2,172 research outputs found
The VIRGO suspensions
No full textThe VIRGO suspensions are chains of passive mechanical filters designed to isolate the interferometer mirrors from seismic noise starting from a few Hz. In order to reduce the low-frequency swing of the mirror along the beam, an active control system, acting at the level of the suspension point, damps the main resonant modes of the system (all below 2.5 Hz). Another control loop, at the level of the optical payload, makes use of a digital camera monitoring the mirror position in all six degrees of freedom. Its main goal is to decrease the rms angular displacements of the mirror, on a time scale of several minutes, down to less than I murad. All the seven suspensions of the VIRGO central interferometer are presently in operation, while the assembly of the last two, for the terminal mirrors, is in progress, The design and performance of the system are described in this paper
Advanced Virgo+ status and future perspectives
No full textThe Virgo detector contributed to the observations in the O3 observing run and increased its sensitivity from the
initial 46 up to 60 Mpc during the run. The detector has undergone to a series of improvements since the end of
the O3 observing run in view of O4, as the implementation of an additional recycling cavity at the output of the
interferometer – the Signal Recycling cavity (SRC) – to broaden the sensitivity band, the Frequency Dependent
Squeezing (FDS) to reduce quantum noise at all frequencies, and a new higher power laser.
Some criticality have emerged mainly due to the presence in Virgo of marginally stable recycling cavities with
respect to the stable recycling cavities present in the LIGO detectors, which increases the difficulty in controlling
the interferometer in presence of defects as those introduced by the high power on the mirrors. This resulted
in a delayed joining the O4 run due to a longer than expected commissioning phase. At present the detector is
running with a lower laser power (and a lower sensitivity w.r.t. the project design).
A new stop of about 2 yr is planned between O4 and O5 starting in 2027, to implement new upgrades (phase
II). To improve the stability of the interferometer, we are considering a large upgrade to introduce stable cavities
and this will imply heavy infrastructural works also with the minimal design. The aim is to reach a Binary
Neutron Star (BNS) sensitivity larger than 100 Mpc.
Plans are being made for the post-O5 period as a bridge between 2nd and 3rd generation detectors and a new
collaborative effort has born under the name of Virgo nEXT with the aim to keep and push the infrastructure
and maintain alive the communit
The antiseismic suspension for the VIRGO project
No full textGravitational waves propagating from rapidly accelerating star masses can be detected by means of interferometric techniques. Several interferometric antennas are presently under construction around the world with the aim of gravitational waves detection in the frequency range starting from a few tens of Hz to a few kHz. In the low frequency region (below a few tens of Hz) their detection is limited by seismic noise which can mask the weak signal induced by a gravitational wave impinging on a suspended mirror. In order to overcome this limitation, the VIRGO collaboration has developed and built a sophisticated suspension system to isolate the optical components from the seismic noise. This mechanical system, called SuperAttenuator, is able to inhibit the transmission of any mechanical disturbances starting from about 4 Hz thus extending the detection band in the low frequency region
A gravitational wave detector: The virgo interferometer
No full textGravitational waves were predicted in 1916 by Einstein as a conse- quence of the theory of General Relativity: accelerated masses can produce ripples propagating at the speed of light, which perturb the space-time metric. Thanks to the extremely weak coupling with matter, gravitational waves can cross the universe undisturbed and, hence, are a probe of the regions where they are produced which is not accessible by the eventual electromagnetic counterpart. The gravitational waves sources of detectable amplitudes are expected to be compact astrophysical sources such as the coalescence of binaries formed by black holes and neutron stars, the collapses of stellar cores, or the rotation of non-axis-symmetric neutron stars. For more than 40 years the search for gravitational waves has been pursued with resonant detectors made of metallic bars. The development of gravitational wave detectors based on laser interferometers started in the early seventies. After more than two decades of development, the construction of the first interferometers with kilometer scale arms started in the nineties. The sensitivity of such detectors is fun- damentally proportional to its length, and with its 3 kilometer long arms Virgo is the largest gravitational wave detector in Europe, and the third largest in the world. It is located at the European Gravitational Observatory (EGO), close to Pisa, and it is designed to detect gravitational waves emitted by astrophysical sources in the frequency range between 10Hz and a few kHz. Among the other current ground- based gravitational wave detectors, Virgo is the one having the best sensitivity at low frequency, thanks to the particular seismic attenuators, from which the mirrors are suspended. Construction started in 1996 and ended in July 2003. After a very intense commissioning phase, the performances of the detector are now very close to the design ones, and the detector is entering the operation phase. In parallel, the design phase of the second generation of interferometers should be finalized this year with a construction planned to start in 2011. Also, the conceptual design is under study for a third generation. The corresponding European project is called the "Einstein Telescope". ©2010 by Società Italiana di Fisica
The inertial damping of the VIRGO superattenuator and the residual motion of the mirror
No full textThe VIRGO superattenuator (SA) is effective in suppressing seismic noise below the expected thermal noise level above 4 Hz. However, the residual mirror motion associated with the SA normal modes can saturate the interferometer control system. This motion is reduced by implementing a wideband (DC-5 Hz) multidimensional active control (the so-called inertial damping) which makes use of both accelerometers and position sensors and of a digital signal processing (DSP) system. Feedback forces are exerted by coil-magnet actuators on the top of an inverted pendulum pre-isolator stage. The residual root mean square motion of the mirror in 10 s is less than 0.1 mum
Interferometer signal detection system for the VIRGO experiment
No full textVIRGO is a laser interferometer aiming at the first detection of gravitational waves emitted by astrophysical sources. The signal detection system consists of all the output optics and the electronics necessary for the measurement of the interferometer output signal. An output mode cleaner has been developed in this context. The system has been installed at the detector site and is now being used for the central interferometer, the first step in the construction of VIRGO. The first results obtained so far are presented
- …
