Showing papers by "Hiroyuki A. Sakaue published in 2012"

M1 transition energies and probabilities between the multiplets of the ground state of Ag-like ions with Z = 47-92

Abstract: Extensive relativistic configuration interaction calculations have been performed for the 4d104f and 4d105s states of the Ag-like isoelectronic ion using the GRASP2K package based on the multi-configuration Dirac–Fock method. The active space techniques have been employed to extend the configuration expansion systematically. The electron correlation effects, Breit interaction and quantum electrodynamics effects to the atomic state wavefunctions and the corresponding energies have been taken into account. Good agreement has been obtained in a general trend with the existing experimental and theoretical values. The change of the ground state configuration from 4d105s to 4d104f is predicted to occur at Z = 62. The transition energy and probability of the M1 transition between the 4d104f multiplets are, respectively, scaled to be 0.01(Z*)4 cm−1 and 1.95 × 10−17(Z*)11.97 s−1, where Z* = Z − 34.42 is the effective nuclear charge number for Ag-like ions with Z ⩾ 62. Our results show the need for more high-precision experiments for Z ⩾ 68 ions.

Visible Transitions in Highly Charged Tungsten Ions: 365 - 475 nm

Abstract: Akihiro KOMATSU1), Junpei SAKODA1), Maki MINOSHIMA1), Hiroyuki A. SAKAUE2), Xiao-Bin DING3), Daiji KATO2), Izumi MURAKAMI2), Fumihiro KOIKE4) and Nobuyuki NAKAMURA1,2) 1)Institute for Laser Science, The University of Electro-Communications, Tokyo 182-8585, Japan 2)National Institute for Fusion Science, Gifu 509-5292, Japan 3)Coll. of Phys. and Elect. Eng., North West Normal University, Lanzhou 730070, China 4)School of Medicine, Kitasato University, Sagamihara, Kanagawa 252-0373, Japan

Collisional-Radiative Modeling of W27+

Abstract: A detailed collisional radiative model of W27+ ions was constructed based on the atomic data calculated by relativistic atomic properties software Flexible Atomic Code. The strong electric dipole (E1) transitions mainly comes from the 4 f → 4d transition in W27+ ions with wavelength falls into VUV region (4.6 5.1 nm), while the wavelength of magnetic dipole (M1) transition among the fine structures of the first excited states falls into the visible optical region. Synthetic spectra in both regions are given theoretically with plasma condition in EBIT for experiment reference. Finally, the dependence of the intensity ratio on the electron density is provided as a potential diagnostic tool of Maxwellian plasmas.

Spectroscopy of highly charged tungsten ions with Electron Beam Ion Traps

Abstract: We present spectra of highly charged tungsten ions in the extreme ultra-violet (EUV) and visible range observed by using two types of electron beam ion traps. The electron energy dependence of spectra is investigated for several electron energies from 630 to 3200 eV. Several tens of previously unreported lines are presented in the EUV and visible range, and some of them are identified by comparing the wavelengths with theoretical calculations.

Effect of high-energy neutral particles on extreme ultraviolet spectroscopy in large helical device

Abstract: Spectra measured by an extreme ultraviolet (EUV) spectrometer frequently suffer large spike noise when Large Helical Device is operated in low-density range (≤3 × 1013 cm−3) with neutral beam injection (NBI). The spike noise completely disappears in electron cyclotron heating discharges. In order to examine the effect of NBI, a carbon filter with thickness of 150 nm was installed in the EUV spectrometer. As a result, the spike noise was reduced by an order of magnitude. It is experimentally verified that the spike noise is caused by escaping high-energy neutral particles resulting from the circulating high-energy hydrogen ions borne from NBI.

Characteristics of the Electron Beam Ion Source

Abstract: The electron beam ion source (Kobe EBIS) has been developed to perform modification of surfaces using highly charged ions (HCIs). Recent study revealed that periodic intermission of electron beam improves charge state distribution of extracted ions. The repetition of ON/OFF of electron beam with the period in the order of 100ms and the width of beam-off time being 1ms or less made it possible to produce Ar15+ to Ar17+ effectively, while the charge is limited less than 14+ under the ordinary operation mode. A spike of HCIs is also produced at each moment of electron beam off.

Ion-Beam Induced Luminescence and Damage of Er2O3

Abstract: Ion-beam induced luminescence of sintered Er2O3 samples irradiated by Ar ion-beams was measured in a visible range. In this experiment, three emission bands were observed at 500-520, 540-570, and 640-690 nm. The measured luminescence band at 640-690 nm is resolved into Lorentzian Stark component having a ∼ 1012 Hz width in frequency. Center wavelengths of the Stark components agree with those of intra-4f transitions of Er3+ (4f11) ions situated at C2 symmetry cation sites in pure Er2O3. However, resonance broadening due to nearby Er3+ in the crystal accounts only 1% of the total width. Depopulation of the crystalline oxide in irradiated regions is inferred from decreasing intensity of the emission band at 640-690 nm during continuous irradiation. The emission bands at 500-520 and 540-570 nm still remained in heavily damaged samples look similar with those observed with a metallic Er target.

Mean velocity of 5d56p excited tungsten atoms sputtered by Kr+ ion bombardment

Abstract: Visible emission spectroscopy was conducted for atoms sputtered from tungsten surfaces under Kr+ ion irradiation (33–60 keV). A number of WI lines were observed in the wavelength of 360–490 nm. The emission intensity of the WI line at 400.88 nm was measured as a function of the distance from the surface. The mean normal velocity of W∗(5d5(6S)6p 7P4) atoms was measured by analyzing the exponential decay curves. No remarkable change in the velocity was found for different projectile energies. The average velocity was 5.6 ± 1.7 kms−1.

Analysis of C V Ions by Measuring Line Ratios in the LHD

Abstract: We measured time-dependent extreme ultraviolet spectra to carry out a quantitative study of impurity spectral lines of C V in the Large Helical Device (LHD) at the National Institute for Fusion Science. In order to analyze these C V spectra, we calculated the intensity ratios of spectral lines of C V using our collisional-radiative model and compared the results to observed time-dependent intensity ratios. We derived the electron temperature from the measured intensity ratio and estimated the location of the C V emitting region by comparing the derived temperature with the electron temperature distribution measured by the Thomson scattering. Through the C V emitting region, we see that the C V appears just after carbon pellet ablation caused by the bulk plasma at 2.8 s and moves toward the wall until ∼3.0 s.