Search results for "methods"
showing 10 items of 4526 documents
Determination of IBIS mask transmission matrix
2005
The high-angular resolution imager IBIS is one of the two main instruments aboard the ESA INTEGRAL satellite launched in October 2002. IBIS uses coded aperture mask technique in order to provide the required imaging capabilities for energies between 15 and 10 MeV.The precise knowledge of the coded mask response function critically determine the IBIS imaging performances. In this paper, we present a general description of the IBIS coded mask design together with its main features. Transparency and homogeneity values of the IBIS mask flight model from our laboratory measurements are presented with indication of the instrumental set-up used and accuracy achieved. Mask transmission as a functio…
Symmetry and Electronic Structure of Noble Metal Nanoparticles and the Role of Relativity
2004
High resolution photoelectron spectra of cold mass selected Cu_n-, Ag_n- and Au_n- with n =53-58 have been measured at a photon energy of 6.42 eV. The observed electron density of states is not the expected simple electron shell structure, but seems to be strongly influenced by electron-lattice interactions. Only Cu55- and Ag55- exhibit highly degenerate states. This is a direct consequence of their icosahedral symmetry, as is confirmed by density functional theory calculations. Neighboring sizes exhibit perturbed electronic structures, as they are formed by removal or addition of atoms to the icosahedron and therefore have lower symmetries. Gold clusters in the same size range show complet…
The European Photon Imaging Camera on XMM-Newton: The MOS Cameras
2000
The EPIC focal plane imaging spectrometers on XMM-Newton use CCDs to record the images and spectra of celestial X-ray sources focused by the three X-ray mirrors. There is one camera at the focus of each mirror; two of the cameras contain seven MOS CCDs, while the third uses twelve PN CCDs, defining a circular field of view of 30 arcmin diameter in each case. The CCDs were specially developed for EPIC, and combine high quality imaging with spectral resolution close to the Fano limit. A filter wheel carrying three kinds of X-ray transparent light blocking filter, a fully closed, and a fully open position, is fitted to each EPIC instrument. The CCDs are cooled passively and are under full clos…
JEM–X: The X-ray monitor aboard INTEGRAL
2003
The JEM-X monitor provides X-ray spectra and imaging with arcminute angular resolution in the 3 to 35 keV band. The good angular resolution and the low energy response of JEM-X plays an important role in the identification of gamma ray sources and in the analysis and scientific interpretation of the combined X-ray and gamma ray data. JEM-X is a coded aperture instrument consisting of two identical, coaligned telescopes. Each of the detectors has a sensitive area of 500 cm 2 , and views the sky through its own coded aperture mask. The two coded masks are inverted with respect to each other and provides an angular resolution of 3 0 across an eective field of view of about 10 diameter.
A Method to Measure the Characteristics of Biological Materials at Millimeter Waves
1976
A new method of biological sample characterization at millimeter waves has been studied to verify and extend Webb's experimental results. This method, based on interferometric measurements, is suitable to obtain an absorption spectrum of a living bacterial sediment with a high sensitivity. It has been applied in the frequency range 66-73 GHz. Some experimental results are reported.
Développements récents de l'étude en temps réel par diffraction des rayons X couplée à une thermographie infrarouge : application au suivi de la réac…
1998
La formation au cours d'une reaction de combustion autoentretenue et mecaniquement activee (MASHS) d'intermetalliques nanometrique, tels que les composes FeAl et MoSi 2 , a pu etre observee in-situ et en temps reel en couplant la diffraction des rayons X, produit par rayonnement synchrotron, et une thermographie infrarouge. La mise en oeuvre d'une telle experience est indispensable en raison de la vitesse importante (10 mm/s) de propagation du front de combustion. Des developpements recents realises au niveau des systemes de detections permettent d'obtenir des temps d'acquisition tres courts (quelques dizaines de millisecondes) et de reveler des etapes intermediaires au cours de la transfor…
Noise-induced effects in nonlinear relaxation of condensed matter systems
2015
Abstract Noise-induced phenomena characterise the nonlinear relaxation of nonequilibrium physical systems towards equilibrium states. Often, this relaxation process proceeds through metastable states and the noise can give rise to resonant phenomena with an enhancement of lifetime of these states or some coherent state of the condensed matter system considered. In this paper three noise induced phenomena, namely the noise enhanced stability, the stochastic resonant activation and the noise-induced coherence of electron spin, are reviewed in the nonlinear relaxation dynamics of three different systems of condensed matter: (i) a long-overlap Josephson junction (JJ) subject to thermal fluctuat…
Suppression of timing errors in short overdamped Josephson junctions
2004
The influence of fluctuations and periodical driving on temporal characteristics of short overdamped Josephson junction is analyzed. We obtain the standard deviation of the switching time in the presence of a dichotomous driving force for arbitrary noise intensity and in the frequency range of practical interest. For sinusoidal driving the resonant activation effect has been observed. The mean switching time and its standard deviation have a minimum as a function of driving frequency. As a consequence the optimization of the system for fast operation will simultaneously lead to minimization of timing errors.
Design of a Compact Dual Circular-Polarized Antenna for L-Band Satellite Applications
2020
In this paper, we propose the design of a dual circular-polarized antenna for L-band applications (1.1-1.6 GHz). The designed antenna has been developed by considering crossed-dipoles on top of which a circular patch has been placed to properly act on the mutual coupling between the dipoles. The dual circular polarization is achieved by feeding dipoles in quadrature. Moreover, to increase the antenna gain and polarization purity at high elevation angles, a fence of passive monopoles has been added. The proposed antenna can profitably used as primary feed of a low-frequency parabolic reflector.
Comparison cosmic ray irradiation simulation and particle beam test on UFFO Burst Alert & Trigger telescope(UBAT) detectors
2017
Ultra-Fast Flash Observatory pathfinder(UFFO-p) was launched onboard Lomonosov on 28th of April, 2016, and now is under various types of calibration for detection of Gamma Ray Bursts (GRBs). Since last September UFFO-p has taken X-ray data in space with UFFO Burst Alert & Trigger telescope (UBAT), those X-rays are mostly diffused backgrounds however, the rate turns out to be higher than expected by a factor of three. We assumed cosmic rays can contribute by making the count rate higher. We did such a simulation to investigate the effect of cosmic rays. In December 2016, we irradiated fragmented high energy heavy ions at CERN on the UBAT detector. We will report the result of comparison betw…