Experimental and Theoretical Determination of the Stopping Power of ZrO2 Films for Protons and α-particles

Abstract. We report the results of an experimental-theoretical study on the stopping power of ZrO2 films for swift H and He ion beams. The experiments, using the Rutherford Backscattering technique, were done for protons with incident energies in the range 200-1500 keV and for α-particle beams with energies in the range 160-3000 keV. The theoretical calculations were done in the framework of the dielectric formalism using the MELF-GOS model to account for the ZrO2 target electronic response. It is shown that for both ion beams, the agreement between theory and experiment is quite remarkable

Energy Loss Function of Solids Assessed by Ion Beam Energy-Loss Measurements: Practical Application to Ta2O5

We present a study where the energy loss function of Ta2O5, initially derived in the optical limit for a limited region of excitation energies from reflection electron energy loss spectroscopy (REELS) measurements, was improved and extended to the whole momentum and energy excitation region through a suitable theoretical analysis using the Mermin dielectric function and requiring the fulfillment of physically motivated restrictions, such as the f- and KK-sum rules. The material stopping cross section (SCS) and energy-loss straggling measured for 300–2000 keV proton and 200–6000 keV helium ion beams by means of Rutherford backscattering spectrometry (RBS) were compared to the same quantities calculated in the dielectric framework, showing an excellent agreement, which is used to judge the reliability of the Ta2O5 energy loss function. Based on this assessment, we have also predicted the inelastic mean free path and the SCS of energetic electrons in Ta2O5.We acknowledge financial support from the Brazilian agencies Coordinação de Aperfeiçoamento de Pessoal de Nivel Superior (CAPES), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and PRONEX-FAPERGS, as well as the Australian Research Council and the Spanish Ministerio de Economía y Competitividad (Project FIS2014-58849-P)

Stopping power and depth dose profile of H+ and He+ ion beams in hydroxyapatite thin films.

Hadron therapy is a promising technique to treat deep-seated tumors. For an accurate treatment planning, the energy deposition in the soft and hard human tissue must be well known. Water has been usually employed as a phantom of soft tissues, but other biomaterials, such as hydroxyapatite (HAp), used as bone substitute, are also relevant as a phantom for hard tissues. The stopping power of HAp for H+ and He+ beams has been studied experimentally and theoretically. The measurements have been done using the Rutherford backscattering technique in an energy range of 450-2000 keV for H+ and of 400-5000 keV for He+ projectiles. The theoretical calculations are based in the dielectric formulation together with the MELF-GOS (Mermin Energy-Loss Function – Generalized Oscillator Strengths) method [1] to describe the target excitation spectrum. A quite good agreement between the experimental data and the theoretical results has been found. The depth dose profile of H+ and He+ ion beams in HAp has been simulated by the SEICS (Simulation of Energetic Ions and Clusters through Solids) code [2], which incorporates the electronic stopping force due to the energy loss by collisions with the target electrons, including fluctuations due to the energy-loss straggling, the multiple elastic scattering with the target nuclei, with their corresponding nuclear energy loss, and the dynamical charge-exchange processes in the projectile charge state. The energy deposition by H+ and He+ as a function of the depth are compared, at several projectile energies, for HAp and liquid water, showing important differences.European Regional Development Fun

Magnetic Reconnection inside a Flux Transfer Event‐like structure in Magnetopause Kelvin‐Helmholtz Waves

This is the final version. Available from the American Geophysical Union via the DOI in this recordMMS data are available from https://lasp.colorado.edu/mms/sdc/public/Magnetopause Kelvin‐Helmholtz (KH) waves are believed to mediate solar wind plasma transport via small‐scale mechanisms. Vortex‐induced reconnection (VIR) was predicted in simulations and recently observed using NASA's Magnetospheric Multiscale (MMS) mission data. Flux Transfer Events (FTEs) produced by VIR at multiple locations along the periphery of KH waves were also predicted in simulations but detailed observations were still lacking. Here we report MMS observations of an FTE‐type structure in a KH wave trailing edge during KH activity on 5 May 2017 on the dawnside flank magnetopause. The structure is characterised by (1) bipolar magnetic B Y variation with enhanced core field (B Z ) and (2) enhanced total pressure with dominant magnetic pressure. The cross‐section size of the FTE is found to be consistent with vortex‐induced flux ropes predicted in the simulations. Unexpectedly, we observe an ion jet (V Y ), electron parallel heating, ion and electron density enhancements, and other signatures that can be interpreted as a reconnection exhaust at the FTE central current sheet. Moreover, pitch angle distributions of suprathermal electrons on either side of the current sheet show different properties, indicating different magnetic connectivities. This FTE‐type structure may thus alternatively be interpreted as two interlaced flux tubes with reconnection at the interface as reported by Kacem et al. (2018) and Øieroset et al. (2019). The structure may be the result of interaction between two flux tubes, likely produced by multiple VIR at the KH wave trailing edge, and constitutes a new class of phenomenon induced by KH waves.Science and Technology Facilities Council (STFC)Thailand Science Research and InnovationNAS

