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Articles 1 - 10 of 10
Full-Text Articles in Physics
Modified Bell-Plesset Effect With Compressibility: Application To Double-Shell Ignition Target Designs, Peter A. Amendt, J. D. Colvin, John D. Ramshaw, H. F. Robey, O. L. Landen
Modified Bell-Plesset Effect With Compressibility: Application To Double-Shell Ignition Target Designs, Peter A. Amendt, J. D. Colvin, John D. Ramshaw, H. F. Robey, O. L. Landen
Physics Faculty Publications and Presentations
The effect of spherical convergence on the fluid stability of collapsing and expanding bubbles was originally treated by Bell [Los Alamos Scientific Laboratory Report No. LA-1321 (1951)] and Plesset [J. Appl. Phys. 25, 96 (1954)]. The additional effect of fluid compressibility was also considered by Bell but was limited to the case of nonzero density on only one side of a fluid interface. A more general extension is developed which considers distinct time-dependent uniform densities on both sides of an interface in a spherically converging geometry. A modified form of the velocity potential is used that avoids an unphysical divergence …
High Frequency-Bandwidth Optical Technique To Measure Thermal Elongation Time Responses Of Near-Field Scanning Optical Microscopy Probes, Andres H. La Rosa, B. Biehler
High Frequency-Bandwidth Optical Technique To Measure Thermal Elongation Time Responses Of Near-Field Scanning Optical Microscopy Probes, Andres H. La Rosa, B. Biehler
Physics Faculty Publications and Presentations
A near-field scanning optical microscopy (NSOM) probe elongates when light is coupled into it. The time response of this thermal process is measured here by a new optical technique that exploits the typical flat-apex morphology of the probe as a mirror in a Fabry-Perot type cavity. Pulsed laser light is coupled into the probe to heat up the tip, while another continuous wave laser serves to monitor the elongation from the interference pattern established by the reflections from the flat-apex probe and a semitransparent metal-coated flat sample. A quarter wave plate is introduced into the interferometer optical path in order …
Nonlocal Electrodynamic Modeling Of Fluorescence Characteristics For Molecules In A Spherical Cavity, Pui T. Leung, M. H. Hider
Nonlocal Electrodynamic Modeling Of Fluorescence Characteristics For Molecules In A Spherical Cavity, Pui T. Leung, M. H. Hider
Physics Faculty Publications and Presentations
The emission characteristics for molecules in a spherical metallic microcavity are computed using a nonlocal electrodynamic model, based on a theory previously published by Fuchs and Claro [Phys. Rev. B 35, 3722 (1987)] for the multipole polarizability of a sphere. Both radially and tangentially oriented molecules at arbitrary locations inside the cavity are considered, and the results are compared with those from both the local response theory and those for molecules outside a spherical particle. The issue of reciprocity of the solutions for each of the sphere and cavity cases, respectively, is examined in the light of the nonlocal effects. …
The Meyer-Neldel Rule For A Property Determined By Two Transport Mechanisms, Ralf Widenhorn, Armin Rest, Erik Bodegom
The Meyer-Neldel Rule For A Property Determined By Two Transport Mechanisms, Ralf Widenhorn, Armin Rest, Erik Bodegom
Physics Faculty Publications and Presentations
We propose that the Meyer-Neldel rule (MNR) arises naturally for a quantity where both an intrinsic process as well as a process involving impurities contribute. The strength of the latter depends solely on the density of the impurities. This leads to a spread in the apparent activation energy of the measured quantity and the observation of the MNR, even though the intrinsic processes have fixed activation energies. A consequence of the MNR is the occurrence of a temperature T[sub MN] where a measured parameter is independent of the activation energy. For the system studied, the MNR does not accurately predict …
Residual Images In Charged-Coupled Device Detectors, Armin Rest, Lars Mündermann, Ralf Widenhorn, Erik Bodegom, T. C. Mcglinn
Residual Images In Charged-Coupled Device Detectors, Armin Rest, Lars Mündermann, Ralf Widenhorn, Erik Bodegom, T. C. Mcglinn
Physics Faculty Publications and Presentations
We present results of a systematic study of persistent, or residual, images that occur in charged-coupled device (CCD) detectors. A phenomenological model for these residual images, also known as "ghosting," is introduced. This model relates the excess dark current in a CCD after exposure to the number of filled impurity sites which is tested for various temperatures and exposure times. We experimentally derive values for the cross section, density, and characteristic energy of the impurity sites responsible for the residual images.
