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Acoustic gw detectors: from
resonant “bar” to wideband “dual”
Massimo Cerdonio
INFN Section and Department of Physics
University of Padova, Italy
AURIGA
www.auriga.lnl.infn.it
DUAL R&D
www.dual.lnl.infn.it
Erice
June 3rd 2006
Edoardo AMALDI in Folgaria (Trento) 1989
evidence for gravitational waves
Neutron Binary System – Hulse & Taylor
PSR 1913 + 16 -- Timing of pulsars
17 / sec


~ 8 hr
Neutron Binary System
• separated by 106 miles
• m1 = 1.4m; m2 = 1.36m; e = 0.617
Prediction from general relativity
• spiral in by 3 mm/orbit
• rate of change orbital period
Emission of gravitational waves
QuickTime™ and a
Sorenson Video decompressor
are needed to see this picture.
L-L
L+L
t=0
t = T /4
t = T/2
1
L  hL
2
L ~ 10-18 m
t = 3T /4
L ~ 103 m
h ~ 10-21
(NS/NS @15 Mpc)
t=T
acoustic gw detectors
Single-mass Dual
gr-qc/0605004 (2006)
Bar
ri
Dual Torus
Phys. Rev. D 68 (2003) 102004
Antenna pattern:
like 2 IFOs colocated and
rotated by 45°
Dual Sphere
Phys. Rev. Lett. 87 (2001) 031101
NS/NS
rivelabile
a 300 Mpc
VIRGO/LIGO range
Adv LIGO/Dual range
physics @ kHz frequencies
 Equation Of State of superdense matter
• isolated ns
deformed pulsars, rotational instabilities, normal modes,
“starquakes”, Sn core collapse, accretion spun-up ms pulsars,
LowMassXrayBinaries, SoftGammaRay repeaters (flares)
• ns-ns binaries
“chirp”, bar instabilities, merging, ringdown
 Extreme gravity
• bh-bh binaries
“chirp”, merging, ringdown
 Cosmology
• stochastic background
Bar Network
Upper limit for burst GWs with random arrival time and
measured amplitude  search threshold
PRL 85 5046 (2000) – Phys. News Upd. 514 Nov. 29 (2000) - PRD 68 022001 (2003)
UPPER LIMIT on the RATE of GW bursts
from the
GALACTIC CENTER
S1
h ~ 2 10-18
IGEC-1 results
LIGO S2, S3 & S4
improve considerably
IGEC-2 will be comparable
LIGO S5 will overcome
E ~ 0.02 Msun converted into gw
at the Galactic Center
bar gw detectors
(brief reminder)
how they detect, SQL, bandwidth, antenna pattern
AURIGA recent upgrades
• three modes operation to widen the band
• approaching the Standard Quantum Limit
• suspensions and seismic insulation
how AURIGA performs
AURIGA and the Dec 27th SGR flare
“bar” gw detectors
M = 2.3 t
L = 3m
“bars” at the Standard Quantum Limit
detect few quanta in a 2.3 tons oscillator
Eabsorbed ~ hPlanck fbar
kBT/Q < hPlanck f
need:
• wide detection bandwidth f~100 Hz, large Q/T ~ 108 K-1
T~ 0.1 K, Q ~ 107
• a quantum limited amplifier: SQUID, optical,…
where are we ?
f~100 Hz
Q ~ 5 106
AURIGA @ 4.5 K
AURIGA @ 0.1 K
Eabsorbed ~ 500 quanta
Eabsorbrd ~ 10 quanta
hSQL ~ 3 10-21
Antenna pattern
sen2 cos2
the bandwidth is potentially infinite
arrival time estimates for -like bursts
AURIGA run II: upgrades
Cryogenic
Switch
Decoupling
Capacitor
Transducer
Charging Line
 three resonant modes operation:
two mechanical modes
one electrical mode
 transducer bias field 8 MV/m
 new SQUID amplifier :
double stage SQUID
~500 energy resolution at 4.5 K in the detector
Cd
M
Bar
L
Mi
Ls Li
CT
Capacitive
Resonant
Transducer
Matching
Transformer
SQUID
Amplifier
Shh sensitivity (2)
AURIGA T=4.5K
1x10
- noise prediction
- mechanical thermal - LC thermal
- SQUID back action - SQUID additive
Very good
agreement with
noise predictions
-20
-1/2
]
1x10
-19
one-sided Shh
Shh
0.5
[Hz
all these noise
sources will scale
with temperature
1x10
-21
1x10
-22
800
850
900
Frequency [Hz]
950
1000
AURIGA
May 19th 2005
AURIGA on the dampers
the three modes of AURIGA
as they keep clean and stable in time
AURIGA II run
stationary gaussian operation of a wideband “bar” detector
 the 3 modes thermal at 4.5 K
 Shh1/2 < 4 10-21 Hz-1/2 over 90 Hz band (one sided)
 ~ 100% operation for acquisition of usable data
(except 3hours/month > He transfer)
 veto time intervals under out-of-band triggers to select
against epochs of external disturbances
 reduce (for bursts) to stationary gaussian operation over
~ 96% of time
P.Falferi et al, “3-modes detection…”
Phys.Rev.Letters 2005
M.Bonaldi et al,“AURIGA suspensions…”
Rev. Sci. Instr. 2005
A.Vinante et al, “Thermal noise in a…”
Rev. Sci. Instr. 2005
red: exp
blue: sim
~ 4 days of
continuous operation
duty cycle
~ 96%
SNR
date
an optomechanical transducer
for the AURIGA “bar” gw detector
cryogenic optics towards the quantum limit:
high finesse cavities, fibers, piezo actuators, etc @ 4.2 K
