VIRGO EXPERIMENT VIRGO a large interferometer for Gravitational

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

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 Roma 1, INFN Roma Tor Vergata September 11, 2007 F. Frasconi / INFN Pisa 2

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

Injection System • Based on a Nd: YVO 4 laser source with 20 W power (l= 1. 064 mm) Laser Cavity September 11, 2007 F. Frasconi / INFN Pisa 4

Injection System (cont. ) • Input mode cleaner cavity about 145 m long based on: - Injection Bench (fall 2005, New Installation) - End Mirror September 11, 2007 F. Frasconi / INFN Pisa 5

Detection System (scheme) • Suspended bench with optics for beam adjustments and OMC • Detection, amplification and demodulation on external bench External Bench Suspended Bench am e B r e Las September 11, 2007 F. Frasconi / INFN Pisa 6

Detection System (cont. ) Output Mode-Cleaner Suspended bench September 11, 2007 F. Frasconi / INFN Pisa External bench 7

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, 2007 F. Frasconi / INFN Pisa 8

Main features of SA • Two types of SA: Short Chains & Long Chains; • Hybrid system: active control below 4 Hz & passive attenuation starting from 4 Hz; The rma l. N oise • Measured attenuation upper limit: 1015 at 10 Hz (detection band extended in the low frequency region) September 11, 2007 F. Frasconi / INFN Pisa 9

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 mrad); - local damping on Reference Mass (RM). September 11, 2007 F. Frasconi / INFN Pisa 10

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, 2007 F. Frasconi / INFN Pisa 11

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, 2007 F. Frasconi / INFN Pisa 12

Fall 2005: detector upgrades (PR) 350 mm 120 mm Incident beam Old New PR mirror transfer function September 11, 2007 R=4100 mm • Non-monolithic & Curved mirror induced: - control problems (spurious resonances); - misalignment and jitter noise for vertical translations. Monolithic flat mirror & Parabolic telescope on IB F. Frasconi / INFN Pisa 13

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, 2007 F. Frasconi / INFN Pisa 14

Activities before VSR 1 • Commissioning activity & noise hunting important for: improve controls & automation improve detector reliability & robustness • Week-end Science run WSR 1 (Sept. 2006)-WSR 10 (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, 2007 F. Frasconi / INFN Pisa 15

Detector sensitivity evolution September 11, 2007 F. Frasconi / INFN Pisa 16

The First Virgo Science Run (VSR 1) • 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 S 5 run September 11, 2007 F. Frasconi / INFN Pisa 17

Improved sensitivity during VSR 1 Sensitivity during VSR 1: Sept. 5, 2007 Sensitivity during VSR 1: May 18, 2007 September 11, 2007 F. Frasconi / INFN Pisa 18

VSR 1 horizon for inspiral sources Mpc BNS inspiral range: ~4. 0 Mpc September 11, 2007 F. Frasconi / INFN Pisa 19

VSR 1: detector statistic September 11, 2007 F. Frasconi / INFN Pisa 20

Data Analysis (DA) • LSC-VIRGO agreement on common data taking & DA has been signed • Data exchange has been activated since May 2007 (start of VSR 1) • 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 VSR 1/S 5) • Final goal: LSC-VIRGO joint analysis - white paper in progress September 11, 2007 F. Frasconi / INFN Pisa 21

After VSR 1 • 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+ & Ad. V) to be implemented in parallel with other GW detectors all over the World (e. LIGO & adv. LIGO). September 11, 2007 F. Frasconi / INFN Pisa 22

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 e. LIGO • 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, 2007 F. Frasconi / INFN Pisa 23

Advanced VIRGO (Ad. V) • Goals - improving the VIRGO design sensitivity by a factor ~10 - back in data taking around 2013 -2014 • 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) • Ad. V Conceptual Design document in preparation • The exact Ad. V upgrades still under discussion September 11, 2007 F. Frasconi / INFN Pisa 24

Conclusions • VIRGO still in Science Mode - VSR 1 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 e. LIGO) • Ad. V 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 September 11, 2007 F. Frasconi / INFN Pisa 25