Keishi Ishii

On the coherent electronic excitation of channelled He+ ions

Abstract Emission of light from He + ions transmitted though [111] axis of thin single crystal of gold has been studied and no effect of coherent electronic excitation could be detected.

Spectroscopic determination of hydrogen and electron densities in plasma in the ionizing phase: Application to WT-III

The Balmer line intensities of atomic hydrogen from the WT-III tokamak plasma have been observed and interpreted in terms of the collisional-radiative model. The atomic and molecular hydrogen densities are deduced together with the electron density. Going from the plasma centre to the edge region along the minor radius, the atomic hydrogen density increases slightly and molecular hydrogen is found only in the periphery. In the edge region, the atomic hydrogen density reaches 1 × 1016 m−3 and the molecular hydrogen density 4 × 10l7 m−3. The electron density distribution is consistent with that determined by infrared laser interferometry.

Spectral Data for Molybdenum Ions, Mo VI–Mo XLII

Wavelengths, intensities, and classifications for the molybdenum ions Mo VI to Mo XLII are compiled. A short review of the work on each stage of ionization is included. The data are critically evaluated and the best results, in our judgement, are quoted.

Experiment on the Spatial Confinement of Plasma in the Heliotron B Magnetic Field

A magnetic field is produced by an electric current in a series of pair coils wound around the discharge tube at regular intervals. The electric current in each coil of the pair differs both in intensity and direction. The lines of force near the tube axis undulate without crossing the wall, while those near the tube wall cross the wall. Thus the high‐temperature plasma can be produced by Ohmic heating in the central region of the field. Experiments were carried out in order to verify the spatial confinement of the plasma in this field. The plasma current flows only within the central region whose mean‐cross‐section diameter is about 3 cm, and the plasma has a sharp boundary. Outside the region there is no current. The spectra from the hydrogen discharge are mainly composed of the pure Balmer series, and the impurity spectral lines are very weak or hardly perceptible. From these experimental results, it can be concluded that the hot plasma is almost perfectly isolated from the stainless‐steel‐tube wall by the Heliotron magnetic field and has very low impurity level.

Beam-Foil Lifetime Measurements in C III, N III, N IV and O III

Using the beam-foil technique with emphasis on high wavelength resolution in VUV region, radiative lifetimes have been measured for some excited levels in C, N and O ions. The line at 764.36 A due to 2s 2 2p 2 P 3/2 -2s2p 2 2 S 1/2 transition in N III was clearly resolved from a nearby lying line of N IV. Some of the irregularity existing in the systematic trend of oscillator strength along the isoelectronic sequence have been removed.

Visible light spectroscopy of Ar6+ ions in high Rydberg states produced with a microcapillary target

We have observed photons in the visible light range emitted from slow (2.0 keV/amu) highly charged Ar6+ ions which have captured one electron and transmitted through a Ni microcapillary target. Observed lines were identified by comparing with an ab initio calculation based on the multi-configuration Hartree-Fock method

Intercombination transitions in beryllium-like and boron-like iron

Beam-foil spectroscopy techniques have been used to study intercombination transitions in Be-like Fe22+ and B-like Fe21+. The method of time delayed spectroscopy was used to identify the Be-like 2s2 1S0-2s2p 3P1 and B-like 2s22p 2P3/2-2s2p2 4P5/2 transitions. Intensity decay curves for these transitions were recorded and level lifetimes were obtained. The latter were found to be 17.5 ± 1.5 ns for the Be-like 2s2p 3P1 level and 14.8 ± 1.0 ns for the B-like 2s2p2 4P5/2 level.

Radial distribution of ion temperature in a WT-III tokamak plasma, as determined from Abel inversion of impurity line profiles

Abstract By using a spectrometer fitted with a multichannel detector, we have observed a chord dependence of emission-line profiles of OV and CV impurities in a WT-III tokamak plasma in a Joule-heating mode. After Abel-inversion of the observed intensity for each channel of the detector, we obtained a Doppler-line profile as a function of radius. Ion temperatures derived from the two lines agree with each other and are consistent with the energy distribution of neutral particles emanating from the plasma.

Spectroscopic Studies of a Helium Plasma in a Linear Z-Pinch Tube

In a linear z-pinch discharge of helium, the continuum emission at the maximum contraction of the plasma and some forbidden lines during the succeeding period of a few µsec were observed at the initial gas pressure of 6.0 Torr. At the maximum contraction the plasma was found to be a black body in the direction through the axis of the discharge tube and a gray body in the direction perpendicular to the axis. From the intensity of continuum and optical thickness the temperature and the electron density have been determined to be (1.5±0.2)×10 4 °K and 5∼7×10 18 cm -3 , respectively. The intensity ratios of the forbidden lines to the allowed ones as well as their shifts were measured in n 3 L –2 3 P series. From these results it has been proved that the electron density of the plasma changes from 1 to 0.1×10 18 cm -3 in a few µsec after the maximum contraction.

Identification of the 3d 9 –3d 8 4f transition in Zr XIV

The XUV spectrum of Co i-like Zr was observed with a low-inductance vacuum spark by using a 10.7-m grazing-incidence spectrograph. Thirty-eight lines of the 3d9–3d84f transition and thirty levels of the 3d84f configuration in Zr xiv were identified for the first time, to our knowledge. The identifications were made with the aid of theoretical calculations based on the Slater–Condon theory of atomic structure. Observed and theoretical spectra and energy levels are displayed in the figures. In addition, energy levels and wavelengths with calculated weighted oscillator strengths are presented in the tables.