VIRGO STATUS REPORT F. Fidecaro Amsterdam, September 22, 2008.
The Virgo interferometer for Gravitational Wave detection Francesco Fidecaro EPFL, November 8, 2010.
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Transcript of The Virgo interferometer for Gravitational Wave detection Francesco Fidecaro EPFL, November 8, 2010.
The Virgo interferometer for Gravitational Wave detection
Francesco Fidecaro
EPFL, November 8, 2010
2
Outline• Gravitational waves: sources and detection• The Virgo interferometer• The global network• Some LSC-Virgo results (for the LSC and Virgo
collaborations)• Advanced Virgo• Perspective
3
Gravitational waves• Tiny perturbations of spacetime geometry
• Predicted by Einstein as consequence of General Relativity– Propagate at the speed of light
– Non relativistic approximation: generated by accelerated masses (quadrupole formula)
– Amplitude h decreases as 1/R (field, as opposed to 1/R2 for energy or particle counting)
– Order of magnitude: RS/R
– Detectable by measuring invariant separation between free falling masses
hg
4
Gravitational wave detection• Measure variations in
curvature of space time• Use clocks on geodetics as
markers• Be careful of pitfalls of
Relativity! Measure only well defined, invariant quantities
1
d dx dxi
i
B
B
g
• Need precise clocks in
different places:– pulsar and atomic clock
t
A1
A2
A3 B1
B2
B3
x
• Need one precise clock in one place: laser
t
A1
A2
A3
B1
B2
B3
x
2d 0 : light rays
6
Detection by time measurement
7
Sources
8
chirp
Compact binary systems
9
Horizon and event rate
> 1 ev/yr
Predictions for the rates of compact binary coalescences observable … CQG, 10.1088/0264-9381/27/17/173001
10
Impulsive events, final evolution of big mass starsCore collapses to NS or BH, GW emitted only in non-spherical collapseBig uncertainties, waveform “unpredictable”Coincidence detection necessary
Amplitude: optimistich~10-21 at 10 Mpc
non-axisymmetric collapse
Rate: several/year in the VIRGO cluster (how many detectable?)
GW emitted
Stellar core collapse (Supernova)
11
1000 galactic pulsars knownPossible sources of GW
Pulsars
12
Non-axisymmetric rotating NS emit periodic GW at f=2fspin but…weak
SNR increases with observation time T as T1/2, T can be monthsBut…
f ~ 10-6 Doppler correction of Earth motion:
f/f ~ 10-4 function of source position: Blind search limited by computing power
109 NS in the galaxy, ~1000 known
Ellipticity determination: EOS nuclear matter.Strange stars?
6
2
24527
10Hz 200g/cm 10
kpc 10103
fI
rh
Pulsars: rotating neutron stars
13
Relic gravitons
Relic neutrinos
CMBR Imprinting of the early expansion of the universeNeed two correlated ITFsStandard inflation produces a background too lowString models ?
Relic stochastic background
14
Dick Manchester, CSIRO
The Gravitational Wave Spectrum
LIGO/VIRGO
15
Noise characterization
16
Signal and noise
18
The Virgo detector
19
The Virgo Collaboration• Early efforts
– Brillet (optics)– Giazotto (suspensions)
• Collaboration started in 1992• LAPP Annecy• EGO Cascina• Firenze-Urbino• Genova• Napoli• OCA Nice• NIKHEF Amsterdam• LAL Orsay• LMA Lyon• APC Paris – ESPCI Paris• Perugia• Pisa• Roma La Sapienza• Roma Tor Vergata• Trento-Padova• IM PAN Warsaw• RMKI Budapest• LKB Paris• 18 groups• About 200 authors
20
Noise in mass position
21
Seismic isolation• Super-attenuators: multi-stage passive
seismic isolation system
MODEL
22
marionetta
mirror
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
23
GW interferometers• Isolated/suspended mirrors:
– z at 10 Hz ~ 10-18 m– z at 100 Hz ~ 10-21 m
• Differential measurement to cancel phase noise
• Effective L ~ 102 km• = 1 m• Effective power ~ 1 kW ~ 1022 • Measurement noise ~ 10-11 rad
• for a 1 s measurement• Record a signal, if high SNR
there is a large information content
L
Light source
23shot 102
hL
25
Issues in sensitivity (Virgo example)• h ~ 3 x 10-21 Hz-1/2 @ 10 Hz
• h ~ 7 x 10-23 Hz-1/2 @ 100 Hz
200 m fused silica suspension fibre
pioneered by Glasgow/GEO600
Mirror coating Beam size
High power laserMirror thermal lensing
compensation for high powerSignal recycling
Use of non standard light
Seismic attenuation
Local gravity fluctuations
26
Virgo site in Cascina
27
The European Gravitational ObservatoryPURPOSE• 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.
