Transcript The Virgo interferometer for Gravitational Wave detection

The Virgo interferometer for Gravitational
Wave detection and its upgrade
Francesco Fidecaro
The First Galileo-Xu Guangqi Meeting
Shanghai, October 26, 2009
Outline
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The Virgo Collaboration
The European Gravitational Observatory
The Virgo interferometer
The LSC Virgo agreement
Performance
Upgrades
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The Virgo Collaboration
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Early efforts
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Brillet (optics)
Giazotto (suspensions)
Collaboration started in 1992
LAPP Annecy
EGO Cascina
Firenze-Urbino
Genova
Napoli
OCA Nice
NIKHEF Amsterdam
LAL Orsay
LMA Lyon – ESPCI Paris
APC Paris
Perugia
Pisa
Roma La Sapienza
Roma Tor Vergata
Trento-Padova
Warsaw
RMKI Budapest (observers)
LKB Paris (observers)
18 groups
About 200 authors
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The Virgo interferometer
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mm fused silica
Issues in sensitivity200
(Virgo
example)
suspension fibre
• h pioneered
~ 3 x 10-21 by
Hz-1/2 @ 10 Hz
• Glasgow/GEO600
h ~ 7 x 10-23 Hz-1/2 @ 100 Hz
Mirror coating
Mirror thermal lensing
compensation for high power
Seismic attenuation
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Virgo site in Cascina
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The European Gravitational Observatory
PURPOSE
• The Consortium shall have as its purpose the promotion of research
in the field of gravitation in Europe.
• In this connection and in particular, the Consortium pursues the
following objectives:
– ensures the end of the construction of the antenna VIRGO, its
operation, maintenance and the upgrade of the antenna as well as its
exploitation;
– ensures the maintenance of the related infrastructures, including a
computer centre and promotes an open co-operation in R&D;
– ensures the maintenance of the site;
– carries out any other research in the field of gravitation of common
interest of the Members;
– promotes the co-operation in the field of the experimental and
theoretical gravitational waves research in Europe;
– promotes contacts among scientists and engineers, the dissemination of
information and the provision of advanced training for young
researchers.
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World wide GW network: LV agreement
• “Among the scientific benefits we hope to achieve from
the collaborative search are:
– better confidence in detection of signals, better duty cycle and
sky coverage for searches, and better source position
localization and waveform reconstruction. In addition, we believe
that the intensified sharing of ideas will also offer additional
benefits.”
• Collaborations keep their identities and independent
governance
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LV Agreement (I)
• “All data analysis activities will be open to all members of
the LSC and Virgo Collaborations, in a spirit of
cooperation, open access, full disclosure and full
transparency with the goal of best exploiting the full
scientific potential of the data.”
• Joint committees set up to coordinate data analysis,
review results, run planning, and computing. The
makeup of these committees decided by mutual
agreement between the projects.
• Joint publication of observational data whether data from
Virgo, or LIGO (GEO) or both
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The low frequency strategy
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Noise in mass position
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Seismic isolation
• Super-attenuators: multistage passive seismic
isolation system (many
exchanges of visits with
UWA group)
• Inverted pendulum: large
amplitude low frequency
motion for tidal control
• Mechanical filters in 6 dof
• Hierarchical actuation:
F0, marionetta, mirror
MODEL
marionetta
mirror
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Superattenuator performance
• Excitation at top
• Use Virgo sensitivity
and stability
• Integrate for several
hours
• Upper limit for TF at
32 Hz:1,7 10-12
• In some
configurations a
signal was found,
but also along a
direction
perpendicular to
excitation:
compatible with
magnetic cross talk
marionetta
mirror
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The optics strategy
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Coating facility – LMA Lyon ESPCI Paris
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Dedicated investment by Virgo
Large area coating
Metrology
Corrective coating procedure
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Virgo mirror performance
Coating Nature
and Clear aperture
(mm)
RMS Wavefront (nm)
Average
Absorption
(ppm)
Average
Scattering
(ppm)
Transmission
Side A
Side B
Side A
Side B
North End
Mirror
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HR
330 mm
3.9
150 mm
3.8
150 mm
0.67
150 mm
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150 mm
42.9 ppm
West End Mirror
