The Status of GEO 600, and Noise Projections

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The Status of GEO 600, and Noise Projections

• Joshua Smith for the GEO600 team GEO DA Meeting
  Glasgow, 31.07.06

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GEO 600 simplified optical layout
600m
Optics suspended as double or triple pendulums
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Prototype for future detectors configuration
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Theoretical sensitivity limit
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Theoretical limit vs. detuning
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Sensitivity development 02-06
3000x better _at_ 500Hz in 4 years
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Sensitivity in runs and theoretical sensitivity
www.geo600.uni-hannover.de/geocurves
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Laser-IFO network sensitivity
Most recent publicly available (from pages like
the one just shown) curves for each project
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Laser IFOs theoretical limits
Most recent publicly available curves for each
project
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GEO 600 in S5 Night and Weekend

• S5 Night and Weekend
• Jan 20 May 1
• Commissioning during normal working hours,
  running for all other times.
• Commissioning focused on increasing sensitivity
  and locking stability
• Changes to the detector occurred quite often
  many different epochs for noise, couplings, etc.
• Signal detuning changed from 350Hz to 550Hz on
  April 18th

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Tuning to 550Hz
Decision made to increase science output above
400Hz, at cost of increased noise below.
Effective after April 18th.
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Night and weekend cumulative statistics
From GEO600 DC pages talk by Hewitson
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GEO 600 in S5 24/7 Mode

• S5 Night and Weekend
• started May 2, ongoing...
• A few maintenance periods for measurements and
  glitch removal
• Focus shifts to data quality see talks by Hild
  and Smith
• Detector stable, with high duty cycle.
• Signal detuning fixed at 550Hz.
• Power increased just prior to 24/7

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24/7 mode cumulative statistics
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Locking performance
Number of unlocked times
Unlocked time minutes

• Typical relock-time 5 minutes
• Relocking completely automated
• gt90 of relocks succeed without manual
  intervention
• Longest unlocked time 19 hours (hardware failure)

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GEO Summary Pages
http//www.geo600.uni-hannover.de/georeports/group
s/georeports.html
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HACR History 24/7
May
June
July
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S5 24/7 vs. S5 Night and Weekend
After turning up power, glitch removal work,
better than or equal to NW at all freqs (for
good time)
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Peak sensitivity BLRMS

• Instrumental duty-cycle gt 90
• Peak RMS strain sensitivity hRMS 2.510-22

June 96 duty cycle

• More frequent interruptions of lock in July due
  to local construction work

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Detector output I
transfer function
detector output
noise source
detector output
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Detector output II
transfer function
detector output
noise source
detector output
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Detector output III
transfer function
detector output
noise source
detector output
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Noise channels
noise channel
transfer function
detector output
noise source
detector output
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Noise projections
noise channel
transfer function
detector output
noise source
detector output
noise projections
noise budget
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Simplified procedure I
Causality key

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

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Simplified procedure II
Causality key
Normal operation
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Simplified procedure III
Causality key
Normal operation
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Noise projection alignment FB
? feedback
noise projection
transfer function
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Noise projection laser frequency noise
? Transfer function calculation would require
very sophisticated model
Noise projections well-suited for very
complicated systems
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Noise removal, eg., frequency noise
Most important role of NPs in commissioning
Identify limiting noise sources team removes
them
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Noise budget for S5
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Noise removal possibilities

• Below 100Hz, factor 3-5 could be gained from work
  on alignment loops.
• The next factor might involve improving
  signal-recycling FB, laser power noise.
• Shot noise limit at high freqs
• Find power-up glitches, turn up power
• Open vacuum and find additional losses??
• Intermediate frequencies search for sources of
  up-conversion
• Scattering in North building causing (some)
  ripples
• Have developed useful techniques for finding
  scattering outside vacuum system
• Evidence of up-conversion in H

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Vetoes of false gravitational waves

• Vetoes crucial for burst search
• Noise channels contain almost no GW info
• Coincident (within windows) events are not GWs !

Example injected burst-like waveform
See talk by P. Ajith
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Noise subtraction alignment FB
Error at a given freq. vs. filter accuracy
H
H
Results of a time-domain subtraction
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Outlook

• Run in 24/7 mode until October.
• Decide then how to continue (2 choices?)
• Commissioning break to increase sensitivity
• Continue full-time data taking
• Input from search groups welcome what impact can
  GEO data make?

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The End
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Automation
Goal Noise projections (full budget) at any time.

• Transfer functions
• Measure occasionally and
• If dynamic, must be tracked
• 2. Fourier transforms of Nj and H
• Signals recorded continuously anyway

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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

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Calibration lines
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Prototype for future detectors suspensions

• Triple pendulum suspensions
• provide f-6 filtering of seismic noise above
  resonances.
• Quasi-monolithic fused silica
• Removed interfaces where possible
• Expect very low thermal noise due to high quality
  factor materials

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Limitations loop gain
Single-path loop
Simulated results
Workarounds exist eg., for high loop gain
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Limitations II
Single-path loop
Split-path loop
Workarounds exist eg., for high loop gain
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Noise projection (de)modulation phase
Works well for very complicated systems
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H vs signal recycling FB