Search

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 estimates from open loop time domain data, the state variables of the system. This allows the observation (and eventually control) of every resonance mode of the IP mechanical structure independently. [ABSTRACT FROM AUTHOR]

The design of the gravitational wave interferometric detectors of third generation is under way. An overall improvement of the detector performance can be obtained by reducing a few noise sources, such as seismic noise, shot noise, and most importantly thermal noise. We report here on the design and fabrication of low thermal-noise suspensions made of a new material presently under investigation. An ad hoc technique to produce crystalline silicon fibers has been developed; the first measurements of the fiber mechanical and thermal properties at room temperature have been performed and interpreted. Preliminary measurements of the mechanical losses at low temperature are also discussed. [ABSTRACT FROM AUTHOR]

Thermal noise in mirror suspension wires is the most severe limit to the low frequency sensitivity of interferometric gravitational wave detectors presently under construction. The pendulum mode mechanical quality factor of the suspension last stage significantly affects the noise level of the detector output. The monolithic design for this suspension stage, using a low dissipation material, is proposed for Virgo. High mechanical Q[sub s] and high breaking strengths have been obtained for monolithic fused silica fibers. A low dissipation and high strength bonding technique using potassium silicate bonding is proposed. [ABSTRACT FROM AUTHOR]

Thermal noise in the mirror substrates sets a most severe limit to the low-frequency sensitivity of the interferometric gravitational wave detectors presently under construction. The mechanical quality of the mirror substrates and the geometry of their suspension are shown to affect markedly the noise level of the detector output. High mechanical Q have been obtained for different large fused silica substrates under Virgo suspension conditions. Moreover, calcium fluoride substrates are shown to provide a more promising option for the design of future cryogenic, low thermal noise interferometers. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The diffusion of a suspended brownian particle along a sinusoidally corrugated narrow channel is investigated to assess the validity of two competing analytical schemes, both based on effective one-dimensional kinetic equations, one continuous (entropic channel scheme) and the other discrete (random walker scheme). For narrow pores, the characteristic diffusion time scale is represented by the mean first exit time out of a channel compartment. Such a diffusion time has been analytically calculated in both approximate schemes; the two analytical results coincide in leading order and are in excellent agreement with the simulation data.