1. New materials for DUAL: the LNL activity

2. Dual detector : Best material parameters Two different materials ‘A’ and ‘B’ with two different Young modulus Y and density  Sensitivity curve optimized in the same frequency window QL readout Toroidal shape No thermal noise Strain PSD of material A,B Young modulus of mat. A,B Density of material A,B

3. Dual detector : Candidate Materials -Diamond 163 ? expensive -Silicon carbide 27 Not well known available in large size -Berillium 24 <10 6 expensive -Sapphire 13 10 8 expensive+need bonding -Molibdenum 6.8 10 7 available in large size -Silicon 4.4 >10 8 need bonding -others ? (i.e. Alumina (17), MoCu (), CuBe) 1.Minimize sensitivity curve i.e. maximize 2.Minimize thermal noise Red= Material under investigation

4. Sintered silicon carbide: results Cantilevers of different thickness (0.3-0.5 mm) and lenght (5-10 cm) Both optical lever and capacitive readout Similar results in E.K. Hu et al. Phys Lett. A 157, 209 (1991) -> Annealing should improve the Q

5. Sintered silicon carbide: results Cantilevers of different thickness (0.3-0.5 mm) and lenght (5-10 cm) Both optical lever and capacitive readout Similar results in E.K. Hu et al. Phys Lett. A 157, 209 (1991) -> Annealing should improve the Q -->Seem not very much

6. Infiltrated silicon carbide C-SiC: results Best achieved loss angle 2x10 -6 Annealing did’nt improve the quality factor Measured samples: two cantilever of different thickness and lenght from Cesic (Germany) Different Carbon matrices Capacitive readout Annealed Not Annealed

7. Silicon samples: bonding research Ready made for many bond proccesses (Anodic bonding, Eutetic bonding,Adhesive bonding,Fusion bonding,Thermocompression bonding) Wafer diameter 100 mm Stack thickness 6 mm Machine capabilities A Silicon Wafer bonder is now availabe at the Mt-Lab in Trento

8. Silicon samples: bonding loss angle Bonding LayerSilicon wafer Bonded silicon disk h=0.9 mm d=100 nm Disk loss angle Ansys Analysis

9. SS pistonSS spring Sapphire balls  1mm Si Disk Not in scale cross section Si disk suspension set-up Al Silicon crystal plane side wall TMAH 175  m deep pyramid hole, with square opening 500  m side silicon bulk wet etching Set up #1

10. SS springSS piston Sapphire balls  1mm Si Disk Not in scale cross section Si disk suspension set-up Al Hole about 300  m in diameter, Milled using dentist’s tools Set up #2

12. Si disk displacement Readout Laser Quadrant photodiode Achieved sensitivity 10 -8 -10 -9 m Observed warm-up effects at low temperature ! Thus not ideal for ultracryogenic operations

13. Si disk displacement Readout Rotate View Capacitive readout V bias V out

14. Si disk: capacitive redout Readout sensitivity Achieved Sensitivity during run #1 (V bias =60 Volt, gap= 0.1 mm) High sensitivity require V bias C(x) Small gap Low parasitic capacitance (Cpar) Low noise voltage preamplifiers (SQUID amplifer can improve sensitivity very much) The comb capacitor capacitance value C(x) is a function of the distance (gap+  x) between them and the opposite dielectric plate

16. Si disk: first cryogenic run set-up Si oriented Boron doped Disk diameter 4 inch Thickness 0.5 mm Misalignement problem Adopted suspension (not optimized) set-up Si disk Sapphire balls SS piston  2mm

17. Si disk: first cryogenic run results

18. First Si Disk cryogenic run: Quality factor limitations The contribution of thermoelastic damping and surface losses at 4.2 K should be less then  10 -8 We are presumably dominated by suspension losses and/or sample microfracture induced by manufacturing the central hole However for this specific run gas damping should play a relelvant role because we had a cold leak Christian’s Model Comb Capacitor Bao et al. Model (sqeezed film damping ) Even worse using true gas dynamic models and outgasing

19. Conclusions SiC is very interesting for its high sound velocity, but the sintered and the infiltrated silicon carbide, that can be fabricated in large size as required for the Dual detector, show at low temperature a quality factor that is at least 2 order of magnitude lower than the required value. The quality factor of monocristalline SiC should be better but in this case we have to develop low losses bonding procedures and take care of the cost. Monocristalline Silicon is also a candidate material but it is not available at the required size. We plan to measure the Si bond losses to evaluate if a big elastic body can be obtained bonding togheter smaller pieces without affecting the overall Q fator Molybdenum is the best candidate material for the Dual detector however we are considering other material considering other materials as MoCu, pure Alumina, CuAl