Download 3 rd generation

Design study
for 3rd generation interferometers
Work Package 1
Site Identification
Jo van den Brand
e-mail: [email protected]
Third generation detector
 Two order of magnitude compared to
initial Virgo
 Underground site
 Multiple interferometers:
–
3 Interferometers; triangular
configuration?
–
10 km long
–
2 polarization + redundancy
 Design study part of ILIAS & FP7
 Construction: 2010-16 ?
LISA
Rüdiger, ‘85
Scientific
Production: fundamental physics in the early universe
- Inflation, phasefor
transitions,
topological defects
justification
3rd generation
ITF
- String-inspired cosmology, brane-world scenarios
Spectrum slope, peaks give masses of key particles & energies
of transitions
A TeV phase transition would have left radiation in 3G band
Primordial
gravitational waves
LISA
Introduction
Features of 3rd generation ITF
•
Sensitivity below 10-24 m/sqrt(Hz)
•
Ultra-low frequency cut-off
•
Vibration isolation
•
Sensitive in range 0.1 – 10 Hz
•
Multiple sites for signal correlation
•
Advanced optical schemes (squeezed light)
•
Cryogenic optics
•
Underground sites
•
LISA
10 kilometer arms
Ultra Low Frequency: 1Hz
1st - 2nd generation
10 Hz cutoff
3rd generation
1 Hz cutoff
One more decade
at low frequency
LISA
Isolation requirements
Required isolation @1 Hz: at least 1010 with ground noise.



LISA
Ultra soft vibration isolation
–
Long pendulums (50, 100 m)
–
Very good thermal stabilization
Active platforms
–
Very low noise sensors
–
Very good thermal stabilization
–
Very low tilt noise
Very quiet site
Site identification process
Even pressure fluctuations due to weather
are a relevant source of gravity gradient
noise [11].
acceleration ( g / sqrt ( Hz ) )
10
10
10
10
10
10
component 2
component 1
-4
-5
-6
-7
-8
-9
10
-5
-4
10
10
frequency ( Hz )
Seismic measurements at LNGS
LISA
-3
10
-2
V. N. Rudenko, A. V.
Serdobolski, K. Tsubono,
“Atmospheric gravity
perturbations measured by a
ground-based interferometer
with suspended mirrors”,
Class. And Quant. Grav., vol.
20, pp. 317-329.
LIGO Site selection criteria
LISA
LIGO Site evaluation criteria
LISA
LIGO Site evaluation criteria
LISA
Seismic noise attenuation
LISA
Not only seismic noise…
 Direct action of wind on buildings
 Strong correlation between mirror
motion and wind speed at f < 0.1 Hz
 Detector operation more difficult in
windy days, duty cycle affected
 Even more difficult in the future, with
high finesse cavities
LISA
Underground interferometers
 LISM: 20 m Fabry-Perot interferometer, R&D for LCGT, moved
from Mitaka (ground based) to Kamioka (underground)
 Seismic noise much lower:
LISA
102 overall gain
103 at 4 Hz
Interferometer operation becomes much
easier underground.
Noise reduced by orders of magnitude
Displacement spectrum m/RHz
S.Kawamura, ‘02
LISA
LISM at Mitaka
LISM at Kamioka
limit by isolation system
Hz
Large-scale Cryogenic Gravitational-wave Telescope: LCGT
LISA
CLIO – Prototype for LCGT
LISA
LISM in Kamioka
LISA
ILC, NLC, Tesla, VLHC, Muon Source – Site requirements
LISA
ILC, NLC, Tesla, VLHC, Muon Source – Site requirements
LISA
Isolation shortcircuit
Newtonian noise
h ( f )  const. 
G0
 x0 ( f )
H( f )
SEISMIC NOISE
Figure: M.Lorenzini
LISA
Seismically generated Newtonian noise
LISA
Newtonian noise estimate
Cella-Cuoco, 98
LISA
NN reduction
Courtesy: G.Cella
Surface waves
Compression waves
 Surface waves give the main contribution to newtonian noise
 Surface movement dominates the bulk compression effect
Surface waves die
exponentially with depth:
GO UNDERGROUND!
LISA
NN reduction in caves
102 less seismic noise x 104 geometrical reduction
106 overall reduction (far from surface)
Reduction
factor
(Compression waves not included)
Spherical Cave
G.Cella
NN reduction of 104 @5 Hz
with a 20 m radius cave
5 Hz
10 Hz
20 Hz
40 Hz
Cave radius [m]
LISA
1st generation
(a) 3 Generation
nd
2 generation
(b) LCGT
(c) advanced LIGO
rd
3 generation
(d) advanced Virgo
-19
10
rd
-20
10
h(f) [1/sqrt(Hz)]
-21
10
(g)
(e) LIGO
(f) Virgo
(g) GEO600
(f)
-22
10
(e)
-23
10
(a)
(d)
(b)
Ground
surface (c)
-24
10
Underground
-25
10
1
10
100
Frequency [Hz]
LISA
1000
10000
NN from compression waves
 In a spherical cave NN is reduced as 1/R3
MAKE LARGE CAVERN
 Beam direction is more important.
ELLIPSOIDAL?
Credit: R. De Salvo
LISA
A possible design
Upper experimental hall
50-100 m well to accomodate
long suspension for
low frequency goal
Ellipsoidal/spherical cave for
newtonian noise reduction
10 km tunnel
LISA
Credit: R.De Salvo
Site identification process
Gran Sasso
Salt mines
LISA
Complementarity with LIGO, VIRGO and LISA
Vast range in wavelength
(8 orders of magnitude)
Rotating
Neutron Stars
LISA
3rd ITF
LIGO/VIRGO
Frequency [Hz]
LISA
Summary


LISA
Expected features of 3rd generation ITF
–
Triangular configuration
–
Advanced optical schemes
–
Low-frequency isolation and suspension
–
Cryogenic optics
–
Multiple underground sites
Design study
–
Develop preliminary ideas
–
Define site identification process