Transcript Optimisation of the Advanced Virgo Sensitivity for

Optimization of the Advanced
Virgo Sensitivity for
astrophysical Sources
Stefan Hild,
Giovanni Losurdo and Andreas Freise
Virgo week July 2008
Overview
 Motivation for sensitivity optimization
 Figures of merit for astrophysical sources
 Parameters used for optimization
 Optimized configurations
Stefan Hild
VIRGO week July 2008
Slide 2
Motivation for sensitivity
optimization
 Reference is the AdV
conceptual design.
Conceptual design: VIR-042A-07
 In the meantime several
things changed:
 Thermo-optic noise
 Ribbons (instead of
cylindrical) Fibers
 New code (Bench =>
GWINC)
Bench-GWINC note: VIR-055A-08
 So far optimization was
done only for Inspiral
sources
Stefan Hild
Conceptual design:
SR-transmittance = 0.04, SR-tuning 0.07
BNS = 121 Mpc and BBH = 856 Mpc
VIRGO week July 2008
Slide 3
What do we want to do ??
http://hubblesite.org/
http://numrel.aei.mpg.de/Visualisations/
Optimisation for as many different
astrophysical sources…
… and we want to scan the full parameter
space of the detector.
Stefan Hild
VIRGO week July 2008
Slide 4
Figure of merit: Inspiral
 Inspiral ranges for BHBH and NSNS
coalesence:
Symmetric
mass ratio
Frequency of last stable orbit
(BNS = 1570 Hz, BBH = 220 Hz)
Spectral weighting = f-7/3
Total mass
Detector sensitivity
[1] Damour, Iyer and Sathyaprakash, Phys. Rev. D 62, 084036 (2000).
[2] B. S. Sathyaprakash, “Two PN Chirps for injection into GEO”, GEO Internal Document
 Parameters usually used:




NS mass = 1.4 solar masses
BH mass = 10 solar masses
SNR = 8
Averaged sky location
Stefan Hild
VIRGO week July 2008
Slide 5
Figure of merit: Pulsars
 Tried to find a figure of merit for Pulsars. Used the summed
SNR of all detectable known pulsars.
 We start from ANTF Pulsar Catalogue (about 1500 radio
Pulsars), http://www.atnf.csiro.au/research/pulsar/psrcat/
Detector sensitivity
Integrated detector
sensitivity
Figure of merrit:
Summed SNR
Observation time
(we used 1yr)
Spin down upper limit
Detectibility
threshold
Factor 10.4 = all-sky, all polarisation average
95% upper limit for the Bayesian known pulsar
pipeline
Stefan Hild
VIRGO week July 2008
Slide 6
Figure of merit: Bursts
 Tried to find a figure of merit for Bursts.
 Used the sum of the inverse sensitivity:
No frequency cuts !
Width of the
frequency bin
 No spectral weighting.
Detector sensitivity
 in bad words: detector bandwidth / average sensitivity. Gives something
like 1025 sqrt(Hz)
Stefan Hild
VIRGO week July 2008
Slide 7
Starting point of the optimization
 Analysis based on Gravitational Wave Interferometer Noise
Calculator (GWINC)
 Using noise levels as presented in VIR-055A-08
(S.Hild and G.Losurdo: “Advanced Virgo design: Comparison of the Advanced Virgo sensitivity from
Bench 4 and GWINC (v1)”)
 Figures of merrit:




Binary ranges (provided by gwinc)
Pulsar (our own Matlab function)
Burst (our own Matlab function)
Stochastic (provided by gwinc)
 Multi-parameter analysis is done by Matlab-scripts querying
GWINC.
Stefan Hild
VIRGO week July 2008
Slide 8
Optimization Parameter 1:
Signal-Recycling (de)tuning
Advanced Virgo, Power = 125W, SR-transmittance = 4%
Radiation
pressure
noise
Shot noise
Opto-mechanical
resonance
Pure optical
resonance
 Frequency of pure optical resonance goes down with SR-tuning.
 Frequency of opto-mechanical resonanced goes up with SR-tuning
Stefan Hild
VIRGO week July 2008
Slide 9
Optimization Parameter 2:
Signal-Recycling mirror transmittance
Advanced Virgo, Power = 125W, SR-tuning = 0.07
 Resonances are less developed for larger SR transmittance.
Stefan Hild
VIRGO week July 2008
Slide 10
Optimization Parameter 3:
Laser-Input-Power
Advanced Virgo, SR-tuning=0.07, SR-transmittance = 4%


High frequency sensitivity improves with higher power (Shotnoise)
Low frequency sensitivity decreases with higher power (Radiation pressure noise)
Stefan Hild
VIRGO week July 2008
Slide 11
Limits of the Parameter
optimization
 Our optimisation is limited by Coating thermal noise and
Gravity Gradient noise.
Stefan Hild
VIRGO week July 2008
Slide 12
Example: Optimizing 2 Parameters
 Inspiral ranges for
free SR-tuning
and free SRMtransmittance, but
fixed Input power
NSNS-range
BHBH-range
Stefan Hild
VIRGO week July 2008
Slide 13
Example: Optimizing 2 Parameters
Parameters
for maximum
Maximum
NSNS-range
Parameters
for maximum
Maximum
BHBH-range
 Different source
usually have their
maxima at different
operation points.
 It is impossible to
get the maximum for
BNS AND BBH both
at the same time !
Stefan Hild
VIRGO week July 2008
Slide 14
Comparison of Baseline and Single
source type optimum
 The crossing point
of the black lines
indicate the SRoperation point
from the conceptual design.
 The parameters of
the conceptual design were chosen
to give a compromise between BNS
and BBH range.
Conceptual design:
SR-transmittance = 0.04,
SR-tuning 0.07
BNS = 121 Mpc and BBH = 856 Mpc
Stefan Hild
VIRGO week July 2008
Slide 15
Example: Optimizing 3 Parameter
for Inspiral range
 Scanning 3
parameter at
the same time:
 SR-tuning
 SR-trans
 Input Power
 Using a video
to display 4th
dimension.
Stefan Hild
VIRGO week July 2008
Slide 16
Example: Inspiral ranges vs Power
Already very low
power (< initial
Virgo) gives
maximum range BBH
sensitivity and 80%
of the maximum BNS
range.
Please note:
Each dot may represent
Different SR-parameter.
Stefan Hild
VIRGO week July 2008
Slide 17
2-Step approach for
Advanced Virgo construction

