Status of VIRGO Lisa Barsotti - University and INFN Pisa – on behalf of the VIRGO collaboration ANNECY - December 15 th, 2004  Status of the Commissioning Activity  Status of Data Analysis - Agenda

VIRGO Optical Scheme BS NI WI PR 3-km Fabry Perot cavities in the arms

Commissioning Plan Steps of increasing complexity: Oct 2003 – Feb 2004 Oct 2003 – Feb 2004 A SINGLE FABRY-PEROT CAVITY PR misaligned

Commissioning Plan Steps of increasing complexity: Oct 2003 – Feb 2004 Oct 2003 – Feb 2004 A SINGLE FABRY-PEROT CAVITY PR misaligned

Commissioning Plan Steps of increasing complexity: Oct 2003 – Feb 2004 Oct 2003 – Feb 2004 A SINGLE FABRY-PEROT CAVITY Feb 2004 – Dec 2004 Feb 2004 – Dec 2004 ITF in RECOMBINED MODE PR misaligned

Commissioning Plan Steps of increasing complexity: Oct 2003 – Feb 2004 Oct 2003 – Feb 2004 A SINGLE FABRY-PEROT CAVITY Feb 2004 – Dec 2004 Feb 2004 – Dec 2004 ITF in RECOMBINED MODE Sept 2004 Sept 2004 ITF in RECYCLED MODE  Final configuration PR aligned

Sensitivity Progress  From a single arm to the recombined mode C3: Automatic alignment and frequency servo tested in a single arm configuration C4: Automatic alignment and frequency servo tested in recombined configuration C1 – November 2003 C4 – June 2004

Commissioning Run C4 - June 2004 ITF controlled with the reflected and the asymmetric beams Automatic alignment of the cavities Laser frequency stabilized to cavities common mode Cavities common mode locked to reference cavity Output Mode Cleaner locked on the dark fringe Tidal control on both arms  Recombined Data Taking Mode

Commissioning Run C4 - June 2004  5 days of run  Lock losses understood  Longest lock ~ 28 h  h reconstruction on line SPECIAL TESTS:  Acoustic noise injection in the laser and detection laboratory Session 7: Environmental noise studies in VIRGO - I. Fiori  Injection of inspiral events Session 9: Inspiral analysis of the VIRGO commissioning run 4 – L. Bosi

Commissioning Run C4 : Noise Characterization Coupling of IB resonances into the michelson controller signal due to a mismatch between modulation frequency and input mode-cleaner length (~ 70 Hz) C4 After frequency modulation tuning Michelson controller signal Problem understood -> not final solution yet

After C4  July – August Upgrade of the terminal benches -> Re-tuning and improvement of the linear automatic alignment Suspension full hierarchical control started Commissioning of the Recycled ITF started Effect of the backscattered light in the IMC -> attenuator installed between the IMC and the ITF  Mid September: Re-Start  October – November: -> Recombined ITF locked with the full hierarchical control of the suspensions -> ITF locked in recycled mode

Suspension Hierarchical Control  10 3  Locking acquired and maintained acting at the level of the mirror z z x y marionette reference mass mirror  Reduce the strength of the mirror actuators by a few 10 3 to reach Virgo design sensitivity

Suspension Hierarchical Control DC-0.01 Hz Hz 8-50 Hz Corrections sent to the marionette Corrections sent to the mirror Force on the mirror reduced of a factor 20  Switch to low noise coil drivers TIDAL CONTROL RE-ALLOCATION OF THE FORCE

Suspension Hierarchical Control  Single arm locked with the hierarchical control for the first time in July -> controllability of the superattenuator demonstrated  Last main result: hierarchical control of the recombined ITF in the C4 configuration, with automatic alignment and frequency servo engaged  Stable lock -> tested in the last commissioning run (C5, 2-6 December 2004)  SUMMARY

The Variable Finesse Locking Strategy “A recycled ITF with a low recycling factor is similar to a recombined ITF “ NINE WE WI BS PR Low Recycling Factor Half Fringe  Lock immediately the 4 degrees of freedom of the ITF on the half fringe:  end photodiodes to acquire the lock of the long cavities  simple michelson locked on the half fringe with the asymmetric DC signal  3f demodulated reflected signal to control the recycling cavity length

