26 research outputs found

    Geant4 simulations of soft proton scattering in X-ray optics. A tentative validation using laboratory measurements

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    Low energy protons (< 300 keV) can enter the field of view of X-ray space telescopes, scatter at small incident angles, and deposit energy on the detector, causing intense background flares at the focal plane or in the most extreme cases, damaging the X-ray detector. A correct modelization of the physics process responsible for the grazing angle scattering processes is mandatory to evaluate the impact of such events on the performance of future X-ray telescopes as the ESA ATHENA mission. For the first time the Remizovich model, in the approximation of no energy losses, is implemented top of the Geant4 release 10.2. Both the new scattering physics and the built-in Coulomb scattering are used to reproduce the latest experimental results on grazing angle proton scattering. At 250 keV multiple scattering delivers large proton angles and it is not consistent with the observation. Among the tested models, the single scattering seems to better reproduce the scattering efficiency at the three energies but energy loss obtained at small scattering angles is significantly lower than the experimental values. In general, the energy losses obtained in the experiment are higher than what obtained by the simulation. The experimental data are not completely representative of the soft proton scattering experienced by current X-ray telescopes because of the lack of measurements at low energies (< 200 keV) and small reflection angles, so we are not able to address any of the tested models as the one that can certainly reproduce the scattering behavior of low energy protons expected for the ATHENA mission. We can, however, discard multiple scattering as the model able to reproduce soft proton funneling, and affirm that Coulomb single scattering can represent, until further measurements, the best approximation of the proton scattered angular distribution at the exit of X-ray optics.Comment: submitted to Experimental Astronom

    Estimates for the background of the ATHENA X-IFU instrument: the cosmic rays contribution

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    The background of the ATHENA X-IFU instrument is evaluated by Geant4 simulations. A new, highly detailed, mass model of the X-IFU and of its cryostat has been produced, a new model for the Galactic Cosmic Ray protons in L2 has been developed from satellite data, and a set of physics models tuned to ATHENA needs has been refined through extensive validations against experimental results. We are going to report the latest results in the estimate of the background of the X-IFU instrument, obtained after the update of all the elements of the Geant4 simulations and of the post processing software

    Science education and teachers\u2019 training. Research in partnership

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    Taking into account the results of international researches concerning science knowledge of young people (TIMMS and PISA) and the worrying decrease in science disciplines\u2019 roll in many countries, especially in European Community, our research group, cooperating within an international context, has designed materials in order to: - improve motivation, learning and pupils' attitudes in science education - develop a critical thinking, stimulate intuition and creativity - increase scientific literacy in the community. According to our experience, the most important school-related factor in raising student achievement is the quality of the teacher. Today, in the era of high standards and increased accountability, boosting teacher quality is more crucial than ever before. So we designed models of courses for pre-service and in-service science teachers as well offering the opportunity to cope with open problems, reflect about teaching models, discuss examples of good practices. Kindergarten initial teachers had to reflect about some basic science concepts (space, time, forces, geometrical shapes), analyze their own mind representations, make simple experiments and design a short item. Mathematics and Physics teachers were trained in laboratory with innovative and flexible devices which stimulated their motivation and creativity. We investigated : - variables affecting teaching models/styles and related students' learning - students' assessment. We present some results concerning kindergarten- primary - high school teachers' training. Method We interacted with initial and in-service science teachers mainly according with a critical social constructivist perspective, stimulating reflection and collaborative learning. We submitted pre-school initial teachers to questionnaires to explore their ideas concerning both their teaching models and basic scientific concepts. Expected Outcomes Outcomes. We have observed in teachers: - increased awareness about conceptual knots concerning scientific concepts - more sensitiveness and attention to students' involvement - reflection about the effectiveness of their daily school work - increased awareness about cooperative learning. References M. De Paz, M. Pilo, C. Pastorino \u2013 Constructivist evaluation of learning. A research through partnership \u2013 Proceedings of EERA Conference, Ecer 1999, Lahti (Finland), September 1999 M. De Paz, M. Pilo \u2013 Examples of constructivist teaching/learning \u2013 Ibidem M. Pilo, M. De Paz, C. Pastorino - \u2018Wrong experiments\u2019: case studies of a constructivist approach to effective learning for science- Contribution to International Conference at University College Worcester on \u201cEffective Learning through Reflective practice\u201d, January 11-14, 2001 M. Pilo - A collaborative Approach in teachers\u2019 training- ECER 2007, Ghent (Belgium), September 19-22 P. Masson, M. Pilo (eds) \u2013 Partnership in Education- Theoretical Approach and case studies (2009) \u2013 The BookEdition \u2013 ISBN 978-2-9533881-0-7 M. Pilo, B. Gavio \u2013 Scientific education: issues of researches in partnership \u2013 Ibidem- p. 153-16

