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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
TAUP2007 Sendai , September 11-15, 2007
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
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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
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Injection System
• Based on a Nd:YVO4 laser source
with 20 W power (l= 1.064 mm)
Laser
Cavity
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F. Frasconi / INFN Pisa
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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
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Detection System (scheme)
• Suspended bench with optics for
beam adjustments and OMC
• Detection, amplification and
demodulation on external bench
External
Bench
Suspended
Bench
September 11, 2007
F. Frasconi / INFN Pisa
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Detection System
(cont.)
Output Mode-Cleaner
Suspended bench
September 11, 2007
F. Frasconi / INFN Pisa
External bench
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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
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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;
•Measured attenuation
upper limit: 1015 at 10 Hz
(detection band extended in
the low frequency region)
September 11, 2007
F. Frasconi / INFN Pisa
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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
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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
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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
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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
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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
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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, 2007
F. Frasconi / INFN Pisa
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Detector sensitivity evolution
September 11, 2007
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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
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Improved sensitivity during VSR1
Sensitivity during VSR1: Sept. 5, 2007
Sensitivity during VSR1: May 18, 2007
September 11, 2007
F. Frasconi / INFN Pisa
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VSR1 horizon for inspiral sources
Mpc
BNS inspiral range: ~4.0 Mpc
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F. Frasconi / INFN Pisa
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VSR1: detector statistic
September 11, 2007
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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
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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
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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
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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
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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
September 11, 2007
F. Frasconi / INFN Pisa
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