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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
September 11, 2007 F. Frasconi / INFN Pisa 3
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, 2007 F. Frasconi / INFN Pisa 4
Injection System
• Based on a Nd:YVO4 laser source with 20 W power (= 1.064 m)
Laser
Cavity
September 11, 2007 F. Frasconi / INFN Pisa 5
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 6
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, 2007 F. Frasconi / INFN Pisa 7
Detection System (cont.)
Output Mode-Cleaner
External bench
Suspended bench
September 11, 2007 F. Frasconi / INFN Pisa 8
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 9
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)
September 11, 2007 F. Frasconi / INFN Pisa 10
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, 2007 F. Frasconi / INFN Pisa 11
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 12
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 13
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, 2007 F. Frasconi / INFN Pisa 14
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 15
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
September 11, 2007 F. Frasconi / INFN Pisa 16
Detector sensitivity evolution
September 11, 2007 F. Frasconi / INFN Pisa 17
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
September 11, 2007 F. Frasconi / INFN Pisa 18
Improved sensitivity during VSR1
Sensitivity during VSR1: Sept. 5, 2007
Sensitivity during VSR1: May 18, 2007
September 11, 2007 F. Frasconi / INFN Pisa 19
VSR1 horizon for inspiral sources
BNS inspiral range: ~4.0 Mpc Mpc
September 11, 2007 F. Frasconi / INFN Pisa 20
VSR1: detector statistic
September 11, 2007 F. Frasconi / INFN Pisa 21
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, 2007 F. Frasconi / INFN Pisa 22
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, 2007 F. Frasconi / INFN Pisa 23
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, 2007 F. Frasconi / INFN Pisa 24
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
September 11, 2007 F. Frasconi / INFN Pisa 25
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