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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: In this article, a new method was developed to determine the mean free path of thin metal films by investigating the thickness dependence of the conductivity of thin thin films, including surface effects as given by the specularity parameter $p$ and the surface roughness amplitude $h$.
Abstract: A new method was developed to determine the mean free path. ${l}_{\ensuremath{\infty}}$. and the conductivity, ${\ensuremath{\sigma}}_{\ensuremath{\infty}}$, of charge carriers in metals by investigating the thickness dependence of the conductivity of thin films. The method includes also surface effects as given by the specularity parameter $p$ and the surface roughness amplitude $h$. Experimental data taken during film growth could be fitted to theoretical size-effect relations only if nonzero specularity and heterogeneous film cross section caused by the surface roughness is introduced. The method allows determination of the Fermi-surface area and the electron density of the isotropic (amorphous) films. Both are smaller than expected from published bulk material data.
123 citations
TL;DR: In this article, the authors examined the usefulness of the lithium zinc bismuth borate glass systems for various radiation shielding applications and for this purpose, the mass attenuation coefficients for the glasses in the composition 50 Bi2O3-15 B2O-3-(35-x) ZnO-(x) Li2O (x = 0, 5, 10, 15, 20)mol%) were calculated by both XCOM software and MCNP5 simulation code, respectively, within the energy range 0.015 MeV-10 MeV.
Abstract: In this work, we examined the usefulness of the lithium zinc bismuth borate glass systems for various radiation shielding applications and for this purpose, the mass attenuation coefficients for the glasses in the composition 50 Bi2O3–15 B2O3–(35-x) ZnO–(x) Li2O (x = 0, 5, 10, 15, 20 mol%) were calculated by both XCOM software and MCNP5 simulation code, respectively, within the energy range 0.015 MeV–10 MeV. The obtained results indicated good agreement between mass attenuation coefficient values derived from XCOM program and MCNP5 code. The obtained mass attenuation coefficients are then used to calculate the effective atomic number (Zeff), half value layer (HVL) and mean free path (MFP) for the glasses. Among the selected glasses, the glass with 35 mol% ZnO was found to possess superior gamma-ray shielding effectiveness due to its higher values of both mass attenuation coefficient and effective atomic number and lower values of both HVL and MFP. The MFP values of the present glasses were compared with different glass systems and ordinary concrete. In addition, the macroscopic effective removal cross-section for fast neutron (ΣR) values was also evaluated. It is found that the ΣR values for the studied glasses lie within the range 0.1286–0.1587 cm− 1.
123 citations
TL;DR: A mathematical analysis based on the Mayadas-Shatzkes model indicates that an effective mean free path may be defined in order to describe electronic conduction in both thin polycrystalline and monocrystalline metallic films as discussed by the authors.
123 citations
TL;DR: Conductance fluctuations in quantum wires are calculated numerically by a scattering-matrix formalism with Landauer's conductance formula and in strong magnetic fields, the conductance becomes nearly quantized and the fluctuations become negligibly small.
Abstract: Conductance fluctuations in quantum wires are calculated numerically by a scattering-matrix formalism with Landauer's conductance formula. The fluctuations are not universal because they are strongly dependent on the system length. When many subbands are occupied, there appears the length region (called the universal region) longer than the mean free path and shorter than the localization length where the fluctuations are almost independent of the length. A crossover from one to two dimensions occurs when the broadening of one-dimensional subbands exceeds their separations. In the presence of a weak magnetic field, the universal region becomes wider and the fluctuations are reduced. In strong magnetic fields, the conductance becomes nearly quantized and the fluctuations become negligibly small due to the formation of edge states with an extremely long mean free path.
120 citations
TL;DR: In this article, a nonlinear perturbation theory is applied to the problem of pitch angle diffusion of energetic particles in random magnetic fields, and the results are shown that the failure of quasilinear theory at small particle velocities parallel to the average field can be overcome by statistically exact treatment of the particle orbits in the first order fields.
Abstract: A nonlinear perturbation theory is applied to the problem of pitch angle diffusion of energetic particles in random magnetic fields. To keep the analysis simple, the discussion is restricted to fluctuation fields, consisting of Alfven waves. It is shown that the failure of quasilinear theory at small particle velocities parallel to the average field can be overcome by a statistically exact treatment of the particle orbits in the first order fields. In fact, for spherical power spectra which, in addition, do not fall off too steeply with increasing frequency, the conventional perturbation theory also leads to formally convergent expressions for the scattering mean free path. These results are shown to be quite satisfactory, even in a quantitative sense. For more general physically realistic power spectra, however, a divergence-free diffusion theory is indispensible. A simple representation for the resulting pitch-angle diffusion coefficient is suggested.
120 citations