Design study
for 3rd generation interferometers Work Package 1
Site Identification
Jo van den Brand
e-mail: jo@nikhef.nl
LISA
Third generation detector
Rüdiger, ‘85
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
Scientific justification for 3rd generation ITF
Primordial gravitational waves
Production: fundamental physics in the early universe - Inflation, phase transitions, topological defects
- 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
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
• 10 kilometer arms
LISA
Ultra Low Frequency: 1Hz
3rd generation 1 Hz cutoff 1st - 2nd generation
10 Hz cutoff
One more decade at low frequency
LISA
Isolation requirements
Required isolation @1 Hz: at least 1010 with ground noise.
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
LISA
Site identification process
Even pressure fluctuations due to weather are a relevant source of gravity gradient noise [11].
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.
10-5 10-4 10-3 10-2
10-9 10-8 10-7 10-6 10-5 10-4
frequency ( Hz )
acceleration ( g / sqrt ( Hz ) )
component 2 component 1
Seismic measurements at LNGS
LISA
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: 102 overall gain 103 at 4 Hz
LISA
LISM at Mitaka LISM at Kamioka
limit by isolation system Interferometer operation becomes much
easier underground.
Noise reduced by orders of magnitude
S.Kawamura, ‘02
Hz
Displacement spectrum m/RHz
LISA
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
0 0
( ) . ( )
( )
h f const G x f H f
Figure: M.Lorenzini
SEISMIC NOISE
LISA
Seismically generated Newtonian noise
LISA
Newtonian noise estimate
Cella-Cuoco, 98
LISA
NN reduction
Surface waves give the main contribution to newtonian noise
Surface movement dominates the bulk compression effect
Surface waves
Compression waves
Courtesy: G.Cella
Surface waves die exponentially with depth:
GO UNDERGROUND!
LISA
NN reduction in caves
Reduction factor
Cave radius [m]
Spherical Cave G.Cella
5 Hz 10 Hz 20 Hz 40 Hz
NN reduction of 104 @5 Hz with a 20 m radius cave
106 overall reduction (far from surface) (Compression waves not included)
102 less seismic noise x 104 geometrical reduction
LISA
1 10 100 1000 10000
10-25 10-24 10-23 10-22 10-21 10-20 10-19
h(f) [1/sqrt(Hz)]
Frequency [Hz]
(a) 3rd Generation (b) LCGT
(c) advanced LIGO (d) advanced Virgo (e) LIGO
(f) Virgo (g) GEO600
(a)
(b) (c)
(d) (e)
(f) (g)
1st generation 2nd generation 3rd generation
New tonia
n noise
Ground surface Underground
LISA
NN from compression waves
In a spherical cave NN is reduced as 1/R3
Beam direction is more important.
Credit: R. De Salvo
ELLIPSOIDAL?
MAKE LARGE CAVERN
LISA
A possible design
Upper experimental hall
Credit: R.De Salvo
50-100 m well to accomodate long suspension for
low frequency goal
Ellipsoidal/spherical cave for newtonian noise reduction 10 km tunnel
LISA
Site identification process
Gran Sasso
Salt mines
LISA
Complementarity with LIGO, VIRGO and LISA
Rotating Neutron Stars
Vast range in wavelength (8 orders of magnitude)
LIGO/VIRGO LISA
Frequency [Hz]
3rd ITF
LISA
Summary
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
