Increasing the Astrophysical Reach of the Advanced Virgo Detector via the Application of Squeezed Vacuum States of Light

Current interferometric gravitational-wave detectors are limited by quantum noise over a wide range of their measurement bandwidth. One method to overcome the quantum limit is the injection of squeezed vacuum states of light into the interferometer’s dark port. Here, we report on the successful application of this quantum technology to improve the shot noise limited sensitivity of the Advanced Virgo gravitational-wave detector. A sensitivity enhancement of up to 3.2±0.1  dB beyond the shot noise limit is achieved. This nonclassical improvement corresponds to a 5%–8% increase of the binary neutron star horizon. The squeezing injection was fully automated and over the first 5 months of the third joint LIGO-Virgo observation run O3 squeezing was applied for more than 99% of the science time. During this period several gravitational-wave candidates have been recorded

A state observer for the Virgo inverted pendulum

International audienceWe 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

Relações de saúde e trabalho em assentamento rural do MST na região de fronteira Brasil-Paraguai Health and work relations in a rural settlement of the MST in the Brazil-Paraguay border region

Com o presente artigo, busca-se relatar e analisar as relações entre saúde e trabalho de pequenos produtores rurais do Movimento dos Trabalhadores Rurais Sem Terra (MST). Quanto à metodologia, adotou-se o aporte da investigação participativa e as bases da educação popular. O estudo realizado tornou possível uma compreensão de saúde e de trabalho mediante as narrativas dos trabalhadores e histórias relativas às lutas coletivas contra a exclusão e a violência no campo. Constataram-se importantes aspectos próprios a esse grupo populacional, como o sentido de conquista da propriedade da terra, os conflitos advindos da 'militância' e as diferenças de gênero e geração. Com base nos relatos, analisaram-se também os acidentes e os riscos relacionados à atividade de trabalho no assentamento rural, principalmente a exposição ao agrotóxico. Confirmaram-se, ainda, a solidariedade e a cooperação como valores importantes e como base de novas relações, um modo distinto de organização social coletiva do trabalho.<br>In this article, we aim to report on and analyze the relationship between health and work of small farmers of the Landless Workers Movement (MST). So far as the methodology is concerned, we used participatory research and the basics of popular education. The study allowed for an understanding of health and work based on the workers' narratives, stories relating to collective struggles against exclusion and violence in the countryside. Important aspects related to this population group as were discovered, such as, for example, the sense of conquest of land ownership, the conflicts arising from 'activism,' and the differences of gender and generations. From the reports that were provided, we also examined the accidents and risks related to work in the rural settlement, particularly exposure to pesticides. It was also found that solidarity and cooperation are important values, basic elements for new relations and a distinctive mode of social organization of collective

Erratum: Commissioning status of the Virgo interferometer (Classical and Quantum Gravity (2010) 27 (084002))

No abstract availabl

The Virgo interferometer for gravitational wave detection

International audienceThe Virgo interferometer for gravitational wave detection is described. During the commissioning phase that followed the first scientific data taking run an unprecedented sensitivity was obtained in the range 10-60 Hz. Since then an upgrade program has begun, with the aim of increasing the sensitivity, mainly through the introduction of fused silica wires to suspend mirrors and by increasing the Finesse of the Fabry-Perot cavities. Plans until the shutdown for the construction of the Advanced Virgo detector are given as well as the status of the upgrade

THE VIRGO INTERFEROMETER FOR GRAVITATIONAL WAVE DETECTION

The Virgo interferometer for gravitational wave detection is described. During the commissioning phase that followed the first scientific data taking run an unprecedented sensitivity was obtained in the range 10-60 Hz. Since then an upgrade program has begun, with the aim of increasing the sensitivity, mainly through the introduction of fused silica wires to suspend mirrors and by increasing the Finesse of the Fabry-Perot cavities. Plans until the shutdown for the construction of the Advanced Virgo detector are given as well as the status of the upgrade

The seismic Superattenuators of the Virgo gravitational waves interferometer

International audienceThe Virgo experiment, located near Pisa, Italy, is a large laser Michelson interferometer aiming at the first direct detection of gravitational waves. The interferometer monitors the relative distance of its mirrors placed at the ends of two 3 km-long perpendicular arms. The goal is to measure spectral differential variations of the arm lengths of 10(-18) m/Hz(1/2) in the frequency range from 10 Hz to 10 kHz. Avoiding spurious motions of the optical components is therefore essential to detect gravitational waves. Since the ground motion is 9 orders of magnitude larger than the arm length variations induced by gravitational waves, the seismic noise is the dominant low frequency noise source for terrestrial gravitational wave interferometers. The seismic isolation is obtained suspending the mirrors by an 8-meter tall chain of cascaded mechanical filters, called "Superattenuator" (SA). The Superattenuator is a passive device acting as a low pass filter in all six degrees of freedom, capable of attenuating the ground motion by more than 10 orders of magnitude, starting from a few Hz. To further reduce the seismic disturbances, the filter chain is suspended from an actively stabilized platform that compensates for low frequency and large amplitude oscillations caused by the mechanical resonances of the chain. In this article we describe the Superattenuator together with its control system, and we report about its performance

Noise from scattered light in Virgo's second science run data

Virgo is one of the large, ground-based interferometers aimed at detecting gravitational waves. One of the technical problems limiting its sensitivity is caused by light in the output beams which is backscattered by seismically excited surfaces and couples back into the main beam of the interferometer. The resulting noise was thoroughly studied, measured and mitigated before Virgo's second science run (VSR2). The residual noise during VSR2, which increases in periods with a large microseism activity, is accurately predicted by the theoretical model. The scattered light has been associated with transient events in the gravitational-wave signal of the interferometer