perugia, italy 20.09.05 reducing the noise in geo600 joshua smith for the geo 600 team
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![Page 1: Perugia, Italy 20.09.05 Reducing the Noise in GEO600 Joshua Smith for the GEO 600 team](https://reader036.vdocuments.net/reader036/viewer/2022062409/5697bf9f1a28abf838c949e6/html5/thumbnails/1.jpg)
Perugia, Italy 20.09.05
Reducing the Noise in GEO600Reducing the Noise in GEO600
Joshua Smith for the GEO 600 team
![Page 2: Perugia, Italy 20.09.05 Reducing the Noise in GEO600 Joshua Smith for the GEO 600 team](https://reader036.vdocuments.net/reader036/viewer/2022062409/5697bf9f1a28abf838c949e6/html5/thumbnails/2.jpg)
Joshua Smith, Perugia, Italy
20.09.05
Noise Projections: hPNoise Projections: hP
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Joshua Smith, Perugia, Italy
20.09.05
Noise Projections: hQNoise Projections: hQ
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Joshua Smith, Perugia, Italy
20.09.05
Non-stationary NoiseNon-stationary Noise
At best the noise is very close to the Projections
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Joshua Smith, Perugia, Italy
20.09.05
Shot + Dark NoiseShot + Dark Noise
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Joshua Smith, Perugia, Italy
20.09.05
MI Detection Noises: PMI Detection Noises: P
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Joshua Smith, Perugia, Italy
20.09.05
MI Detection Noises: QMI Detection Noises: Q
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Joshua Smith, Perugia, Italy
20.09.05
Optimal h(t) Optimal h(t) Shot Noise Shot NoiseCombination optimized for SNR of h given:
hP = h + nP hQ = h + nQ
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Joshua Smith, Perugia, Italy
20.09.05
Shot Noise: Next stepsShot 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 levelo 10s of % from optimizations, reduction of dark noiseo rest (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:
o Search for losses in power-recycling cavityo Reduce loss in modecleaners?
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Joshua Smith, Perugia, Italy
20.09.05
Signal Recycling LongitudinalSignal Recycling Longitudinal
More aggressive filtering to reach design below 100Hz
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Joshua Smith, Perugia, Italy
20.09.05
Laser Power NoiseLaser Power Noise
• Investigate quality of current signal after second modecleaner
• Use Input Port as error-signal for power stabilization 2nd/3rd loop
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Joshua Smith, Perugia, Italy
20.09.05
MI Fast Auto-alignmentMI Fast Auto-alignment
• Implemented digital fast auto-alignment this week!
• Will allow aggressive filtering like that used in the SR loop
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Joshua Smith, Perugia, Italy
20.09.05
Oscillator Phase NoiseOscillator 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
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Joshua Smith, Perugia, Italy
20.09.05
Michelson Diff. LongitudinalMichelson 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 ?
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Joshua Smith, Perugia, Italy
20.09.05
Nonlinear Actuator: Up-conNonlinear Actuator: Up-con
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Joshua Smith, Perugia, Italy
20.09.05
Nonlinear Actuator: BeatsNonlinear Actuator: Beats
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Joshua Smith, Perugia, Italy
20.09.05
Nonlinear Noise vs. Bias 600VNonlinear Noise vs. Bias 600V
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Joshua Smith, Perugia, Italy
20.09.05
Nonlinear Noise vs. Bias 60VNonlinear Noise vs. Bias 60V
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Joshua Smith, Perugia, Italy
20.09.05
Nonlinear Noise vs Bias VNonlinear Noise vs Bias V
Further decrease in bias not optimal !
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Joshua Smith, Perugia, Italy
20.09.05
Summary Summary
Shot Noise (4x above design) sqrt(2) from power increase, 10-20% from modulation depth, etc. o Something else needed. Decrease finesse of MCs?
Oscillator Phase Noise Improved RF distribution to ensure –165dBc @ 1kHz limit from oscillatoro More 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. o Something else needed. Decrease finesse of MCs?
Oscillator Phase Noise Improved RF distribution to ensure –165dBc @ 1kHz limit from oscillatoro More 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
![Page 21: Perugia, Italy 20.09.05 Reducing the Noise in GEO600 Joshua Smith for the GEO 600 team](https://reader036.vdocuments.net/reader036/viewer/2022062409/5697bf9f1a28abf838c949e6/html5/thumbnails/21.jpg)
Joshua Smith, Perugia, Italy
20.09.05
Optical LayoutOptical Layout