noise projections for geo 600
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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:. - PowerPoint PPT PresentationTRANSCRIPT
Noise Projections for GEO 600
Joshua Smith GEO Meeting
11.10.06
Detector output decomposed
detector output:
detector output
noise source
transfer function
Noise channels
noise channel
detector output:
detector output
noise source
transfer function
noise channels:
Noise projections
noise channel
detector output:
detector output
noise source
transfer function
noise projections:
noise channels:
noise budget:
Simplified procedure I
Causality key
Notes:
1. Causality key
2. Simultaneous DFTs allow comparison
3. Other variants exist, eg open-loop which requires CLTF
Simplified procedure II
Causality key
Normal operation
Simplified procedure III
Causality key
Normal operation
Latest noise budget for S5
Noise projection: alignment FB
transfer function
feedback
noise projection
Noise projection: (de)modulation phase I
P
Q H
Noise projection: (de)modulation phase II
S5 NP ReconstructionGoal: Noise projections (full budget) at any time.
Coming soon: ProjMon
1. Transfer functions:
• Measure accurately about once per month
• Track using calibration lines
2. Fourier transforms of Nj and H:
• Signals recorded continuously anyway…
Calibration lines
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
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
Noise subtraction: alignment FB
Results of a time-domain subtraction
Error at a given freq. vs. filter accuracy
H’
H
The End
Noise removal, eg., frequency noise
Most important role of NPs in commissioning: Identify limiting noise sources – team removes them
Noise projection: laser frequency noise
Noise projections well-suited for very complicated systems
Transfer function calculation would require very sophisticated model
Limitations: loop gain
Single-path loop
Workarounds exist:
eg., for high loop gain
Simulated results
Limitations IISingle-path loop
Split-path loop
Workarounds exist: eg., for high loop gain
H’ vs signal recycling FB
Detector output I
detector output:
detector output
noise source
transfer function
Detector output II
detector output:
detector output
noise source
transfer function