Temperature Dependence Of Dark Current In A Ccd, Ralf Widenhorn, Morley M. Blouke, Alexander Weber, Armin Rest, Erik Bodegom
Temperature Dependence Of Dark Current In A Ccd, Ralf Widenhorn, Morley M. Blouke, Alexander Weber, Armin Rest, Erik Bodegom
Physics Faculty Publications and Presentations
We present data for dark current of a back-illuminated CCD over the temperature range of 222 to 291 K. Using an Arrhenius law, we found that the analysis of the data leads to the relation between the prefactor and the apparent activation energy as described by the Meyer-Neldel rule. However, a more detailed analysis shows that the activation energy for the dark current changes in the temperature range investigated. This transition can be explained by the larger relative importance at high temperatures of the diffusion dark current and at low temperatures by the depletion dark current. The diffusion dark current, …
A Compact Method For Optical Induction Of Proximal Probe Heating And Elongation, Andres H. La Rosa, Hans D. Hallen
A Compact Method For Optical Induction Of Proximal Probe Heating And Elongation, Andres H. La Rosa, Hans D. Hallen
Physics Faculty Publications and Presentations
A tapered, metal-coated, optical fiber probe will elongate when heated by light input through a fiber. The induced motion can be used for data storage or nanostructuring of a surface. The elongation produced by this alignment-free system is measured with force feedback in a near-field scanning optical microscope (NSOM). The input light intensity controls the elongation magnitude, which ranges from a few nanometers to more than 100 nm. A 0.5-mW input energy yields ~20 nm of probe elongation. The elongation quantified here can create artifacts in any experiment using pulsed laser light with a NSOM or an atomic force microscope.
Indirect-Drive Noncryogenic Double-Shell Ignition Targets For The National Ignition Facility: Design And Analysis, Peter A. Amendt, J. D. Colvin, R. E. Tipton, D. E. Hinkel, M. J. Edwards, O. L. Landen, John D. Ramshaw, L. J. Suter, W. S. Varnum, R. G. Watt
Indirect-Drive Noncryogenic Double-Shell Ignition Targets For The National Ignition Facility: Design And Analysis, Peter A. Amendt, J. D. Colvin, R. E. Tipton, D. E. Hinkel, M. J. Edwards, O. L. Landen, John D. Ramshaw, L. J. Suter, W. S. Varnum, R. G. Watt
Physics Faculty Publications and Presentations
Analysis and design of indirect-drive National Ignition Facility double-shell targets with hohlraum temperatures of 200 eV and 250 eV are presented. The analysis of these targets includes the assessment of two-dimensional radiation asymmetry and nonlinear mix. Two-dimensional integrated hohlraum simulations indicate that the x-ray illumination can be adjusted to provide adequate symmetry control in hohlraums specially designed to have high laser-coupling efficiency [Suter et al., Phys. Plasmas 7, 2092 (2000)]. These simulations also reveal the need to diagnose and control localized 10?15 keV x-ray emission from the high-Z hohlraum wall because of strong absorption by the high-Z inner shell. Preliminary …
Analytically Continued Hypergeometric Expression Of The Incomplete Beta Function, Jack C. Straton
Analytically Continued Hypergeometric Expression Of The Incomplete Beta Function, Jack C. Straton
Physics Faculty Publications and Presentations
The Incomplete Beta Function is rewritten as a Hypergeometric Function that is the analytic continuation of the conventional form, a generalization of the finite series, which simpifies the Stieltjes transform of powers of a monomial divided by powers of a binomial.
Fluid Dynamics And Energetics In Ideal Gas Mixtures, John D. Ramshaw
Fluid Dynamics And Energetics In Ideal Gas Mixtures, John D. Ramshaw
Physics Faculty Publications and Presentations
The generalization of fluid dynamics from pure to multicomponent fluids (fluid mixtures composed of different components or species) requires the introduction of new concepts, some of which are rather subtle and are less widely appreciated than they deserve to be. The purpose of this paper is to provide a simple didactic introduction to some of these concepts based on a detailed analysis of the equations governing the flow of ideal gas mixtures. The treatment is based entirely on a continuum description and makes no explicit use of the kinetic theory of gases. We include a straightforward and physically transparent derivation …