STREGA legacy for ET
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Transcript of STREGA legacy for ET
STREGA & ET - 4th ILIAS-GW general meeting
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STREGA legacy for ET
Michele Punturo
INFN Perugia
STREGA & ET - 4th ILIAS-GW general meeting
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STREGA target• The STREGA mission is the development of
the technologies needed to reduce the thermal noise in the GW detectors by a factor 10 respect to the advanced detectors design– The target is the 3rd generation detectors
• STREGA is born as European (FP6) support and glue for the R&D activities already (and independently) started by the different GW research group in Europe
STREGA & ET - 4th ILIAS-GW general meeting
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ET
• Einstein GW Telescope– Design study submitted to the European Commission
under the 7th Framework Programme• Project in the negotiation phase
– Conceptual design of a 3rd generation GW interferometric detector
• Fully dedicated session tomorrow• Cryogenic suspension is one of the keywords of the possible
design of ET• No R&D activity expected inside the ET DS projects• Obviously the outcomes of STREGA are of fundamental
importance for the ET design phase
STREGA & ET - 4th ILIAS-GW general meeting
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Sensitivity evolution
1st generation2nd generation3rd generation ?
1 10 100 1000 1000010
-25
10-24
10-23
10-22
10-21
10-20
10-19
Thermal Noise
Seismic
Shot Noise
STREGA contribution
STREGA & ET - 4th ILIAS-GW general meeting
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Reduction of the thermal noise
• Reduction of the suspension and bulk thermal noise– New materials at cryogenic temperature
• Jena University research on CaF2 substrates– http://www.ego-gw.it/ILIAS-GW/documents/London_Talks/2nd_day/Jena-Nawrodt
.ppt
• Glasgow University research on Si substrates and blades
• INFN (Fi, Pg, Pi) measurements on Si fibres
STREGA & ET - 4th ILIAS-GW general meeting
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Advantages of the cryo-suspensions• Reduction of the Brownian thermal
noise– <X2>~T
• Reduction of the thermo-elastic noise– <X2>~T2
– Some “magic” behavior of special material
S.Reid et al.
M.Alshourbagy et al.
STREGA & ET - 4th ILIAS-GW general meeting
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Problems of a Cryo-Suspension• A GW detector has many noise constrain that make very
difficult the realization of a cryo-suspension• STREGA started the first studies of the compatibility of the
cryo-technologies with a GW detector suspension system– Low noise cryo-cooler (Roma 1)
STREGA & ET - 4th ILIAS-GW general meeting
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… problems of a cryo-suspension• Realization of a full Si Payload• Extraction of the large amount of heat deposited by the
high power laser light circulating in the FP cavities – EGO R&D activity with STREGA collaboration
• EGO, INFN Pi, et al.
• http://www.ligo.caltech.edu/docs/G/G050529-00/G050529-00.ppt
90 50 100 150 200 250 300
1.0x10-5
1.5x10-5
2.0x10-5
2.5x10-5
3.0x10-5
3.5x10-5 4th mode undoped Ta
2O
5
4th mode, TiO2 doped Ta
2O
5
Me
cha
nic
al l
oss
of c
oa
ted
sili
con
ca
ntil
eve
r
Temperature (K)
Coatings• Coating thermal noise will be dominant in the 2nd
generation GW detectors• Groups participating to STREGA are studying the possible
scenario in a 3rd generation detector
•Coating loss measured in a single layer doped tantala coating applied to Si cantilever substrate
0 50 100 150 200 250 300
1E-5
1E-4
1E-3
0.01
Temperature [k]
Uncoated slab Coated slab B Coating
Cobalt doped tantala (LMA production) on FS substrate(F. Travasso et al.)
STREGA & ET - 4th ILIAS-GW general meeting
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Escaping from the coating problem• Problems due to high power laser and transmittive
optics• Reduce the coating thickness
– High reflectivity grating waveguide coatings
• Use a different approach:– Full reflective optics and grating coatings
http://wwwcascina.virgo.infn.it/collmeetings/presentations/2006/2006-10/TNworkshop/burmeister_tnws_ego06.pdf
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Studies in Glasgow on silicate bonding of silica in relationto the Advanced generation and future GW detectors
Bond mechanical &thermal properties
Bond structuralproperties
Settling time
experiments
S. Reid et al.,PLA 363 341-345 (2006)
Activation energy:Ea = 0.545 eV permolecule of OH−
Above plot showing settling time as a function of
temperature for silica-silica bonds
Above plot showing two bonded silica cylinders, studied before and after
silicate bonding.
Experiments suggest that the level of loss associated with
silicate bonding may lie:bond ~ (0.3→1.2)×10-1
SEM SEM
TEM
TEM
AFM
(81±4) nm
7.9 GPa
measurements Firenze/Glasgow
STREGA & ET - 4th ILIAS-GW general meeting
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Direct thermal noise measurement• An interferometer devoted to direct measurement of
thermal noise in fused silica suspensions and composite structures built using hydroxy-catalysis (silicate) bonding has been realized in Glasgow– Mike Plissi e al.
• Excess noise from the reference cavity is currently limiting the thermal noise measurement• Work in progress
STREGA & ET - 4th ILIAS-GW general meeting
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STREGA legacy for ET
• The WITCH is not dead, hence it is too early to talk about legacy– ET is a conceptual design study
• Any R&D budget is included in ET design study, but in the proposal it is stated that ET will benefit of the R&D activities already active in Europe
– STREGA must act as the solutions supplier for ET
– STREGA people must enter in the ET Science Team
• Discussion after this session