F. Frasconi I.N.F.N. Pisa for the Virgo Collaboration TAUP2007 Sendai, September 11-15, 2007 VIRGO...

F. Frasconi I.N.F.N. Pisafor 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, 2007 F. Frasconi / INFN Pisa 2

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


VIRGO Optical scheme

Laser 20 W

Input Mode Cleaner (145 m)

Power

Recycling

3 km long Fabry-Perot

Cavities

Output Mode

Cleaner (4 cm)


Injection System

• Based on a Nd:YVO4 laser source with 20 W power (= 1.064 m)

Laser

Cavity


Injection System (cont.)

• Input mode cleaner cavity about 145 m long based on:

- Injection Bench

(fall 2005, New Installation)- End Mirror


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


Detection System (cont.)

Output Mode-Cleaner

External bench

Suspended bench


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.


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: 1015 at 10 Hz (detection band extended in the low frequency region)


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).


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


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).


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


Fall 2005: detector upgrades (IB)

• New suspended IB characteristics:- Faraday isolator (fixing back-scattered light)- parabolic telescope- thinner monolithic suspension wires

Faraday Isolator


Activities before VSR1

• Commissioning activity & noise huntingimportant for: improve controls & automation

improve detector reliability & robustness

• Week-end Science runWSR1 (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


Detector sensitivity evolution


The First Virgo Science Run (VSR1)

• The run started on 18th May 2007• It will last 4 months (till end of Sept. 2007)• In coincidence with the last period of LIGO S5 run


Improved sensitivity during VSR1

Sensitivity during VSR1: Sept. 5, 2007

Sensitivity during VSR1: May 18, 2007


VSR1 horizon for inspiral sources

BNS inspiral range: ~4.0 Mpc Mpc


VSR1: detector statistic


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


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).


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


Advanced VIRGO (AdV)

• 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)

• AdV Conceptual Design document in preparation• The exact AdV upgrades still under discussion


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

F. Frasconi I.N.F.N. Pisa for the Virgo Collaboration TAUP2007 Sendai, September 11-15, 2007 VIRGO...

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