concept and optics: Livia Conti, Maurizio DeRosa, Francesco Marin
cryogenics: Michele Bonaldi, Giovanni A. Prodi, Luca Taffarello, Jean-Pierre Zendri
The Dec. 27th 2004 giant flare of the soft
gamma ray repeater SGR1806-20
• on a ~ 10 kpc distance scale in the direction of Sagittarium
• 100 times more energetic than any other
• after peaking with ms rise time, decayed to 1/10 intensity
in ~ 300 ms
a catastrophic instability involving global crustal failure in a “magnetar”,
which possibly triggers the excitation of f- and p-modes in the neutron
star
the excited mode damps out by gw emission, the energetics of which
would be ~ 100 times larger of that of the X-rays flare
AURIGA and the flare
• was optimally oriented towards 1806-20 at the flare time
• was performing as a stationary gaussian detector
• was covering a ~ 100 Hz band in which neutron star
f- and p-modes may fall
we test if, at the flare time, gw emission is found, as a damped sinusoidal
wave train at any frequency f within AURIGA band, with damping time s
• divide the band in sub-bands of width f~1/s around each f
• integrate for a time t~s the output energy
• check the statistics of the time series
• test for any excess in
e in the sub-band
e(t) in each sub-band f
e(t) at the flare peak time
tp
we take s = 100 ms as ~ 1/3 of the observed flare decay
Baggio et al. (AURIGA collaboration) Phys.Rev.Letters 95 081103 (2005)
the time origin corresponds to the arrival time
of the flare peak tp at the AURIGA site
upper limits
on emitted gw energy as fraction of solar mass
Over the sub-band at frequency f of width f
models predict
egw
~ 5 10-6
comments on
AURIGA & the flare
•
stationary operation allows relevant searches
even with a single detector
• obtained an upper limit about neutron stars
dynamics, which is relevant as it invades part
of the parameter region of existing models
• stronger upper limits could be put with optimal
search methods ( I did not discuss this point > see PRL paper)
AURIGA gaussianity -100s to +100s around flare time
Optical Transducer
The Concept
transducer
cavity
Variations of the transducer
cavity length are measured
by the stabilized laser
optical fiber
beam-splitter
Nd:YAG
laser
Phase
mod.
Power
stab.
bar
Frequency
locking
FM sidebands
technique
reference
cavity
FM sidebands
technique
Data
acquisition
Low frequency
locking
temperature
control
Transducer cavity:
a Fabry-Perot cavity between
the bar and the resonant plate
Reference cavity:
a stable Fabry-Perot cavity
acting as length reference
pzt actuator
Laser source frequency
locked to the reference cavity
Optical Transducer
Status: Room temperature test
Experimental set-up
Achieved gw sensitivity
L.Conti et al,. Jour. Appl. Phys. 93 (2003) 3589
Optical Transducer
Status: Cryogenics
Q measurements in the
Transducer Test Facility
New Cryostat for the bar
resonator under construction
[a prototype gw detector in coincidence with AURIGA will operate at
4.2 K ~ 1 year]
>>> CANCELED
R&D for Dual: optics with high finesse cavities at low T, coating
thermal noise and substrate thermoelastic noises (“thermodynamic”
and “photothermal”) at levels of displacement ~ 10-20 m/Hz1/2
1E-19
Optical transducer 4.2 K
Shh
1/2
(1/Hz
1/2
)
1E-18
1E-20
Auriga now
1E-21
800
850
900
Frequency (Hz)
950
1000
DUAL
how to open wide, many kHz, the band of an
acoustic detectors
the DUAL R&D collaboration:
Firenze, Legnaro, Padova, Trento, Urbino
Dual detector:
the concept
measurement of differential deformations of two
oscillators, resonating at different frequencies and
both sensitive to the gw signal
Intermediate frequency range:
• the slow oscillator is driven
above resonance,
• the fast oscillator is driven
below resonance
phase difference of p
A possible 2D implementation:
differential measurement:
signals sum up
readout back action noise
subtracts out
the new ideas of the DUAL detector
1 –the “dual” concept : read displacement between two massive
resonators (or modes of one mass) with a non-resonant read-out
M. Cerdonio et al. Phys. Rev. Lett. 87 031101 (2001); M.Bonaldi et al. (2006)
avoid resonant bandwidh limit and thermal noise
contribution by the resonant transducer
2 - selective readout: only the motion corresponding to GW
sensitive normal modes is measured
M. Bonaldi et al. Phys. Rev. D 68 102004 (2003)
reduce overall thermal noise by rejecting the
contribution of not useful modes