POWER IN THE RECYCLING CAVITY  With the ITF in a stable state, bring it adiabatically on the dark fringe evolving the control scheme Recombined interferometer (~ 60 mW) Recycled interferometer (~ 17 W) T PR=8% -> Recycling factor ~ 25  frequency servo (SSFS) engaged to control the common mode of the arms  from DC to demodulated signal to control the simple michelson length The Variable Finesse Locking Strategy

 First lock of the recycled ITF on the end of last October  Stable lock of the recycled interferometer ~ minutes  no linear automatic alignment yet  next step  Locking procedure tested several times  lock acquired in few minutes  New original lock acquisition procedure established, combining end photodiodes, frequency servo, 3f-demod signal, slightly misalignement of PR mirror, and lock on the half fringe  M. Evans (LIGO) and K. Arai (TAMA) present on Virgo site  1 day and half of test in the last commissioning run C5  SUMMARY

Commissioning Run C5 - December 2004 Best VIRGO Sensitivity  Injection of bursts and inspiral events during the run -> Analysis in progress 10 times more power than C5

Data Analysis Activity  h reconstruction (F. Marion - LAPP )  Physics group activity: Burst (P. Hello - LAL ) Coalescent Binary (A. Vicerè – INFN Urbino) Pulsar Source Software (S. Frasca – Roma University ) Stochastic Background (G. Cella – INFN Pisa) Noise Analysis (J. Y. Vinet – NICE)  Network analysis

Agenda - I  A new time-frequency tool: the S-Trasform Session 15: A burst search method based on the S-transform (A-C. Clapson – LAL )  Network analysis of bursts Session 15: A couple of techniques to improve sensibility preserving robustness in gravitational wave's burst detection (G. Cella – INFN Pisa)  Injection of bursts and inspiral events in C4 Off–line analysis -> (see L.Bosi’s talk) Session 15: Chirplet chains: a quasi-physical model for near- optimal detection of gravitational wave chirps  New algorithm for generic chirp (Eric Chassande-Mottin – NICE ) Burst and Inspiral Search POSTER: New definition of discrete time-frequency unitary Wigner-Ville distribution (A. Pai – Roma University)

Agenda - II POSTER: Simulation of gravitational wave stochastic background (G. Cella – INFN Pisa)  Session 12: Adaptive Hough transform for the search of periodic sources (C. Palomba – INFN Roma) Periodic Sources  POSTER: Simulation of a population of gravitational wave-driven neutron stars (C. Palomba – INFN Roma)  POSTER: Evaluation of sensitivity and of computing power for the Virgo hierarchical search for periodic sources (S. Frasca – Roma University) Stochastic Background  Session 15: Pade and symmetrized Pade approximants in data processing (J. Fournier – CNRS)

Agenda – III  So far mainly carried out in the commissioning activity -> Peculiar tests performed to study the environmental noise and its coupling with the interferometer (see I. Fiori ‘s talk)  Line detection POSTER: NAP: a tool for noise data analysis (E. Cuoco – EGO) POSTER: A simple line detection algorithm applied to Virgo data (Eric Chassande-Mottin – I. Fiori)  Extended noise analysis to be added -> Software tool development: Noise Analysis Package Noise Analysis

Network Analysis  LSC – Virgo Collaboration - Joint working group for inspiral and burst search on simulated data Session 9: First comparison between the LIGO/Virgo inspiral search pipelines (F. Beauville – LAPP ) Session 13: Comparison of methods for gravitational wave burst search using simulated LIGO and VIRGO data (M. Zanolin – MIT)

Conclusions  Well advanced status of the commissioning activity -> Suspension hierarchical control in recombined mode -> Lock of the recycled ITF  Next steps: -> Linear automatic alignment of the recycled ITF -> Frequency servo optimization  Last Commissioning Run Data -> analysis in progress  Data analysis main activities will be presented