Francisca Sacchetti

• University of Porto

We develop a semiempirical model to describe the creation of an electron plasma in matter at extreme conditions, as excited by high-intensity, extreme ultraviolet (EUV) or x-ray radiation pulses currently available at free-electron laser (FEL) facilities. In typical FEL experiments, EUV and x-ray pulses are used to investigate highly excited states...

We study the Thomson scattering from highly oriented pyrolitic graphite excited by the extreme ultraviolet, coherent pulses of FERMI free electron laser. A nonlinear behaviour is observed and fully described in terms of a coherent phonon scattering process. The short FEL pulses trigger the generation of coherent, low-q ($<$ 0.3 {\AA}^{-1}) phonons,...

A Compton spectroscopy investigation is carried out in hydrated Nafion membranes enabling to identify distortions in the hydrogen bond distribution of the polymer hydrating water, by means of the subtle changes reflected by the Compton profiles. Indeed, deformations of the Compton profiles are observed when varying hydration and two different bondi...

An extreme ultraviolet pump and visible-light probe transmission experiment in crystalline LiF, carried out at the Free Electron Laser facility FERMI, revealed an oscillating time dependence of the plasmon mode excited in the high-density high-temperature electron plasma. The effect is interpreted as a fingerprint of the electron-ion interaction: t...

We present the concept of a novel time-focusing technique for neutron spectrometers, which allows us to disentangle time-focusing from beam divergence. The core of this approach is a double rotating-crystal monochromator that can be used to extract a larger wavelength band from a white beam, thus providing a higher flux at the sample compared to st...

We present the concept of a novel time-focusing technique for neutron spectrometers, which allows to disentangle time-focusing from beam divergence. The core of this approach is a double rotating-crystal monochromator that can be used to extract a larger wavelength band from a white beam, thus providing a higher flux at the sample compared to stand...

The application of Si sensors coupled to Gd converters as thermal neutron counters is assessed in a series of test experiments on the neutron beam, among which scattering from standard samples. The prototype 1d detector is a Si microstrip sensor directly coupled to natural Gd converter and equipped with standard front-end electronics. The raw scatt...

A series of test experiments on three different Si-based neutron detectors, namely a 1-d 128 channel, 0.5 mm space resolution Si microstrip sensor coupled to natural Gd converter, a medium size ? 1 cm2 PIN diode coupled to nGd2O3 or 157Gd2O3 converters, and a SiPM photomultiplier coupled to neutron scintillators, are presented to show the performan...

The magnetic states of iron and their dependence on crystal structure represent an important case study for the physics of magnetism and its role in fundamental and applied science, including geophysical sciences. hcp iron is the most elusive structure as it exists only at high pressure but, at the same time, it is expected to be stable up to very...

To date, the BRISP spectrometer represents the state-of-the-art for every instrument aiming to perform Brillouinneutron scattering. Exploiting accurate ray-tracing McStas simulations, we investigate an improved configuration of the BRISP primary spectrometer to provide a higher flux at the sample position, while preserving all the present capabilit...

Below the melting temperature $T_m$ crystals are the stable phase of typical elemental or molecular systems. However, cooling down a liquid below $T_m$, crystallization is anything but inevitable. The liquid can be supercooled, eventually forming a glass below the glass transition temperature $T_g$. Despite their long lifetimes and the presence of...

Below the melting temperature $T_m$ crystals are the stable phase of typical elemental or molecular systems. However, cooling down a liquid below $T_m$, crystallization is anything but inevitable. The liquid can be supercooled, eventually forming a glass below the glass transition temperature $T_g$. Despite their long lifetimes and the presence of...

We present the principle and the first prototypes of a double rotating-crystal monochromator, based on an assembly of smaller rotating elements. Such a device was developed as the key element to implement a parallel-beam modification of the time-focusing technique for neutron spectrometers. This concept is particularly promising for long-pulse sour...

The importance of the design for the realization of an intense 14 MeV neutron facility devoted to test and validate materials suitable for harsh neutron environments, such as a fusion reactor, is well established. The "New Sorgentina" Fusion Source (NSFS) is a project that proposes an intense D-T 14 MeV neutron source achievable with T and D ion be...

