Status of Advanced Virgo Aiello, L.; Amato, A.; Baldaccini, F. ...
EPJ Web of Conferences,
01/2018, Letnik:
182
Journal Article, Conference Proceeding
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Odprti dostop
The LIGO and the Virgo collaborations have recently announced the first detections of Gravitational Waves. Due to their weak amplitude, Gravitational Waves are expected to produce a very small effect ...on free-falling masses, which undergo a displacement of the order of 10
-18
m for a Km-scale mutual distance. This discovery showed that interferometric detectors are suitable to reveal such a feeble effect, and therefore represent a new tool for astronomy, astrophysics and cosmology in the understanding of the Universe. To better reconstruct the position of the Gravitational Wave source and increase the signal-to-noise ratio of the events by means of multiple coincidence, a network of detectors is necessary. In the USA, the LIGO project has recently concluded its second Observation Run (O2) with a couple of twin 4 kilometer-long arms detectors which are placed in Washington State and Louisiana. Advanced VIRGO (AdV) is a 3 kilometer-long arms second generation interferometer situated in Cascina, near Pisa in Italy. The installation of AdV has been completed in 2016, and the first commissioning phase allowed to get to the target early-stage sensitivity, which was sufficient to join LIGO in the O2 scientific run. In this paper, the challenges of the commissioning of AdV will be presented, together with its current performances and future perspectives. Finally, in the last paragraph the latest discoveries that occurred after the ICNFP 2017 conference will be also described.
The measurement of the finesse and the longitudinal locking of a 100 μm long plane mirrors Fabry-Perot cavity is described. a finesse of up to 5400 has been found. If attached to the Virgo antenna ...suspension (SA), a similar device is sensitive enough to detect the thermal displacement noise of the SA test mass, which is expected to limit the Virgo antenna sensitivity between 10 and 600 Hz. Reducing the Virgo noise floor is a challenge for future antenna development, as this region is the most promising one for coalescing binary stars and pulsar signals.
An ultralow resonant frequency vertical seismic activity attenuation filter prototype has been designed and built as the vertical component of a Pre-Isolation Stage (PIS) for low-frequency Seismic ...Attenuation (SA) chains. The task of the PIS is to reduce the excitation of the chain payload's resonant residual motions. A characterization and the performance of the prototype are reported along with some design considerations. An attenuation of 45
dB has been achieved in the region of interest (the SA chain resonant frequency band) and an upgrade to more than 50
dB attenuation is easily achievable. Tests of active feedback loop attenuation driven by electro magnetic actuators and controlled by a Digital Signal Processor reading a precision vertical accelerometer have been successfully performed. The filter also effectively acts as a precision positioner for the suspended payload.
The gravitational wave detector VIRGO aims at extending the detection band down to a few Hertz by isolating the mirrors of the interferometer from seismic noise. This result is achieved by hanging ...each mirror through an elastic suspension (Superattenuator), designed to filter mechanical vibrations in all the degrees of freedom. An experimental upper limit of the mirror residual seismic noise at a few Hertz is provided in this paper. This is lower than the thermal noise floor, expected to limit the antenna sensitivity in the low frequency range.
The data collected by a gravitational wave interferometer are inevitably affected by instrumental artefacts and environmental disturbances. In particular, for continuous gravitational wave (CW) ...studies it is important to detect narrow-band disturbances (the so-called "noise lines") during science runs, and to help scientists to identify and possibly remove or mitigate their sources. The NoEMi (Noise Frequency Event Miner) framework exploits some of the algorithms implemented for the CW search to identify, on a daily basis, the frequency lines observed in the Virgo science data and in a subset of the environmental sensors, looking for lines that match in frequency. A line tracker algorithm reconstructs the lines over time, and stores them in a database, which is made accesible via a web interface. We describe the workflow of NoEMi, providing examples of its use for the investigation of noise lines in past Virgo runs (VSR2, VSR3) and in the most recent run (VSR4).
Virgo is designed to detect gravitational waves of both astrophysical and cosmological origin in the frequency range from a few Hz to a few kHz. After the end of the first science run, partially ...overlapped with the LIGO fifth science run, the detector underwent several upgrades to improve its sensitivity. The second Virgo science run started at the beginning of July 2009 in coincidence with LIGO. A further upgrade is planned at beginning of 2010 with the installation of new suspensions for the test masses and of new mirrors. This will lead to a considerable improvement in the sensitivity and represents an intermediate step toward the development of the advanced detectors.
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