Virgo-Material “macro” group M.Punturo

VIRGO-MAT2 VIRGO-MAT components Virgo-MAT is composed by three INFN groups –Firenze/Urbino M.Lorenzini, G.Losurdo, F. Martelli, F. Piergiovanni, F.Vetrano –Perugia P.Amico, C.Bernardini, L.Gammaitoni, F.Marchesoni, M.Punturo, F.Travasso, H.Vocca –Pisa M. Al-Shourbagy, S.Bigotta, A.Di Lieto, L.Predolin, A.Toncelli, M.Tonelli

VIRGO-MAT3 M1 Activities Advanced materials for mirror substrates –Michelson-Morley ITF in Perugia (next slide) –Mechanical characterization of the VIRGO Mirror substrates in Perugia and in the site ( Vir-Not-Per ) –Measurement of substrates for future ITF CaF2 substrate ( P. Amico et al, Rev.Sci.Instr. 73 (2002), ) Monocrystalline Si substrate “Virgo like”

4 M1:Large substrate measurement facility PZT PHD Vacuum -6 mbar x HV Locking electronics Read-out electronics Pusher

VIRGO-MAT5 M2 Activities Advanced materials and techniques for resonant detectors “Support” role: –Long history in measurement of low losses materials –Several infrastructures to measure thermo-mechanical properties of fibers in Perugia and Firenze, at room temperature and at low temperature (M5 task) Two “clamp free” loss angle measurement facilities One cryostat under completion

VIRGO-MAT6 M4 activities Development of low loss dielectric coatings for advanced detectors Fabry-Perot facility to measure directly thermal noise in thin membranes (see P.Amico report in T1 task) –Coating effect of thin membranes and small mirrors Facility to measure the Q of coated membranes realized under the EGO R&D program and delivered to Lyon

VIRGO-MAT7 M5 activities R&D activities for next generation ITF suspension Realization of mono-crystalline fibers that could improve the suspension thermal noise at room temperature and at low temperature –Best candidate: silicon fibers/ribbons –Exotic cooling technique: anti-stokes fluorescence

VIRGO-MAT8 Micro-Pulling-Down furnace in Pisa

VIRGO-MAT9 Produced mono-crystalline fibers 10/03/04 L  4 cm 12/03/04 L  13 cm 16/03/04 L  13 cm 18/03/04 L  17 cm 22/03/04 L  11 cm 25/03/04 L  21 cm

VIRGO-MAT10 Evaluation of the thermo-elastic contribution 300K 200K 300K 300K 200K 200K Thermoelastic loss angle

VIRGO-MAT11 Particular behavior of Si Crystalline Silicon

VIRGO-MAT12 Magic temperature 100K 117K 100K

VIRGO-MAT13 How to cool locally? It is important to cool locally the flexural point –Cold finger Easy to implement Commercial Liquid N2 is enough Noisy –Anti-stokes fluorescence High difficulties Low (?) efficiency And the noise?

VIRGO-MAT14 Anti-Stokes Cooling To evaluate the temperature distribution along the wire, we must take in account the thermal conduction/dissipation processes Laser T0=300K Si fiber 200  m diameter 700 mm height SiO 2 clamp, 35mm diameter

VIRGO-MAT15 Thermal conduction mechanisms Usual thermo-dynamical sign definition Anti-stokes cooling Laser T0=300K  0 is the temperature where the efficiency goes to zero For ZPLAN we have M.T.Murtagh, J.of Non-Crystalline solids 253 (1999) 50-57

VIRGO-MAT16 Thermal conduction Conduction law qkqk qkqk For each small section we can discretize: IR Radiation

VIRGO-MAT17 Differential Equation The differential equation is, where T=T(t,y) It is a “bordello” then, I adopted a numerical solution

VIRGO-MAT18 Temperature distribution It is not linear and the noise evaluation must take in account it

VIRGO-MAT19 Noise contribution due to optical cooling Fundamentally, the optical cooling can introduce a length noise in the interferometer through the cooling laser power fluctuation coupled with the fiber length The laser power fluctuation causes a wire length fluctuation filtered by –Thermal conduction process –Vertical spring behavior of the suspension wire Laser power fluctuation Optical cooling efficiency Subtracted power fluctuation

VIRGO-MAT20 … noise evaluation 2 The integral length fluctuation is given by: Where T f is the temperature of the (cooled) flexural point, m the mass of the wire, c(T) is the specific heat and the average expansion coefficient is: Taking in account also the filtering effect of the thermal conduction:

VIRGO-MAT21 … noise evaluation 3 Taking into account that the loaded wire acts like a spring: Considering the (minimal) Vertical to Horizontal coupling:

VIRGO-MAT22 M5-Cx: “Classical” cryogenic design Drawing of a cryogenic payload for the EGO-VIRGO cryogenic facility –G.Cella, A.Giazotto, R.Passquieti, M.Punturo, F.Richard