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Noise Projections for GEO 600PowerPoint Presentation

Noise Projections for GEO 600

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### Noise Projections for GEO600

Joshua Smith GEO Meeting 11.10.06

Noise channels

noise channel

transfer function

detector output

noise source

detector output:

Noise projections

noise channel

transfer function

detector output

noise source

detector output:

noise projections:

noise budget:

Simplified procedure I

Causality key

- Notes:
- Causality key
- Simultaneous DFTs allow comparison
- Other variants exist, eg open-loop which requires CLTF

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…

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

Error at a given freq. vs. filter accuracy

H

H’

Results of a time-domain subtraction

Noise removal, eg., frequency noise

Most important role of NPs in commissioning: Identify limiting noise sources – team removes them

Noise projection: laser frequency noise

Transfer function calculation would require very sophisticated model

Noise projections well-suited for very complicated systems

Limitations: loop gain

Single-path loop

Simulated results

Workarounds exist:

eg., for high loop gain

H’ vs signal recycling FB

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