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.

Monte Carlo simulation of phonon transport in silicon including a realistic dispersion relation

Abstract: Thermal conductivities in bulk Si and Si films are analyzed using a Monte Carlo method to solve the phonon Boltzmann transport equation. By taking into account the realistic phonon dispersion relation calculated from the adiabatic bond charge model along with pure diffuse boundary scattering based on Lambert's law, simulated results that were in good agreement with the experimental ones were obtained. In addition, it was found that the approximated dispersion curves fitted along the [100] direction underestimate the density of states for mobile phonons, which results in a smaller specific heat and a longer phonon mean free path. The resulting impact on the simulation of heat transfer in nanostructures is discussed.

Anisotropic multiple scattering in diffusive media

Abstract: The multiple scattering of scalar waves in diffusive media is investigated by means of the radiative transfer equation. This approach, which does not rely on the diffusion approximation, becomes asymptotically exact in the regime of most interest, where the scattering mean free path is much larger than the wavelength . Quantitative predictions are derived in that regime, concerning various observables pertaining to optically thick slabs, such as the mean angle-resolved reflected and transmitted intensities, and the width of the enhanced backscattering cone. Special emphasis is put on the dependence of these quantities on the anisotropy of the cross section of the individual scatterers, and on the internal reflections due to the optical index mismatch at the boundaries of the sample. The large index mismatch regime is studied analytically, for arbitrary anisotropic scattering. The regime of very anisotropic scattering, where the transport mean free path is much larger than the scattering mean free path , is then investigated in detail. The relevant Schwarzschild - Milne equation is solved exactly in the absence of internal reflections.

The importance of the electron mean free path for superconducting radio-frequency cavities

Abstract: Impurity-doping of niobium is an exciting new technology in the field of superconducting radio-frequency accelerators, producing cavities with record-high quality factor Q0 and Bardeen-Cooper-Schrieffer surface resistance that decreases with increasing radio-frequency field. Recent theoretical work has offered a promising explanation for this so-called “anti-Q-slope,” but the link between the decreasing surface resistance and the shortened electron mean free path of doped cavities has remained elusive. In this work, we investigate this link, finding that the magnitude of this decrease varies directly with the mean free path: shorter mean free paths correspond to stronger anti-Q-slopes. We draw a theoretical connection between the mean free path and the overheating of the quasiparticles, which leads to the reduction of the anti-Q-slope towards the normal Q-slope of long-mean-free-path cavities. We also investigate the sensitivity of the residual resistance to trapped magnetic flux, a property that is great...

Infrared spectra and radiative thermal conductivity of minerals at high temperatures

Abstract: Minerals radiative thermal conductivity at high temperatures from IR measurement of absorption coefficient and refractive index