The dynamics of the human oligonucleotide AG3(T2AG3)3 has been investigated by incoherent neutron scattering in the sub-nanosecond timescale. A hydration-dependent dynamical activation of thermal fluctuations in weakly hydrated samples was found, similar to that of protein powders. The amplitudes of such thermal fluctuations were evaluated in two d...

A detailed inelastic neutron scattering investigation of the THz dynamics of liquid zinc is presented. The observed Q dependence clearly reveals the existence of a complex dynamics made up of two distinct excitations. The highest energy mode is the prolongation of the longitudinal acoustic density fluctuations whereas the comparison with the phonon...

The shortage of 3He isotope to be used as optimum neutron absorber in various neutron detection applications is considered. Here we present some general requirements in different applications to introduce more specialized papers which describe recent progresses. Considering that the neutron detection is important in a very wide range of application...

Experimental tests of Bell-type inequalities distinguishing between quantum mechanics and local realistic theories remain of considerable interest if performed on massive particles, for which no conclusive result has yet been obtained. Only two-particle experiments may specifically test the concept of spatial nonlocality in quantum theory, whereas...

Greenhouse gases emission of power generation plants will be continuously tightened to achieve European targets in terms of CO2 emissions. In particular, the switching to a sustainable power generation using fossil fuels will be strongly encouraged in the future. In this context, sorption- enhanced steam reforming (SE-SR) is a promising process bec...

Considering that various investigations identified a correlation between the interstitial electron density in crystalline metals and some ground-state properties, including the compressibility, we propose a procedure to estimate the interstitial electron density in liquid metals starting from the experimental static structure factor. From the calcu...

The terahertz dynamics of human cells of the U937 line and their chromatin has been investigated by high-resolution inelastic X-ray scattering. To highlight its dynamical features in situ, nuclear DNA has been stained by uranyl-acetate salt. The general behavior of the collective dynamics of the whole cell is quite similar to that of bulk water, wi...

This paper describes the scientific aims and potentials as well as the preliminary technical design of IRIDE, an innovative tool for multi-disciplinary investigations in a wide field of scientific, technological and industrial applications. IRIDE will be a high intensity “particles factory”, based on a combination of high duty cycle radio-frequency...

Positron annihilation lifetime spectroscopy is employed to measure the size of the interstitial void spaces characterizing the structure of a set of permanently densified SiO2 glasses. The average volume of the voids is markedly affected by the densification process and linearly shrinks by almost an order of magnitude after a relative density varia...

The implementation of a hydrogen energy policy will be an interesting way to reduce the greenhouse effect. In this perspective, sorption-enhanced steam reforming (SE-SR) is a promising process for the hydrogen generation. In fact, it allows, in a single reactor, the production of a hydrogen-rich syngas, from natural gas or not fossil gas (syngas fr...

This report describes the scientific aims and potentials as well as the preliminary technical design of IRIDE, an innovative tool for multi-disciplinary investigations in a wide field of scientific, technological and industrial applications. IRIDE will be a high intensity 'particle factory', based on a combination of a high duty cycle radio-frequen...

We have employed neutron Brillouin spectroscopy to study coherent collective density fluctuations in the biological macromolecular components of living Escherichia coli cells. To highlight the contribution of the macromolecular material alone, a suitably prepared mixture of light and heavy water was exploited to cancel the scattering length of intr...

The software package ANTS (Anger-camera type Neutron detector: Toolkit for Simulations), developed for simulation of Anger-type gaseous detectors for thermal neutron imaging was extended to include a module for experimental data processing. Data recorded with a sensor array containing up to 100 photomultiplier tubes (PMT) or silicon photomultiplier...

A detailed investigation of the THz dynamics in glassy SiSe2 by means of neutron inelastic scattering is presented. To carefully map the translational dynamics and the region of the boson peak, we carried out two different experiments with sharp and broad resolutions coupled with a narrow and a wide kinematic range, respectively. Data show a comple...

The role of water in the behaviour of biomolecules is well recognized. The coupling of motions between water and biomolecules has been studied in a wide time scale for the self part while collective dynamics is still quite unexplored. Self dynamics provide information about the diffusion processes of water molecules and relaxation processes of the...

We use Brillouin spectra collected in the visible, ultraviolet and X-ray frequency regions to derive the imag-inary part of acoustic compliance, J″(ω), over an extended frequency range from fractions of GHz to tens of THz. We find that J″(ω) accurately reproduces the shape of the self-particle susceptibility as determined by incoherent neutron scat...

