Showing papers by "Hiroyuki A. Sakaue published in 2010"

Tungsten spectra recorded at the LHD and comparison with calculations

Abstract: We have measured extreme ultraviolet (EUV) spectra from highly charged tungsten ions in low-density and high-temperature plasmas produced in the Large Helical Device at the National Institute for Fusion Science. The EUV spectra emitted after injection of a tungsten pellet into a hydrogen plasma were recorded at plasma temperatures of 1.5 and 3 keV and were dominated by an intense transition array in the 4.5–6.5 nm region, the profile and extent of which was different in both spectra. Some discrete lines present were identified by comparison with existing spectral data while atomic structure calculations showed that the dominant emission in both arose from Δn = 0, n = 4–n = 4 transitions and the main differences could be attributed to the appearance of the 4p–4d and 4s–4p transitions from W XXXIX to W XLVI in the higher temperature spectrum. Comparison with calculations showed that the dominant emission in both temperature regimes arose from stages where the 4f subshell was either almost or completely stripped. We also investigated if the effect of low density favours transitions to the lowest level as observed in recently reported results.

Analysis of EUV spectra of Sn XIX-XXII observed in low-density plasmas in the Large Helical Device

Abstract: We have measured extreme ultraviolet (EUV) spectra from highly charged tin ions in low-density and high-temperature plasmas produced in the Large Helical Device at the National Institute for Fusion Science. The EUV spectra emitted after injection of a tin pellet into a hydrogen plasma were monitored by a grazing incidence spectrometer whose wavelength resolution is about 0.01 nm. Two different types of spectral feature were measured in the 13–17 nm region depending on whether the discharge was stably sustained or underwent radiation collapse. The measured EUV spectra were analyzed by considering the difference in dominant charge states observed in the two types of spectra. Apart from the complex quasi-continuum structure around 13.5 nm, several strong lines occurring at wavelengths longer than 14 nm were found to originate from the transitions between excited states of Sn XXI and Sn XXII by comparison with the other experimental data including the charge exchange collisions experiments. Most of the strong spectral lines which were not identified as Sn XXI or Sn XXII were assigned to the resonance transitions of Sn XIX and Sn XX from comparison with the results of theoretical calculations.

A compact EBIT for spectroscopic studies of moderate charge state ions

Abstract: We have developed a compact electron beam ion trap (EBIT) with a high-Tc superconducting magnet. The electron energy range of the new EBIT is 100-2500 eV, which enabled us to downsize the device. The performance of the compact EBIT has been investigated through extreme ultra-violet (EUV) spectroscopy of highly charged iron ions and visible spectroscopy of highly charged tungsten ions.

Analysis of Fe XXI Spectral Lines Measured in LHD Plasma

Abstract: We measured extreme ultraviolet spectra of plasmas in the Large Helical Device after an Fe pellet was injected and analyzed the Fe XXI spectral lines λ 12.12 nm (2s22p2 3P2-2s2p3 3P2) and λ 12.875 nm (2s22p2 3P0-2s2p3 3D1). By constructing a collisional-radiative model for Fe XXI, we obtained the electron density dependence of the line intensity ratio, which is the result of the excitation process among the fine-structure levels of the ground state, 2s22p2 3PJ by electron and proton impact. Using the obtained electron density dependence, we estimated the electron density from the measured intensity ratio. By comparing the estimated density with the electron density distribution measured by a far infrared interferometer, we could estimate the location of the Fe XXI emitting region. We found that Fe XXI appeared first around the density peak formed by the pellet and later expanded toward a low-density region. The corresponding electron temperature of the location is lower than that for ionization equilibrium, and the Fe XXI ions are expected to be in a non-equilibrium ionization state.

Observation of Magnetic Dipole Forbidden Transitions in LHD and Its Application to Burning Plasma Diagnostics

Abstract: Magnetic dipole forbidden (M1) transition was studied in large helical device (LHD) and F-, Si- and Ti-like Ml transitions are successfully observed for highly ionized Ar, Kr, Mo and Xe ions. The wavelengths measured in visible range for the heavy elements, which are carefully determined with extremely small uncertainties of 0.02 ~ 0.05 A as a standard wavelength of usual electric dipole (E1) plasma emissions, are compared with theoretical predictions. The result shows a good agreement with recent Hatree-Fock calculation including semi-empirical adjustment. The M1 intensity for the F-like ions is examined by analyzing the intensity ratio of M1 to E1. Density dependence of the ratio is experimentally verified by comparing with collisional- radiative model calculation on level population. The M1/E1 line ratio for the F-like ions is applied to the α (He2+) particle diagnostics in ITER, in which a steady-state operation of burning plasmas based on D-T fusion reaction is expected with α particle heating. Unfortunately, the present estimation suggests a negative result for the α particle measurement because the ratio is largely enhanced by the collisional excitation with bulk ions due to high ion temperature of ITER of 10 keV as assumed and the resultant effect of the collisional excitation with α particles becomes less. Meanwhile, the Ml transition, in particular, Ti-like WLIII (W52+) transition (3627 A) emitted in visible range, is very useful for diagnostics of the impurity behavior and the core plasma parameters in ITER.

Low dielectric constant films and manufacturing method thereof, as well as electronic parts using the same

Abstract: While a fine porous diamond particle film has been known as a high heat resistant and low dielectric constant film and also has high mechanical strength and heat conductivity, and is expected as an insulating film for multi-layered wirings in semiconductor integrated circuit devices, it is insufficient in current-voltage characteristic and has not yet been put into practical use. According to the invention, by treating the fine porous diamond particle film with an aqueous solution of a salt of a metal such as barium and calcium, the carbonate or sulfate of which is insoluble or less soluble, and a hydrophobic agent such as hexamethyl disilazane or trimethyl monochlolo silane, as well as a reinforcing agent containing one of dichlorotetramethyl disiloxane or dimethoxytetramethyl disiloxane, thereby capable of putting the dielectric breakdown voltage and the leak current within a specified range of a practical standard.

Activities at the Tokyo EBIT 2010

Abstract: In this paper, we present recent activities at the Tokyo EBIT after giving an overview of the present status of the devices. We have been studying dielectronic recombination processes by means of several techniques. In addition to X-ray observations and charge abundance observations, 2-photon observations have been recently used to study DR processes which emit two photons successively (but practically simultaneously). Recent efforts on spectroscopic work are mainly concentrated on Fe and W ions, which are relevant to astrophysical and fusion plasmas. Several spectrometers that can cover a wide range of wavelength, such as visible, EUV, and X-rays, were used for accumulating useful data for plasma diagnostics applications. HCI-surface collision processes were studied using ions extracted through the beam line, that has recently been modified. Very highly charged ions up to Bi81+ were used for studying the effect of huge potential energy.