Showing papers in "Canadian Journal of Physics in 2008"
TL;DR: In this paper, a complete software package for the computation of various atomic data such as energy levels; radiative transition; collisional excitation; ionization by electron impact, photoionizatio...
Abstract: We describe a complete software package for the computation of various atomic data such as energy levels; radiative transition; collisional excitation; ionization by electron impact, photoionizatio...
1,055 citations
TL;DR: In the autumn of 1986, the first electron beam ion trap, EBIT, was put into service as a light source for the spectroscopy of highly charged ions as mentioned in this paper.
Abstract: In the autumn of 1986, the first electron beam ion trap, EBIT, was put into service as a light source for the spectroscopy of highly charged ions. On the occasion of the twentieth anniversary of EB...
107 citations
TL;DR: In this paper, the authors summarized the key aspects of CX X-ray emission and its astrophysical relevance, and reviewed related laboratory measurements and theoretical predictions with particular attention to spectroscopy experiments conducted on electron beam ion traps.
Abstract: The past decade has seen a surge of interest in astrophysical charge exchange (CX). The impetus was the discovery of X-ray emission from comets in 1996, soon followed by the observation of CX emission in planetary atmospheres and throughout the heliosphere. Geocoronal and heliospheric CX are now recognized as contributing a considerable fraction of the soft X-ray background, and stellar-wind charge exchange is expected to occur in the astrospheres surrounding many stars. CX may also contribute to X-ray line emission in supernova remnants, the Galactic Center, and the Galactic Ridge. This article summarizes the key aspects of CX X-ray emission and its astrophysical relevance, and reviews related laboratory measurements and theoretical predictions with particular attention to spectroscopy experiments conducted on electron beam ion traps.PACS Nos.: 32.30.Rj, 34.70.+e, 39.10.+j, 95.30.Dr
62 citations
TL;DR: The X-ray spectrometer (XRS) microcalorimeter instrument has been operating at the electron beam ion trap (EBIT) facility at Lawrence Livermore National Laboratory since July of 2000 as mentioned in this paper.
Abstract: NASA’s X-ray spectrometer (XRS) microcalorimeter instrument has been operating at the electron beam ion trap (EBIT) facility at Lawrence Livermore National Laboratory since July of 2000. The spectrometer is currently undergoing its third major upgrade to become an easy to use and extremely high-performance instrument for a broad range of EBIT experiments. The spectrometer itself is broadband, capable of simultaneously operating from 0.1 to 12 keV and has been operated at up to 100 keV by manipulating its operating conditions. The spectral resolution closely follows the spaceflight version of the XRS, beginning at 10 eV FWHM at 6 keV in 2000, upgraded to 5.5 eV in 2003, and will hopefully be ~3.8 eV in the fall of 2007. Here we review the operating principles of this unique instrument, the extraordinary science that has been performed at EBIT over the last six years, and prospects for future upgrades. Specifically, we discuss upgrades to cover the high-energy band (to at least 100 keV) with a high quantum ...
56 citations
TL;DR: In this article, a survey of developments in the theory of both thermoelasticity and fluid mechanics has been reviewed, and appropriate references are supplied throughout, and a review of the method of the matrix exponential, which constitutes the basis of the state-space approach is given.
Abstract: In this survey, developments in the theory of both thermoelasticity and fluid mechanics have been reviewed, and appropriate references are supplied throughout. Review of the method of the matrix exponential, which constitutes the basis of the state-space approach, is given.PACS Nos.: 46.35+z, 47.65+a
53 citations
TL;DR: The International Thermonuclear Experimental Reactors (ITRE) as mentioned in this paper is the world's largest experimental site for fusion-energy development, with 7 nations, representing over half the world population, having signed an agreement to build it.
Abstract: Fusion-energy development has reached an exciting stage with the agreement by seven nations, representing over half the world population, to build the International Thermonuclear Experimental React...
53 citations
TL;DR: In this article, the Ricci soliton was used to discuss the renormalization group (RG) flow of a nonlinear sigma model in two dimensions and was shown to arise in general relativity, particularly for static metrics.
Abstract: I discuss certain applications of the Ricci flow in physics. I first review how it arises in the renormalization group (RG) flow of a nonlinear sigma model. I then review the concept of a Ricci soliton and recall how a soliton was used to discuss the RG flow of mass in two dimensions. I then present recent results obtained with Oliynyk on the flow of mass in higher dimensions. The final section discusses how Ricci flow may arise in general relativity, particularly for static metrics.PACS Nos.: 02.40Ky, 02.30Ik, 04.20.–q
52 citations
TL;DR: In this paper, the radiation characteristics of anticipated sample elements, from H through W, in the International Thermonuclear Experimental Reactor (ITER) have been modelled using the diffusion equilibrium model SANCO for the ion concentrations coupled with the spectral signature of the ions, throughout the X-ray and VUV regions (0.1-100 keV), using the Atomic Data and Analysis Structure population code and database, ADAS.
