Joshua Smith for the GEO 600 team

1
Instrumental and environmental noise in GEO600
Picture of GEO in stormy weather??
Or pics of tractors with trees?
North building

• Joshua Smith for the GEO 600 team

2
Overview
A selection of recent detector characterization
work

• Environmental
• Seismic
• Dust
• Magnetic fields / Mains

• Instrumental
• Noise Projections
• Tracking couplings
• Noise subtraction
• Noise vetoes

3
Seismic / up-conversion
H _at_ 240Hz
H _at_ 290Hz
Amplitude (max)
H _at_ 340Hz
Seis _at_ 49Hz
0 Time h
3.5
4
Dust
5
Power glitches
Input port power
Detector output
6
Back-coupling?
Strain back-coupling doesnt explain instrumental
channel coincidence
Dark port DC Power
Strain coupling to DC power
7
Power glitches vs. dust
Particle count
Dark port DC power glitch count
Dark port DC power glitch count
Dark port DC power glitch count
Input port DC power glitch count
0 Time
m 180
8
Particle waves filtered
140?20
45?5
(Particles/cu.ft)/1000
3?0.2
A a
9
Dust made loudest glitches
Det. output BLRMS _at_ 170Hz
Time h
Time h
Before filter
After filter
10
Magnetic fields / Mains
11
Magnetic field glitches
H glitches
B glitches
Linear coupling, coherence
12
Magnetic field projection

• B-field nearly limiting noise around 100Hz?
• Coupling not yet understood
• Checks magnetometer measures B-field, IFO
  back-coupling ruled out

13
Hourly mains glitches

• Hourly series start
• 24 secs after GPS hour
• 10 secs after UTC hour

14
Mag./mains coinc. with H
Magnetometer central building 50coinc./8hrs
Mains monitor central building 30coinc./8hrs
Time-freq glitch maps
Frequency Hz
Frequency Hz
0
0
8
8
Time h
Time h
50
50
Time-shifted coincidence
0
0
1
1
-1
-1
Time shift s
Time shift s
15
Noise Projections
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Noise Budget
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Tracking noise transfer funcs
Amp ratio 1 phase diff 0
Tracked Signal Recycl. FB Osc. Phase Laser int
ensity
Frequency
18
Transfer funcs long-term (10d)
Ratio/Diffs drifts
Histogram of drifts
10 days, most projections /- 10 mag /- 10 de
gs phase
So, long-term stable
19
Noise transfer funcs short-term
/- 20 mag. variations on second timescales!
20
Noise Subtraction
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Detector output and noise
Detector output
Noise projection
Noise budget
Noise chans.
Record subset
Improved H
22
Noise subtraction requirements
Subtraction factor depends on amplitude ratio and
phase difference of filter used and real transfer
function response.
23
Noise subtraction results
Ratio H/(H-Projs)
Time domain subtraction, simple IIR filters fit
to measured TF response.
But, no reduction of up-conversion
24
Technical noise veto
25
Noise veto eg. injection
H
Michelson oscillator phase noise
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Noise veto performance
Estimated veto efficiency vs. rejection
probability for the chosen thresholds.
Robust vetoes for gravitational-wave burst
triggers using known instrumental couplings
P. Ajith, M. Hewitson, J. R. Smith, K. A. Strain,
submitted to CQG, http//arxiv.org/abs/gr-qc/06050
79
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The end
'falco tinnunculus', better know as 'Turmfalke'
28
Noise subtraction II

• Used simple IIR filters
• - good match to simple transfer function

29
Statistical dust veto?
MID VIS veto TF map and timeshifted results