A 2D position sensitive gas scintillation detector for thermal neutrons is under development as part of the European FP7 NMI3 JRA program (Project 226507). The aim of the project is to have a detector with: sub-millimetre position resolution, high rate capability (>1 MHz), high efficiency (>50% for 1 Angstrom neutrons) and an active area of 200×200...

A custom and fully interactive simulation package ANTS (Anger-camera type Neutron detector: Toolkit for Simulations) has been developed to optimize the design and operation conditions of secondary scintillation Anger-camera type gaseous detectors for thermal neutron imaging. The simulation code accounts for all physical processes related to the neu...

The role of water in the behaviour of biomolecules is well recognized. The coupling of motions between water and biomolecules has been studied in a wide time scale for the self part while collective dynamics is still quite unexplored. Self-dynamics provides information about the diffusion processes of water molecules and relaxation processes of the...

In the next years the slow neutron scattering community is waiting for a continuous improvement of the neutron detectors because of the development of the new and more intense neutron sources and to obtain a better performance of the neutron instrumentation to face the higher demands and new capabilities necessary for the novel experiments. In part...

The vibrational dynamics of vitreous glucose has been investigated by means of inelastic neutron scattering experiments, exploiting the coherent scattering cross section of deuterium in a fully deuterated sample and the high incoherent scattering cross section of hydrogen in a hydrogenated sample. The first part of the experiment allowed a rather d...

The dynamics of water as subtly perturbed by both the interaction with biomolecules and the variation of temperature and pressure has been investigated via neutron scattering spectroscopy. A measurement of inelastic neutron scattering devoted to the study of the coherent THz dynamics of water in a water-rich mixture with DNA (hydration level of 1 g...

Water dynamics plays a fundamental role for the fulfillment of biological functions in living organisms. Decades of hydrated protein powder studies have revealed the peculiar dynamical properties of hydration water with respect to pure water, due to close coupling interactions with the macromolecule. In such a framework, we have studied coherent co...

We present a data treatment procedure, based on an iterative technique, properly developed to subtract the multi-phonon contributions from the dynamic structure factor in a self-consistent way. With this technique, we derive the one-phonon vibrational density of states from the dynamic structure factor of different disordered systems, in the framew...

We report on the observation of a significant softening of the Boson peak (BP) frequency of vitreous GeO(2) above the glass transition temperature. The softening reminds a critical trend, with a transition temperature intermediate between the glass transition temperature, T(g), and the melting point. The softening of the BP frequency corresponds to...

The ion dynamics of a saturated lithium ammonia solution was investigated by inelastic neutron scattering with optimized resolution. The experimental dispersion curve and mode damping, here carefully probed in a wave-vector range extending well below and above 1 Å−1, display visible anomalies around 0.8 Å−1. We relate the dispersion relation anomal...

We describe an experiment confirming the evidence of the antibunching effect on a beam of non interacting thermal neutrons. The comparison between the results recorded with a high energy-resolution source of neutrons and those recorded with a broad energy-resolution source enables us to clarify the role played by the beam coherence in the occurrenc...

We present incoherent neutron scattering measurements which reveal the presence of non-harmonic motions of protons in ordinary ice Ih down to 5K. A quasi-elastic scattering contribution, corresponding to a fast (~3 ps) and localized motion, has been observed. The corresponding dynamics is related to the hydrogen disorder since it is absent in the h...

The vibrational dynamics of vitreous germanium diselenide (v-GeSe2), an amorphous glass belonging to the family of continuous random network forming glasses, has been investigated by means of inelastic neutron scattering. We employed three different neutron spectrometers, each of them providing different energy resolutions and spanning different po...

We present incoherent quasielastic neutron scattering measurements on ice Ih (ordinary ice) and Ic (cubic ice) which show the existence of nonharmonic motion of hydrogen at low temperatures, down to 5 K. We show that this dynamics is localized, nonvibrational, and related to the hydrogen disorder since it is absent in ordered ice VIII. A main jump...

We present a systematic characterization of Mg1−xLixB2 polycrystalline samples with nominal Li content x up to 0.30. We explore the effectiveness of the substitution and investigate its influence on superconducting and normal state properties. The structural analyses by neutron and x-ray diffraction indicate that, despite the lattice parameters rem...

