arXiv subjects

Viviana Fafone

Publications and source records attributed to Viviana Fafone.

8 recordsLinked to original sources

arXiv2026

High-Stability Deformable Mirrors for Correcting Non-Axisymmetric Residual Aberrations in Thermal Compensation of Future Gravitational Wave Interferometers

In gravitational wave detectors, optical aberrations arise mainly from laser absorption in coatings and production process defects in the optics along the laser path. If left uncorrected, these optical path distortions drive the interferometer away from its optimal working point, degrading both stability and sensitivity. Future instruments such as the Einstein Telescope high-frequency detector will operate with unprecedented circulating power, further amplifying the aberration budget. In the current detectors Advanced Virgo and Advanced LIGO, the axisymmetric distortions are corrected using thermal actuators and CO2 laser projectors, however, non-axisymmetric wavefront distortions remain unmitigated. Deformable mirrors are investigated as a flexible solution for mitigating such defects: by shaping the CO2 beam phase upon reflection, they can imprint the required asymmetric intensity pattern on the lensing optics without introducing frequency dependent noise. The target phase map is computed via a modified Gerchberg-Saxton algorithm. We present simulations of this projection strategy and experimental validation demonstrating consistent reproduction of the desired intensity patterns.

gr-qc↗

arXiv2023

Transverse Mode Control in Quantum Enhanced Interferometers: A Review and Recommendations for a New Generation

Adaptive optics has made significant advancement over the past decade, becoming the essential technology in a wide variety of applications, particularly in the realm of quantum optics. One key area of impact is gravitational-wave detection, where quantum correlations are distributed over kilometer-long distances by beams with hundreds of kilowatts of optical power. Decades of development were required to develop robust and stable techniques to sense mismatches between the Gaussian beams and the resonators, all while maintaining the quantum correlations. Here we summarize the crucial advancements in transverse mode control required for gravitational-wave detection. As we look towards the advanced designs of future detectors, we highlight key challenges and offer recommendations for the design of these instruments. We conclude the review with a discussion of the broader application of adaptive optics in quantum technologies: communication, computation, imaging and sensing.

physics.optics↗

arXiv2021

Multimessenger Analysis Strategy for Core-Collapse Supernova Search: Gravitational Waves and Low-energy Neutrinos

Core-collapse supernovae are fascinating astrophysical objects for multimessenger studies. Gravitational waves (GWs) are expected to play a role in the supernova explosion mechanism, but their modelling is also challenging due to the stochastic nature of the dynamics and the vast possible progenitors, and moreover, the GW detection from these objects is still elusive with the already advanced detectors. Low-energy neutrinos will be emitted enormously during the core-collapse explosion and can help for the gravitational wave counterpart search. In this work we develop a multi-messenger strategy to search for such astrophysical objects by exploiting a global network of both low-energy neutrino and gravitational wave detectors. First, we discuss how to improve the detection potential of the neutrino sub-network by exploiting the temporal behaviour of a neutrino burst from a core-collapse supernova. We show that with the proposed approach neutrino detectors can gain at least $10\%$ of detection efficiency at the distance where their efficiency drops. Then, we combine the information provided by GW and neutrino in a multimessenger strategy. In particular, we obtain an increase of the probability to detect the GW signal from a CCSN at $60$ kpc from zero when using only GW analysis to $\sim 33\%$ with our combined GW-$ν$ approach. Keywords: multimessenger, supernova, core-collapse, low-energy neutrino, gravitational wave.

astro-ph.HE↗

arXiv2021

Core-Collapse Supernova Search Strategy: GravitationalWaves and Low-Energy Neutrinos

Core-collapse supernovae are expected to produce multimessenger signals. Low-energy neutrinos and gravitational waves are important to study the explosion mechanism of these events. The simulations and detections of gravitational waves from these events are still challenging due to broad range of expected progenitors as well as their stochasticity. In this work, we present a possible method to combine low-energy neutrinos and gravitational waves to search for core-collapse supernovae, which is based on \cite{Halim2021} (arXiv:2107.02050). We discuss how to exploit the time profile of the neutrino signals in order to improve the efficiency search. Moreover, we describe the combination of neutrino data from several detectors. The goal is to produce a strategy for combining the neutrinos and gravitational waves as a multimessenger search.