Abstract: The radiation characteristics of anticipated sample elements, from H through W, in the International Thermonuclear Experimental Reactor (ITER) have been modelled using the diffusion equilibrium model SANCO for the ion concentrations coupled with the spectral signature of the ions, throughout the X-ray and VUV regions (0.1-100 keV), using the Atomic Data and Analysis Structure population code and database, ADAS. The spectral signature varies greatly depending on whether the viewing line-of-sight (LOS) encompasses the divertor and (or) core regions of the plasma volume. Bound-bound transitions required for line profile analyses of nonfuel core ions can locally dominate the continuum spectrum in the 0.1-10 keV region at acceptably low elemental concentrations. While the background continuum is the main source of noise in the line profile analyses, the intensity and features of the continuum when divided into many spectral bands covering 0.1-100 keV are themselves powerful diagnostics of the plasma composition, Z[subeff] and the electron temperature. The spectral signature of the divertor LOSs where 1 40 A. Appropriate instrumentation, relying on imaging Bragg reflectors and diffractors and position-sensitive energy-resolving detectors, is designed to cover the full spatial extent of the core plasma. Estimates of the core signal/noise based on experience with tritium experiments on the Joint European Torus indicates substantial signal levels with tolerable neutron-induced noise and component degradation. The divertor diagnostics make use of a suite of aspheric diffraction grating spectrometers designed to measure impurity ion influxes and are essential for plasma control. The EBIT could be conceived as a neutron-free adjunct facility to the ITER spectroscopic programme. At its simplest level, it provides standards for instrument performance and for the spectroscopic signature of selected ions subjected to electronic and atomic collisions over a wide range of ITER-relevant impacting energies.
38 citations
TL;DR: In this article, the effects of thermophoresis and the homogeneous chemical reactions of first order on magneto-hydrodynamic mixed convective flow past a heated inclined permeable flat plate in the presence of heat generation or absorption considering the viscous dissipation and Joule heating were investigated.
Abstract: The present paper deals with the effects of thermophoresis and the homogeneous chemical reactions of first order on magneto-hydrodynamic mixed convective flow past a heated inclined permeable flat plate in the presence of heat generation or absorption considering the viscous dissipation and Joule heating. The resulting governing partial differential equations are transformed into non-dimensional ordinary differential equations using the usual similarity transformations and then solved numerically by applying the Nachtsheim–Swigert shooting iteration technique together with the sixth-order Runge–Kutta integration scheme. Comparison with previously published work is performed and very good agreement is obtained. A parametric study of the governing parameters is carried out and the results are displayed graphically. The results show that viscous drag, rate of heat transfer, and wall deposition flux decreases as the angle of inclination increases. It is also observed that due to the presence of the first-orde...
36 citations
TL;DR: A review of recent progress in high-precision calculations for the ground state and low-lying excited states of helium, including the nonrelativistic energy, relativistic correc
Abstract: This paper presents a review of recent progress in high-precision calculations for the ground state and low-lying excited states of helium, including the nonrelativistic energy, relativistic correc
35 citations
TL;DR: In this paper, an unsteady laminar boundary-layer flow over a continuously stretching surface in a viscous and incompressible quiescent fluid is studied, where the unsteadiness in the flow and temperature fields is caused by the time dependence of the stretching velocity and the surface heat flux.
Abstract: The unsteady laminar boundary-layer flow over a continuously stretching surface in a viscous and incompressible quiescent fluid is studied. The unsteadiness in the flow and temperature fields is caused by the time dependence of the stretching velocity and the surface heat flux. The nonlinear partial differential equations of continuity, momentum, and energy, with three independent variables, are reduced to nonlinear ordinary differential equations, before they are solved numerically by the Keller-box method. Comparison with available data from the open literature as well as the exact solution for the steady-state case of the present problem is made, and found to be in good agreement. Effects of the unsteadiness parameter and Prandtl number on the flow and heat transfer characteristics are thoroughly examined.PACS No.: 47.15.Cb
TL;DR: The EBIT spectroscopy that now seems routine would not be possible without considerable good luck in several areas of EBIT technology as mentioned in this paper, among these are x-ray background, ion cooling, neutral gas density, and electron current density and energy control.