The propagation of acoustic waves in water-hydrated Nafion membrane has been monitored using heterodyne-detected transient grating spectroscopy. At room temperature, upon increasing the water content, the speed of sound drops to a value lower than the respective velocities of sound in pure Nafion and pure water. This counterintuitive effect can be...

The spectral behaviour of a protein and its hydration water has been investigated through neutron scattering. The availability of both hydrogenated and perdeuterated samples of maltose-binding protein (MBP) allowed us to directly measure with great accuracy the signal from the protein and the hydration water alone. Both the spectra of the MBP and i...

The vibrational dynamics of water molecules confined inside the cavities of a nafion membrane has been investigated exploiting the experimental technique of Brillouin neutron scattering to cover two different kinematic regions. Despite the complexity of the experiments, the inelastic data show unambiguously that confined water still sustains collec...

The low-frequency modes of protein hydration water are investigated by inelastic neutron scattering. Experiments on both protonated and fully deuterated maltose binding protein samples allow us to unambiguously single out the contribution from water. The low-energy vibrational density of states of hydration water at 100 K is similar to the density...

The temperature dependence of the non-ergodicity factor of vitreous GeO$_2$, $f_{q}(T)$, as deduced from elastic and quasi-elastic neutron scattering experiments, is analyzed. The data are collected in a wide range of temperatures from the glassy phase, up to the glass transition temperature, and well above into the undercooled liquid state. Notwit...

The new Time-of-Flight (TOF) Brillouin Spectrometer (BRISP) for inelastic neutron scattering has been developed and constructed at ILL's High Flux Reactor (HFR) for investigating a host of open scientific problems in the low-momentum region and relatively high incoming neutron energies with a dedicated instrument [11. Aisa , D. , Babucci , E. , Bar...

In the Joint Research Activity DETNI (DETectors for Neutron Instrumentation) of the FP6 ED Integrated Infrastructure Initiative for Neutron Scattering and Muon Spectroscopy (NMI3) prototypes of three novel modular thermal neutron area detector types, based on thin solid neutron converters, were built and tested, which were developed for time- and w...

An unified description of liquid metals dynamics based on an interacting two-component model for the ion-electron plasma is tempted. The propagation velocity of the collective modes in alkali and polyvalent metals, derived from inelastic neutron and x-rays scattering experiments, is compared with the estimates obtained by different theoretical appr...

An outline is given of the new neutron Brillouin Spectrometer BRISP which was installed during the last years and recently became fully operational at the Institute Laue-Langevin in Grenoble (France). The main technical features are described and some of the first experimental results are presented, demonstrating the present capabilities of this ne...

A new high resolution (400 nm) Fresnel Zone Plate (ZP) of 1 mm diameter has been designed and produced in order to accurately measure its spatial resolution and efficiency. This experiment is an extension of the previous tests performed to measure the efficiency of these devices. The measurements were carried out on the diffractometer Morpheus at P...

Neutron Brillouin spectroscopy is a powerful tool for studying the microscopic dynamics of soft matter. At the same time, it is an intrinsically difficult technique: for this reason the collective dynamics of some complex systems is still waiting for deeper investigations. An important such case is the study of coherent collective modes in protein...

The dynamic structure factor S(Q, ω) of liquid Bi was measured at 580 K in the Q range from 0.15 to 0.6 Å−1 using inelastic neutron scattering. The obtained spectra clearly demonstrate the existence of well defined longitudinal propagating modes. A positive dispersion is found in the low Q region, where the mode velocity undergoes a transition betw...

We propose here a new interpretation of recent quasi-elastic neutron scattering (QENS) measurements on water. A line-shape analysis based on a stretched exponential ansatz for the time decay of density fluctuations enabled us to observe an anomalous dependence on the exchanged momentum of relevant relaxation parameters. We discuss this effect and r...

We prepared a series of Mg1−x(AlLi)xB2 samples with 0 ⩽ x ⩽ 0.45 in order to compensate with Li the electron doping induced by Al. Structural characterization by means of neutron and X-ray diffraction confirms that Li enters the MgB2 structure even though in an amount less than nominal one. Experimental evidence points out that Li has almost no eff...

