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Thermal noises at room and cryogenic temperatures

Thermal noises at room and cryogenic temperatures. Janyce Franc, Nazario Morgado, Raffaele Flaminio Laboratoire des Matériaux Avancés-Lyon Ronny Nawrodt, Iain Martin, Liam Cunningham, Alan Cumming, Sheila Rowan, James Hough University of Glasgow. WP2 meeting – Genova – 15 th September 2009.

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Thermal noises at room and cryogenic temperatures

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  1. Thermal noises at room and cryogenic temperatures Janyce Franc, Nazario Morgado, Raffaele Flaminio Laboratoire des Matériaux Avancés-Lyon Ronny Nawrodt, Iain Martin, Liam Cunningham, Alan Cumming, Sheila Rowan, James Hough University of Glasgow WP2 meeting – Genova – 15th September 2009 Janyce Franc-WG2-GENOVA

  2. CONTENTS • Introduction • Objective • Formulae • Parameters values and simulations @ 300K • Different coatings • Total thermal noise in a HR mirror • Mirror size effect • Parameters and simulations @ 10K • Substrates studies • HR mirror • Mirror size effects Janyce Franc-WG2-GENOVA

  3. INTRODUCTION THE AIM OF THE PRESENTATION IS A BRIEF DESCRIPTION OF THE E.T. NOTE : “Mirror thermal noise in laser interferometer gravitational wave detectors operating at room and cryogenic temperature”, ET-021-09, Issue 2 • The main points of the document are : • Outlined Thermal Noises formula at room and cryogenic Temperature • List of parameters of substrates and coatings at room and cryogenic temperature • Draw up by simulation a synthetic approach of Total thermal noise at room and cryogenic temperature Janyce Franc-WG2-GENOVA

  4. Sources of Thermal Noises Janyce Franc-WG2-GENOVA

  5. Substrate parameters values at 300K Unsuitable @ 300K Best  Limiting factors Janyce Franc-WG2-GENOVA

  6. Coating parameters values at 300K : low n materials Higher Brownian Noise Higher TE Noise Janyce Franc-WG2-GENOVA

  7. Coating parameters values at 300K : high n materials Coating made by evaporation HIGH Brownian and Thermo-optic Noise Janyce Franc-WG2-GENOVA

  8. OTHER COATINGS AT 300K TOTAL THERMAL NOISES ON SIO2 SUBSTRATE w=6 cm Infinite mirror Unless otherwise specified SiO2-Ti:Ta2O5 coating offers the best result SiO2-Nb2O5 is also clearly a good candidate Janyce Franc-WG2-GENOVA

  9. Total Thermal noise at 300K vs. substrates STANDARD COATING : SiO2-TiTa2O5 for 4 ppm transmission TE noise limits at low frequencies Silica and sapphire substrates reach good sensitivity Janyce Franc-WG2-GENOVA

  10. Total Thermal noise in Interferometer Mirror sizes effects : thickness dependency w=6.7 cm Ø=35 cm Finite and Infinite mirrors analyses Silica substrate Arm = 3 km T=300K High dependency on the thickness mirror Janyce Franc-WG2-GENOVA

  11. Total Thermal noise in Interferometer Mirror sizes effects : Diameter dependency For 1 ppm diff. losses Silica substrate Arm = 3 km T=300K High dependency on the diameter Janyce Franc-WG2-GENOVA

  12. Substrate parameters values at 10K Unsuitable @ 10K Janyce Franc-WG2-GENOVA

  13. THERMAL NOISE OF  SUBSTRATES w=6 cm Infinite mirror Unless otherwise specified SiO2 is unsuitable at 10K Silicon and sapphire have the same tendency With an advantage for silicon substrate Janyce Franc-WG2-GENOVA

  14. SILICON SUBSTRATE AT LOW TEMPERATURE TOTAL THERMAL NOISES SUBSTRATE HIGH SENSITIVITY VARIATIONS vs TEMPERATURES!! Janyce Franc-WG2-GENOVA

  15. TOTAL THERMAL NOISE with coating Standard coating for 4 ppm transmission : HIGH REFLECTIVE MIRROR Several parameters of Ti:Ta2O5 unknown at low T° With coating : sapphire lightly better substrates -Si works at 1550 nm -Si implies a thicker coating -Saphirre is more rigid Janyce Franc-WG2-GENOVA

  16. Total Thermal noise in interferometer Mirror sizes effects For 1 ppm diff. losses Silicon substrate Arm = 10 km T=10K Stefan Hild et al. arXiv:0906.2655v2 [gr-qc] Janyce Franc-WG2-GENOVA

  17. Total Thermal Noise in FINITE MIRRORS LAGUERRE-GAUSS effects T : 300K Arm length : 3 km Beam : 6 cm • Thermal Noise for 3rd generation GWD • Long interferometer arms : 10 km • Temperature : 10K • Large beams : 11.9 cm (gaussian beam) and 7,2 cm (LG33 mode) Exemple @ 10K : LG33 modes efficiency Reduction factor : 1.71 Stefan Hild et al. arXiv:0906.2655v2 [gr-qc] WORK IN PROGRESS… Janyce Franc-WG2-GENOVA

  18. CONCLUSIONS • Results of bibliography search about coating and substrate materials parameters are available in the note ET-021-09 • Simulation confirms that silica is best materials at room temperature • Ti:Ta2O5 best material at room temperature. Nb2O5 promising material. • Sapphire and Silicon have comparable performances at low T • Many coating parameters are unknown at low T. Coating quality factors are slightly worst at low temperature • Use of Silicon + Large diameter substrate + Low temperature + (LG modes) allow reaching the ET sensitivity at low frequency with a relatively low power (see Stefan Hild et al. arXiv:0906.2655v2 [gr-qc]) Janyce Franc-WG2-GENOVA

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