1. Joshua Smith July 2004 Identifying limiting noise sources of GEO600 ILIAS WG1 Meeting Joshua Smith for the GEO team

2. Joshua Smith July 2004 Sensitivity Progress

3. Joshua Smith July 2004 June ‘04 vs. Theoretical

4. Joshua Smith July 2004 Noise Projections Idea: consider example measurement points (chans), N and P determine how noise in N will appear in P based on properties of system Procedure: 0: Identify noise that could couple to P 1: Find/create channel (N) that represents this noise 2: Quantify coupling from this channel to P with a TF 3: Quantify noise in N and P by their ASDs 4: Project the noise in N to how it will appear in P Drawbacks: assumes linearity not reliable at frequencies with loop gain.

5. Joshua Smith July 2004 Transfer Function Dominate noise present in system with injected signal Measure TF

6. Joshua Smith July 2004 Projection Remove signal Measure ASDs simultaneously at N and P Multiply by TF to form projection

7. Joshua Smith July 2004 MI loop (MI diff. arm-length) LSC_MID_EP-P_HP  main GW signal, P quadrature LSC_MID_FP-MCE-MCN  diff. FB to ESDs (> 15 Hz) LSC_MID_FP-MCE-HV, LSC_MID_FP-MCN-HV  feedback to MCe, MCn ESDs sampled after HVA

8. Joshua Smith July 2004 MI Fast Path

9. Joshua Smith July 2004 MI Fast Path TFs

10. Joshua Smith July 2004 MI Fast Path ASDs

11. Joshua Smith July 2004 MI Fast Path Projections

12. Joshua Smith July 2004 Current Noise Projections

13. Joshua Smith July 2004 Oscillator noises

14. Joshua Smith July 2004 Some other noises MI oscillator noises amplitude:2-3 below from 400Hz to 1.1kHz (at least)! Phase: 8 below @ 1kHz acoustic noise Couples at some level, output bench and TCMb-West breadboard strongest MIC VIS a `hot spot’ for acoustic coupling scattered light visible problem, nonlinear, excited with e.g. stomps frequency noise complex PR loop difficult to characterize, requires more work gain reduction of 100 just increases noise in P apparent arm length difference for freq coupling is about 2.8m

15. Joshua Smith July 2004 In the works Acoustic/air fluctuations, scattering output optics, HPD in vacuum Acoustic shield for TCMb-West, other places? MI fast path noise switch out sqrt-circuit – electronics finished, installation imminent MI oscillator noises phase – new generator or 2f amplitude – stabilization loop dark, shot noises Increase laser power + new HPD Front end-limited loops (SRC, MI slow, etc.) noise may reduce with reduction of noise in other loops Cross-projections : MI to SRC, etc. –

16. Joshua Smith July 2004 The End

17. Joshua Smith July 2004 Future of projections? Things to address for projections: use phase information for split paths, etc produce reliable information in loops with high loop gain Automation track TFs using callines monitor veto channels during data runs Overall Goal speed progress towards design sensitivity