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A stochastic background of gravitational waves is expected to arise from a superposition of a large number of unresolved gravitational-wave sources of astrophysical and cosmological origin. It should carry unique signatures from the earliest epochs in the evolution of the Universe, inaccessible to standard astrophysical observations. Direct measurements of(More)
We present a LIGO search for short-duration gravitational waves (GWs) associated with soft gamma ray repeater (SGR) bursts. This is the first search sensitive to neutron star f modes, usually considered the most efficient GW emitting modes. We find no evidence of GWs associated with any SGR burst in a sample consisting of the 27 Dec. 2004 giant flare from(More)
Digitally enhanced heterodyne interferometry is a laser metrology technique employing pseudo-random codes phase modulated onto an optical carrier. We present the first characterization of the technique's displacement sensitivity. The displacement of an optical cavity was measured using digitally enhanced heterodyne interferometry and compared to a(More)
We report on an all-sky search with the LIGO detectors for periodic gravitational waves in the frequency range 50-1100 Hz and with the frequency's time derivative in the range -5 x 10{-9}-0 Hz s{-1}. Data from the first eight months of the fifth LIGO science run (S5) have been used in this search, which is based on a semicoherent method (PowerFlux) of(More)
We describe and verify the dynamic behavior of a novel technique to optimize and actively control the optical impedance matching condition of a coupled resonator system. The technique employs radio frequency modulation and demodulation to interrogate the reflection amplitude response of the coupled cavity system. The sign and magnitude of the demodulated(More)
We present a new technique for the fine alignment sensing of optical interferometers. Unlike conventional wavefront sensing systems, which use multielement photodiodes, this approach works with a single-element photodiode, in combination with a spatial light modulator (SLM) and digitally enhanced heterodyne interferometry. As all signals pass through a(More)
Gravity gradient noise generated by seismic displacements may be the limiting factor for the sensitivity of third-generation gravitational wave detectors at frequencies below 10 Hz. A finite element framework has been developed to calculate the soil response to various excitations. The accompanying gravity gradients as a result of the seismic displacement(More)
There is a strong scientific case for the study of gravitational waves at or below the lower end of current detection bands. To take advantage of this scientific benefit, future generations of ground based gravitational wave detectors will need to expand the limit of their detection bands towards lower frequencies. Seismic motion presents a major challenge(More)
In-vacuum Faraday isolators (FIs) are used in gravitational wave interferometers to prevent the disturbance caused by light reflected back to the input port from the interferometer itself. The efficiency of the optical isolation is becoming more critical with the increase of laser input power. An in-vacuum FI, used in a gravitational wave experiment(More)
We report an application of Kalman filtering to the inverted pendulum (IP) of the Virgo gravitational wave interferometer. Using subspace method system identification techniques, we calculated a linear mechanical model of Virgo IP from experimental transfer functions. We then developed a Kalman filter, based on the obtained state space representation, that(More)