Spectroscopic studies for emissions released from tungsten ions have been conducted in the Large Helical Device (LHD) for contribution to the tungsten transport study in tungsten divertor fusion devices and for expansion of the... more
Spectroscopic studies for emissions released from tungsten ions have been conducted in the Large Helical Device (LHD) for contribution to the tungsten transport study in tungsten divertor fusion devices and for expansion of the experimental database of tungsten line emissions. Tungsten ions are distributed in the LHD plasma by injecting a pellet consisting of a small piece of tungsten metal wire enclosed by a carbon tube. Line emissions from W0, W5+, W6+, W24+–W28+, W37+, W38+, and W41+–W46+ are observed simultaneously in the visible (3200–3550 Å), vacuum ultraviolet (250–1050 Å), and extreme ultraviolet (5–300 Å) wavelength ranges and the wavelengths are summarized. Temporal evolutions of line emissions from these charge states are compared for comprehensive understanding of tungsten impurity behavior in a single discharge. The charge distribution of tungsten ions strongly depends on the electron temperature. Measurements of emissions from W10+ to W20+ are still insufficient, which...
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The NIFS (National Institute for Fusion Science) Atom and Molecular Database, which has been available online since 1997, is a numerical atomic and molecular database of collision processes that is important for fusion research. This... more
The NIFS (National Institute for Fusion Science) Atom and Molecular Database, which has been available online since 1997, is a numerical atomic and molecular database of collision processes that is important for fusion research. This database provides the following: (1) the cross-sections and rate coefficients for ionization, excitation, and recombination caused by electron impact; (2) the charge transfer caused by heavy particle collision and collision processes of molecules; and (3) the sputtering yields of solids and backscattering coefficients from solids. It also offers a bibliographic database. We recently reconstructed the database system. The main purpose of the reconstruction was to migrate the database into an open-source architecture to make the system more flexible and extensible. The previous system used proprietary software and was difficult to customize. The new system consists of open-source software, including PostgreSQL database and Ruby on Rails. New features were...
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The electron beam ion trap in Tokyo (Tokyo-EBIT)[1] is suitable for studying relativistic effects in the collisions of highly charged heavy ions with electrons because it can produce and trap very highly charged heavy ions which interact... more
The electron beam ion trap in Tokyo (Tokyo-EBIT)[1] is suitable for studying relativistic effects in the collisions of highly charged heavy ions with electrons because it can produce and trap very highly charged heavy ions which interact with a mono-energetic and unidirectional relativistic electron beam with an energy of up to 200 keV. Recently, we have been studying resonant processes
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Photoionized plasma was studied experimentally under laboratory conditions by means of high intensity short pulse lasers. The experiment consists of a gold cavity filled with nitrogen gas. Six laser beams were focused on the inner surface... more
Photoionized plasma was studied experimentally under laboratory conditions by means of high intensity short pulse lasers. The experiment consists of a gold cavity filled with nitrogen gas. Six laser beams were focused on the inner surface of the gold cavity, thereby generating an ...