28
EGO• 5 year renewal approved this year• Current members: CNRS, INFN participating equally to
budget (ca 10 M€ / year)• Management:
– EGO Council and its President– EGO Director– Board of auditors– Currently 48 staff, EGO Scientific Director, Adminstrative Head
• Scientific and Technical Advisory Committee– Experts of the field or of related questions
• VESF:Virgo-EGO Scientific Forum– Implementation of one of the EGO purposes– Gathers people interested in gravitational waves and their
detection
29
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
30
Virgo sensitivity progress
VSR1: May 18-Sep 30 2007 4 month continuous data taking simultaneously with LIGO Analysis in progress
31
Virgo & LIGO: 2008-09-10
Stability• Robust interferometer
– 95% Science Mode duty cycle – Good sensitivity
• Stable horizon:
8-8.5 Mpc (1.4-1.4 Ns-Ns) - averaged
42-44 Mpc (10-10 BH-BH) - averaged – fluctuating with input mirror etalon
effect• Low glitch rate: factor 10 lower than VSR1• Preparing for installation of monolithic
suspensions
33
Environmental noises studiesInvestigations to understand the sources and the path to dark fringe
Coupling (paths) to dark fringe
- diffused light from in air optical benches
- diffused light related to Brewster window
- beam jitter on injection bench
Sources of environmental noise:
- air conditioning
- electronic racks
Laser
Brewster window
End benches
External bench
Injection bench
Detectionsuspended bench
Beam jitter
DAQ room
Need to work both on:- reduction of coupling- reduction of environmental noise
Elec
racks
34
The global network
35
Motivation for a Global GW Detector Network
LIGOGEO VIRGO TAMA
AIGO
t1
t2
t3 t5
t4
t6
• Time-of-flight to reconstruct source position
36
Motivation for a Global GW Detector Network
source location
• Source location: – Ability to triangulate (or ‘N-angulate’) and more accurately pinpoint source
locations in the sky– More detectors provides better source localization Multi-messenger
astronomy
• Network Sky Coverage:– GW interferometers have a limited antenna pattern; a globally distributed
network allows for maximal sky coverage
• Detection confidence: – Redundancy – signals in multiple detectors
• Maximum Time Coverage - ‘Always listening’: – Ability to be ‘on the air’ with one or more detectors
• Source parameter estimation:– More accurate estimates of amplitude and phase– Polarization - array of oriented detectors is sensitive to two polarizations
• Coherent analysis: – Combining data streams coherently leads to better sensitivity ‘digging
deeper into the noise’– Also, optimal waveform and coordinate reconstruction
37
LIGO
Abbott, et al., “The laser interferometer gravitational-wave observatory” http://stacks.iop.org/0034-4885/72/076901
38Credit: Albert Einstein Institute Hannover
39
Large Cryogenic Gravitational wave TelescopeLCGT is almost entirely financed to be built underground at Kamioka, where the prototype CLIO detector is placed.
