GEO report Thomas Adams

21/10/2011

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

Basic Michelson

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•  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

Layout of GEO N

E

S

W

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Near Hannover Germany

Layout of GEO N

E

S

W

600 m Arms

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Central Building

North Station

East Station

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

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

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

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

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)

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%

Detector characterisation •  On-site detector characterisation

•  Motion of Mirror Far East(MFE)

•  Near 900 glitches

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

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

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

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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