lisbon, 8 january 20081 research and development for gravitational wave detectors raffaele flaminio...
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Lisbon, 8 January 2008 1
Research and Developmentfor Gravitational Wave Detectors
Raffaele Flaminio
CNRS/LMA Lyon
Lisbon, 8 January 2008 2
Ground-based GW detectors
Focus on ground based laser interferometers Most sensitive detectors in operation LIGO, Virgo, GEO, TAMA, Some of the following applies to other kind of detectors (e.g. resonant detectors)
Lisbon, 8 January 2008 3
Present reach
Gravitational collapses in the galaxy (or nearby ones) Test upper limits of known galactic pulsars (and look for unknown ones) Search for coalescing neutron stars up to a max distance of ~ 30 Mpc Search for merger of binary black holes to a max distance of ~150 Mpc
Lisbon, 8 January 2008 4
Toward GW astronomy
Present detectors will test upper limits
Even in the optimistic case rate too low to start GW astronomy
Need to improve thesensitivity
Increase the sensitivity by 10 increase the probed volume by 1000
Plans to improve thepresent detectors
Lisbon, 8 January 2008 5
GW roadmap: time scale
E.T.
LISA
LIGO
GEO
Virgo
´22´21´20´19´18´17´16´15´14´13´12´11´10´09´08´07´06
E.T.
LISA
LIGO
GEO
Virgo
´22´21´20´19´18´17´16´15´14´13´12´11´10´09´08´07´06
Virgo+
LIGO+
Advanced Virgo
GEO HF
Advanced LIGO
DS PCP Construction Commissioning
HanfordHanford
LivingstonLivingston
Launch Transfer data
data
ET: Einstein Telescope Design study selected by the EU within FP7
Lisbon, 8 January 2008 6
GW roadmap: sensitivity scale
Ad LIGO/Virgo NB
1 10 100 1000 1000010-25
10-24
10-23
10-22
10-21
10-20
10-19
h(f) [1
/sqrt(H
z)]
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)
Credit: M.Punturo
LIGO 2005 AURIGA 2005
Advanced LIGO/Virgo (2014)
Virgo Design
GEO-HF2009
Virgo+ 2009
Einstein GW Telescope
DUAL Mo(Quantum Limit)
Lisbon, 8 January 2008 7
1 10 100 1000 1000010-23
10-22
10-21
10-20
10-19
10-18
(a) Virgo Nominal sensitivity (b) Seismic noise (c) Pendulum thermal noise (d) Mirror thermal noise (e) Shot Noise
h(f) [1/
sqrt(H
z)]
Frequency [Hz]
(a)
(b)
(c)
(d)
(e)
Present limitations ….
• Shot noise- Depends on quantum nature of light- Decreases when more photons are used- Depends on the optical configuration adopted
Lisbon, 8 January 2008 8
…. and possible improvements
• Increase power stored in the interferometer- increase laser power- decrease optical losses
• But pay attention to:
1) Mirrors heating and thermal lensing- better thermal compensation- decrease light absorption
2) Radiation pressure noise - increase mirror mass- optimize optical configuration
signal recycling- use non classical light
light squeezing/quantum optics
3) Non-linear coupling between the light fields and the mirror suspensions
1 10 100 1000 1000010-23
10-22
10-21
10-20
10-19
10-18
(a) Virgo Nominal sensitivity (b) Seismic noise (c) Pendulum thermal noise (d) Mirror thermal noise (e) Shot Noise
h(f) [1/
sqrt(H
z)]
Frequency [Hz]
(a)
(b)
(c)
(d)
(e)
Lisbon, 8 January 2008 9
Present limitations …
1 10 100 1000 1000010-23
10-22
10-21
10-20
10-19
10-18
(a) Virgo Nominal sensitivity (b) Seismic noise (c) Pendulum thermal noise (d) Mirror thermal noise (e) Shot Noise
h(f) [1/
sqrt(H
z)]
Frequency [Hz]
(a)
(b)
(c)
(d)
(e)
• Mirror thermal noise- brownian motion- due to temperature ….- …plus any source of friction in the mirror
Lisbon, 8 January 2008 10
… and possible improvements
1 10 100 1000 1000010-23
10-22
10-21
10-20
10-19
10-18
(a) Virgo Nominal sensitivity (b) Seismic noise (c) Pendulum thermal noise (d) Mirror thermal noise (e) Shot Noise
h(f) [1/
sqrt(H
z)]
Frequency [Hz]
(a)
(b)
(c)
(d)
(e)
• Reduce friction in the mirrors
• Friction in the coating- Main source of friction today- Multi-layers SiO2/Ta2O5 used today- Ta2O5 is the lossy material
look for new materialsmaterials science
- SiO2 layer lossier than raw materialimprove deposition process
• Friction in the substrate- Best material so far: silica- Avoid attaching anything to preserve mechanical quality- Move to electrostatic actuators avoiding magnets attached to the mirror
Lisbon, 8 January 2008 11
Present limitations …
1 10 100 1000 1000010-23
10-22
10-21
10-20
10-19
10-18
(a) Virgo Nominal sensitivity (b) Seismic noise (c) Pendulum thermal noise (d) Mirror thermal noise (e) Shot Noise
h(f) [1/
sqrt(H
z)]
Frequency [Hz]
(a)
(b)
(c)
(d)
(e)
• Pendulum thermal noise- same kind of brownian motion- due to temperature …- … plus friction in the suspension wires- or friction between the wires and the mirror
Lisbon, 8 January 2008 12
… and possible improvements
1 10 100 1000 1000010-23
10-22
10-21
10-20
10-19
10-18
(a) Virgo Nominal sensitivity (b) Seismic noise (c) Pendulum thermal noise (d) Mirror thermal noise (e) Shot Noise
h(f) [1/
sqrt(H
z)]
Frequency [Hz]
