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For the continued improvement and development of large negative hydrogen ion sources for NBI applications, beam characterisation is of critical importance for understanding and predicting the interaction of a large beam with, for example, a gas neutraliser system. As large ion beams are comprised of collections of individual beamlets, the relationship between the results of beam diagnostics and the physical properties of the beam is not a trivial one. Measured quantities come from the mixing of information from different beamlets, and the extraction of beamlet level data may not be possible. To establish the links between diagnostic results and beamlet behaviour, the particle tracking code BBCNI has been designed to forward calculate simulated diagnostics from particle level data, including beam emission spectroscopy (BES) and calorimeter measurements. Full traceability of these synthetic diagnostics allows features to be linked to specific particle populations and areas of the beam, providing a much-needed understanding of experimental results. In order to demonstrate the capability of the code, the first experimental BES results from the BATMAN Upgrade test facility are also presented. Measurements of beam divergence as calculated from real and synthetic data are shown to be in good agreement, and it is demonstrated how the code can give details of individual beamlet properties and how these build into synthetic diagnostic data. [ABSTRACT FROM AUTHOR]

Modelling electron statistics in a cold, dense plasma by the Fermi-Dirac distribution leads to complications in the calculations of atomic rate coefficients. The Pauli exclusion principle slows down the rate of collisions as electrons must find unoccupied quantum states and adds a further computational cost. Methods to calculate these coefficients by direct numerical integration with a high degree of parallelism are presented. This degree of optimization allows the effects of degeneracy to be incorporated into a time-dependent collisional-radiative model. Example results from such a model are presented. [ABSTRACT FROM AUTHOR]

A 100 keV, negative hydrogen ion based neutral beam system is in the developmental stage at a test facility (Indian Test Facility) in India. This test facility is used for characterizing Diagnostic Neutral Beam (DNB) of ITER.A large number of diagnostics are planned for monitoring and characterization of the beam. The Doppler Shift Spectroscopy (DSS) diagnostics is chosen for characterizing the beam by evaluating the beam divergence, stripping losses and beam uniformity from the observed Balmer-alpha emission from the fast-neutral hydrogen atom, produced from accelerated negative hydrogen ions (H-) ions. In order to design and develop the DSS diagnostics, a forward model to estimate the signal to noise ratio and beam divergence is developed. For the chosen lines of sight (LOS), at different operating scenarios and instrument settings, the model is applied. The expected performance of the diagnostics based on this model is discussed and a brief description of the proposed diagnostics is presented. [ABSTRACT FROM AUTHOR]

We have performed the first energy-resolved measurement of the associative detachment (AD) reaction H- + H → H2- → H2 + e-, which is the dominant process forming molecular hydrogen in the early universe. We find excellent agreement between our measurements and the most recent theoretical calculation of the AD process. We also present model calculations of the formation of protogalaxies in the early universe uitilizing the experimentally confirmed rate coefficient. [ABSTRACT FROM AUTHOR]

Schwinger variational approach to the process of direct electronic excitation of atoms by impact of ions at intermediate and high impact energies was shown to be successful in predicting the excitation cross sections of ion-atom collisions [1,2]. In this study, we present a new method based on the fractional form of the Schwinger variational principle to evaluate the Balmer-α excitation cross sections σ (Hα) of hydrogen atom by proton impact. We study also in this work, the linear polarization fraction Π (Hα) (first Stokes parameter). For impact energies between 10 to 200 keV, our theoretical predictions stay globally in good agreement with the available experimental data [3-5] and other theoretical calculations [6-13]. [ABSTRACT FROM AUTHOR]

The homogeneity of the extracted current density from the large RF driven negative hydrogen ion sources of the ITER neutral beam system is a critical issue for the transmission of the negative ion beam through the accelerator and the beamline components. As a first test, the beam homogeneity at the IPP long pulse test facility MANITU is measured by means of the divergence and the stripping profiles obtained with a spatially resolved Doppler-shift spectroscopy system. Since MANITU is typically operating below the optimum perveance, an increase in the divergence corresponds to a lower local extracted negative ion current density if the extraction voltage is constant. The beam Hα Doppler-shift spectroscopy is a rather simple tool, as no absolute calibration-both for the wavelength and the emission-is necessary. Even no relative calibration of the different used lines of sight is necessary for divergence and stripping profiles as these quantities can be obtained by the line broadening of the Doppler-shifted peak and the ratio of the integral of the stripping peak to the integral of the Doppler-shifted peak, respectively. The paper describes the Hα MANITU Doppler-shift spectroscopy system which is now operating routinely and the evaluation methods of the divergence and the stripping profiles. Beam homogeneity measurements are presented for different extraction areas and magnetic filter field configurations both for Hydrogen and Deuterium operation; the results are compared with homogeneity measurements of the source plasma. The stripping loss measurements are compared with model calculations. [ABSTRACT FROM AUTHOR]