Abstract: The EBIT spectroscopy that now seems routine would not be possible without considerable good luck in several areas of EBIT technology. Among these are x-ray background, ion cooling, neutral gas density, and electron current density and energy control. A favourable outcome in these areas has enabled clean x-ray spectra, sufficient intensity for high resolution spectroscopy, production of very high charge states, and a remarkable variety of spectroscopic measurements. During construction of the first EBIT 20 years ago, it was not clear that any of this was possible.
TL;DR: The results from the last six years of X-ray spectroscopy and spectropolarimetry of high-energy density Z-pinch plasmas complemented by experiments with the electron beam ion trap (EBIT) at the Law...
Abstract: The results from the last six years of X-ray spectroscopy and spectropolarimetry of high-energy density Z-pinch plasmas complemented by experiments with the electron beam ion trap (EBIT) at the Law...
TL;DR: In this paper, the authors investigated the inherent irreversibility in the flow of a variable (temperature-dependent) viscosity fluid through a channel with parallel plates, and derived the important properties of overall flow structure, including velocity field, temperature field, and thermal criticality conditions.
Abstract: This study investigates the inherent irreversibility in the flow of a variable (temperature-dependent) viscosity fluid through a channel with parallel plates. The channel is narrow so that the lubrication approximation may be applied, and the temperature-dependent nature of viscosity is assumed to follow an exponential model. The system is assumed to exchange heat with the ambient surroundings following Newton’s cooling law. Using a perturbation method coupled with a special type of Hermite–Pade approximation technique, the simplified governing nonlinear equations are solved and the important properties of overall flow structure, including velocity field, temperature field, and thermal criticality conditions are derived, which essentially expedite obtaining expressions for volumetric entropy generation numbers, irreversibility distribution ratio, and the Bejan number in the flow field. PACS Nos.: 44.10.+a, 47.11.–j, 47.15.gm
TL;DR: In this article, a measurement of the K-shell spectrum of He-like through Be-like praseodymium ions trapped in the Livermore SuperEBIT electron beam ion trap using a bismuth absorber pixel on the XRS/EBIT microcalorimeter is presented.
Abstract: We present a measurement of the K-shell spectrum of He-like through Be-like praseodymium ions trapped in the Livermore SuperEBIT electron beam ion trap using a bismuth absorber pixel on the XRS/EBIT microcalorimeter. This measurement is the first of its kind where the n = 2 to n = 1 transitions of the various charge states are spectroscopically resolved. The measured transition energies are compared with theoretical calculations from several atomic codes.PACS Nos.: 32.30.–r, 32.30.Rj, 39.30.+w
TL;DR: Transition probabilities relate to atomic structure and dynamics in ways that are different from straightforward spectra as discussed by the authors, and are essential for applications in plasma physics and astrophysics, and have been used for fundamental physics studies.
Abstract: Transition probabilities relate to atomic structure and dynamics in ways that are different from straightforward spectra. Besides being a tool for fundamental physics studies, the knowledge of transition probabilities is essential for applications in plasma physics and astrophysics. Techniques and procedures used for measuring the lifetimes of levels in highly charged ions by employing an electron beam ion trap are reviewed to illustrate the state of the art. Examples are drawn from experiments that involve observations in the visible, extreme-ultraviolet, and X-ray ranges, and cover atomic lifetimes in the femtosecond to second range.PACS Nos.: 32.70.Cs, 32.30.Jc, 32.30.Rj
TL;DR: In this article, a soft X-ray/EUV grating spectrometer with wavelength coverage up to 400 µm was described, which was used at the Sustained Spheromak Physics Experiment.
Abstract: Multiple spectrometers originally designed for and used at the University of California Lawrence Livermore National Laboratory’s electron beam ion trap have found use at various magnetically confined plasma facilities. Three examples will be described. First is a soft X-ray/EUV grating spectrometer (6–150 A), which is operating at the National Spherical Torus Experiment. Second is an EUV spectrometer with wavelength coverage up to 400 A, which has just recently started operating at the Sustained Spheromak Physics Experiment. The last is a high-resolution transmission-grating spectrometer for visible light that has been used at the Compact Toroid Injection Experiment and is currently at the Alcator C-Mod tokamak.PACS Nos.: 39.30.+w, 52.55.–s, 32.30.Rj, 07.60.Rd, 52.70.La
TL;DR: In this article, the authors present a survey of the work performed at the Lawrence Livermore EBIT facility in compiling comprehensive spectral catalogues, discovery of a magnetic field line diagnostic in the EUV and soft X-ray regimes, and density diagnostics on EBIT and at the NSTX tokamak.
