Korea Atomic Energy Research Institute

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The Atomic Spectroscopy Research Group (ASRG)in the Laboratory for Quantum Optics at the Korea Atomic Energy Research Institute (KAERI) has an experimental program devoted to the precision measurement of atomic spectroscopic parameters such as energy levels, autoionization levels, isotope shifts, hyperfine structures, multi-photon ionization schemes, etc., using the resonance ionization spectroscopy methods. The ASRG is also responsible for the atomic, molecular and optical (AMO) database systems (AMODS).

Supporting theoretical work at ASRG is concerned with relativistic electronic structure calculations, electron collision processes, and density-matrix based calculations. The research in the group is motivated by basic atomic physics and by applications to magnetic and inertial confinement fusion energy research, industrial plasmas and laboratory astrophysics.

Recently the ASRG has made many studies of lanthanide elements, particularly La, Sm, Eu, Gd, Dy, Er and Yb. Isotope shifts were measured in transition lines in neutral Sm and were compared with single-configuration and multi-configuration Dirac-Fock calculations. Isotope shifts and hyperfine structure were also studied in neutral Yb. The MCDF code due to Desclaux, Indelicato and Kim, is used for the calculations and an interface to this code is available through the AMODS web service. The laboratory has also studied and modelled spectra of highly charged heavy ions such as W, Mo and V. Tungsten (W) is of particular interest for fusion as the primary plasma-facing material in ITER. The MCDF code has been used to calculate emission lines and line shapes for highly charged W ions. Spectra were calculated for W33+ to W46+.

In addition to spectra, electron impact ionization cross sections are essential data for fusion plasma and can be calculated by using MCDF code. The calculations rely on the Binary Encounter Bethe (BEB) model and employ the plane wave Born (PWB) approximation for a neutral atom and the Coulomb Born (CB) approximation for a singly charged ion. Electron impact ionization cross sections of neutral atoms are very difficult to obtain experimentally; however, W, Mo, V, Li, Be, C and others have been studied in the ASRG recently. Also electron impact ionization cross sections of W+ have been calculated and compared with experiments. Electron impact ionization cross sections of neutral W atom have been calculated at ASRG and compared with other calculations. AMODS now offers an interface that permits online calculation of direct ionization cross section bases on BEB for W and Mo.

The AMODS database contains information on atomic and molecular structures, transition lines and probabilities, laser propagation characteristics, collisional ionization cross sections, and fundamental constants. Dr Rhee showed the interface in his presentation. Spectral lines can be searched per atom or ion with or without specification of the precise charge state, and the information is connected to bibliographical data. Computational tools are provided that interact with the database to obtain population dynamics and to calculate the deposited power of a laser beam. Total and differential electron impact excitation and ionization cross-sections are available in AMODS for several target atoms and molecules; see http://amods.kaeri.re.kr/impact/IMPACT.html. Both theoretical and experimental data are included. In collaboration with NIFS data for autoionizing states and dielectronic satellite lines are being assembled into AMODS.

The Atomic Spectroscopy Research Group at KAERI is a unique atomic spectroscopy facility in KOREA in which experiments and theoretical studies are being pursued. Recent spectroscopic studies for fusion research have addressed electron impact ionization cross sections (W, Mo, Be, C, etc) as well as radiative transitions of highly charged ions and of moderately charged W ions. The BEB model was extended to higher charged states and the MCDF code was upgraded. High energy density science for inertial fusion and laboratory astrophysics is another concern and the ASRG has been involved in the production of data (EOS, opacity) and in simulation (HYADES, MULTI). Computer codes for fusion plasma are under development, including codes for non-LTE plasma and for a two-temperature model.

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