40
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
41
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
43
Some results from L-V
44
Some results from LV
• MoU for data sharing: now common data analysis groups (Bursts, Coalescing Binaries, Periodic Sources, Stochastic Background), weekly (and more) telecons
• An Upper Limit on the Amplitude of Stochastic Gravitational-Wave Background of Cosmological Origin
• Joint searches for GRBs (LV)• GRB 070201 (LSC)• Crab spindown limit (LSC) and Vela (Virgo)
45
46
Stochastic Background (SB)• A stochastic background can be
• a GW field which evolves from an initially random configuration: cosmological background
• the result of a superposition of many uncorrelated and unresolved sources : astrophysical background)
• Typical assumptions
• Gaussian, because sum of many contributions
• Stationary, because physical time scales much larger than observational ones
• Isotropic (at least for cosmological backgrounds)
If these are true, SB is completely described by its power spectrum
47
Detection method• It is stochastic and presumably overwhelmed by noise• Need (at least) two detectors to check for statistical correlations
• Optimal filtering
SignalsUncorrelated
(?) noises
* 21 2 12
6,1 ,2
12
,
GWGW
GW
( ) ( ) ( ) ( )
( ) ( )
( ) : data from detector
( ) : overlap function between detectors
( ) : noise power spectrum in detector
( )
( )100Hz
GW
n n
i
n i
c
h f h f f fY df
f S f S f
h f i
f
S f i
dff
df
ff
48
Detection performance
• Sensitivity improves as T1/2
• Better performances when coherence is high ( )– detectors near each
other compared to – detectors aligned
12
22
6,1 ,20
( ) ( )
( ) ( )GW
n n
f fSNR T df
f S f S f
49
Isotropic search: results• Data collected during S5 run (one year integrated data of
LIGO interferometers)• Point estimate of Y: no evidence of detection integrating
over 40-170 Hz (99% of sensitivity)
60 6.9 10 95% C.L.
50
Isotropic search: results• Now we are
beyond indirect BBN and CMB bounds
• We are beginning to probe models
51
Joint LIGO/Virgo Search for GRBs• 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!
• 212 GRBs detected during S5/VSR1– 137 in double coincidence (any two of LIGO Hanford, LIGO Livingston, Virgo)
• No detections, we place lower limits on distance assuming EGW = 0.01 Mc2
52
M31The Andromeda Galaxy
by Matthew T. RussellDate Taken:
10/22/2005 - 11/2/2005
Location:Black Forest, CO
Equipment:RCOS 16" Ritchey-Chretien
Bisque Paramoune MEAstroDon Series I Filters
SBIG STL-11000Mhttp://gallery.rcopticalsystems.com/gallery/m31.jpg
Refs:GCN: http://gcn.gsfc.nasa.gov/gcn3/6103.gcn3
GRB 070201
X-ray emission curves (IPN)
9 November 2007 GRB 2007 53
GRB070201: Not a Binary Merger in M31!
Inspiral (matched filter search:
Binary merger in M31 (770 kpc) scenario excluded at >99% level
Exclusion of merger at larger distances
90%
75%
50%
25%
Inspiral Exclusion Zone
99%
Abbott, et al. “Implications for the Origin of GRB 070201 from LIGO Observations”, Ap. J., 681:1419–1430 (2008).
Burst search:Cannot exclude an SGR in M31
SGR in M31 is the current best explanation for this emission
Upper limit: 8x1050 ergs (4x10-4 Mc2) (emitted within 100 ms for
isotropic emission of energy in GW at M31 distance)
54
The Crab Pulsar: Beating the Spin Down Limit!• Remnant from supernova in year 1054
• Spin frequency EM = 29.8 Hz
gw = 2 EM = 59.6 Hz
• observed luminosity of the Crab nebula
accounts for < 1/2 spin down power
•spin down due to:
• electromagnetic braking
• particle acceleration
• GW emission?
• early S5 result: h < 3.9 x 10-25 ~ 4X below
the spin down limit (assuming restricted priors)
• ellipticity upper limit: < 2.1 x 10-4
• GW energy upper limit < 6% of radiated energy is in GWs
Abbott, et al., “Beating the spin-down limit on gravitational wave emission from the Crab pulsar,” Ap. J. Lett. 683, L45-L49, (2008).
55
VSR2 sensitivity for CW searches
Targeted searches.
Vela
56
5
5
5
4
4-
3
3
4
sup
109.8 04.124 6910-J0537
108.7 56.59 Crab
105.7 68.55 1011J1913
101.1 58.50 3252J1952
108.9 46.38 2809-J1747
101.1 32.32 1034-J1833
104.1 44.30 6449J0205
100.8 38.22 Vela
Name
gwf
Compatible with some ‘exotic’ EOS
Marginally compatible with standard EOS
(Vela spin-down limit in ~80 days)
may improve on Crab
VSR2 sensitivity
Spin-down limit can be beaten for a few pulsars
57
Recent papers Burst• Search for gravitational-wave bursts associated with gamma-ray
bursts using data from LIGO Science Run 5 and Virgo Science Run 1Ap. J.:http://iopscience.iop.org/0004-637X/715/2/1438.