Compósito para a construção civil a partir de resíduos industriais

RESUMO Os estudos que visam à utilização dos resíduos industriais vêm se intensificando diante da pressão das organizações ambientais, escassez de recursos naturais, busca de certificações para ganho de mercado e minimização de impacto ambiental. O presente trabalho desenvolveu um novo compósito a base de resíduos industriais como cinzas de madeira, lodo de estação de tratamento de água (ETA) e resíduos de produção de cal com propriedades mecânicas que atendem às exigências da ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS - NBR 15270-1/2005, NBR 15270-2/2005 e NBR 5739/2007, objetivando a sua utilização na construção civil sem o acréscimo de cimento Portland. As resistências à compressão variaram de 2,35 a 16,48 MPa. O índice de absorção de água das amostras testadas também atendeu às normas aplicadas, demonstrando que ao longo do tempo de cura houve diminuição da porosidade com possível hidratação da cal. Os resultados do ensaio de resistência à compressão apresentaram variações durante o tempo de cura que podem ser justificadas pela presença de material orgânico no lodo de ETA e pelo tamanho das partículas de cinza de madeira que durante a homogeneização não foram destruídas completamente. Apesar das variações observadas nos resultados, as resistências dos compósitos se enquadram na classificação para blocos cilíndricos de concreto e blocos cerâmicos para alvenaria

Impact-parameter dependence of the electronic energy loss of fast cluster projectiles

Abstract Electronic energy loss of molecular clusters as a function of impact-parameter is less understood than atomic energy loss. Vicinage effects due to mutual interference between cluster fragments play a key role in the determination of the cluster electronic energy loss. In this work, we describe a molecular extension of the perturbative convolution approximation (PCA) energy loss model, namely MPCA (molecular PCA), which yields remarkable agreement with first-order Born semiclassical approximation (SCA) results. The physical inputs of the model are the oscillators strengths of the target atoms and the projectile electron density. A very good agreement is obtained with time consuming full first-order calculations for bare incident molecular clusters for several angles between cluster axis and velocity direction

A theoretical-experimental straggling study of H ions into HfO2 films

Paper submitted to the 9th International Conference on Applications of Nuclear Techniques, Crete, Greece, 8–14 June 2008.We present an experimental study of the energy-loss straggling of protons into HfO2 films, as well as a comparison with the theoretical predictions of the MELF-GOS model. The experiments were performed using a H beam provided by a 3 MV Tandetron accelerator in an energy range between 40 and 2000 keV. The targets were HfO2 films with thicknesses of 40, 60, 80, 100 and 150 nm. We have used nuclear reaction analysis (NRA) and Rutherford backscattering (RBS) techniques with a Si barrier detector, having a resolution of 7 keV. By comparing the front and back edge of the RBS spectra we extract the corresponding energy loss straggling values for each one of the energies we have studied. The calculations were done in the framework of the dielectric formalism, paying especial attention to a proper description of the Energy Loss Function (ELF) of the HfO2 targets, which accounts for the electronic excitations produced in the material by the passage of a charged projectile. The experimental data and the theoretical results of the energy-loss straggling of swift H beams in HfO2 films show a very good agreement.Work financially supported by the Spanish Ministerio de Educación y Ciencia (Projects Nos. FIS2006-13309-C02-01 and FIS2006-13309-C02-02). CDD thanks the Spanish Ministerio de Educación y Ciencia and Generalitat Valenciana for support under the Ramón y Cajal Program

Role of electronic excitations in the energy loss of H2+ projectiles in high-κ materials

In the present work we report on the energy loss ratio Rn of fast H2+ clusters in thin films (30–50 Å) of LaScO3 and HfO2. The medium energy ion scattering technique was employed covering a broad energy range (40–200 keV/amu). The energy loss ratio data showed no clear evidence of collective excitations in these materials. The experimental results were interpreted in terms of three different theoretical approaches: the dielectric formalism with the Brandt-Reinheimer theory for semiconductor materials; the detailed simulation of the molecular fragments dynamics through the target; and finally the unitary convolution approximation adapted for hydrogen molecules. Only the simulation agrees with the experimental results for both oxides. The unitary convolution approximation works quite well for HfO2 but overestimates slightly the LaScO3 data. The overall results indicate that the energy loss ratio depends critically on the description of the electronic properties of such oxides.This research was supported by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul (FAPERGS), the Spanish Ministerio de Educación y Ciencia (Projects No. FIS2006-13309-C02-01 and No. FIS2006-13309-C02-02 and support under the Ramón y Cajal Program)

Diagnóstico ambiental expedito do Parque Cambuí, Campo Largo-PR, aplicado à educação ambiental.

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