The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
Kenji Kimura - One of the best experts on this subject based on the ideXlab platform.
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Effect of multiple scattering on high-resolution Rutherford backscattering spectroscopy
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2012Co-Authors: Kaoru Sasakawa, Kaoru Nakajima, Motofumi Suzuki, Kenji KimuraAbstract:Abstract The effect of multiple scattering on high-resolution Rutherford backscattering spectroscopy was studied for 450 keV He+ ions incident on ultrathin HfO2 films on Si. There was a tail at the low energy Hf edge in the observed spectrum. The tail increases with increasing HfO2 thickness and decreasing Exit Angle (Exit Angle with respect to the surface). A notable tail was observed even for HfO2 films of 2 nm thickness at a small Exit Angle of 7°. The observed tail was reproduced by Monte Carlo simulations showing that the origin of the tail is multiple scattering. An analytical model was developed to estimate the tail for practical use. The derived analytical formula roughly reproduced the observed tail.
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Exit Angle dependence of charge state distribution of backscattered he ions
Applied Surface Science, 2009Co-Authors: Kaoru Sasakawa, Kaoru Nakajima, Motofumi Suzuki, Kenji KimuraAbstract:Exit Angle and energy dependences of the charge-state distribution of backscattered He ions were investigated when 500 keV He + ions were incident on SiO 2 . The energy dependence of the He + fraction was estimated by comparing the measured He + spectra with the simulated spectra of He ions in all charge states at the Exit Angles of 5-25° with respect to the SiO 2 surface. We found that the He + fraction is almost independent of the Exit Angle at energies higher than 250 keV and the observed energy dependence of the He + fraction is in good agreement with that for the carbon-foil-transmission experiment. In the low energy region (<250 keV), however, the He + fraction decreases as the Exit Angle decreases.
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Exit Angle dependence of charge-state distribution of backscattered He ions
Applied Surface Science, 2009Co-Authors: Kaoru Sasakawa, Kaoru Nakajima, Motofumi Suzuki, Kenji KimuraAbstract:Exit Angle and energy dependences of the charge-state distribution of backscattered He ions were investigated when 500 keV He + ions were incident on SiO 2 . The energy dependence of the He + fraction was estimated by comparing the measured He + spectra with the simulated spectra of He ions in all charge states at the Exit Angles of 5-25° with respect to the SiO 2 surface. We found that the He + fraction is almost independent of the Exit Angle at energies higher than 250 keV and the observed energy dependence of the He + fraction is in good agreement with that for the carbon-foil-transmission experiment. In the low energy region (
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Charge-state distribution of 400 keV He ions scattered from solid surfaces
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2004Co-Authors: Kaoru Nakajima, Motofumi Suzuki, Yasutaka Okura, Kenji KimuraAbstract:Abstract Charge-state distribution of backscattered He ions was investigated when 400 keV He+ ions were incident on three different surfaces; clean Si(0 0 1)(2 × 1), SiO2 (2.5 nm)/Si(0 0 1) and Ag(0.31 ML)/Si(0 0 1). The dependence of the charge state on the Exit Angle of the scattered ions was obtained by measuring the energy spectra of both the scattered He+ and He2+ ions at various Exit Angles for each surface. For the Si(0 0 1)(2 × 1) surface, the charge state of the scattered ions shows a considerable dependence on the Exit Angle, while no dependence is observed for the SiO2/Si(0 0 1) surface. For the Ag/Si(0 0 1) surface, the He+ fractions in the ions scattered from the surface Si and Ag atoms are different significantly from each other at large Exit Angle from the surface. These dependences are explained by a model including the nonequilibrium charge-exchange process of the Exiting ions with the valence electrons at the surface.
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Charge-state distribution of MeV He ions scattered from the topmost atomic layer of the SnTe(001) surface.
Physical review letters, 1992Co-Authors: Kenji Kimura, Hisashi Ohtsuka, Michi-hiko MannamiAbstract:The charge-state distribution of 0.5-MeV He ions scattered from a SnTe(001) surface has been investigated using a new technique of high-resolution high-energy ion scattering spectroscopy. The ions scattered from successive atomic layers can be resolved in the energy spectra of the scattered ions. The observed charge-state distribution of the ions scattered from the topmost atomic layer coincides with that of ions scattered from the subsurface region and does not depend on the incident charge state but depends on the Exit Angle. The observed Exit-Angle dependence is explained by a model which includes the charge-exchange process with the valence electrons in the tail of the electron distribution at the surface.
Runsheng Tang - One of the best experts on this subject based on the ideXlab platform.