(a)
(b)
(c)
(d)
(e)
• Decrease pendulum friction- better suspensions wires (new materials)- better wire clamping- monolithic suspensions- fused silica fibers- silicate bonding
Lisbon, 8 January 2008 13
Further reduction of thermal noise
• Thermal noise decrease as √T- go to low temperatures- friction vs temperature?- depends on materials (materials science)- look for optical materials with good mechanical properties at low temperature (silica not a good choice)
• Thermal lensing- due to laser power deposited in the mirror- higher mirror thermal conductivity
lower thermal lensing- higher wires thermal conductivity
heat extraction more efficient
• Silicon- silicon a good candidate- silicate bonding behavior at low T?- thermal conductivity across bonding?- on-going R&D
Si
Lisbon, 8 January 2008 14
Cryogenics for GW detectors
• Need to cool large masses• Vibration free cryogenics• Soft thermal links• Points of contact with underground detectors for rare events search
COLD FINGER
Lisbon, 8 January 2008 15
ILIAS: the STREGA joint research activity
Strong component within the ILIAS project Goal: thermal noise reduction for GW detectors
All the european groups working in thermal noise reduction involved
INFN (Ge, Fi, Fr, Le, Pd, Pi, Pg, Rm1, Rm2), CNRS (LKB, ESPCI,LMA), Univ Glasgow, CNR (Trento), Leiden, Jena, …
All collaborations: Virgo, GEO, ROG, Auriga, MiniGRAIL Ingredients:
Cryogenics suspensions Cryogenics mirrors Materials Thermo-elastic studies
A key role for starting the ET design study A lot more to do But ILIAS ends in 2009 and support available
within ILIAS-NEXT very much reduced
Lisbon, 8 January 2008 16
Present limitations: seismic noise
1 10 100 1000 1000010-23
10-22
10-21
10-20
10-19
10-18
(a) Virgo Nominal sensitivity (b) Seismic noise (c) Pendulum thermal noise (d) Mirror thermal noise (e) Shot Noise
h(f) [1/
sqrt(H
z)]
Frequency [Hz]
(a)
(b)
(c)
(d)
(e)
• Seismic noise– residual transmission of seismic motion through the suspensions system– 'relatively large' motion at very low frequency
→ need for a control system→ control system noise
- sensitivity to weather conditions
Lisbon, 8 January 2008 17
Seismic noise: possible improvements
Better active isolation More sensitive accelerometers Very low-frequency tilt-meters Gryo-lasers
Softer springs ?
1 10 100 1000 1000010-23
10-22
10-21
10-20
10-19
10-18
(a) Virgo Nominal sensitivity (b) Seismic noise (c) Pendulum thermal noise (d) Mirror thermal noise (e) Shot Noise
h(f) [1/
sqrt(H
z)]
Frequency [Hz]
(a)
(b)
(c)
(d)
(e)
Lisbon, 8 January 2008 18
Forthcoming limitations
Gravity gradient noise Limitation to existing infrastructure Will limit advanced detectors
Figure: M.Lorenzini
1 10 100 1000 1000010-23
10-22
10-21
10-20
10-19
10-18
(a) Virgo Nominal sensitivity (b) Seismic noise (c) Pendulum thermal noise (d) Mirror thermal noise (e) Shot Noise
h(f) [1/
sqrt(H
z)]
Frequency [Hz]
(a)
(b)
(c)
(d)
(e)
Lisbon, 8 January 2008 19
Improvement: go underground !
LISM: 20 m Fabry-Perot interferometer, R&D for LCGT, moved from Mitaka (ground based) to Kamioka (underground) Seismic noise much lower Operation easier
102 overall gain103 at 4 Hz
Lisbon, 8 January 2008 20
Further improvements: spherical cavern
Reductionfactor
Spherical CavernG.Cella
5 Hz10 Hz20 Hz40 Hz
NN reduction of 104 @5 Hzwith a 20 m radius cave
106 overall reduction (far from surface)
(Compression waves not included)
102 less seismic noise x 104 geometrical reduction
Lisbon, 8 January 2008 21
Combination of improvements
Upper experimental hall
Credit: R.De Salvo
50-100 m tower to accommodatelong suspension for low frequency goal
Ellipsoidal/spherical cave fornewtonian noise reduction
10 km tunnel
Lisbon, 8 January 2008 22
The ET concept Need to improve sensitivity at low frequencies
More physics is there Present facilities limited by environmental disturbances
Seismic noise Gravity gradients
ET Einstein Telescope Concepts
Underground» Less seismic noise» No wind» Temperature stability
Cryogenic 30 km beam tube 100 m suspensions Different geometry
» Triangle?
Rüdiger, ‘85
Lisbon, 8 January 2008 23
Conclusion
Present detectors are testing upper limits of GW predictions A few upgrades ready to be implemented (Virgo+, Enhanced LIGO)
Advanced detectors should see several events/month Sensitivity will profit from on-going R&D (e.g. coating thermal noise) Engineering needed (e.g. monolithic suspensions)
ET Einstein Telescope Design study should start soon R&D activity started within FP6 (STREGA) Should continue within FP7 More investment needed Points of contact with other fields of astroparticle physics
» Cryogenics» Vibration isolation» Underground operation
GW will participate to ILIAS-NEXT GW networking Networking with underground labs A few small R&D activities But more investment will be needed