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Mean free path
About: Mean free path is a research topic. Over the lifetime, 4412 publications have been published within this topic receiving 114418 citations.
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TL;DR: Transport, as well as scattering, mean free paths are calculated within the weak-scattering approximation and within a recently developed extension of the well-known coherent-potential approximation for a random arrangement of dielectric spheres.
Abstract: Transport, as well as scattering, mean free paths are calculated within the weak-scattering approximation and within a recently developed extension of the well-known coherent-potential approximation for a random arrangement of dielectric spheres. The different theoretical results of the mean free paths are compared with experiments on scattering from dielectric spheres.
50 citations
TL;DR: In this paper, the authors used the nonlinear guiding center theory to obtain the perpendicular diffusion coefficient of the cosmic rays and found that the radial mean free path is dominated by the parallel component before 30 AU, after which the perpendicular component becomes important.
Abstract: [1] We calculate the cosmic ray diffusion tensor based on a recently developed model of magnetohydrodynamic (MHD) turbulence in the expanding solar wind. Parameters of this MHD model are tuned by using published observations from Helios, Voyager 2, and Ulysses. We present solutions of two turbulence parameter sets and derive the characteristics of the cosmic ray diffusion tensor for each. We determine the parallel diffusion coefficient of the cosmic rays following the method presented by Bieber et al. (1995). We use the nonlinear guiding center theory to obtain the perpendicular diffusion coefficient of the cosmic rays. We find that (1) the radial mean free path decreases from 1 to 30 AU for both turbulence scenarios; (2) after 30 AU the radial mean free path is nearly constant; (3) the radial mean free path is dominated by the parallel component before 30 AU, after which the perpendicular component becomes important; (4) the rigidity dependence of the parallel mean free path is proportional to P.404 for one turbulence scenario and P.374 for the other at 1 AU from 0.1 to 10 GV, but in the outer heliosphere its dependence steepens above 4 GV; and (5) the rigidity dependence of the perpendicular mean free path is very weak.
50 citations
TL;DR: In this article, the authors investigated the temperature dependence of the carrier mean free path for optical phonon scattering and the mean energy loss per collision for any operating temperature once the appropriate parameters have been determined.
Abstract: Expressions for the temperature dependence of the carrier mean free path for optical phonon scattering and the mean energy loss per collision are presented which predict avalanche multiplication as a function of electric field for any operating temperature once the appropriate parameters have been determined at a single temperature. This has been verified for electrons in Si by the correlation of measurements at 300°K, 213°K, and 100°K. The temperature dependence of the breakdown voltages of a variety of abrupt and linear‐graded Si and Ge p‐n junctions has also been predicted. The fractional change in breakdown voltage with increasing temperature is predicted to decrease with increased doping concentration and, for the same breakdown voltage, to be less for linear‐graded junctions than for abrupt junctions.
50 citations
TL;DR: In this article, the authors explored the neutron-gamma attenuation characteristics of the TeO2-Bi2O-PbO-MgO-B2O3 glasses based on MCNPX simulation and theoretical calculations.
Abstract: The present study aims to explore the neutron-gamma attenuation characteristics of the TeO2–Bi2O–PbO–MgO–B2O3 glasses based on MCNPX simulation and theoretical calculations. 252Cf neutron source is important as it emits both neutron and gamma and thus its shielding is essential. The glass samples were irradiated by the 252Cf neutron sources and the watt fission distribution was used to extract the neutron spectrum, then the obtained results were reported in the presence and absence of the glass sample. Also, the other attenuation parameters such as effective removal cross section, mass removal cross section, mean free path (MFP), half value thickness (HTV), and tenth value thickness (TVT) were demonstrated graphically against neutron. Using Doppler effect gamma spectrum in shielding materials for spontaneous fission 252Cf source was extracted and expressed. The linear attenuation coefficient (µ), MFP, HVT, and TVT for wide energy ranges of incident gamma rays were estimated. Furthermore, oxygen molar volume (OMV) and oxygen packing density (OPD) of the selected glasses by the use of molar volume values show a less tight packing of the glass network and a strong packing in the glass network versus MgO and PbO ratio, respectively. The acquired data represents that glass coded TePbMg5 has the higher fast neutron-gamma-shielding ability in comparison to the rest of the glass materials
49 citations
TL;DR: In this paper, the elastic and inelastic mean free paths in the (0-8.5)-eV energy region were extracted from Xe films (0, 3000 \AA{}) deposited at various temperatures on different metal substrates [Nb,Pt,W(100].
Abstract: Electron transmission experiments in the (0-20)-eV energy range have been performed on Xe films (0-3000 \AA{}) deposited at various temperatures on different metal substrates [Nb,Pt,W(100)]. A theoretical model is used to extract from these experiments the elastic and inelastic mean free paths in the (0-8.5)-eV energy region. Some structures in the transmitted current arise from inelastic processes and yield information on electronic excitations (excitons and electron-hole-pair creation) and the energy of the bottom of the conduction band. Other structures present in the elastic mean free path appear to be caused by structural effects and thermal disorder of the deposited film.
49 citations