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Irradiation distribution on solar cells inside CPCs with a restricted Exit Angle
2016Co-Authors: Runsheng Tang, Chaofeng XiaAbstract:Abstract. In this work, irradiation distribution on the base of ideal two-dimensional CPCs with and without a restricted Exit Angle, to which solar cells are attached, are analyzed by the ray-tracing technique. Results show that, given an acceptance half-Angle ( a θ), for CPCs without a restricted Exit Angle (CPC-1), radiation flux distribution on the base depends on the incidence Angle of solar rays (θ); whereas for CPCs with a restricted Exit Angle (CPC-2), the flux distribution depends on θ and the restricted Exit Angle ( e θ). For both CPC-1 and 2 with identical geometric concentration factor (Ct=2) and acceptance half-Angle ( aθ =20), the peak flux concentration ratio on the base of CPC-2 with e θ =6
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Performance comparison of CPCs with and without Exit Angle restriction for concentrating radiation on solar cells
Applied Energy, 2015Co-Authors: Nianyong Liu, Runsheng TangAbstract:Abstract To perform this comparison, the compound parabolic concentrator with a restricted Exit Angle of 65° (CPC-65) and the one without Exit Angle restriction (CPC-90) were fabricated and tested for concentrating radiation on multi-crystalline solar cells. Both CPC-65 and CPC-90 are identical in the acceptance half-Angle (20°) and geometrical concentration factor (2×). Theoretical calculations showed that CPC-90 based PV system (CPV-90) annually concentrated about 3–5% more radiation on solar cells as compared to CPC-65 based PV system (CPV-65). For CPV-65, all radiation would arrive on the solar cells at the incidence Angle less than 65°, but for CPV-90, about 8–10% of annual collectible radiation would arrive on solar cells at the incidence Angle larger than 65°. Measurements at outdoor conditions showed that the CPV-65 performed slightly better than CPV-90 in terms of short-circuit current and power output as the projection incidence Angle of solar rays on the cross-section of CPC-troughs (θp) less than the acceptance half-Angle, otherwise the CPV-90 did better. Compared to CPV-90, the power output at maximum power points from CPV-65 were slightly higher, and increases of 2.1%, 5.4% and 8.17% were measured for θp = 0°, 10° and 16°, respectively. Analysis indicated that effect of solar flux distribution over solar cells on power output of both CPVs was almost identical and insignificant, and the CPV-65 performed slightly but insignificantly better than the CPV-90 in terms of annual power output except in areas with poor solar resources where the annual power output from both systems was almost identical.
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Irradiation Distribution on Solar Cells inside CPCs with a Restricted Exit Angle
Advanced Materials Research, 2012Co-Authors: Runsheng Tang, Chaofeng XiaAbstract:In this work, irradiation distribution on the base of ideal two-dimensional CPCs with and without a restricted Exit Angle, to which solar cells are attached, are analyzed by the ray-tracing technique. Results show that, given an acceptance half-Angle (Θa), for CPCs without a restricted Exit Angle (CPC-1), radiation flux distribution on the base depends on the incidence Angle of solar rays (Θ ); whereas for CPCs with a restricted Exit Angle (CPC-2), the flux distribution depends on and the restricted Exit Angle (Θe). For both CPC-1 and 2 with identical geometric concentration factor (Ct=2) and acceptance half-Angle ( Θa=20), the peak flux concentration ratio on the base of CPC-2 with =65o decreases about 43%, 30% and 49% for the radiation at the incident Angle of 0o, 10o and 18o, respectively, as compared to CPC-1. This implies that solar flux distribution on the base of CPC-2 is more uniform, thus, more efficient for photovoltaic conversion as compared with CPC-1.
N R Arista - One of the best experts on this subject based on the ideXlab platform.
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energy loss versus Exit Angle for h and he ions channeled in au 100 at very low energies and observation of a molecular effect for incident h2
Physical Review A, 2008Co-Authors: E. A. Figueroa, E. D. Cantero, J. C. Eckardt, G. H. Lantschner, M. L. Martiarena, N R AristaAbstract:The variation of the energy loss versus the Exit Angle in channeling experiments using ${\mathrm{H}}^{+}$, ${\mathrm{He}}^{+}$, and ${\mathrm{H}}^{+}$ fragments produced by the incidence of $\mathrm{H}_{2}{}^{+}$ on thin gold crystals oriented in the ⟨100⟩ direction has been investigated in the low-velocity range, corresponding to energies below $10\phantom{\rule{0.3em}{0ex}}\mathrm{keV}∕\mathrm{u}$. The experimental results for ${\mathrm{H}}^{+}$ and ${\mathrm{He}}^{+}$ were compared with computational simulations performed with the MARLOWE code, considering an impact-parameter-dependent energy loss based on electron density calculations and low-energy stopping power models. The comparisons provide information on the impact-parameter dependence of the energy loss for channeled ions and serve as a test of theoretical models in the present low-energy range. A molecular effect is observed for the transmitted ${\mathrm{H}}^{+}$ fragments corresponding to $\mathrm{H}_{2}{}^{+}$ incidence. This effect is explained based on geometrical considerations and a vicinage effect in the energy loss of correlated protons.