• All-sky search for gravitational-wave bursts in the first joint LIGO-GEO-Virgo runPhys. Rev. D.: Phys. Rev. D 81(2010) 102001
CBC• Search for gravitational-wave inspiralsignals associated with short
gamma-ray bursts during LIGO'sfifth and Virgo's first science runAp. J.:http://iopscience.iop.org/0004-637X/715/2/1453.
• Search for gravitational waves from compact binary coalescence in LIGO and Virgo data from S5 and VSR1provisionally accepted in Phys. Rev, D
CW• Searches for Gravitational Waves from Known Pulsars with S5 LIGO
Data”Ap. J. http://stacks.iop.org/0004-637X/713/67• First search for gravitational waves from the youngest known neutron
star”, accepted for publication in Ap. J.
58
59
60
61
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Prepare multi-messenger searches
• Multi-messenger astronomy - connecting different kinds of observations of the same astrophysical event or system
– Coincidence allows to decrease (somewhat) detection threshold– EM or particle presence may provide more information about the GW source
• Sky position, host galaxy type, distance, emission characteristics / astrophysical processes
• Require (at least) three operational and comparably sensitive GW detector sites
– LIGO Hanford, Livingston, GEOHF and Virgo
• With S6/VSR2 : begin connecting with other alert networks or provide data for immediate telescope pointing
– Requires rapid online analysis, data quality flagging – Ongoing development by LIGO Lab, Data Analysis Software Working
Group, and Search Groups– Example: P5 Swift ToO– Contacts with High Energy Neutrino detectors, pointing telescopes– Wide Optical Field telescopes
• Connection with Astroparticle community
63
Advanced Virgo
6464
108 ly
Enhanced LIGO/Virgo+ Virgo/LIGO
Credit: R.Powell, B.Berger
Adv. Virgo/Adv. LIGO
2nd generation detectors– BNS inspiral range >10x
better than Virgo– Detection rate: ~1000x better
– 1 day of Adv data ≈ 3 yrs of data
2nd generation network. – Timeline: commissioning to
start in 2014.
Advanced detectors
65
Advanced Virgo baseline design
• First orders placed. Plan to be backin 2015 with LIGO
Signal Recycling (SR)
Non degenerate rec. cavities
High power laser
High finesse3km FP cavities
Heavier mirrors
Large spot size on TM
Larger central linksCryotraps
Monolithicsuspensions
DC readout
66
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Perspective
68
The Future – AIGO (Australia)
• A comparably sensitive detector in Australia will bring increased angular sensitivity and better sky coverage
• Australian Interferometer Gravitational- wave Observatory conceived as a 5 km interferometer
– will follow the AdvLIGO design• Possible variation in suspension and seismic isolation system• Likely location in Western Australia
– Aim for operation in 2017• 2 year lag behind AdvLIGO
69
The future: go around shot noise• Squeezed vacuum states as a tool are becoming reality• 6 dB reduction in shot noise is equivalent to an increase
in power on beam splitter of 16 x• That reduction goes into radiation pressure fluctuations
that can be important at low frequency• Next steps: frequency dependent squeezing
GEO600
70
The Future: The Einstein Telescope (Europe)
71
Perspectives for third generation• Sources are waiting
– Systems at cosmological distance– High statistics in binary systems (inspiral waveforms, matter
distribution)– Increased sensitivity in merge and ringdown phase (GR, EOS)– Increased number of pulsars (EOS, population, )– Stochastic background (cosmological and astrophysical)– Coincidences with and X-ray satellites, observatories, …
(system dynamics)
• Gaining another factor 10 in sensitivity• Extending frequency down to a few Hz• Extending further frequency spectrum spectrum
– Pulsar timing– High frequency gravitational waves
72
Sensitivity future evolution
73
Einstein Telescope: time scale
74
Conclusions• We are at the edge of starting a new, fascinating field of
science• After “first words”, there is room for a large expansion in
observations• Phenomenology, theory will follow• Room for unexpected• In spite of the size, the instrument can be run by a single
(clever) person• New developments will be first by table top experiments• High interdisciplinary views required• Will reward junior and senior scientists
75
Thank you !
76
The Fluctuation-Dissipation Theorem