The UNISA Folded Pendulum class of horizontal and vertical sensors, based on an innovative configuration of the classical Watt׳s linkage mechanical architecture, allows the design and implementation ...of very large band monolithic sensors (10−7Hzto102Hz), whose sensitivities for the most common applications are defined by the noise introduced by their readouts (e.g. <10−12m/Hz with classical LVDT readouts). These unique features, coupled other relevant properties like scalability, compactness, lightness, high directivity, frequency tunability (typical resonance frequencies in the band 10−1Hzto102Hz), very high immunity to environmental noises and low cost make this class of sensors very effective for the implementation of uniaxial (horizontal and/or vertical) and triaxial seismometers and accelerometers for ground, space and underwater applications, including UHV and cryogenics ones.
This paper describes a mechanical horizontal monolithic sensor developed at the University of Salerno. The instrument is basically a monolithic tunable folded pendulum, shaped with precision ...machining and electric-discharge-machining, that can be used both as seismometer and, in a force-feedback configuration, as accelerometer. It is a very compact instrument, very sensitive in the low-frequency band, with a very good immunity to environmental noises, with tunable resonance frequency and integrated laser optical readout.
In this paper we describe the architecture and the performances of a hybrid modular acquisition and control system prototype we developed in Napoli for distributed monitoring and control systems. The ...system, developed by our group within the framework of R&D for interferometric detectors of gravitational waves, is based on a dual-channel 18-bit low noise ADC and 16-bit DAC module at 800 kHz, managed by an Altera FPGA. The module is designed to be used standalone or mounted as mezzanine on a motherboard, in parallel with other modules. In particular, the modules can send/receive the configuration and the acquired/correction signal for control through a standard EPP parallel port to/from an external PC, where the real-time computation is performed. Experimental tests have demonstrated that this architecture allows the implementation of distributed control systems with a sustained sampling frequency up to , using a standard PC for the control signals computation. Each module is also equipped with a 20-bit slow ADC necessary for the acquisition of an external calibration signal. The system is now being extensively tested in on a prototype of suspended optical interferometer for gravitational wave detection we are developing at the INFN in Napoli, made of three superattenuators of the same class of the TAMA Interferometer.
Independent component analysis (ICA) is used to analyze the seismic signals produced by explosions of the Stromboli volcano. It has been experimentally proved that it is possible to extract the most ...significant components from seismometer recorders. In particular, the signal, eventually thought as generated by the source, is corresponding to the higher power spectrum, isolated by our analysis. Furthermore, the amplitude of the source signals has been found by using a simple trick and so overcoming, for this specific case, the classical problem of ICA regarding the amplitude loss of the separated signals.
ABSTRACT
We describe a search for gravitational waves from compact binaries with at least one component with mass $0.2$–$1.0 \, \mathrm{M}_\odot$ and mass ratio q ≥ 0.1 in Advanced Laser ...Interferometer Gravitational-Wave Observatory (LIGO) and Advanced Virgo data collected between 2019 November 1, 15:00 utc and 2020 March 27, 17:00 utc. No signals were detected. The most significant candidate has a false alarm rate of $0.2 \, \rm {yr}^{-1}$. We estimate the sensitivity of our search over the entirety of Advanced LIGO’s and Advanced Virgo’s third observing run, and present the most stringent limits to date on the merger rate of binary black holes with at least one subsolar-mass component. We use the upper limits to constrain two fiducial scenarios that could produce subsolar-mass black holes: primordial black holes (PBH) and a model of dissipative dark matter. The PBH model uses recent prescriptions for the merger rate of PBH binaries that include a rate suppression factor to effectively account for PBH early binary disruptions. If the PBHs are monochromatically distributed, we can exclude a dark matter fraction in PBHs $f_\mathrm{PBH} \gtrsim \, 0.6$ (at 90 per cent confidence) in the probed subsolar-mass range. However, if we allow for broad PBH mass distributions, we are unable to rule out fPBH = 1. For the dissipative model, where the dark matter has chemistry that allows a small fraction to cool and collapse into black holes, we find an upper bound fDBH < 10−5 on the fraction of atomic dark matter collapsed into black holes.
Independent component analysis (ICA), applied on low-frequency (LF) events recorded at Stromboli volcano, reveals that these signals are composed of three independent components in three different ...frequency bands (approximately 0.8–1.2, 2.4–3.0, 3.2–4.5 Hz, respectively). The first two frequency ranges are mainly composed of body waves coming from a direction in a range of −30°, 30° around the crater area. This result is a clear indication that the entire signal, in these frequency bands, comes from the source area. In fact, any scattered wave should have different back azimuth propagation, due to the random distribution of scatterers' location. However, the last independent component is dominated by other kinds of waves, coming from many different directions.
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