The conceptual design
proposes:
1. Start AdV without SignalRecycling, but with high
power.
2. At a later stage install
Signal-Recycling.

We should investigate if it
would not be easier to go
for a different approach:
1. Start AdV with SignalRecycling, but with only 5W
(no TCS required)
2. At a later stage increase
the power gradually
Stefan Hild
Please note:
Each dot may represent
Different SR-parameter.
VIRGO week July 2008
Slide 18
Maximum we can achieve
 We performed
identical 3-parameter optimization
for Burst, Stochastic
and Pulsar sources.
 Traces show the
maximum value
achievable vs input
power. All traces are
normalized to their
maximum value.
Please note:
Each dot may represent
Different SR-parameter.
 BNS and Burst have their maximum at high power.
 BBH, Pulsars and Stochastic have their maximum at low power (3-5W).
Stefan Hild
VIRGO week July 2008
Slide 19
Optimal configurations
Curves show the optimal sensitivity for a single source type.
Stefan Hild
VIRGO week July 2008
Slide 20
Optimal configurations
Optimal REFERNCE Scenarios:
Stefan Hild
VIRGO week July 2008
Slide 21
Optimal configurations
Optimal REFERNCE Scenarios:
Using SR-parameters from Conceptual design with GWINC (new noise levels):
Stefan Hild
VIRGO week July 2008
Slide 22
Heavy mirror option (63kg)
PRELIMINARY: non comprehensive Analysis !!!
42kg:
BNS= 152 Mpc
BBH= 747 Mpc
63kg:
BNS= 161 Mpc
BBH= 961 Mpc
 Used the reference BNS scenario (pink) and only changed the
mirror weight to 63 kg (green dashed).
 High frequency performance unchanged, but significant
improvement below 50 Hz.
Stefan Hild
VIRGO week July 2008
Slide 23
Summary
 Recent results changed the noise boundaries of Advanced Virgo
=> new sensitivity optimization required.
 Performed a detailed 3-parameter Optimization for 5 figures of
merit (BNS, BBH, Burst, Pulsar, Stochastic).
 Each source requires different parameters for optimal detection:
 Can get optimal sensitivity only for a single source type.
 Can get not optimal, but moderate sensitivity for more than one
source type
 We have now 5 optimized reference scenarios (optimal
parameter sets + values of performance for each astrophysical
source type).
 Low power scenarios seem (at least for the beginning of
Advanced Virgo) to be promising.
Stefan Hild
VIRGO week July 2008
Slide 24
Outlook
Technical point of view:
 Optimization is an continuous process … (until the design is fixed)
 Include cavity finesse as 4th parameter into future optimization.
 Proper modeling of suspension thermal noise (volunteers needed)
 Investigate the effect of 62kg mirror option
Scientific point of view:
 Interaction with data analysis groups (Virgo and LSC):
 How to make the trade-off between the different source-types?
Can there be a sensible multi-source-type figure of merit?
 Define the Science case (includes final figure of merit)
Stefan Hild
VIRGO week July 2008
Slide 25
More details …
… will soon be
available in:
Stefan Hild
VIRGO week July 2008
Slide 26
Acknowledgements
 We wish to thank the LIGO Scientific Collaboration for
making the GWINC code
 available for public use.
 We are also very grateful to Matthew Pittkin (Glasgow) and
Alberto Vecchio
 (Birmingham) for their help defining the figure of merit for
pulsar sources.
END
Stefan Hild
VIRGO week July 2008
Slide 27
Example: Optimising 3 Parameter
for Burst figure of merit
 Scanning 3
parameter at
the same time:
 SR-tuning
 SR-trans
 Input Power
 Using a video
to display 4th
dimension.
Stefan Hild
VIRGO week July 2008
Slide 28
Example: Optimising 3 Parameter
for the Pulsar figure of merit
 Scanning 3
parameter at
the same time:
 SR-tuning
 SR-trans
 Input Power
 Using a video
to display 4th
dimension.
Stefan Hild
VIRGO week July 2008
Slide 29
Figure of merrit: Stochastic
 Omega is provided as standard output of
GWinc
Stefan Hild
VIRGO week July 2008
Slide 30
Example: Optimising 3 Parameter
for 1/Omega(stochastic)
 Scanning 3
parameter at
the same time:
 SR-tuning
 SR-trans
 Input Power
 Using a video
to display 4th
dimension.
Stefan Hild
VIRGO week July 2008
Slide 31
Limited Parameter space
 After we fixed the
design of Advanced
Virgo, there will
probably some
restrictions about
accessible range of
SR-parameter.
 For instance: for very
small SR detunings the
errorsignals “vanish”.
S Hild et al 2007 Class. Quantum Grav. 24 1513-1523
Stefan Hild
VIRGO week July 2008
Slide 32