Hitoshi Oyama

Experiment on the Anisotropy of Electron Temperature in ECR Plasma

Measurements of electron temperatures in the direction parallel and perpendicular to the magnetic field are made in a plasma produced by ECR (electron cyclotron resonance) in order to investigate the temperature anisotropy. It is found that the temperature perpendicular to the field is higher than the temperature parallel to the magnetic field by 3%-30% depending on the experimental condition. Dependence of anisotropy on the gas pressure, the resonance field configuration and the microwave power is studied. Discussion is made on the mechanisms causing the anisotropy and the energy relaxation.

In situ calibration of a flat-field grazing incidence spectrograph with an x-ray charge-coupled device camera using a transmission grating and a laser-produced plasma for x-ray laser research

An in situ calibration experiment of a soft x-ray spectrograph for x-ray laser research has been performed. The calibrated spectrograph was a flat-field grazing incidence spectrometer with an x-ray charge-coupled device camera. The absolute sensitivity of the spectrograph was obtained for the wavelength range from 2.6 to 4.0 nm using a transmission grating spectrograph as a reference spectrograph set along the axial direction of a line-focused laser-produced plasma. The absolute sensitivity determined in this work shows nearly the same value as that deduced from the calibration experiment using synchrotron radiation.

High-resolution soft X-ray spectroscopy of 2.3 keV/u N7+ ions through a microcapillary target

X-rays emitted from 2.3 keV/u 15 N 7þ ions transmitted through a highly ordered Ni microcapillary were measured with a high-resolution soft X-ray spectrometer. The highly ordered microcapillary has recently become available employing a nano-lithographic technique. A transmission ratio and charge state distribution of ions through the microcapillary target were found to be consistent with theoretical predictions. A preliminary analysis showed that a series of X-rays from np–1s transitions with n as high as 8 were identified,which is consistent with the classical over barrier model. 2002 Elsevier Science B.V. All rights reserved.

Electron Temperature Measurement Using Intensity Ratio of H2 Fulcher α(d3Πu-a3Σg) to Hα Emissions in a Weakly Ionized Plasma

A spectroscopic method for obtaining electron temperature is proposed by observing the intensity ratio of the H2 Fulcher α system (d3Πu-a3Σg) and Hα emissions. Experimentally, this method was applied to a weakly ionized plasma produced by a 2.45 GHz microwave source. The obtained electron temperature showed good agreement with the result from the elecrostatic probe.

Characteristics of Cleaning and Carbonizing Plasmas in TEXTOR

Plasma parameters for discharge cleaning and carbonization in TEXTOR (Torus Experiment on Technology Oriented Research in the Kernforschungsanlage Julich) have been measured with Langmuir probes. In the rf-assisted glow (RG) discharge of hydrogen, at 1.6×10-1 Pa, the plasma density is ne = 3.0-4.0×108 cm-3, the electron temperature Te = 10-12 eV, and the space potential Vs265 V. In the electron cyclotron resonance (ECR) discharge, at 1.1 × 10-2 Pa, ne=2.0-2.7×1010 cm-3, Te=3.5-5.2 eV, and Vs=20 V in the resonance region. The width of this region is about 20 cm. In the carbonization by the RG discharge with an admixture of methane into deuterium at a volume ratio of 33%, at 1.7×10-1 Pa, ne = 0.9-1.4×109 cm-3, Te = 2.7-3.3 eV and Vs280 V. The flux of ions and neutral atoms are estimated from measured parameters. In RG(H2), both H+2 and H are effective for cleaning. In ECR, an appreciable flux of H is obtained, and the H+2 flux, though reduced by the radial magnetic field, has an effect of cleaning. In RG(CH4/D2), the positive ion flux of the order of 6×1013 cm-2s-1 is responsible for the carbonization.

High-resolution soft X-ray spectroscopy of slow highly charged ions transmitted through a microcapillary target

Abstract To detect weak X-rays with a high-resolution spectrometer, a charge-coupled device was operated in a single X-ray photon detection mode. A procedure to effectively identify single X-ray was established. In the case of 2.3 keV/u N7+ and Ne9+ incidence, X-rays emitted from ions transmitted through a Ni microcapillary target were measured with the spectrometer using the procedure of the single event mode. The signal-to-noise ratio was improved by using the single photon counting method.

Metastable states produced with beam–capillary interaction

Abstract The formation and relaxation processes of hollow atoms and related excited states of ions produced with a Ni microcapillary thin foil have been studied employing various experimental techniques. The first stage of the charge transfer from the surface to the ions was studied by using visible light measurements. On the other hand, X-ray measurements revealed the core electronic configurations of ions at the last moment of the hollow atom evolution. The overall feature of the electron capture processes in the capillary was given by the charge state distribution measurements.

Fundamental study of ECR multicharged ion sources

Abstract Multicharged argon ions were observed up to Ar 11+ in an ECR discharge with a microwave of 2.45 GHz in an octupole-mirror field. The yield of the ions was increased by increasing the mirror ratio of the magnetic field and by choosing a suitable intensity of the octupole field.

The continuing saga of the Si-like intercombination lines in highly charged ions, Si-like rhodium

The 3s(2)3p(2 3)P(1.2)-3s3p(3) S-5(2) intercombination lines for Si-like Rh have been investigated using the techniques of beam-foil spectroscopy. Two lines have been identified as belonging to these transitions having, however, different wavelengths from what would be expected based on published iso-electronic trends. The identifications suggested here are strengthened by requirements on (a) the known fine structure splitting in the ground configuration, (b) an intensity ratio based on branching ratios, (c) similar decay characteristics and (d) expected behaviour of the lines as a function of the ion beam energy

Temperature and density measurements in the RIKEN electron cyclotron discharge ECR-3

Abstract Measurements of the ion and electron temperature and density in an electron cyclotron discharge by means of the rotatable double probe and an retarding field analyser are reported. A significant resonance absorption at the second harmonic is observed. The relevance of the results for the optimum operation of such a discharge as an ion source is discussed.