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GEO report Thomas Adams
21/10/2011
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Outline
• GEO outline
• Recent upgrades to GEO
• On-site detector characterisation
• Recent science run and single detector era
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GEO outline • Layout and components
• Advanced interferometry techniques
• GEO sensitivity
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Basic Michelson
4
• Gravitational waves produce differential length changes in arms
• Laser interferometer compares the length of the two arms
• Observer length changes in interference pattern at output
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Layout of GEO N
E
S
W
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Near Hannover Germany
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Layout of GEO N
E
S
W
600 m Arms
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Central Building
North Station
East Station
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Layout of GEO
• GEO is a bit more complicated
• OptoCAD layout schematic (Roland Schilling)
• Main laser paths
• Vacuum tanks
• Arms are cut
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Laser input
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Mode cleaners
• Two triangular resonant cavities
• Ensure Gaussian beam profile (TEM00) entering interferometer
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Arms
• Single fold 600 m arms separated by 94°
• No arm cavities like in LIGO and Virgo
• 2 less degrees of freedom to control that using arm cavities
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Power recycling
• Operate near dark fringe
• Reuse light that would be wasted at input port
• Increase light power stored in the arms, the same as using a more powerful laser
• Reduces shot noise
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Signal recycling • Increase signal storage time,
same as using longer arms
• Optimal signal storage time is half a signal cycle • 75 km arms for 1 KHz signal
• Resonant for laser frequency (Broadband)
• Option to detune, improve sensitivity for signal which is resonant in signal recycling cavity
• Use Signal recycling with delay lines or low finesse arms
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Dual recycling
• Can control storage time of power and signal separately
• Large thermal effect as all power is transmitted through beam splitter
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Output mode cleaner
• Clean up higher order modes output from interferometer before photo-diode
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GEO sensitivity
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GEO sensitivity
HF REGION
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Recent upgrades • Beam Directional output Optics suspension
upgrade
• Using squeezed light
• High power upgrade
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BDO suspension upgrade
• BDO optics had no pre-isolation
• Broad resonances near violin modes of suspension wires
• Causing noise structures at a few hundred hertz
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BDO suspension upgrade
• New suspensions are stiffer with high frequency resonances
• Rubber/ steel isolation stages
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BDOs are quieter
19 Jake Slutsky for the LVC, LIGO-G1100639
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Squeezer
• Squeezer is a non-invasive upgrade
• Inject squeezed light into the output port of the detector
• Reduces shot noise at high frequency
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Squeezed light
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• Replace vacuum fluctuations entering output port with squeezed light
• Less phase noise but more amplitude noise
• We measure phase so this reduces the shot noise limited sensitivity
Amplitude
Phase
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Improvement in shot noise
3.5 db of squeezing gives reduction in shot noise of 55%)
22 A gravitational wave observatory operating beyond the quantum shot-noise limit (2011)
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High power
• 10W laser replaced by Enhanced LIGO style 35W laser
• New laser currently operating at 10W while other high power upgrades are made
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High power
24 Hartmut Grote for the LSC, LIGO-G1100999
Increase in power of 50% gives reduction in shot noise of 18%
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Detector characterisation • On-site detector characterisation
• Motion of Mirror Far East(MFE)
• Near 900 glitches
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On-site detector characterisation
• Monitor the detector sensitivity spectrum for changing features
• Use online HACR to monitor excess noise transients in Data and auxiliary channels
• Categorise glitch types and investigate possible source
• Perform experiment to confirm source
• Commissioning work to remove noise source
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Motion of MFE
• Swaying of MFE was seen in the spot position on MCE, similar frequency to MFE suspension resonance
• Believed to be 200th harmonic of the 50 Hz power line beating with the 10 kHz modulation of the shadow sensors
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Motion of MFE
• Once demodulated this produced low frequency noise which rings up the suspension resonances
• Investigation of changing the modulation frequencies removed this problem
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900 Hz glitches
• Large SNR sine-Gaussian like glitches
• Occur mainly in the local day time
• Investigation of possible sources for these glitches was performed ruling them out • Looked for any pattern in the distribution over
different time scales • Fluctuations in the frequency of the 50Hz mains
power line • Looked for dependency on the spot positions
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900 Hz glitches
• Signal generator was used to make injections into actuator of one of the arm mirrors to compare relative amplitude of signals in common and differential feedback channels
• This ruled out common feedback channels as the source of these glitches
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Science run and single detector era
• S6eVSR4 science run
• Single detector era
• Possible sources
• GEO HF program
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S6eVSR4
• Joint GEO and Virgo observation
• Start 3rd of June 2011
• End 5th of September 2011
• Over 80% observation time for both detectors
• Down time mainly due to commissioning
• Number of GRBs observed in coincident time which will be used for externally triggered search
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Single detector era
• Limit to sensitivity will be the noise tail of high SNR outliers • Commissioning work
to improve stability • Noise
characterisation to understand sources of noise transients
• Develop analysis pipeline
33 Patrick Sutton, GEODC meeting Feb 2011
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Possible sources
• Inspiral range < 10 Mpc
• Sensitive range to core collapse supernova of a few Kpc
• Major focus is for a loud, rare, gravitational wave burst while the other detectors are off line for upgrades • GRBs and Supernova alerts • Maximize data taking over nights and weekends
when there is no commissioning • Detector characterisation work to inform
commissioning efforts to the sources of transient noise that would limit a burst search
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GEO HF program
• Series of upgrades planned for improving high frequency sensitivity • Increase laser power 10W to 35W • Stable locking at high power by accounting
for effect of increased scattered light • Improved input mode cleaner performance • Correct for thermal effects on mirrors from high
power • Squeezed light injected into the output port • Characterisation of upgrades to ensure
stationary data
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GEO HF program
36 Hartmut Grote for the LSC, LIGO-G1100999
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Summary
• GEO has comparable sensitivity to other first generation detectors at high frequency
• Improve shot noise using increase laser power, improve mode matching, increase squeezing and reducing losses
• Expect 60-80% science data taken at nights and weekends
• Prepare for any serendipitous event
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