Topic
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, the mean free path and shear viscosity in the color-flavor locked (CFL) phase of dense quark matter at low temperature T, when the contributions of mesons, quarks and gluons to the transport coefficients are Boltzmann suppressed.
Abstract: We compute the mean free path and shear viscosity in the color-flavor locked (CFL) phase of dense quark matter at low temperature T, when the contributions of mesons, quarks and gluons to the transport coefficients are Boltzmann suppressed. CFL quark matter displays superfluid properties, and transport phenomena in such cold regime are dominated by phonon-phonon scattering. We study superfluid phonons within thermal field theory and compute the mean free path associated to their most relevant collision processes. Small-angle processes turn out to be more efficient in slowing transport phenomena in the CFL matter, while the mean free path relevant for the shear viscosity is less sensitive to collinear scattering due to the presence of zero modes in the Boltzmann equation. In analogy with superfluid He4, we find the same T power law for the superfluid phonon damping rate and mean free path. Our results are relevant for the study of rotational properties of compact stars, and correct wrong estimates existing in the literature.
59 citations
TL;DR: In this paper, a glass with 20% Bi2O3 (BCNZB20.0) added to the glass system not only improved the optical and structural features but also the nuclear radiation shielding properties.
Abstract: Novel transparent glasses with nominal composition of 50B2O3 +15Na2O+15ZnO+(20−x)CaO+xBi2O3; x = 0, 5, 10, 15, and 20 were synthesized using melt quenching method. The molar volume and density of the produced glasses with boosting the substitution ratio of Bi2O3 were measured. X-ray diffraction (XRD) patterns of the glasses were obtained for confirming their amorphous structure. UV–Vis spectra of the prepared samples were detected over the range of 190–1100 nm. By using UV–Vis results, Fermi level energy (Ef), refractive index (n), optical energy gap (Eg), Urbach's energy (Eu), and optical dispersion parameters were estimated. Results exposed that the optical energy gap (Eg) and single-oscillator energy (Eo) were decreased however other parameters increased with increasing Bi2O3 content. Mass attenuation coefficient (μ/ρ), as an essential variable for photon protecting research, was attained at 0.015–15 MeV photon energies for investigated glasses. Other relevant variables that can define the photon protecting features like Mean Free Path (MFP), Half Value Layer (HVL), equivalent atomic number (Zeq), gamma-ray exposure buildup factor (EBF), energy-absorption buildup factor (EABF) were obtained for the prepared glasses. The corollaries revealed that the BCNZB20.0 glass can be a strong shield material against gamma radiation. Finally, the proficiency of proposed glasses to stop fast neutrons charged alpha and proton particles was explored utilizing effective removal cross section (ΣR) and Mass Stopping Power (MSP) parameters. The glass with 20% Bi2O3 (BCNZB20.0) addition is very effective in preventing charged and uncharged particles. The addition of Bi2O3 to the studied glass system not only improved the optical and structural features but also the nuclear radiation shielding properties.
59 citations
TL;DR: In this article, the mean escape depth of photoelectrons leaving a target without being scattered inelastically was submitted to extensive theoretical analysis, and the authors derived a simple explicit expression for this function by solving a kinetic equation and by the Monte Carlo technique.
Abstract: • Escape depth of photoelectrons leaving a target without being scattered inelastically was submitted to extensive theoretical analysis. Dependence of the mean escape depth on the X-ray angle of incidence and the electron initial angular distribution inside the sample was considered. The Monte Carlo algorithm was developed basing on a differential elastic scattering cross-section calculated within the partial-wave expansion method and a realistic electron-atom mteraction potential. The mean escape depth was evaluated by means of the depth distribution function found analytically by solving a kinetic equation and by the Monte Carlo technique. The agreement between the results obtained from two methods is excellent. Elastic scattering was found to reduce considerably the escape depth. This reduction may reach up to 25% in the case of heavy elements in the practical X-ray photoelectron spectroscopy analysis. It was shown that the mean escape depth expressed in units of the electron transport mean free path is a universal function of the ratio of the inelastic to the transport mean free paths, the asymmetry parameter and the X-ray angle of incidence. A simple explicit expression for this function is proposed.
59 citations
TL;DR: In this article, the authors considered the adiabatic energy loss effect, provided by the divergence of the solar wind flows, into the focused transport equation and solved numerically using a time-backward stochastic integration method.
Abstract: The focused transport equation without adiabatic energy loss is widely used to model solar energetic particles' (SEP) interplanetary propagation by fitting spacecraft data. We incorporate the adiabatic energy loss effect, provided by the divergence of the solar wind flows, into the focused transport equation. The equation is then solved numerically using a time-backward stochastic integration method. We show the comparison between solutions of focused transport equations with and without energy loss. We found the effect of adiabatic cooling is significant on the time profile of the intensity of SEPs. It is also shown that without energy loss, for gradual events, we can only fit the initial phase of SEP events. However, with energy loss, we can fit the entire ( initial and decaying) phases. In addition, the values of the mean free path obtained by fitting the SEP events with energy loss is always smaller than that without. The results suggest that including adiabatic cooling effect is another way to partially fix the solar energetic particle mean free paths' "too small'' problem discussed by Bieber et al. ( 1994), i.e., the mean free paths obtained by fitting transport equation to observation data are much larger than the quasi-linear theory results.
59 citations
01 Feb 1949
TL;DR: In this article, measurements have been made of the low temperature resistivity of mercury wires down to 6 μ diameter and of rolled tin foils down to 3 μ thickness, and a continuous increase of resistivity with decrease of diameter and thickness was found, and it was concluded that this was due to a shortening of the mean free path of the conduction electrons by inelastic collision with the boundary surfaces of the metal.
Abstract: Measurements have been made of the low temperature resistivity of mercury wires down to 6 μ diameter and of rolled tin foils down to 3 μ thickness. A continuous increase of resistivity with decrease of diameter and thickness was found, and it is concluded that this was due to a shortening of the mean free path of the conduction electrons by inelastic collision with the boundary surfaces of the metal. The theory of this effect for a wire is examined; a rigorous theory for a foil already exists (Fuchs 1938). By comparing the experimental results with the theory, values of the product ιρ are found for both metals; (ι is the mean free path and ρ the resistivity for the metal in bulk). These values of ιρ are in satisfactory agreement with those obtained from Pippard's measurements on the anomalous skin effect for the two metals.
59 citations