Cosmic atomic plasmas can be divided into two broad classes: electron ionized and photoionized. Electron-ionized plasmas are formed in objects such as the sun and other stars, supernova remnants, galaxies, and the intercluster medium in clusters of galaxies. Photoionized plasmas are formed in objects such as planetary nebulae, H II regions, X-ray binaries, and active galactic nuclei. Understanding the spectral and thermal properties of these objects requires an accurate knowledge of the ionization level of the gas. This in turn depends on a reliable understanding of the underlying ionization and recombination processes which determine the ionization balance. Here we review some of the various atomic collision processes which determine the charge state distribution in a cosmic atomic plasma and briefly discuss some of the recent theoretical and experimental advances in generating the needed atomic data. We close by describing the relevant atomic data needs for the near future. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

Dr. Kim made internationally recognized contributions in many areas of atomic physics research and applications, and was still very active when he was killed in an automobile accident. He joined NIST in 1983 after 17 years at the Argonne National Laboratory following his Ph.D. work at the University of Chicago. Much of his early work at Argonne and especially at NIST was the elucidation and detailed analysis of the structure of highly charged ions. He developed a sophisticated, fully relativistic atomic structure theory that accurately predicts atomic energy levels, transition wavelengths, lifetimes, and transition probabilities for a large number of ions. This information has been vital to model the properties of the hot interior of fusion research plasmas, where atomic ions must be described with relativistic atomic structure calculations. In recent years, Dr. Kim worked on the precise calculation of ionization and excitation cross sections of numerous atoms, ions, and molecules that are important in fusion research and in plasma processing for manufacturing semiconductor chips. Dr. Kim greatly advanced the state-of-the-art of calculations for these cross sections through development and implementation of highly innovative methods, including his Binary-Encounter-Bethe (BEB) theory and a scaled plane wave Born (scaled PWB) theory. His methods, using closed quantum mechanical formulas and no adjustable parameters, avoid tedious large-scale computations with main-frame computers. His calculations closely reproduce the results of benchmark experiments as well as large-scale calculations requiring hours of computer time. This recent work on BEB and scaled PWB is reviewed and examples of its capabilities are shown. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

The theory of electron impact ionization of one- and two-electron atoms has advanced significantly in the past two years. This paper will summarize the progress that the members of our research center have contributed to. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Reliably interpreting spectra from both photoionized and electron-ionized cosmic plasmas requires an accurate understanding of the ionization balance of the source and the underlying atomic physics which produces the ionization structure. Uncertainties in ionization balance calculations hamper our ability to model cosmic sources and to infer reliably their properties. Of particular importance are accurate rate coefficients for electron impact ionization (EII) and dielectronic recombination (DR). Here I briefly review the astrophysical implications due to current uncertainties in EII and DR and discuss our ongoing laboratory work aimed to remove these uncertainties. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Hyperspherical partial wave theory has been applied in the study of ionization of hydrogen atoms by electron impact from very low energies (1.0eV, 0.5eV and 0.3eV above threshold) to intermediate energies (60eV). The various ionization cross sections which have been calculated are generally in good agreement with the experiments. Some times the agreements are even better than those of other high level theories, like ECS and CCC theories, requiring elaborate computations. © 2003 American Institute of Physics [ABSTRACT FROM AUTHOR]

Beams of light elements, such as lithium, are important diagnostics in controlled plasma fusion devices. Consequently there is a great need for accurate atomic data for excitation and ionization processes in neutral lithium and its ions. In recent years, much progress has been made in calculating accurate cross sections for electronimpact excitation and ionization processes using non-perturbative techniques. These methods can now provide benchmark accuracy for the electron-impact excitation and ionization of simple atomic systems. For example, for the electron-impact ionization of hydrogen, all the non-perturbative methods yield total cross section results that are in excellent agreement with experimental measurements. These techniques have recently been extended to calculate excitation and ionization cross sections for neutral lithium and its ions. Excellent agreement is found between the three non-perturbative methods employed, and in some cases, large disagreements are found with previous existing experimental measurements. [ABSTRACT FROM AUTHOR]

The previous decade has seen immense progress in the field of electron-atom scattering. The availability of accurate computed data has revitalised numerical modelling of plasmas in astrophysics, fusion, lighting, and elsewhere. Here we summarise the contribution that the Convergent Close-Coupling (CCC) method has made to the generation of such data. [ABSTRACT FROM AUTHOR]

Collisions between ions belong to the elementary processes occurring in all types of plasmas in astrophysical objects as well as in laboratory discharges. In recent years, the impetus for accurate cross section data for such collisions has become greater due to research in thermonuclear fusion using either magnetic or inertial confinement. Data are reviewed for collisions between light ions, in which only one or two electrons are involved. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A new scaling law for ionization is presented. Our new model scales the cross sections by Z4/3 and the impact energies by Z2/3, rather than by Z in both cases as suggested by Olson et al. Using available CDW-EIS calculations and experimental data for ionization of helium by fully stripped ions, it is shown that this "modified Z" scaling yields a universal curve throughout the entire energy regime, not just for the region above the cross section maximum. Similar results are obtained for ionization of molecular hydrogen. [ABSTRACT FROM AUTHOR]