Abstract: Electron beam ion traps are uniquely well suited for laboratory astrophysics because they can produce nearly any charge state of any element in a collisionally excited plasma that is comparable in density and temperature to many astronomical sources. The Lawrence Livermore EBIT facility has been optimized for laboratory astrophysics with a suite of dedicated instruments and has made significant advances in this field. This paper reviews some of the work performed at LLNL in compiling comprehensive spectral catalogues, discovery of a magnetic field line diagnostic in the EUV and soft X-ray regimes, and density diagnostics on EBIT and at the NSTX tokamak.PACS Nos.: 95.30.Ky, 32.30.Rj, 95.75.–z, 95.85.Nv, 97.10.Ex, 95.55.Ka, 95.85.Mt, 52.55.Fa
TL;DR: In this article, a comparison of experimental atomic transition probabilities in rare-earth spectra is provided, and the two recent and nearly simultaneous publications, which were based on very different experimental methods, provide transition probability in good, but not perfect, agreement.
Abstract: This Research Note provides a comparison of experimental atomic transition probabilities in Sm~II from two recent publications. Basic data of this type for rare-earth spectra, including Sm~II, are very difficult to determine using ab-initio theoretical methods. Experimental programs are underway in several laboratories to determine these data for ongoing astrophysical studies of the origins of the chemical elements. The two recent and nearly simultaneous publications, which were based on very different experimental methods, provide transition probabilities in good, but not perfect, agreement.PACS Nos.: 32.70.Cs, 32.70.Fw, 32.30.Jc
TL;DR: In this paper, the results from tokamak experiments and measurements on electron beam ion traps for the line ratios x/w, y/w and z/w in the spectra of helium-like ions with Z in the range from 14 to 28 were reviewed.
Abstract: The paper reviews the results from tokamak experiments and measurements on electron beam ion traps for the line ratios x/w, y/w, and z/w in the spectra of helium-like ions with Z in the range from 14 to 28. With the exception of the DITE experiments, where these line ratios were found to be in agreement with theoretical predictions, all other tokamak experiments yielded values that were significantly greater than predicted. The reasons for these discrepancies are not yet understood. It is possible that radial profile effects were not properly taken into account in the majority of the tokamak experiments. The paper also gives a short historical review of the X-ray diagnostic developments and presents very recent data from a new type of X-ray imaging crystal spectrometer, which records spatially resolved spectra with a spatial resolution of about 1 cm in the plasma. These new data can be Abel inverted, so that it will be possible to determine line ratios at each radial position in the plasma. Effects of rad...
TL;DR: In this article, a brief overview of measurements of the intensities of the lines 3C and 3D from laboratory and celestial sources and their comparison to model calculations, with an emphasis on measurements completed using an electron beam ion trap.
Abstract: X-ray emission from neon-like Fe XVII has been measured with high-resolution spectrometers from laboratory or celestial sources for nearly seven decades. Two of the strongest lines regularly identified in these spectra are the 1P1 → 1S0 resonance and the 3D1 → 1S0 intercombination line, known as 3C and 3D, respectively. This paper gives a brief overview of measurements of the intensities of the lines 3C and 3D from laboratory and celestial sources and their comparison to model calculations, with an emphasis on measurements completed using an electron beam ion trap. It includes a discussion of the measured absolute cross sections compared with results from modern atomic theory calculations as well as the diagnostic utility of the relative intensity, R = I3C/I3CD, as it applies to the interpretation of spectra measured from the Sun and extra-solar sources. PACS Nos.: 32.30.Rj, 32.30.–r, 32.70.Cs, 52.72.+v, 95.85.Nv, 96.60.P–, 97.10.Ex
TL;DR: In this article, the authors reviewed the electron impact excitation (EIE) measurements at electron beam ion trap (EBIT) facilities in the last 20~30 years and found that EIE cross sections are important atomic parameters fundamental.
Abstract: This paper reviews the electron-impact excitation (EIE) measurements at electron beam ion trap (EBIT) facilities in the last 20~years. EIE cross sections are important atomic parameters fundamental...
TL;DR: In this article, a two-fluid model for blood flow through a horizontal channel is studied, which essentially consists of a core region assumed to be a micropolar fluid and two viscous regions.
Abstract: In the present analysis, a two-fluid model for blood flow through a horizontal channel is studied. The model essentially consists of a core region assumed to be a micropolar fluid and two viscous (...
