F. Frasconi I.N.F.N. Pisa for the Virgo Collaboration TAUP2007 Sendai, September 11-15, 2007 VIRGO EXPERIMENT VIRGO: a large interferometer for Gravitational Wave detection started its first scientific run

September 11, 2007F. Frasconi / INFN Pisa2 The Interferometer at EGO site NIKHEF Amsterdam, LAPP Annecy, INFN Firenze-Urbino, INFN Genova, IPN Lyon, INFN Napoli, OCA Nice, LAL Orsay, ESPCI Paris, INFN Perugia, INFN Pisa, INFN Roma1, INFN Roma Tor Vergata

September 11, 2007F. Frasconi / INFN Pisa3 VIRGO Optical scheme Laser 20 W Input Mode Cleaner (145 m) Power Recycling 3 km long Fabry-Perot Cavities Output Mode Cleaner (4 cm)

September 11, 2007F. Frasconi / INFN Pisa4 Injection System Based on a Nd:YVO4 laser source with 20 W power ( =  m) Laser Cavity

September 11, 2007F. Frasconi / INFN Pisa5 Injection System (cont.) Input mode cleaner cavity about 145 m long based on: - Injection Bench (fall 2005, New Installation ) - End Mirror

September 11, 2007F. Frasconi / INFN Pisa6 Detection System (scheme) Suspended bench with optics for beam adjustments and OMC Detection, amplification and demodulation on external bench Laser Beam Suspended Bench External Bench

September 11, 2007F. Frasconi / INFN Pisa7 Detection System (cont.) Output Mode-Cleaner External bench Suspended bench

September 11, 2007F. Frasconi / INFN Pisa8 Mirror Suspensions The Superattenuator (SA) is the mechanical system adopted to isolate the optical components from seismic activities (local disturbances). It is based on the working principle of a multistage pendulum. Thanks to the isolation performance the system is compliant with future detector upgrades.

September 11, 2007F. Frasconi / INFN Pisa9 Main features of SA Thermal Noise Two types of SA: Short Chains & Long Chains; Hybrid system: active control below 4 Hz & passive attenuation starting from 4 Hz; Measured attenuation upper limit: at 10 Hz (detection band extended in the low frequency region)

September 11, 2007F. Frasconi / INFN Pisa10 Mirror Suspension Control The Inverted Pendulum (IP) is the elastic structure conceived to allow a wide positioning control of the suspension point Hierarchical control of the mirror (3 actuation points): - Inertial Damping on IP (to control tidal strain and drift of any origin ); - Local Control on Marionette (angular mirror displacements reduced down to fraction of  rad); - local damping on Reference Mass (RM).

September 11, 2007F. Frasconi / INFN Pisa11 Mirror Suspension Control improvements Several improvements have been done at the control level of the mirror: - global positioning IP control (GPIPC) - better stability for bad weather conditions – “guardian software” for earthquake oscillation high detector stability and high duty cycle

September 11, 2007F. Frasconi / INFN Pisa12 Fall 2005 Shutdown The shutdown was suggested by a few major problems found during the commissioning phase: - control problems and alignment drift on PR mirror; - spurious resonances and back-scattered light on suspended IB (no possibility to operate ITF at full power).

September 11, 2007F. Frasconi / INFN Pisa13 Fall 2005: detector upgrades (PR) Non-monolithic & Curved mirror induced: - control problems (spurious resonances); - misalignment and jitter noise for vertical translations. Monolithic flat mirror & Parabolic telescope on IB 120 mm R=4100 mm 350 mm Incident beam PR mirror transfer function Old New

September 11, 2007F. Frasconi / INFN Pisa14 Fall 2005: detector upgrades (IB) New suspended IB characteristics: - Faraday isolator (fixing back-scattered light) - parabolic telescope - thinner monolithic suspension wires Faraday Isolator

September 11, 2007F. Frasconi / INFN Pisa15 Activities before VSR1 Commissioning activity & noise hunting important for:improve controls & automation improve detector reliability & robustness Week-end Science run WSR1 (Sept. 2006)-WSR10 (Mar. 2007) important for:test shift organization data collection Collected data used for: detector characterization data analysis playground prepare joint analysis with LIGO

September 11, 2007F. Frasconi / INFN Pisa16 Detector sensitivity evolution

September 11, 2007F. Frasconi / INFN Pisa17 The First Virgo Science Run (VSR1) The run started on 18 th May 2007 It will last 4 months (till end of Sept. 2007) In coincidence with the last period of LIGO S5 run

September 11, 2007F. Frasconi / INFN Pisa18 Improved sensitivity during VSR1 Sensitivity during VSR1: Sept. 5, 2007 Sensitivity during VSR1: May 18, 2007

September 11, 2007F. Frasconi / INFN Pisa19 VSR1 horizon for inspiral sources BNS inspiral range: ~4.0 Mpc Mpc

September 11, 2007F. Frasconi / INFN Pisa20 VSR1: detector statistic

September 11, 2007F. Frasconi / INFN Pisa21 Data Analysis (DA) LSC-VIRGO agreement on common data taking & DA has been signed Data exchange has been activated since May 2007 (start of VSR1) Organization: - DA groups have been merged (joint review committee created for each working group); - Joint DA committee and run planning committee have been created (discussing the DA activities and run schedule even after VSR1/S5) Final goal: LSC-VIRGO joint analysis - white paper in progress

September 11, 2007F. Frasconi / INFN Pisa22 After VSR1 VIRGO is competitive at high frequency with LIGO detectors; VIRGO has the best sensitivity at low frequency (below 40 Hz) even if: the design sensitivity is still far away in the low-medium frequency range. Future activities: - a better understanding of the detector behavior - starting a detector upgrades campaign (VIRGO+ & AdV) to be implemented in parallel with other GW detectors all over the World (eLIGO & advLIGO).

September 11, 2007F. Frasconi / INFN Pisa23 VIRGO+ Main goals: - improving the design sensitivity by a factor ~2 - VIRGO+ should be back in Science Mode in 2009 (second half) in coincidence with eLIGO VIRGO+ is meant as a series of detector upgrades: - new IMC payload (new end mirror: better optical quality & larger size) - thermal compensation system - higher laser power (laser amplifier by LZH/GEO) - new mirrors (reduced losses -> higher finesse) - new control electronics

September 11, 2007F. Frasconi / INFN Pisa24 Advanced VIRGO (AdV) Goals - improving the VIRGO design sensitivity by a factor ~10 - back in data taking around Main scheduled changes: - higher power laser (optical readout noise) - heavier mirrors (optical readout noise) - better coatings (thermal noise) - signal recycling (shape the sensitivity curve) - beam waist position (thermal noise) AdV Conceptual Design document in preparation The exact AdV upgrades still under discussion

September 11, 2007F. Frasconi / INFN Pisa25 Conclusions VIRGO still in Science Mode - VSR1 started in May: data taking 4 months long - very good detector stability (thanks to control improvements) - good duty cycle in science mode (~ 82%) - 18 locking periods longer than 40 hours - BNS inspiral range at 4.0 Mpc level VIRGO+ upgrades - improving the design sensitivity of a factor ~2: preparation in advanced status - commissioning period of the upgrades -> back in science mode within the second half of 2009 (in coincidence with eLIGO) AdV upgrades - working groups & coordinators: defined - improving the design sensitivity of a factor ~10: conceptual design document in progress to be submitted to the Funding Institutions by the end of the year