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Noise Projections for GEO 600

Noise Projections for GEO 600. Joshua Smith GEO Meeting 11.10.06. Detector output decomposed. transfer function. detector output. noise source. detector output:. noise channels:. Noise channels. noise channel. transfer function. detector output. noise source. detector output:.

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Noise Projections for GEO 600

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  1. Noise Projections for GEO600 Joshua Smith GEO Meeting 11.10.06

  2. Detector output decomposed transfer function detector output noise source detector output:

  3. noise channels: Noise channels noise channel transfer function detector output noise source detector output:

  4. noise channels: Noise projections noise channel transfer function detector output noise source detector output: noise projections: noise budget:

  5. Simplified procedure I Causality key • Notes: • Causality key • Simultaneous DFTs allow comparison • Other variants exist, eg open-loop which requires CLTF

  6. Simplified procedure II Causality key Normal operation

  7. Simplified procedure III Causality key Normal operation

  8. Latest noise budget for S5

  9. Noise projection: alignment FB  feedback noise projection transfer function

  10. Noise projection: (de)modulation phase I P Q H

  11. Noise projection: (de)modulation phase II

  12. S5 NP Reconstruction Goal: Noise projections (full budget) at any time. Coming soon: ProjMon • Transfer functions: • Measure accurately about once per month • Track using calibration lines • 2. Fourier transforms of Nj and H: • Signals recorded continuously anyway…

  13. Calibration lines

  14. Tracking transfer functions • At calibration line, projection and H should have same amplitude, phase. • Ratio and difference indicate TF accuracy. • For 10 day test, about 10% 10o

  15. Vetoes of false gravitational waves • Noise channels contain almost no GW info • Coincident (within windows) events are not GWs ! • See Ajith and Martin’s talks ! Example: injected burst-like waveform

  16. Noise subtraction: alignment FB Error at a given freq. vs. filter accuracy H H’ Results of a time-domain subtraction

  17. The End

  18. Noise removal, eg., frequency noise Most important role of NPs in commissioning: Identify limiting noise sources – team removes them

  19. Noise projection: laser frequency noise  Transfer function calculation would require very sophisticated model Noise projections well-suited for very complicated systems

  20. Limitations: loop gain Single-path loop Simulated results Workarounds exist: eg., for high loop gain

  21. Limitations II Single-path loop Split-path loop Workarounds exist: eg., for high loop gain

  22. H’ vs signal recycling FB

  23. Detector output I transfer function detector output noise source detector output:

  24. Detector output II transfer function detector output noise source detector output:

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