Stefan Hild for the GEO600 team

15th ILIAS WG1 meeting, March 2008, Cascina

Very brief update on the GEO mystery noise investigations

Stefan Hild ILIAS WG1, March 2008 Slide 2

IntroductionJust a quick update: following up the mystery noise session + brainstorming at last ILIAS meeting.See: http://www.ego-gw.it/ILIAS-GW/WP1docs/hild_231007.ppt for further detail…

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Stefan Hild ILIAS WG1, March 2008 Slide 3

How to tackle the mystery noise ?

Mystery noise

Stefan Hild ILIAS WG1, March 2008 Slide 4

How to tackle the mystery noise ?

Mystery noise

Characteristics ofthe mystery noise

Displacement noiseYes / No ?

Any clues from the observation? Displacement-like or not? Stationary? Related to glitches? ....

Stefan Hild ILIAS WG1, March 2008 Slide 5

How to tackle the mystery noise ?

Mystery noise

Fundamentalnoises

Projectednoises

Characteristics ofthe mystery noise

Displacement noiseYes / No ?

Is the gap real? All projections correct? Are all noises projected? Calculations of fundamental noises correct?

Stefan Hild ILIAS WG1, March 2008 Slide 6

How to tackle the mystery noise ?

Mystery noise

Fundamentalnoises

Projectednoises

UpconversionScattered light

Characteristics ofthe mystery noise

Exotic noises

Displacement noiseYes / No ?

Can we rule out the usual candidates: non-linearly coupling noises? How about exotic noises ? ....

Stefan Hild ILIAS WG1, March 2008 Slide 7

Stefan Hild ILIAS WG1, March 2008 Slide 8

Low vs high power

The gap looks smaller at low power, but …

Nominal power low power

Stefan Hild ILIAS WG1, March 2008 Slide 9

Low vs high power

… but the mystery stays roughly the same

Stefan Hild ILIAS WG1, March 2008 Slide 10

Stefan Hild ILIAS WG1, March 2008 Slide 11

Stefan Hild ILIAS WG1, March 2008 Slide 12

Frequency noise projection: A smoking gun ?

The change of the mystery noise from 550Hz to 1kHz tuning looks suspiciously similar to the change of the frequency noise transfer function.

Slide from October presentation

Is there any correlation at SR-tuning of 350 Hz ???

Stefan Hild ILIAS WG1, March 2008 Slide 13

Mystery noise vs frequency-noise-TF

550 Hz and 1kHz fit pretty well, but 350 Hz does not.

Could indicate that part of the noise is caused by frequency noise

Stefan Hild ILIAS WG1, March 2008 Slide 14

Frequency noise

Part of the mystery noise was caused by frequency noise.

See Hartmut’s talk

Stefan Hild ILIAS WG1, March 2008 Slide 15

Projections to uncalibrated errorpoints

In order to rule out any strange effects from calibration process we wanted to do noise projections to the uncalibrated errorpoints.

The gap turns to be of same size as for h(t) projections.

Stefan Hild ILIAS WG1, March 2008 Slide 16

Time domain noise projections

Wanted to perform noise projections in time domain => taking phase correlations into account.

Frequency domain and time domain projections agree pretty well.

For more details, see Jerome‘s talk

Stefan Hild ILIAS WG1, March 2008 Slide 17

New Projection: Beam jitter on main PD

Stefan Hild ILIAS WG1, March 2008 Slide 18

Stefan Hild ILIAS WG1, March 2008 Slide 19

Holographic noise

http://arxiv.org/abs/0709.0611http://arxiv.org/abs/0706.1999http://arxiv.org/abs/astro-ph/0703775

Needs more attention and investigations ….

Stefan Hild ILIAS WG1, March 2008 Slide 20