    Dimensionality Changes in Crystalline Complexes Induced by Exposure to Air: Solid-State Studies Using Single Crystal and Powder X-ray Diffraction Methods

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    When they come into contact with air, coordination compounds can often change their appearance. For instance, the colour of the compound can change as transparent crystals become opaque microcrystalline solids. This visible transformation of the compound is frequently accompanied by structural modifications due to loss of solvent molecules or in the reverse case, the reaction with water from the air. Often, the dimensionality of the structures also varies and this aspect is demonstrated for three pairs of copper(II) complexes (1D ? 0D, 1D ? 2D and 3D ? 2D). The complementary use of single crystal and powder X-ray diffraction methods is indispensable for the evaluation of these structural changes

    Control and dynamic systems : advances in theory and applications

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    A general system to perform a Geant4-based simulation in a distributed computing environment is presented. The architecture developed makes the system transparent to sequential or parallel execution and to the environment where the simulation is run: a single machine, a local cluster or a geographically distributed grid

    Electron backscattering simulation in Geant4

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    The backscattering of electrons is a key phenomenon in several physics applications which range from medical therapy to space including AREMBES, the new ESA simulation framework for radiation background effects. The importance of properly reproducing this complex interaction has grown considerably in the last years and the Geant4 Monte Carlo simulation toolkit, recently upgraded to the version 10.3, is able to comply with the AREMBES requirements in a wide energy range. In this study a validation of the electron Geant4 backscattering models is performed with respect to several experimental data. In addition a selection of the most recent validation results on the electron scattering processes is also presented. Results of our analysis show a good agreement between simulations and data from several experiments, confirming the Geant4 electron backscattering models to be robust and reliable up to a few tens of electronvolts

    Validation of Geant4 10.3 simulation of proton interaction for space radiation effects

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    Monte Carlo simulation of space radiation effects induced by protons is important for design of space missions. Geant4 is a well established toolkit for Monte Carlo simulation focused on high energy physics applications. In this work, a set of new validation results versus data for Geant4 electromagnetic and hadronic interaction of protons is presented and discussed. Optimal configuration of Geant4 physics for space applications is proposed

    Validation of the Geant4 PIXE component for incident carbon ions

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    The goal of this study is to experimentally validate PIXE modelling using the Geant4-ANSTO model (“G4-ANSTO”), distributed for the first time in Geant4 11.0, as well as the Geant4 default model (“G4-default”), for targets bombarded with carbon ions of energies up to 3 MeV/amu, an energy range of importance for PIXE applications. The experimental validation was performed using a variety of target materials, spanning a broad atomic number range. The reference experimental measurements were performed at the ANSTO heavy ion microprobe beamline ANTARES. To the authors’ knowledge, this is the first benchmarking investigation for PIXE simulations in Geant4 utilising carbon ions and it is significant for PIXE-based elemental analysis, encompassing archaeological samples, gas samples, environmental and planetary samples for geological and planetary research studies. It is also of relevance for any physics application, requiring the modelling of particle induced atomic de-excitation or atomic de-excitation only