The European Physical Society (EPS) is a not for profit association whose members include 41 National Physical Societies in Europe, individuals from all fields of physics, and European research institutions. As a learned society, the EPS engages in activities that strengthen ties among the physicists in Europe. As a federation of National Physical...

We report on a novel simultaneous observation of two inelastic doublets in the dynamic structure factor of the liquid alloy Li30Bi70. This result establishes the coexistence of two density fluctuation modes in a liquid binary system with disparate mass components. The measurements of the dynamic structure factor of the alloy have been performed on...

The non-Thomson contribution to the quasi-elastic X-ray cross-section in non-magnetic metallic Beryllium has been investigated by synchrotron radiation. Such a term is brought about by scattered photons with polarization perpendicular to that of the incoming beam. A properly designed polarization analysis device has been employed for the measuremen...

The single particle dynamics of liquid water has been investigated as a function of pressure and momentum transfer by quasielastic neutron scattering. A line-shape analysis of the experimental spectra enabled us to extract the values of the microscopic diffusion coefficients. As a result, we observe that the pressure evolution of the translational...

High resolution inelastic neutron scattering measurements on a wide class of liquid metals are reported. The driving role of the electron density in the propagation and decay of collective excitations is emphasized. A quantitative relation between the anomalous sound velocity dispersion in liquid metals and the screening of the ionic potential due...

X-ray magnetic circular dicroism at the K absorption edge of iron is exploited to elucidate the local spin structure of Fe in metastable, ferromagnetic fcc Fe–Cu alloys. At Fe concentrations as high as 50 at.%, Fe–Cu alloys are particularly suitable for studying the magnetic state of iron in an fcc environment, because of the negligible contributio...

We describe the main technical features of the novel thermal neutron small-angle time-of-flight spectrometer BRISP, which recently entered its commissioning phase at the High-Flux Reactor of the Institut Laue-Langevin in Grenoble (France). The state of art of the spectrometer development is described, and results of the first important calibration...

The static structure factor of electrons in fullerene has been obtained by a properly designed x-ray diffraction experiment. Due to the intense diffuse scattering caused by the orientational disorder of the C60 molecules in fullerene, the experiment presented several difficulties. Nonetheless, the data were accurate enough to provide an estimate of...

Fermion antibunching was observed on a beam of free noninteracting neutrons. A monochromatic beam of thermal neutrons was first split by a graphite single crystal, then fed to two detectors, displaying a reduced coincidence rate. The result is a fermionic complement to the Hanbury Brown and Twiss effect for photons.

We report on a high-resolution, high-statistics, quasielastic neutron scattering (QENS) experiment on liquid water, aimed at accurately measuring the pressure dependence of the single-particle dynamic response function at low wave vector transfers, namely, from 0.26 to 1.32 A(-1). High-pressure QENS data were collected along the T = 268 K isotherma...

We prepared a series of Mg{sub 1-x}(AlLi)âBâ samples with 0{

In the current (2004-2008) Joint Research Activity DETNI (Detectors for Neutron Instrumentation) in the EU Integrated Infrastructure Initiative for Neutron Scattering and Muon Spectroscopy (NMI3), three detector types and a common ASIC and data acquisition board family are being developed. Two of these detector types, i.e., silicon microstrip (Si-M...

Fermion antibunching was observed on a beam of free noninteracting neutrons. A monochromatic beam of thermal neutrons was first split by a graphite single crystal, then fed to two detectors, displaying a reduced coincidence rate. The result is a fermionic complement to the Hanbury Brown and Twiss effect for photons.

We prepared a series of Mg_{1-x}(AlLi)_{x}B_2 samples with 0≤x≤0.45 in order to compensate with Li the electron doping induced by Al. Structural characterization by means of neutron and X-ray diffraction confirms that Li enters the MgB2 structure even though in an amount less than nominal one. We performed susceptibility, resistivity and specific h...

Inelastic neutron scattering experiments for advanced investigations of the atomic and spin dynamics of matter at low momentum transfers (Neutron Brillouin Spectroscopy) require new instrumentation and efficient measuring techniques. In this paper we describe the development and expected performance of the BRISP thermal neutron spectrometer, which...