Mode selection strategy
Geometrically based
mode selection
Large interrogation
regions
Bandwidth free from
acoustic modes not
sensitive to GW
Reject high
frequency resonant
modes which do not
carry any GW signal
Capacitive transducer
design
Also FFP optical scheme
2-D Quadrupolar filter:
X=X1 +X3 –X2 –X4
F. Marin et.al, Phys. Lett. A
309, 15 (2003)
Dual R&D : 3 main research topics
Current technology
DUAL requirements
Readout system:
• mechanical amplification
• displacement sensitivity
and wide sensing area
resonant
15 x
100 Hz BW
not resonant
10x
4 kHz BW
5x10 -20 m
5x10-22 (100x)
Test masses:
• underground operation
• high cross section (
vs2-3 )
not necessary
Al 5056
define requirements
Mo, SiC, Sapph. (50 x)
Detector design
• seismic noise control
external passive
embedded active
Readout system for DUAL:
mechanical amplification stage
• Broadband amplification up to 5.0 kHz
• Displacement gain factor about 10
• Negligible intrinsic thermal noise
• Compliance
H.J. Paik, proceedings First
AMALDI Conference (1995)
Leverage type
amplifier
Mechanical gain measurements
direct gain = y/x
Leverage
behavior
Frequency shift
Next step: measure the thermal noise
ANSYS Prediction by using Fluctuation
Dissipation Theorem
Leverage behavior:
scaling with gain
gain
T=300 K, Q=104, Al 7075, w0 =365 m
Progress towards a wide area optical readout
Usual cm-long cavities have small spot size ( 1mm)
higher order acoustic modes of the real system contribute to the noise
To average out the noise, we
need a spot size > 10 cm !!!!
M3
M4
Folded Fabry-Perot: FFP
F.Marin et al Phys. Lett. A 309, 15 (2003)
M1
D
effective increase
of spot size
M2
relative shot noise limited displacement sensitivity: constant
relative freq. noise due to Brownian noise
1/N
relative freq. noise due to rad pressure noise
 1/N2
+ spatial correlation effects
DUAL is based on
a deep revision of the resonant detector design
and
a R&D on readout systems
currently funded by: INFN, EGO, EC (ILIAS)
timeline
R&D + design : 2006 – 2008 (500 k€)
construction: 2009 – 2013 (15 M€- apply to “Ideas” in FP7)
FP7 new “Ideas” programme: at last fundamental science (all)…!!!
“Enhance the dynamism, creativity and excellence of European research at
the frontier of knowledge. <...> Open to proposals from individuals and groups
without constraint on size, composition or participation in the projects”
sensitivities at SQL (Dual & Advanced ifos)
Mo Dual 16.4 ton height 3.0m
SiC Dual 62.2 ton height 3.0m
Q/T=2x108 K-1
0.94m
2.9m
M. Bonaldi et al.
Phys. Rev. D 68 102004 (2003)
Antenna pattern: like 2 IFOs
colocated and rotated by 45°
gw sources in the kHz band for DUAL
(after first fully general relativistic simulations in 3-D with realistic
nuclear Equation Of State)
cosmological ( > 3 events/year: the “reference” signals for DUAL)
• merging of binary black-holes & vibrations of remnant
30+30 MO to 3+3 MO out to 100 Mpc (Pretorious PRL 2005 Camp)
• merging of binary neutron stars & vibrations of remnant
quasi periodic oscillations @ 3-4 kHz depending on EOS
formation of black-hole depending on EOS (Shibata PRL 2005)
both out to 100 Mpc (short GRBs are ns-ns mergers Nature 2005)
Virgo cluster ( many events/year ?)
• rotating stellar core collapses (supernovae)
“bar mode” instabilities @ 1 Khz out to 10 Mpc (Shibata PRD 2005)
galactic
• fast rotating isolated ns (ms pulsars) & accreting ns (LMXB)
continous emission, X-ray flares out to 10 kPc (Owen @ Amaldi6 2005)
“characteristic” gw strength hc=hn1/2 for gw of amplitude h lasting n cycles
all sources at best orientation (DUAL is fairly isotropic)
“assured rate” > 3 ev/y for ns-ns mergers
World-wide
gravitational wave network
GWIC http://gwic.gravity.psu.edu/ is helping with steps toward a
world-wide network including the large interferometers and
(more recently) bars. So far, bi-lateral exchanges
– GEO - LIGO continuing exchange & joint papers
– LIGO- TAMA exchange data for S2 data (60 days Spring 03).
Small joint working group to coordinate the joint analysis
– Virgo and LIGO exchanging environmental data, and Virgo
preparing for future gravitational data exchange
– AURIGA- LIGO exchanged 15 days of S3 data and are tuning
tools
– AURIGA+EXPLORER+NAUTILUS+VIRGO are developing
methods for joint analysis of bursts and stochastic
– EXPLORER+NAUTILUS and TAMA exchange data
– AURIGA and TAMA are preparing for data exchange