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:.

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Noise Projections for GEO 600

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Noise projections for geo 600

Noise Projections for GEO600

Joshua Smith GEO Meeting 11.10.06


Detector output decomposed

Detector output decomposed

transfer function

detector output

noise source

detector output:


Noise channels

noise channels:

Noise channels

noise channel

transfer function

detector output

noise source

detector output:


Noise projections

noise channels:

Noise projections

noise channel

transfer function

detector output

noise source

detector output:

noise projections:

noise budget:


Simplified procedure i

Simplified procedure I

Causality key

  • Notes:

  • Causality key

  • Simultaneous DFTs allow comparison

  • Other variants exist, eg open-loop which requires CLTF


Simplified procedure ii

Simplified procedure II

Causality key

Normal operation


Simplified procedure iii

Simplified procedure III

Causality key

Normal operation


Latest noise budget for s5

Latest noise budget for S5


Noise projection alignment fb

Noise projection: alignment FB

 feedback

noise projection

transfer function


Noise projection de modulation phase i

Noise projection: (de)modulation phase I

P

Q

H


Noise projection de modulation phase ii

Noise projection: (de)modulation phase II


S5 np reconstruction

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…


Calibration lines

Calibration lines


Tracking transfer functions

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

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

Noise subtraction: alignment FB

Error at a given freq. vs. filter accuracy

H

H’

Results of a time-domain subtraction


The end

The End


Noise removal eg frequency noise

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 projection: laser frequency noise

 Transfer function calculation would require very sophisticated model

Noise projections well-suited for very complicated systems


Limitations loop gain

Limitations: loop gain

Single-path loop

Simulated results

Workarounds exist:

eg., for high loop gain


Limitations ii

Limitations II

Single-path loop

Split-path loop

Workarounds exist: eg., for high loop gain


H vs signal recycling fb

H’ vs signal recycling FB


Detector output i

Detector output I

transfer function

detector output

noise source

detector output:


Detector output ii

Detector output II

transfer function

detector output

noise source

detector output:


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