TL;DR: The observation of forbidden transitions in the visible range was the first experimental sign of the existence of highly charged ions in nature as discussed by the authors, and such lines can nowadays be excited in electron beam...
Abstract: The observation of forbidden transitions in the visible range was the first experimental sign of the existence of highly charged ions in nature. Such lines can nowadays be excited in electron beam ...
TL;DR: In this article, high-precision relativistic atomic-structure calculations based on the relativist many-body perturbation theory and relativism configuration-interaction method are presented.
Abstract: High-precision relativistic atomic-structure calculations based on the relativistic many-body perturbation theory and the relativistic configuration-interaction method are shown to provide stringen...
TL;DR: A theoretical study of the electronic structure of including spin-orbit effects has been performed in this article, where potential energy curves for the 58 molecular states in the representation Ωg,u are presented.
Abstract: A theoretical study of the electronic structure of including spin-orbit effects has been performed. Potential energy curves for the 58 molecular states in the representation Ωg,u are presented. Equ...
TL;DR: In this paper, the authors study two toy models of quantum information processing, using the language of quantum walks, and incorporate decoherence in three ways: coupling to a noisy projective measurement system, coupling to oscillator and spin baths.
Abstract: Decoherence is the major stumbling block in the realization of a large-scale quantum computer. Ingenious methods have been devised to overcome decoherence, but their success has been proven only for over-simplified models of system-environment interaction. Whether such methods will be reliable in the face of more realistic models is a fundamental open question. In this partly pedagogical article, we study two toy models of quantum information processing, using the language of quantum walks. Decoherence is incorporated in three ways — by coupling to a noisy “projective measurement” system, and by coupling to oscillator and spin baths.PACS Nos.: 03.65.Yz, 03.67.Lx
TL;DR: In this paper, the (1 + 1)-dimensional m-cKdV hierarchy of evolution equations is derived, and its expanding integrable model is obtained by the use of a enlarged Lie algebra.
Abstract: A few isospectral problems are introduced by referring to that of the cKdV equation hierarchy, for which two types of integrable systems called the (1 + 1)-dimensional m-cKdV hierarchy and the g-cKdV hierarchy are generated, respectively, whose Hamiltonian structures are also discussed by employing a linear functional and the quadratic-form identity. The corresponding expanding integrable models of the (1 + 1)-dimensional m-cKdV hierarchy and g-cKdV hierarchy are obtained. The Hamiltonian structure of the latter one is given by the variational identity, proposed by Ma Wen-Xiu as well. Finally, we use a Lax pair from the self-dual Yang–Mills equations to deduce a higher dimensional m-cKdV hierarchy of evolution equations and its Hamiltonian structure. Furthermore, its expanding integrable model is produced by the use of a enlarged Lie algebra.PACS Nos.: 02.30, 03.40.K
TL;DR: In this paper, the authors scrutinize the metric associated with a quasi-Hermitian Hamiltonian and its physical implications and investigate the consequences of the non-uniqueness such as the question of the probability interpretation and the possible and forbidden choices of additional observables.
Abstract: A recent surge of publications about non-Hermitian Hamiltonians has led to considerable controversy and — in our opinion — to some misunderstandings of basic quantum mechanics. The present paper scrutinizes the metric associated with a quasi-Hermitian Hamiltonian and its physical implications. The consequences of the non-uniqueness such as the question of the probability interpretation and the possible and forbidden choices of additional observables are investigated and exemplified by specific illustrative examples. In particular, it is argued that the improper identification of observables lies at the origin of the claimed violation of the brachistchrone transition time between orthogonal states. The need for further physical input to remove ambiguities is pointed out.PACS Nos.: 03.65.–w, 03.65.Ca, 03.65.Ta, 03.65.Xp
TL;DR: In this article, the authors extended the Bessel functions from the real number field to the complex number field and defined a new type of Bessel function, called the phased Bessel Function.
Abstract: In the study of photon-state transitions, we found a natural extension of the first kind of Bessel functions that extends both the range and domain of the Bessel functions from the real number field to the complex number field. We term the extended Bessel functions as phased Bessel functions. This extension is completely different from the traditional “analytical extension”. The new complex Bessel functions satisfy addition, subtraction, and recurrence theorems in a complex range and a complex domain. These theorems provide short cuts in calculations. The single-phased Bessel functions are generalized to multiple-phased Bessel functions to describe various photon-state transitions.PACS Nos.: 02.30.Gp, 32.80.Rm, 42.50.Hz