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Geppo Cagnoli INFN Sez. Firenze University of Glasgow ESF Workshop – 22 nd Sep. 2005, Perugia

Low noise Fused Silica suspensions: from the GEO600 experience to the 2 nd generation requirements. Geppo Cagnoli INFN Sez. Firenze University of Glasgow ESF Workshop – 22 nd Sep. 2005, Perugia. Braginsky, Mitrofanov, Tokmakov. Fundamental milestones. Advanced LIGO.

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Geppo Cagnoli INFN Sez. Firenze University of Glasgow ESF Workshop – 22 nd Sep. 2005, Perugia

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  1. Low noise Fused Silica suspensions: from the GEO600 experience to the 2nd generation requirements Geppo Cagnoli INFN Sez. Firenze University of Glasgow ESF Workshop – 22nd Sep. 2005, Perugia

  2. Braginsky, Mitrofanov, Tokmakov Fundamental milestones • Advanced LIGO • EGO R&D onCO2 laser machine • 2nd silica suspensions in GEO600 • Silica cradle (Glasgow) • 1st silica suspensions in GEO600 • Silicate bonding, J. Gwo • First flame pullingmachine in Glasgow • Bi-filar pendulum,Glasgow-Perugia • Bi-filar pendulum,Moscow-Glasgow 02 03 04 98 99 01 1990 95 96 97 2000 2010 ESF Workshop - Perugia 05 - Silica suspensions

  3. Thermal noise Low mech. losses Low Young’s modulus Monolithic suspensions Other issues Tapering Low excess noise(bursts ?) Safety Careful handling Ears breaking Cleanness Welding on situ Electrical Charging of test masses Pro and Cons of Silica ESF Workshop - Perugia 05 - Silica suspensions

  4. Something we have learned • Broken fibres can be replaced • Teflon can be applied on the fibres • The reproducibility of fibres was not optimal • The flame blows the fibre during welding • Manual welding is dirty and not reproducible • Probably side welding better than bottom welding (work in progress) • After all the fibres are still there… ESF Workshop - Perugia 05 - Silica suspensions

  5. Limitation of the H2-O2 technology in GEO600 • Metal nozzles • Surface contamination by combustion products can limit strength • Shape control - limited • Very approximate with pulling machines • More accurate with feed & pull • Reproducibility - limited • Uniformity of cross sectional area at ~ 10% level in GEO 600 • Welding • Contamination with combustion products • Blowing of the flame ESF Workshop - Perugia 05 - Silica suspensions

  6. Flames at work ESF Workshop - Perugia 05 - Silica suspensions

  7. The new technology: CO2 laser 10.6 mm McLachlan & Meyer, Applied Optics Vol 26 No. 9, 1987 • Use CO2 laser radiation (10.6 mm) to melt silica • Potential advantages of laser fabrication & weld: • Very fine control of quantity andlocalization of heating • Reduced contamination • Diameter self-regulation effect • Precision welding – improved weld shape • Welding of thin fibres on thick rods • No blowing • Full control on beam delivering • Re-correction of shape, stress relief/annealing afterwards ESF Workshop - Perugia 05 - Silica suspensions

  8. CO2 laser at work ESF Workshop - Perugia 05 - Silica suspensions

  9. Machine conceptual design 3 axes machine • Able to pull: • Circular fibres • Ribbons • Able to weld • Modular design ESF Workshop - Perugia 05 - Silica suspensions

  10. Conceptual design for cylindrical fibres PULL Silica fibre FEED Silica rod CO2 laser beam 10.6mm Conical mirror Rotating45° mirror Motor • Current conceptual design of cylindrical fibre machine • fibre stock clamped to base of machine • focus of laser (ring) moved downwards to progressively melt stock • upper stock clamp moves upwards to draw fibre Block C ESF Workshop - Perugia 05 - Silica suspensions

  11. Conceptual design for ribbons and welding • Block C is here an XY scanner (mirror galvanometers) mounted on a rotational stage • A3 and the rotational stage are used for welding • The laser path is the b one ESF Workshop - Perugia 05 - Silica suspensions

  12. Some results Fibre profile First ribbonwith the newmachine The new3 axespullingmachine The neck problem ESF Workshop - Perugia 05 - Silica suspensions

  13. Some pictures ESF Workshop - Perugia 05 - Silica suspensions

  14. The ears for Advanced LIGO New ears design for the 40 kg masses of Advanced LIGO 9 cm2 is the maximum bonding surface. Triangular shape for peeling reduction ESF Workshop - Perugia 05 - Silica suspensions

  15. Ear strength tests Flame polished 37.5 kg breakingload Breaking load: 9.5 kg 12 kg load On since 19/08 ESF Workshop - Perugia 05 - Silica suspensions

  16. Suspension thermal noise in Advanced LIGO ESF Workshop - Perugia 05 - Silica suspensions

  17. Conclusions • How much is the confidence in the low frequency performance of the Advanced Detectors? • The effect of metal suspensions on the internal thermal noise of mirrors is not clear • The CO2 laser machine seems to be able to produce fibres with the advanced detectors requirements • The silicate bonded ears are giving a positive response to the test ESF Workshop - Perugia 05 - Silica suspensions

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