Synthesis and characterization of nanocrystalline LaNi5 hydrogen storage materials

With the growing environmental concerns of greenhouse gas emissions from the burning of fossil fuels, it is becoming increasingly important to switch to cleaner alternative fuels such as hydrogen [1]. Inter-metallic LaNi5 is one of the most widely used and studied solid-state hydrogen storage material \u2013 a pet material for the prototype systems using hydrogen fuel. However, nanostructuring effects on this systems are not yet fully explored. Recently we have carried out systematic studies regarding the effect of nanostructuring on the hydrogen sorption properties of this material [2]. Unlike some other potential hydrogen storage materials, which shows faster kinetics upon nanostructuring, the long time ball-milling of the bulk LaNi5 results in the formation of an anomalous-state resistant to hydrogen absorption-desorption reactions. In this contribution, we present the preliminary differential scanning calorimetry (DSC), x-ray diffraction (XRD) and x-ray photoemission spectroscopy (XPS) data on the nanostrutured LaNi5 powders. XRD and XPS results indicate the long-time ball-milled and annealed LaNi5 to be of pure nanocrystalline phase. DSC results indicate a partial elimination of defects at 500oC, in a more efficient way for the short-time ball-milled powders compared to the long-time ball-milled samples. These results will be discussed in the light of the hydrogen sorption properties of the bulk and nanocrystalline LaNi5 samples

EUSO-A Space mission searching for Extreme Energy Cosmic Rays and neutrinos

The \u201cExtreme Universe Space Observatory \u2013 EUSO\u201d is an international, multi-agency mission, led by ESA, aimed at measuring from a Low Altitude Earth Orbiting Space Platform the flux and investigating the nature and origin of the charged and neutral particles of the Extreme Energy Cosmic Ray (EECR) with energy above the conventional value (E = 5x10^19 eV) of the Greisen Zatsepin and Kuzmin (GZK) effect EGZK =5x1019 eV). EUSO will pioneer the observation from Space of EECR-induced Extensive Air Showers (EASs), making measurements of the primary energy,arrival direction and possibly composition of the incoming flux by using a sensitive area and target volume far greater than achievable from the ground. Such data will shed light on the origin of EECRs, on their sources , on the propagation environment from the source to Earth on the particle physics mechanisms at energies well beyond the ones achievable in man-made accelerators. We will discuss in this paper the scientific motivations, the observational approach, the experimental set-up and the expected performances of the proposed mission

I raggi cosmici: cosa sono, da dove provengono, che messaggio portano.

Una pioggia continua di oltre 100 particelle al secondo ci colpisce e ci attraversa, in ogni luogo della Terra, in ogni istante della nostra vita. Si tratta dei raggi cosmici che pervadono l\u2019universo e colpiscono la Terra in modo isotropo (senza alcuna direzione privilegiata) proveniendo dal cosmo, e verosimilmente sia dall\u2019interno che dall\u2019esterno della nostra Galassia. La loro energia \ue8 estremamente variabile, ma pi\uf9 \ue8 grande, meno frequenti essi sono. Essi contengono dei messaggi la cui interpretazione ci consentirebbe di conoscere una grande messe di informazioni sui fenomeni che avvengono nello spazio e che coinvolgono la nascita, la formazione e la morte delle stelle e degli altri corpi celesti. La loro origine, nel senso dei meccanismi che li generano, le loro sorgenti nel cosmo, laloro composizione sono tuttora in larga misura sconosciuti. L\u2019articolo fornisce una breve carrellata sui maggiori interrogativi che la loro osservazione pone, sulle loro principali caratteristiche, sullo stato attuale delle tecniche sperimentali utilizzate per il loro studio, con una breve introduzione storica sulle tappe fondamentali che, dall\u2019inizio dello scorso secolo, hanno scandito la loro osservazione e la comprensione che oggi abbiamo di essi

Local structure of ball-milled LaNi5 hydrogen storage material by Ni K-edge EXAFS

Local structure of the nanostructured LaNi5 hydrogen storage alloys, prepared by ball-milling, has been studied using Ni K-edge extended X-ray absorption fine structure spectroscopy. Results indicate that the ball-milling up to 100 h results in the production of nanoparticles characterized by large atomic disorder and slightly reduced unit-cell volume, compared to the bulk LaNi5. High temperature annealing appears to help in partial recovery of atomic order in the ball-milled samples; however, longtime ball-milled samples retain large disorder even after the high temperature annealing. The results suggest that the large disorder and the reduced unit-cell volume might be causing a higher energybarrier for the hydride-phase formation in the long time ball-milled LaNi5 powders

EUSO Science

EUSO is a mission to explore the extreme universe by the probe of Ultra High Energy Cosmic Rays (LTHECRs) and LTHE neutrinos [1]. EUSO monitors a gigantic volume of atmosphere from Space and measures showers induced by UHECRs and UHE neutrinos. Scientifically, it is important to measure the energy spectrum of UHECRs well beyond GZK energy with high statistics. EUSO ensures the observation of UHECRs up to 10(21) eV even in the case of GZK mechanism working [2-7], and gives us a clear picture of the existence / non-existence of the GZK effect and the behavior of the spectrum beyond GZK energy, which represents the contributions from nearby sources. The anisotropy study of UHECR arrival directions in a small scale angle above GZK energy may allow us to identify individual source, because of the limited propagation distance and the high rigidity of particles. If event clusters observed by AGASA are real, it is expected from Monte Carlo simulation that EUSO will see similar to 100 particles from individual brightest sources and will give us a good opportunity to test the relativity in high precision. The UHE neutrino is a unique channel to explore the universe much deeper than UHECRs. EUSO essentially can measure URE neutrinos free from background proton showers. The number of GZK neutrino events in a EUSO three years' mission is expected to be only a few. Nevertheless, it is a definitely conceivable opportunity to begin UHE neutrino astrophysics at GZK energy

A large-area modular electromagnetic shower detector for the CERN intersecting storage rings

The authors describe the design and performances large-area (13 m/sup 2/) shower detector built for an experiment at the CERN ISR to detect electrons and gamma rays with energies up to 4 GeV. The main characteristics of the detector are: a) linearity of the energy response from 0.5 to 4 GeV; b) good energy, time and space resolutions; c) modularity of the mechanical assembly; d) low cost of construction. (3 refs)

Extensive Air Showers and Diffused Cerenkov Light Detection: the ULTRA Experiment

The Uv Light Transmission and Reflection in the Atmosphere (ULTRA) experiment has been designed to provide quantitative measurements of the backscattered Cherenkov signal associated to the Extensive Air Showers (EAS) at the impact point on the Earth surface. The knowledge of such information will test the possibility to detect the diffused Cherenkov light spot from space within the Ultra high-energy cosmic ray observation. The Cherenkov signal is necessary to give an absolute reference for the track, allowing the measurement of the shower maximum and easing the separation between neutrino and hadronic showers. In this paper we discuss the experimental set-up with detailed information on the detection method; the in situ and laboratory calibrations; the simulation of the expected detector response and finally the preliminary results on the detector performance

Software timing calibration of the ARGO-YBJ detector

The ARGO-YBJ experiment is mainly devoted to search for astronomical gamma sources. The arrival direction of air showers is reconstructed thanks to the times measured by the pixels of the detector. Therefore, the timing calibratin of the detector pixels is crucial in ordere to get the best angular resolution abd pointing accuracy. Because of the large number of pixels a hardware timing calibration is practically impossible. Therefore, an off-line software calibration. Here, the details of the procedure and the results are presented