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ABSTRACT INTRODUCTION From a sur vey of atomic tran si tions us ing the multiconfigurationDirac -Fock (MCDF) method, Feldman, Indelicato and Sugar 1 re ported that a for bid den tran si tion between the low est fine-structure lev els of... more
ABSTRACT INTRODUCTION From a sur vey of atomic tran si tions us ing the multiconfigurationDirac -Fock (MCDF) method, Feldman, Indelicato and Sugar 1 re ported that a for bid den tran si tion between the low est fine-structure lev els of (3d 4 ) J = 2 and J = 3 was to be ob served in the op ti cal re gion for most high-Z ti tanium-like ions. Be sides its po ten tial im por tance for high-temperature plasma di ag nos tics, the tran si tion serves as a test-ground for many-body atomic struc ture the o ries, as will be seen shortly. The first ob ser va tion of the tran si tion was made by Mor gan et al. 2 for Xe 32+ and Ba 34+ . How ever, mea sured wavelengths were found to have an un ex pect edly large dis crepancy ( 5%) from state-of-the-art MCDF calculations. 3 Indelicato 4 tried to re fine the MCDF cal cu la tions by in cl
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We present a clear observation of a resonant contribution to electron impact ionization of Li-like highly charged ions (I50+) . Li-like ions are the simplest in which resonant-excitation double autoionization (REDA) can occur. REDA was... more
We present a clear observation of a resonant contribution to electron impact ionization of Li-like highly charged ions (I50+) . Li-like ions are the simplest in which resonant-excitation double autoionization (REDA) can occur. REDA was observed by measuring the ratio of the numbers of trapped ions of two neighbring charge states as a function of electron energy under equilibrium conditions
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Relying on an entirely ab initio quantum-mechanical scheme, we investigate the threshold behavior of a model electron-impact ionization problem in which the target hydrogen atom interacts with the incident electron only by monopole. The... more
Relying on an entirely ab initio quantum-mechanical scheme, we investigate the threshold behavior of a model electron-impact ionization problem in which the target hydrogen atom interacts with the incident electron only by monopole. The total ionization cross section for a singlet is shown to follow the threshold law of an exponential form as proposed by Macek and Ihra [Phys. Rev.
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ABSTRACT INTRODUCTION From a sur vey of atomic tran si tions us ing the multiconfigurationDirac -Fock (MCDF) method, Feldman, Indelicato and Sugar 1 re ported that a for bid den tran si tion between the low est fine-structure lev els of... more
ABSTRACT INTRODUCTION From a sur vey of atomic tran si tions us ing the multiconfigurationDirac -Fock (MCDF) method, Feldman, Indelicato and Sugar 1 re ported that a for bid den tran si tion between the low est fine-structure lev els of (3d 4 ) J = 2 and J = 3 was to be ob served in the op ti cal re gion for most high-Z ti tanium-like ions. Be sides its po ten tial im por tance for high-temperature plasma di ag nos tics, the tran si tion serves as a test-ground for many-body atomic struc ture the o ries, as will be seen shortly. The first ob ser va tion of the tran si tion was made by Mor gan et al. 2 for Xe 32+ and Ba 34+ . How ever, mea sured wavelengths were found to have an un ex pect edly large dis crepancy ( 5%) from state-of-the-art MCDF calculations. 3 Indelicato 4 tried to re fine the MCDF cal cu la tions by in cl
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Multiple-hydrogen trapping by mono-vacancies in tungsten was investigated based upon the first-principle (density functional) calculation. An equilibrium thermodynamic model is presented to describe a bulk tungsten crystal containing the... more
Multiple-hydrogen trapping by mono-vacancies in tungsten was investigated based upon the first-principle (density functional) calculation. An equilibrium thermodynamic model is presented to describe a bulk tungsten crystal containing the mono-vacancies and hydrogen atoms by taking account of the first-principle calculations of vacancy-hydrogen interaction. The present model gives average numbers for trapped hydrogen atoms at the single mono-vacancy and the vacancy concentration as functions of local hydrogen concentrations for different temperatures. Based on the present results, we examine a speculation suggested from recent experimental observations, that new hydrogen traps may be created by super-saturated low-energy hydrogen implantation.
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We study an evolutional system to assist an individual to collect articles, which contain atomic and molec- ular data, and to develop the database automatically. A text classification technique based on LVQ (Learning Vector Quantization)... more
We study an evolutional system to assist an individual to collect articles, which contain atomic and molec- ular data, and to develop the database automatically. A text classification technique based on LVQ (Learning Vector Quantization) is proposed and its performance is evaluated using abstracts from atomic and molecular bibliographic databases as training and test samples.
