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SCATTERED LIGHT CONTROL in ADVANCED LIGO Michael Smith LIGO Laboratory Caltech, Pasadena, CA

SCATTERED LIGHT CONTROL in ADVANCED LIGO Michael Smith LIGO Laboratory Caltech, Pasadena, CA. Scattered Light Displacement Noise Theory. Min Gravity Wave Signal. Scattered Light. Noise. Phase Shift due to motion of surface. Requirement:. Stray Light Design Requirement.

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SCATTERED LIGHT CONTROL in ADVANCED LIGO Michael Smith LIGO Laboratory Caltech, Pasadena, CA

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  1. SCATTERED LIGHT CONTROL in ADVANCED LIGO Michael Smith LIGO Laboratory Caltech, Pasadena, CA Advanced LIGO

  2. Scattered Light Displacement NoiseTheory • Min Gravity Wave Signal • Scattered Light • Noise • Phase Shift due to motion of surface • Requirement: LIGO II

  3. Stray Light Design Requirement • <1/10 of the thermal noise limit strain LIGO II

  4. Total Scattered Light Displacement Noise from Multiple Sources, m/rtHz • Sources Are Random, Add in Quadrature • Scattered Light Transfer functions LIGO II

  5. Scattered Light Transfer Functionsfrom FFT simulation Worse scatter paths LIGO T060073 Hiro Yamamoto LIGO II

  6. Scattered Injection Points LIGO II

  7. Scattered Power into IFO • Scattered power depends upon: • Incident power hitting scattering surface, W • Bidirectional Scatter Distribution Function of scattering surface, BRDF, sr^-1 • Solid angle subtended by the mode inside IFO arm, sr • Relative area ratio of IFO mode area to the area of incident beam waist • Transmissivity of optical path from scatter surface to the injection point LIGO II

  8. Measuring BRDF LIGO II

  9. Cleanliness Is Next To Godliness • Dust particles scattering light on the sample surface! LIGO II

  10. Example Of BRDF Data LIGO II

  11. Motion Of Scattering Surface, m/rtHz LIGO II

  12. Scattered Light ControlSuspended Output Faraday Isolator BS for squeezed light injection from Dark-port Signal to Gravity Wave Detector Eddy current damping magnets LIGO II

  13. Output Faraday Isolator Scatter Displacement Noise Damping to frame Self damping LIGO II

  14. Other Examples Damped suspension Test mass Cavity Beam Dump Wide-angle Baffle Arm Cavity Baffle LIGO II

  15. Modeling Of Ghost Beams Modeling with ZEMAX: beam splitter chamber—ghost beams from internal reflections in the wedged compensation plate next to Input Test Mass (ITM) elliptical baffle BS from ITMX LIGO II

  16. Putting It All TogetherScattered Light Meets Requirement!! Requirement Total Scatter Thermal noise LIGO II

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