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HR
330 mm
2.8
150 mm
3.4
150 mm
0.69
150 mm
6.5
150 mm
38.3 ppm
North Input
Mirror
HR
200 mm
AR
200 mm
2.6
60 mm
3.8
60 mm
1.25
60 mm
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60 mm
11.80 %
West Input
Mirror
AR
200 mm
HR
200 mm
2.6
60 mm
2.5
60 mm
1.20
60 mm
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60 mm
11.66 %
Recycling Mirror
2006
HR
200 mm
AR
200 mm
1.4
60 mm
1.08
60 mm
0.54
100 mm
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60 mm
5.13 %
Beam Splitter
n°1
AR
210 mm
HR
210 mm
3.9
100 mm
5.4
120 mm
1.35
center
5.5
100 mm
49.8 %
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Upgrades from VSR1 (2007)
to VSR2 (2009-2011)
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Virgo+ upgrade: injection system
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New laser amplifier (LZH): up to 50 W (25 W at interferometer input)
New pre-mode-cleaner
Remotely tunable in-vacuum Faraday Isolator
Heavier input-mode-cleaner end-mirror
High power operation
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Power increased in steps from 8 W (VSR1) to 17 W now
– limited by mismatching of reference cavity due to thermal effects
No major problems with interferometer stability
Some alignments loops more critical
Quadrature signals (B1_ACq or B5_ACq) kept close to zero using slow servos on TCS power
Currently about 1.5 W on both mirrors: interferometer similar to 8W
'Cold interferometer' with about 2x 6W
– More optical gain, ideal frequency stabilization TF, but TCS too noisy
without TCS
with TCS
Noise understanding
• Noise sources
and coupling are
well understood
• Low frequency
shows more
structures
• Noise reduction
in advanced
detectors
achieved with
proper design
• Virgo+ in 2010:
fused silica
suspensions and
higher Finesse
– risk reduction for
Advanced
detectors
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Virgo sensitivity progress
VSR1: May 18-Sep 30 2007 4 month continuous data
taking simultaneously with LIGO Analysis in progress
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Very latest sensitivity
Calibration lines moved
Environmental noise
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Stability
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Robust interferometer
– 95% Science Mode duty cycle (if no
commissioning is made)
– Good sensitivity
• Stable horizon:
8-8.5 Mpc (1.4-1.4 Ns-Ns) - averaged
(now 8-9.5 Mpc)
42-44 Mpc (10-10 BH-BH) - averaged
– fluctuating with input mirror etalon
effect
• Low glitch rate: factor 10 lower than VSR1
• Taking data since July 7th with 80% duty
cycle in science mode and locks alasting
days
• Preparing for installation of monolithic
suspensions
Data Analysis
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Joint LIGO/Virgo Search for GRBs
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Gamma Ray Bursts (GRBs) - brightest EM emitters in the sky
– Long duration (> 2 s) bursts, high Z  progenitors are likely core-collapse
supernovae
– Short duration (< 2 s) bursts, distribution about Z ~ 0.5  progenitors are likely
NS/NS, BH/NS, binary merger
– Both progenitors are good candidates for correlated GW emissions!
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212 GRBs detected during S5/VSR1
– 137 in double coincidence (any two of LIGO Hanford, LIGO Livingston, Virgo)
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No detections, we place lower limits on distance assuming EGW = 0.01 Mc2
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VSR2 sensitivity for CW searches
Targeted searches.
Vela
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VSR2 sensitivity
Spin-down limit can be beaten for a few pulsars
Name
f gw
 sup
Vela
22.38
8.0 10  4
J0205  6449
30.44
1.4 10 3
J1833 - 1034
32.32
1.1 10 3
J1747 - 2809
38.46
8.9 10-4
J1952  3252
50.58
1.1 10  4
J1913  1011
55.68
7.5 10 5
5
Crab
59.56
7.8 10
J0537 - 6910
124.04
8.9 10 5
(Vela spin-down limit in ~80 days)
Compatible with some ‘exotic’ EOS
may improve on Crab
Marginally compatible with standard EOS
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Monolithic fused silica suspension
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Clamp design
Steel box to host the upper silica
clamp on the marionetta
Monolithic Suspensions
Coupling to the mirror flats with New Ears
Silica Clamps
on the marionette
Silica anchors
Silicate bonding
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Summary
• After many years of blood, sweat and tears, Virgo is now
working very well
• The low frequency region appears to be well understood
and other project will be able to profit from the
experience;
• Not only seismic, but all environmental noise has to be
mitigated
• We look forward trying to push further down the noise
with the monolithic suspensions as it could give to the LV
network a Poisson rate for NSNS coalescences of more
than one event per year.
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The Fluctuation-Dissipation Theorem
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