arXiv subjects

Giacomo Ciani

Publications and source records attributed to Giacomo Ciani.

6 recordsLinked to original sources

arXiv2026

In-situ total scattering investigation of crystalline ordering in amorphous ion-beam sputtered thin films for interferometric gravitational wave detectors

Amorphous tantala is an important optical material used in a number of high-precision optical applications, including gravitational wave interferometry. In this paper, we study in-situ the structural changes that occur in amorphous ion-beam sputtered coatings during an annealing treatment by means of a synchrotron radiation scattering experiment. The scattering signal is measured as a function of time on a large range of the Q-space. X-Ray diffraction and Rietveld analysis are used to study crystallization during the annealing treatment, whereas pair distribution function analysis allows to inspect the structural changes occurring during the amorphous to crystalline transition. Our findings indicate that several structural rearrangements occur in parallel, namely a first quick establishment of a backbone structure in the cationic substructure appearing on a rather extended range (up to 100 Angstrom), followed by a progressive rearrangement of the oxygen atoms environment which gradually increases the crystallinity of the structure.

cond-mat.mtrl-sci↗

arXiv2025

Scattered light noise due to dust particles contamination in the vacuum pipes of the Einstein Telescope

High-sensitivity optical measurements such as those performed in interferometric gravitational wave detectors are prone to scattered light noise. To minimize it, optical components must meet tight requirements on surface roughness and bulk defects. Nonetheless, the effectiveness of these measures can be undermined by other sources of scattered light. In this article, we examine scattered light noise caused by particles deposited on surfaces, especially on the baffles inside the vacuum pipes of the Einstein Telescope's interferometer arms. First, we study light scattering by particles deposited on a surface and having diameters from about one tenth to hundred times the light wavelength: we discuss its angular distribution and dependence on particle size and refractive index, and on polarization. Then, we specialize to the case of the Einstein Telescope arms and quantify the maximum allowed density of particles on each arm baffle. We conclude with cleanliness guidelines for the assembly of the vacuum pipes, including the required cleanliness class of the installation environment.

gr-qc↗

arXiv2017

A New Torsion Pendulum for Gravitational Reference Sensor Technology Development

We report on the design and sensitivity of a new torsion pendulum for measuring the performance of ultra-precise inertial sensors and for the development of associated technologies for space-based gravitational wave observatories and geodesy missions. The apparatus comprises a 1 m-long, 50 um-diameter, tungsten fiber that supports an inertial member inside a vacuum system. The inertial member is an aluminum crossbar with four hollow cubic test masses at each end. This structure converts the rotation of the torsion pendulum into translation of the test masses. Two test masses are enclosed in capacitive sensors which provide readout and actuation. These test masses are electrically insulated from the rest of the cross-bar and their electrical charge is controlled by photoemission using fiber-coupled ultraviolet light emitting diodes. The capacitive readout measures the test mass displacement with a broadband sensitivity of 30 nm / sqrt(Hz), and is complemented by a laser interferometer with a sensitivity of about 0.5 nm / sqrt(Hz). The performance of the pendulum, as determined by the measured residual torque noise and expressed in terms of equivalent force acting on a single test mass, is roughly 200 fN / sqrt(Hz) around 2 mHz, which is about a factor of 20 above the thermal noise limit of the fiber.

physics.ins-det↗

arXiv2016

Overview of Advanced LIGO Adaptive Optics

This is an overview of the adaptive optics used in Advanced LIGO (aLIGO), known as the thermal compensation system (TCS). The thermal compensation system was designed to minimize thermally-induced spatial distortions in the interferometer optical modes and to provide some correction for static curvature errors in the core optics of aLIGO. The TCS is comprised of ring heater actuators, spatially tunable CO$_{2}$ laser projectors and Hartmann wavefront sensors. The system meets the requirements of correcting for nominal distortion in Advanced LIGO to a maximum residual error of 5.4nm, weighted across the laser beam, for up to 125W of laser input power into the interferometer.

physics.ins-det↗

arXiv2016

The Advanced LIGO Input Optics

The Advanced LIGO gravitational wave detectors are nearing their design sensitivity and should begin taking meaningful astrophysical data in the fall of 2015. These resonant optical interferometers will have unprecedented sensitivity to the strains caused by passing gravitational waves. The input optics play a significant part in allowing these devices to reach such sensitivities. Residing between the pre-stabilized laser and the main interferometer, the input optics is tasked with preparing the laser beam for interferometry at the sub-attometer level while operating at continuous wave input power levels ranging from 100 mW to 150 W. These extreme operating conditions required every major component to be custom designed. These designs draw heavily on the experience and understanding gained during the operation of Initial LIGO and Enhanced LIGO. In this article we report on how the components of the input optics were designed to meet their stringent requirements and present measurements showing how well they have lived up to their design.

physics.ins-det↗

arXiv2006

Upper limits to surface force disturbances on LISA proof masses and the possibility of observing galactic binaries

We report on the measurement of parasitic surface force noise on a hollow replica of a LISA (Laser Interferometer Space Antenna for the observation of gravitational waves) proof mass surrounded by a faithful representation of its in flight surroundings, namely the capacitive sensor used to detect proof-mass motion. Parasitic forces are detected through the corresponding torque exerted on the proof mass and measured with a torsion pendulum in the frequency range 0.1 30 mHz. The sensor electrodes, electrode housing and associated readout electronics have the same nominal design as for the flight hardware, including 4 mm gaps around the proof mass along the sensitive laser interferometry axis. We show that the measured upper limit for surface forces would allow detection of a number of galactic binaries signals with signal to noise ratio up to approximately 40 for 1 year integration. We also discuss how the flight test under development, LISA Pathfinder, will substantially improve this limit, approaching the performance required for LISA.

gr-qc↗