Linear projection of technical noise for interferometric gravitational-wave detectors

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This paper describes measurements and simulations related to power fluctuations of the laser light in the GEO 600 laser-interferometric gravitational wave detector. Measurements of the relative fluctuations of the light power at three different ports of the main interferometer are presented. In addition, measurements and simulations of the coupling transfer functions from power fluctuations at the input laser to these ports are shown. The transfer function from the input laser to the output port of the interferometer is found to be non-trivial. Despite this, the numerical simulation produces an excellent match to it and gives insight to the mechanisms leading to the complicated shape. Furthermore, the coupling transfer functions of power fluctuations to the main (heterodyne) detector outputs are measured and simulated. These are used to evaluate the level with which laser power fluctuations contribute to the overall noise level of the instrument.PACS numbers: 04.80. Nn, 95.55.Ym

Section: Transfer Functions From Power Noise To the Detector Outputsmentioning

confidence: 90%

Measurement and simulation of laser power noise in GEO 600

Smith¹,

Degallaix²,

Freise³

et al. 2008

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“…In GEO 600 it is believed [8] that the noise sources associated with the interferometric measurement of the relative positions of the mirrors (i.e. laser noise, sensing noise, oscillator noise, etc.)…”

Section: Confidential: Not For Distribution Submitted To Iop Publishmentioning

confidence: 99%

Violin mode amplitude glitch monitor for the presence of excess noise on the monolithic silica suspensions of GEO 600

Sorazu¹,

Strain²,

Heng³

et al. 2010

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Abstract. Non-Gaussian features of data from gravitational wave detectors are of interest as unpredictable "glitches" limit the sensitivity of searches for many kinds of signal. We consider events due to non-random excitations of the test masses and their suspension fibres. These events could, for example, be related to acoustic emissions in the fibres due to the presence and propagation of cracks or another type of structural perturbation, and they would generate excess noise above the Gaussian background, which matches the level expected due to thermal noise. We look for excess noise in the fundamental violin modes of the monolithic silica suspension fibres of GEO 600. We describe the algorithm used to monitor the violin mode amplitude for glitches, present our results and consider how these may be applied to advanced detectors. The conclusion of our analysis is that no excess noise above what was considered to be thermal noise was observed for several days of h(t) data analysed at the frequency of selected violin modes.PACS numbers: 04.80. Nn, 95.55.Ym, 95.75.Kk, 95.75.Pq

“…The noise spectrum of the main GW channel comprises noise from many subsystems within the interferometer. Identifying the limiting noise sources and determining how much each contributes to the total noise observed in the main GW channel is a process termed 'noise projections' [5]. The result of a set of noise projections is a 'noise budget'.…”

Section: Noise Projectionsmentioning

confidence: 99%

Detector and data characterization at GEO 600

Hewitson

2007

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GEO 600 is one of a few detectors in the world searching for gravitational wave signals from various astronomical sources. The commissioning and characterization of gravitational wave detectors is a highly complex activity that requires the use of many sophisticated analysis procedures. In order to extract all possible astronomical information from the data recorded at GEO 600, the detector and the data must be understood and characterized as well as possible so that the data can make the largest possible contribution in any subsequent analyses. This paper provides a review of some of the aspects of detector and data characterization that takes place at GEO 600.