – Virgo++ – Advanced Virgo • Short term planning MG 11 - Berlin Virgo upgrades planning • Short – – – – Now 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 2007 • Virgo+ upgrades high freq. shot noise reduction! – High power laser amplifier 2008 low and inter. freq. thermal noise reduction! – Monolithic payload – New DAQ electronics (R&D) 2009 MG 11 - Berlin Virgo+ scientific outreach -18 10 -19 10 h(f) [1/sqrt(Hz)] Thermal noise decrease 50W/2 + new losses model 50W/2 + current mirrors Nominal Virgo 50W/2 + new losses model+FS suspensions Virgo+ with Newtonian Noise -20 10 Shot noise decrease -21 10 -22 10 -23 10 1 10 100 1000 10000 Frequency [Hz] NS-NS signal detection benefits Of the sensitivity improvement at intermediate frequency MG 11 - Berlin Outline • Ground based gravitational wave detectors • Virgo detector commissioning – 2006 • Virgo data taking – 2005 • Virgo data analysis – searches and detector characterization • Virgo future preparation – Virgo++ – Advanced Virgo • Short term planning MG 11 - Berlin Short term planning - Conclusions MG 11 - Berlin MG 11 - Berlin