The coating design for mirrors used in interferometric detectors of gravitational waves currently consists of stacks of two alternating dielectric materials with different refractive indexes. In ...order to explore the performance limits of such coatings, we have formulated and solved the design problem as a multiobjective optimization problem consisting in the minimization of both coating transmittance and thermal noise. An algorithm of global optimization (Borg MOEA) has been used without any a priori assumption on the number and thicknesses of the layers in the coating. The algorithm yields a Pareto tradeoff boundary exhibiting a continuous, decreasing and non convex (bump-like) profile, bounded from below by an exponential curve which can be written in explicit closed form in the transmittance-noise plane. The lower bound curve has the same expression of the relation between transmittance and noise for the quarter wavelength design where the noise coefficient of the high refractive index material assumes a smaller equivalent value. An application of this result allowing to reduce the computational burden of the search procedure is reported and discussed.
•Solution of the design optimization problem of two-materials coatings for Gravitational Wave detectors.•Pareto front computation by (state of art) multi-objective optimizations algorithm (Borg MOEA).•Analytic expression bounding the Pareto fronts.•Noise reduction in realistic Gravitational Waves detectors.
Following a successful period of data-taking between 2006 and 2011, the Virgo gravitational-wave detector was taken offline for a major upgrade. The changes made to the instrument significantly ...increased the complexity of the control systems and meant that an extended period of commissioning was required to reach a sensitivity appropriate for science data-taking. This commissioning period was completed in July of 2017 and the second-generation Advanced Virgo detector went on to join the Advanced LIGO detectors in the O2 science run in August of the same year. The upgraded detector was approximately twice as sensitive to binary neutron star mergers as the first-generation instrument. During the August 2017 science run, Advanced Virgo detected its first gravitational wave signal, with the binary black hole merger, GW170729. This paper describes the control of the longitudinal degrees of freedom in the Advanced Virgo instrument during the O2 science run and the process that brought the detector from an uncontrolled, non-resonant state to its target working point.
The coating design for mirrors used in interferometric detectors of gravitational waves currently consists of stacks of two alternating dielectric materials with different refractive indexes. In ...order to explore the performance limits of such coatings, we have formulated and solved the design problem as a multiobjective optimization problem consisting of the minimization of both coating transmittance and thermal noise. An algorithm of global optimization (Borg MOEA) has been used without any a priori assumption on the number and thicknesses of the layers in the coating. The algorithm yields to a Pareto tradeoff boundary exhibiting a continuous, decreasing and non convex (bump-like) profile, bounded from below by an exponential curve which can be written in explicit closed form in the transmittance-noise plane. The lower bound curve has the same expression of the relation between transmittance and noise for the quarter wavelength design where the noise coefficient of the high refractive index material assumes a smaller equivalent value. An application of this result allowing to reduce the computational burden of the search procedure is reported and discussed.
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