astro-ph.HE↗

arXiv2019

Expanding Core-Collapse Supernova Search Horizon of Neutrino Detectors

Core-Collapse Supernovae, failed supernovae and quark novae are expected to release an energy of few $10^{53}$ ergs through MeV neutrinos and a network of detectors is operative to look online for these events. However, when the source distance increases and/or the average energy of emitted neutrinos decreases, the signal statistics drops and the identification of these low statistic astrophysical bursts could be challenging. In a standard search, neutrino detectors characterise the observed clusters of events with a parameter called multiplicity, i.e. the number of collected events in a fixed time-window. We discuss a new parameter called $ξ$ (=multiplicity/duration of the cluster) in order to add the information on the temporal behaviour of the expected signal with respect to background. By adding this parameter to the multiplicity we optimise the search of astrophysical bursts and we increase their detection horizon. Moreover, the use of the $ξ$ can be easily implemented in an online system and can apply also to a network of detectors like SNEWS. For these reasons this work is relevant in the multi-messengers era when fast alerts with high significance are mandatory.

astro-ph.IM↗

arXiv2016

The next detectors for gravitational wave astronomy

This paper focuses on the next detectors for gravitational wave astronomy which will be required after the current ground based detectors have completed their initial observations, and probably achieved the first direct detection of gravitational waves. The next detectors will need to have greater sensitivity, while also enabling the world array of detectors to have improved angular resolution to allow localisation of signal sources. Sect. 1 of this paper begins by reviewing proposals for the next ground based detectors, and presents an analysis of the sensitivity of an 8 km armlength detector, which is proposed as a safe and cost-effective means to attain a 4-fold improvement in sensitivity. The scientific benefits of creating a pair of such detectors in China and Australia is emphasised. Sect. 2 of this paper discusses the high performance suspension systems for test masses that will be an essential component for future detectors, while sect. 3 discusses solutions to the problem of Newtonian noise which arise from fluctuations in gravity gradient forces acting on test masses. Such gravitational perturbations cannot be shielded, and set limits to low frequency sensitivity unless measured and suppressed. Sects. 4 and 5 address critical operational technologies that will be ongoing issues in future detectors. Sect. 4 addresses the design of thermal compensation systems needed in all high optical power interferometers operating at room temperature. Parametric instability control is addressed in sect. 5. Only recently proven to occur in Advanced LIGO, parametric instability phenomenon brings both risks and opportunities for future detectors. The path to future enhancements of detectors will come from quantum measurement technologies. Sect. 6 focuses on the use of optomechanical devices for obtaining enhanced sensitivity, while sect. 7 reviews a range of quantum measurement options.

physics.ins-det↗

arXiv2013

Measurement of the thermal expansion coefficient of an Al-Mg alloy at ultra-low temperatures

We describe a result coming from an experiment based on an Al-Mg alloy (~ 5% Mg) suspended bar hit by an electron beam and operated above and below the termperature of transition from superconducting to normal state of the material. The amplitude of the bar first longitudinal mode of oscillation, excited by the beam interacting with the bulk, and the energy deposited by the beam in the bar are the quantities measured by the experiment. These quantities, inserted in the equations describing the mechanism of the mode excitation and complemented by an independent measurement of the specific heat, allow us to determine the linear expansion coefficient of the material.

cond-mat.mtrl-sci↗

arXiv2002

Resonance widening in spherical GW detectors: model descriptions of the dissipation processes

Internal friction effects are responsible for line widening of the resonance frequencies in mechanical oscillators and result in damped oscillations of its eigenmodes with a decay time Q/ω. We study the solutions to the equations of motion for the case of spherical oscillators, to be used as next generation of acoustic gravitational wave detectors, based on various different assumptions about the material's constituent equations. Quality factor dependence on mode frequency is determined in each case, and a discussion of its applicability to actual gravitational wave detectors is made on the basis of available experimental evidence.

gr-qc↗