1. A new facility for thermal conductivity measurements Filippo Martelli Univ. of Urbino and INFN Florence GWADW 2006 – 27/5-02/06 2006 – La Biodola

2. GWADW 20062 of 16 Activities on thermal noise in Florence Modelling of thermal noise for Virgo optics and suspensions Measurements on crystalline silicon fibres Study of new materials for 3rd generation interferometric GW detectors (JRA3-STREGA collaboration)

3. GWADW 20063 of 16 Study of the thermo-mechanical properties of materials for 3 rd generation GW detectors Cryogenic facility Crystalline Silicon Samples Measurements concern Thermal conductivity Thermal expansion coefficient Q measurements (possible, but our set up is not optimized for this)

4. GWADW 20064 of 16 Thermoelastic properties Amplitude of thermoelastic peak Position (cylindrical sample) Knowledge of the thermoelastic peak is important for identification of the various contribution to the loss angle (study of bulk, surface, clamp….losses) Knowledge of thermal conductivity is crucial for suspensions to be used in cryogenic detectors (heat extraction)

5. GWADW 20065 of 16 100 1000 10000 1101001000 T (K) Th. conductivity (W/mK) Thermal conductivity of Si From Y.S. Touloukian, E.H. Buyco, “Thermo-physical properties of matter”, Plenum, NY, 1970

6. GWADW 20066 of 16 The cryostat 30 cm A.S. Scientific cryostat Experimental volume: about 14 dm 3 Inner cold shield Outer cold shield Optical windows Inner tank Liquid He Outer tank Liquid N 2 Vacuum chamber Experimental chamber

7. GWADW 20067 of 16 Thermal conductivity measurement INSULATOR BOX HEATER COPPER BOX CLAMP SAMPLE THERMOMETERS SAMPLE HEATER

8. GWADW 20068 of 16 Evaluation of the power loss Heat loss is due mainly to radiation (small contribution by wire conduction) INSULATOR BOX HEATER COPPER BOX CLAMP SAMPLE THERMOMETERS SAMPLE HEATER 1mW of heating power From the heating-cooling cycle at room T Conductive losses through wires are negligible (0.1 % of radiative losses at room temperature) we evaluate the unknown parameter in radiative losses

9. GWADW 20069 of 16 Power loss estimation

10. GWADW 200610 of 16 Power loss estimation

11. GWADW 200611 of 16 Results

12. GWADW 200612 of 16 Thermal expansion measurement facility No hope with a simple Michelson ! Simple Fabry-Perot cavity Problems from frequency stability ! if L=10 cm

13. GWADW 200613 of 16 Thermal expansion measurement facility

14. GWADW 200614 of 16 Measuring cavity Sample Mirrors Fixed clamp Mobile clamp Laser Very soft elastic blades

15. GWADW 200615 of 16 The reference cavity Vacuum chamber hosting reference cavity Heating wires for RC temperature control Mirror Reference material: zerodur Piezo actuator Elastic Cu/Be blades 1 h 1 K Result of the temperature stabilization (Matteo Lorenzini) T fluctuations must stay below 0.01 K We now have a few mK stability

16. GWADW 200616 of 16 Conclusions We have a facility for direct measurements of thermal conductivity in samples shorter than 20 cm from 4 K up to room temperature First measurements on a Si sample down to 40 K show that the instrument is properly working (we need a better calibration) The setup for LHe should still be optimized We are studying the possibility of measuring the thermal expansion coefficient as well