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energy loss and Exit Angle distributions of fragmented h 2 ions after traversing carbon foils
Physical Review A, 2000Co-Authors: Rafael Garciamolina, Isabel Abril, Cristian D. Denton, N R AristaAbstract:This work was financed by the Spanish DGES (project PB96-1118), the Generalitat Valenciana (Project No. GV99-54-1-01), and the Argentinian FONCYT (Project No. PICT 0303579). C.D.D. thanks the Argentinian CONICET for financial support and the Fundacion Seneca (Comunidad Autonoma de la Region de Murcia) for economical support during his stay at the Universidad de Murcia.
Néstor R. Arista - One of the best experts on this subject based on the ideXlab platform.
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Energy loss versus Exit Angle for H + and He + ions channeled in Au ⟨100⟩ at very low energies, and observation of a molecular effect for incident H2+
Physical Review A, 2008Co-Authors: E. A. Figueroa, E. D. Cantero, J. C. Eckardt, G. H. Lantschner, M. L. Martiarena, Néstor R. AristaAbstract:The variation of the energy loss versus the Exit Angle in channeling experiments using ${\mathrm{H}}^{+}$, ${\mathrm{He}}^{+}$, and ${\mathrm{H}}^{+}$ fragments produced by the incidence of $\mathrm{H}_{2}{}^{+}$ on thin gold crystals oriented in the ⟨100⟩ direction has been investigated in the low-velocity range, corresponding to energies below $10\phantom{\rule{0.3em}{0ex}}\mathrm{keV}∕\mathrm{u}$. The experimental results for ${\mathrm{H}}^{+}$ and ${\mathrm{He}}^{+}$ were compared with computational simulations performed with the MARLOWE code, considering an impact-parameter-dependent energy loss based on electron density calculations and low-energy stopping power models. The comparisons provide information on the impact-parameter dependence of the energy loss for channeled ions and serve as a test of theoretical models in the present low-energy range. A molecular effect is observed for the transmitted ${\mathrm{H}}^{+}$ fragments corresponding to $\mathrm{H}_{2}{}^{+}$ incidence. This effect is explained based on geometrical considerations and a vicinage effect in the energy loss of correlated protons.
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Exit Angle, energy loss and internuclear distance distributions of H2+ ions dissociated when traversing different materials
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2000Co-Authors: Rafael Garcia-molina, Isabel Abril, Cristian D. Denton, Néstor R. AristaAbstract:Abstract We have performed computer simulations of the trajectory followed by each proton resulting from the dissociation of H2+ molecules when traversing a thin solid target. We use the dielectric formalism to describe the forces due to electronic excitations in the medium, and we also consider the Coulomb repulsion between the pair of protons. Nuclear collisions with target nuclei are incorporated through a Monte Carlo code and the effect of the coherent scattering is taken into account by means of an effective force model. The distributions of Exit Angle, energy loss and internuclear separations of the protons fragments are discussed for the case of amorphous carbon and aluminum targets.
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Exit Angle, energy loss and internuclear distance distributions of H2+ ions dissociated when traversing different materials
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2000Co-Authors: Rafael Garcia-molina, Isabel Abril, Cristian D. Denton, Néstor R. AristaAbstract:We have performed computer simulations of the trajectory followed by each proton resulting from the dissociation of H2+ molecules when traversing a thin solid target. We use the dielectric formalism to describe the forces due to electronic excitations in the medium, and we also consider the Coulomb repulsion between the pair of protons. Nuclear collisions with target nuclei are incorporated through a Monte Carlo code and the effect of the coherent scattering is taken into account by means of an effective force model. The distributions of Exit Angle, energy loss and internuclear separations of the protons fragments are discussed for the case of amorphous carbon and aluminum targets.This work has been supported by the Spanish Dirección General de Enseñanza (project PB96-1118) and the Generalitat Valenciana (project GV99-54-1-01). CDD thanks the Fundación Séneca (Comunidad Autónoma de la Región de Murcia) for economical support during his stay at the Universidad de Murcia and the Argentinian CONICET for a posdoctoral fellowship
G. Andermann - One of the best experts on this subject based on the ideXlab platform.
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An Evaluation of the Variable-Exit-Angle Ultrasoft X-Ray Fluorescence Technique as Applied to Ni/Fe Thin-Film Multilayers
Applied Spectroscopy, 1992Co-Authors: T. Scimeca, G. AndermannAbstract:The variable-Exit-Angle ultrasoft x-ray fluorescence technique has been evaluated for Ni/Fe thin-film multilayers. The theoretical and experimental agreement is reasonable. The experimental results demonstrate that on these Ni/Fe samples quantitative information can be obtained in the presence of surface contamination.
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The characterization of the oxidation of Fe by variable Exit Angle ultrasoft x-ray fluorescence spectroscopy
Applied Surface Science, 1991Co-Authors: T. Scimeca, G. AndermannAbstract:Abstract The oxidation of Fe has been characterized qualitatively by variable Exit Angle ultrasoft X-ray fluorescence spectroscopy (USXFS). The results indicate that the Lβ/Lα intensity ratio can be used to evaluate the extent of Fe oxidation and that the oxidation is believed to penetrate to a certain degree within Fe such that discrete Fe oxide layers are not formed.