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ABSTRACT Bright narrow band emission observed in optically thin plasmas of high-Z elements in the extreme ultraviolet spectral region follows a quasi-Moseley's law. The peak wavelength can be expressed as... more
ABSTRACT Bright narrow band emission observed in optically thin plasmas of high-Z elements in the extreme ultraviolet spectral region follows a quasi-Moseley's law. The peak wavelength can be expressed as λ=(21.86±12.09)×R∞−1×(Z−(23.23±2.87))−(1.52±0.12), where R∞ is the Rydberg constant. The wavelength varies from 13.5 nm to 4.0 nm as the atomic number, Z, increases from Z = 50 to Z = 83. The range of emission wavelengths available from hot optically thin plasmas permits the development of bright laboratory-scale sources for applications including x-ray microscopy and x-ray absorption fine structure determination.
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ABSTRACT We have developed a data-warehouse system designed for research data centres, which is currently tested in the National Institute for Fusion Science (NIFS) in Japan. The data warehouse integrates an online builder of... more
ABSTRACT We have developed a data-warehouse system designed for research data centres, which is currently tested in the National Institute for Fusion Science (NIFS) in Japan. The data warehouse integrates an online builder of multi-dimensional numerical databases a crawler engine, which classifies the papers retrieved from various online databases of electronic journals for relevance. The present data warehouse functions as an autonomous intelligent database of scientific abstracts; it is also a precursor for an autonomous self-updating database of numerical data, our ultimate goal.
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Electron-impact ionization of hydrogen is investigated based upon ab initio quantal calculations. In the present calculations, strong interelectronic correlations are represented by the hyperspherical channel functions and accurate... more
Electron-impact ionization of hydrogen is investigated based upon ab initio quantal calculations. In the present calculations, strong interelectronic correlations are represented by the hyperspherical channel functions and accurate numerical solutions of the two-electron atomic Schrödinger equation are obtained by means of the smooth-variable-discretization method in combination with the R-matrix propagation method. The double-continuum boundary condition is represented by matching the numerical solutions to asymptotic solutions, which are described by superpositions of approximate asymptotic channel functions. We obtained the ionization threshold law, which is in good agreement with Wannier's conjecture, and also an almost uniform energy distribution in double-continuum states at low energies, say ~0.1 a.u. At low energies, the angular distributions of the electrons in double-continuum states of 1Se localize where the interelectronic angular distance theta12=pi. As the energy increases, the binary-encounter and the dipolelike transition mechanisms manifest themselves in the angular distribution. The spin-averaged total ionization cross section and the spin asymmetry from the present method agree well with experimental measurements as well as the convergent-close-coupling result, while for the spin asymmetry there is a noticeable disagreement with the hidden-crossing result at moderately low energies. An essential role of the potential ridge during the ionization process is apparent in the convergence of the present calculations.
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We have constructed and made available atomic and molecular (AM) numerical databases on collision processes such as electron-impact excitation and ionization, recombination and charge transfer of atoms and molecules relevant for plasma... more
We have constructed and made available atomic and molecular (AM) numerical databases on collision processes such as electron-impact excitation and ionization, recombination and charge transfer of atoms and molecules relevant for plasma physics, fusion research, astrophysics, applied-science plasma, and other related areas. The retrievable data is freely accessible via the internet. We also work on atomic data evaluation and constructing collisional-radiative models for spectroscopic plasma diagnostics. Recently we have worked on Fe ions and W ions theoretically and experimentally. The atomic data and collisional-radiative models for these ions are examined and applied to laboratory plasmas. A visible M1 transition of W26+ ion is identified at 389.41 nm by EBIT experiments and theoretical calculations. We have small non-retrievable databases in addition to our main database. Recently we evaluated photo-absorption cross sections for 9 atoms and 23 molecules and we present them as a new database. We established a new association ``Forum of Atomic and Molecular Data and Their Applications'' to exchange information among AM data producers, data providers and data users in Japan and we hope this will help to encourage AM data activities in Japan.
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The collision processes of highly charged ions with electrons have been studied with an electron beam ion trap. Resonant inner-shell processes such as dielectronic recombination and resonant excitation double autoionization were... more
The collision processes of highly charged ions with electrons have been studied with an electron beam ion trap. Resonant inner-shell processes such as dielectronic recombination and resonant excitation double autoionization were investigated by observing the number ratio of extracted ions with adjacent charge states.