STREGA & ET - 4th ILIAS-GW general meeting 1 STREGA legacy for ET Michele Punturo INFN Perugia

STREGA & ET - 4th ILIAS-GW general meeting 2 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 3 rd 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 3 ET Einstein GW Telescope –Design study submitted to the European Commission under the 7 th Framework Programme Project in the negotiation phase –Conceptual design of a 3 rd 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 4 Sensitivity evolution Thermal Noise Seismic Shot Noise STREGA contribution

STREGA & ET - 4th ILIAS-GW general meeting 5 Reduction of the thermal noise Reduction of the suspension and bulk thermal noise –New materials at cryogenic temperature Jena University research on CaF2 substrates – Nawrodt.ppthttp:// 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 6 Advantages of the cryo-suspensions Reduction of the Brownian thermal noise – ~T Reduction of the thermo-elastic noise – ~  T 2 –Some “magic” behavior of special material S.Reid et al. M.Alshourbagy et al.

STREGA & ET - 4th ILIAS-GW general meeting 7 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 8 … 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.

9 Coatings Coating thermal noise will be dominant in the 2 nd generation GW detectors Groups participating to STREGA are studying the possible scenario in a 3 rd generation detector Coating loss measured in a single layer doped tantala coating applied to Si cantilever substrate Cobalt doped tantala (LMA production) on FS substrate (F. Travasso et al.)

STREGA & ET - 4th ILIAS-GW general meeting 10 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 / /TNworkshop/burmeister_tnws_ego06.pdf

11 Studies in Glasgow on silicate bonding of silica in relation to the Advanced generation and future GW detectors Bond mechanical & thermal properties Bond structural properties Settling time experiments S. Reid et al., PLA (2006) Activation energy: Ea = eV per molecule 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 TEM AFM (81±4) nm 7.9 GPa  measurements Firenze/Glasgow

STREGA & ET - 4th ILIAS-GW general meeting 12 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 13 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