The microscopic ion dynamics of liquid gallium was investigated at 320 K—that is, just above the melting point—and 970 K by inelastic neutron scattering experiments and molecular dynamics simulations. The high quality of the experimental data allowed the observation of density fluctuation modes extending up to 1.0 Å−1 and existing at both temperatu...

Neutron incoherent scattering measurements were performed on (H3O)Zr2(PO4)3 Nasicon by the quasi-elastic spectrometer IN13 (ILL, Grenoble), to characterize the slow proton dynamics of the H3O+ ion in this compound. Both quasi-elastic and elastic data were collected at temperatures above and below the order−disorder phase transition (Tc = 177 K). Qu...

Advanced nano-technology is exploited to produce a set of Fresnel neutron zone plates of large aperture and with similar and reproducible characteristics. These zone plates have been employed to test the performance of a stack of them. It is found that the stack of many zone plates can be effective in handling a neutron beam.

The BRISP project is an Italian–German collaboration for the construction of a thermal neutron Brillouin scattering time-of-flight spectrometer at the Institut Laue-Langevin (ILL, Grenoble). Such instrument will allow small momentum transfer investigations of the dynamic structure factor of disordered and magnetic systems, with good energy and mome...

A high resolution (1.5 meV) inelastic neutron scattering experiment was carried out, aiming at an accurate investigation of the high frequency and low momentum dynamic response in heavy water. The experimental data confirm the existence of a dispersionless mode, besides the ordinary longitudinal collective dynamics. A simplified model, based on the...

We performed large scale molecular dynamics simulations of liquid gallium at 320 and 970 K, exploiting a phenomenological model of the ion-pair potential depending only on the electron density. The simulations provided a description of the structure and of several dynamic properties of the system, in quantitative agreement with the experimental fin...

We present the operation of a matrix of Fresnel zone plates consisting of 900 individual zone plates. The individual efficiency of the zone plate lenses is close to 30% for λ=13.7 Å. We discuss the use of such a matrix as an optical element for performing high-resolution neutron imaging (at a sub 50 μm resolution).

Here we report on new results obtained by ad hoc developed McStas simulations of the time-of-flight thermal neutron Brillouin spectrometer BRISP, presently under construction at the ILL. In such a spectrometer a doublecurvature focusing monochromator is combined with a multi-beam converging collimator. This configuration, first exploited for BRISP,...

The low-momentum collective ion dynamics of molten potassium has been investigated by means of a high-resolution inelastic neutron-scattering experiment. Collective vibrational modes were found to contribute to the coherent response function over the wave-vector transfer region from 0.2 up to 1Å-1. The analysis of the quasielastic features of the d...

A high-resolution inelastic neutron-scattering experiment has been carried out on a saturated solution of lithium in deuterated ammonia to investigate the vibrational dynamics at low wave-vector transfer. The response function of the system, dominated by the deuterium dynamics, showed clear coherent contributions arising from collective excitations...

The forward and backward scattering parts (phase II) of the new neutron spectrometer, TOSCA, replacing the old TFXA and TOSCA (phase I), have been successfully installed at the ISIS pulsed neutron source. The results show a significant enhancement in the counting rate due to the larger detector area. The improved resolution (to 1.5-3% of the energy...

Spaghetti-like structures made of fibers whose diameter are of about 1-2 microns, straight structures from about 10-20 microns and optically semitransparent particles, with linear dimension up to about 0.3 mm, were obtained from fine graphite powder in water subjected for 20 h to acoustic cavitation at a frequency of 19.5 kHz. A picture of spaghett...

The low momentum dynamics of liquid mercury has been investigated by means of inelastic neutron scattering and molecular dynamics (MD) simulations. Due to the rather high incoherent cross-section and the high mass of mercury, the measured dynamic structure factor is dominated by the self-correlation function which has been studied in details. The l...

A new collimator for thermal neutrons, based on the honeycomb design, has been produced in a few prototype versions. The method of construction is simple and the overall cost of the device is rather low. Development of this collimator has been stimulated by the technical specifications of the spectrometer BRISP for thermal neutron Brillouin scatter...

The low-momentum dynamics of liquid mercury has been investigated by means of inelastic neutron scattering and molecular dynamics (MD) simulations. Because of the rather high incoherent cross-section and the high mass of mercury, the measured dynamic structure factor is dominated by the self-correlation function, although the low-momentum collectiv...