1. Perugia, Italy 20.09.05 Reducing the Noise in GEO600 Joshua Smith for the GEO 600 team

2. Joshua Smith, Perugia, Italy 20.09.05 Noise Projections: hP

3. Joshua Smith, Perugia, Italy 20.09.05 Noise Projections: hQ

4. Joshua Smith, Perugia, Italy 20.09.05 Non-stationary Noise At best the noise is very close to the Projections

5. Joshua Smith, Perugia, Italy 20.09.05 Shot + Dark Noise

6. Joshua Smith, Perugia, Italy 20.09.05 MI Detection Noises: P

7. Joshua Smith, Perugia, Italy 20.09.05 MI Detection Noises: Q

8. Joshua Smith, Perugia, Italy 20.09.05 Optimal h(t)  Shot Noise Combination optimized for SNR of h given: hP = h + nP hQ = h + nQ

9. Joshua Smith, Perugia, Italy 20.09.05 Shot Noise: Next steps Shot model: 5W to MPR, 7kW @ BS Currently have: 2W to MPR, 1.5-2kW @ BS Expect to be: sqrt(7/1.5) to sqrt(7/2) = 2.2 to 1.9 above design (just from cavity power) Are currently about factor 4 from design level o10s of % from optimizations, reduction of dark noise orest (perhaps sqrt(2)) not yet understood Next Week: Replace Laser Increase input laser power from 5W to 10W This will give sqrt(2), for the rest perhaps: oSearch for losses in power-recycling cavity oReduce loss in modecleaners?

10. Joshua Smith, Perugia, Italy 20.09.05 Signal Recycling Longitudinal More aggressive filtering to reach design below 100Hz

11. Joshua Smith, Perugia, Italy 20.09.05 Laser Power Noise Investigate quality of current signal after second modecleaner Use Input Port as error-signal for power stabilization 2 nd /3 rd loop

12. Joshua Smith, Perugia, Italy 20.09.05 MI Fast Auto-alignment Implemented digital fast auto-alignment this week! Will allow aggressive filtering like that used in the SR loop

13. Joshua Smith, Perugia, Italy 20.09.05 Oscillator Phase Noise -Wenzel specs = -165dBc @ 1kHz -Unable to measure better than 15dB above OPN in current setup - Better RF setup aims to be limited by phase noise from oscillator - Possible reduction of coupling coefficient with increased MI loop gain

14. Joshua Smith, Perugia, Italy 20.09.05 Michelson Diff. Longitudinal -Required factor for fast path by whitening, bias reduction? -Intermediate Mass FB not front-end limited, improve servo, possibly digital steeper low-passing above ~40Hz ?

15. Joshua Smith, Perugia, Italy 20.09.05 Nonlinear Actuator: Up-con

16. Joshua Smith, Perugia, Italy 20.09.05 Nonlinear Actuator: Beats

17. Joshua Smith, Perugia, Italy 20.09.05 Nonlinear Noise vs. Bias 600V

18. Joshua Smith, Perugia, Italy 20.09.05 Nonlinear Noise vs. Bias 60V

19. Joshua Smith, Perugia, Italy 20.09.05 Nonlinear Noise vs Bias V Further decrease in bias not optimal !

20. Joshua Smith, Perugia, Italy 20.09.05 Summary Shot Noise (4x above design)  sqrt(2) from power increase, 10-20% from modulation depth, etc. oSomething else needed. Decrease finesse of MCs? Oscillator Phase Noise  Improved RF distribution to ensure –165dBc @ 1kHz limit from oscillator oMore MI gain Michelson  More whitening, noise mitigation slow path Signal Recycling  Increased digital filtering Laser Power  Use MIC VIS in-loop Auto-alignment  Digital servo allows more aggressive noise filtering Shot Noise (4x above design)  sqrt(2) from power increase, 10-20% from modulation depth, etc. oSomething else needed. Decrease finesse of MCs? Oscillator Phase Noise  Improved RF distribution to ensure –165dBc @ 1kHz limit from oscillator oMore MI gain Michelson  More whitening, noise mitigation slow path Signal Recycling  Increased digital filtering Laser Power  Use MIC VIS in-loop Auto-alignment  Digital servo allows more aggressive noise filtering

21. Joshua Smith, Perugia, Italy 20.09.05 Optical Layout