Yavne, Israel
Yavne, Israel

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Akkerman A.,Soreq NRC | Murat M.,Soreq NRC | Barak J.,Soreq NRC
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms | Year: 2014

The energy spectrum of the δ-electrons ejected by an ion moving in the bulk of a solid is the origin of numerous effects which follow the transport of these electrons. This spectrum cannot be measured directly. Therefore, it should be derived theoretically. The present work aims to investigate the uncertainties introduced when applying commonly used theoretical approaches like BEA, CDFT, and PWBA to calculate δ-electron spectrum. Our calculations show that, above a certain δ-electron energy, the energy spectra of the δ-electrons obtained using the various approaches behave similarly. Below this energy, the spectra found using these approaches differ significantly due to the manner in which the solid state character of the target material is taken into account in each approach. This results in differences in the inelastic cross sections and stopping powers for the ions, which in turn result in different ion track structures. Also discussed in this paper is the effect of the uncertainty in the effective ion charge on the accuracy of ion track calculations. The results obtained for silicon allow estimating the possible uncertainties of the calculated ion track properties and related effects. © 2013 Elsevier B.V. All rights reserved.


Katz S.,Soreq NRC | Barak J.,Soreq NRC
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms | Year: 2014

With the advent of devices sensitive to SEU due to direct ionization by protons, it became important to know the flux and energies of protons behind aluminum shielding or within satellites. We present new analytically derived expressions for the energy distribution of incident protons, after passing the shielding, and of secondary protons emitted within the shielding. The results are compared with those of the MULASSIS code. In some cases, like a satellite in a GCR orbit, the contribution of the secondary protons to SEU might be the dominant one. Proton energy-distributions behind shielding are proportional, at low energy values, to inverse proton-LET in aluminum. Their calculated LET-spectra in silicon can be used for evaluating SEU-rate in space. The analytic expressions presented here can be useful in calculating the influence of shielding on other incident ions and secondary ions. © 2014 Elsevier Inc. All rights reserved.


Akkerman A.,Soreq NRC | Murat M.,Soreq NRC | Barak J.,Soreq NRC
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms | Year: 2011

Spatial and temporal characteristics of energy deposition events and electron-hole distributions as a result of the passage of energetic ions in silicon are studied using Monte Carlo simulations, for incident ion energies in the range of 0.5-100 MeV/amu. Ion track radii as function of the incident ion energy are presented. The range of ion energies and masses for possible melting in the track region is calculated. It is also found that it is not possible to separate between the temporal and spatial characteristics. © 2010 Elsevier B.V. All rights reserved.


Eliezer S.,Soreq NRC | Eliezer S.,Polytechnic University of Mozambique
Laser and Particle Beams | Year: 2012

In this work, it is suggested that the ponderomotive force, induced by a multi-petawatt laser on the interface of a vacuum with solid target, can accelerate a micro-foil to relativistic velocities. The extremely high velocities of the micro-foil can be achieved due to the very short time duration (about a picosecond) of the laser pulse. This accelerated micro-foil is used to ignite a pre-compressed cylindrical shell containing the deuterium tritium fuel. The fast ignition is induced by a heat wave produced during the collision of the accelerated foil with the pre-compressed target. This approach has the advantage of separating geometrically the nanoseconds lasers that compress the target with the picosecond laser that accelerates the foil. © 2012 Cambridge University Press.


Lev A.,Soreq NRC | Sfez B.,Soreq NRC
Optics Express | Year: 2015

Optical detection of objects hidden behind opaque screening layers is a challenging problem. We demonstrate an optically detected echographic-like method that combines collimated acoustic and laser beams. The acoustic waves cross the screening layers, and their backreflection from the hidden objects is detected through the analysis of a dynamic laser speckle pattern created at the outer surface of the screening layer. Real-time remote detection of moving targets 15 meters away, with a few mm resolution is demonstrated using a very sensitive camera detection scheme. © 2015 Optical Society of America.


Ruppin R.,Soreq NRC
Journal of Optics | Year: 2011

Exact analytic expressions for the time-averaged electric and magnetic energies within a negative refractive index metamaterial sphere, which is irradiated by a plane wave, are presented. The metamaterial is dispersive and lossy, with both the permittivity and the permeability frequency-dependent and containing damping terms. The frequency dependence of the magnetic and electric energies inside the sphere is obtained, and it is found that the highest energies occur in the frequency range in which the sphere material is left-handed. © 2011 IOP Publishing Ltd.


Krief M.,Hebrew University of Jerusalem | Feigel A.,Soreq NRC
High Energy Density Physics | Year: 2015

We have recently completed developing a new super transition array (STA) code for calculating absorption and emission spectra of LTE plasmas. The code follows the theory of Bar-Shalom etal. with various improvements. In this work we focus on the first order correction for the Boltzmann populations for which traditional calculations can be very costly. We present here a method faster by an order of magnitude than the traditional method. We then investigate the effect of this correction on the opacity spectra of several elements. Finally we interpret results of a recent opacity experiment on gold plasma. A good agreement is reached. © 2015 Elsevier B.V..


Krief M.,Hebrew University of Jerusalem | Feigel A.,Soreq NRC
High Energy Density Physics | Year: 2015

Generalized analytical expressions for the two-electron relativistic Unresolved-Transition-Array (UTA) energy variance and shift for electric and magnetic transitions of general multipole order are presented. The revised expressions are shown to agree with the exact moments calculated directly from the energy levels of two-electron configurations. We show that for electric transitions of even multipole order and for magnetic transitions, the available expressions in the literature, which are implemented in widely used atomic codes, are incorrect. We suggest an alternative method for the calculation of the UTA energy variance and shift by using the analytical expressions for the two-electron energy levels and line-strengths. The method is much more efficient and simple than the use of the traditional lengthy analytic expressions. Finally, the effect of UTA widths on Super-Transition-Array (STA) spectral opacity is shown for several examples. © 2015 Elsevier B.V.


Shamir Y.,Soreq NRC | Shamir Y.,Tel Aviv University | Sintov Y.,Soreq NRC | Shtaif M.,Tel Aviv University
Optics Letters | Year: 2011

We show the feasibility of producing a low-mode all-fiber combiner fabricated from a large core and extremely small NA fibers. Although these fibers support multiple modes, the combiner that we produce can be operated nearly at the single mode regime while preserving the brightness of the combined beam almost perfectly with respect to the inputs. The M-square parameter of the combined beam was 2.3 and the power transfer efficiency was close to 100%. Such an all-fiber beam combining device is a rugged solution for high-brightness, high-efficiency beam delivery. © 2011 Optical Society of America.


Ruppin R.,Soreq NRC
Journal of Optics (United Kingdom) | Year: 2015

The optical properties of layered nanoparticles containing at least one metallic layer and one gain medium layer are calculated. The mean free path effect, resulting from the surface scattering of the conduction electrons, is taken into account in the usual way, by modifying the dielectric function of the metallic shell. There exist in the literature a number of effective mean free path model choices for the shell geometry. We investigate the dependence of the optical spectra, as well as the critical gain values, on the choice of the surface scattering model. © 2015 IOP Publishing Ltd.

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