Kiyohiko Okazaki

ECR-Discharge Cleaning for Liner-Containing Tokamaks

An experiment on electron-cyclotron-resonance (ECR) discharge cleaning was conducted in the TEXTOR device. A clean-up time for the liner was determined by estimating a total atomic flux integrated over spatial distributions of the ECR plasmas. It was proved that the vacuum components between the liner and vacuum vessel of tokamaks can be cleaned by this method.

A 10.7-m Grazing Incidence Spectrometer for the Study of Highly-Ionized Atoms

A high-resolution grazing incidence spectrometer has been constructed for the purpose of analysing the spectra of highly-ionized atoms. The diameter of the Rowland circle is 10.7 m and the grazing angle can be varied from 0.5 to 1.0 degrees. The wavelength coverage is from 100 A down to several A. The characteristics of the spectrometer are described here in detail. The shortest wavelength observed in our light source is the 8.34 A line of Al Kα. The resolution is found experimentally to be better than 0.016 A at about 42.2 A, judged from two close lines of the Mo XVII spectrum taken with an entrance slit 3 µm wide and a grating of 300 grooves/mm. This spectrometer is used mainly as a spectrograph, but it can also be used as a monochromator.

A Multichannel System for Determination of Time Varying Spectral Line Profiles

An instrument has been constructed which can directly display on an oscilloscope time-resolved profiles of a spectral line emitted from a transient plasma. It has closely spaced 17 optical channels, and the wavelength coverage between the outermost channels can be varied from 10.4 to about 0.8A by the proper choice of a grating and a magnifying cylindrical lens. Profile measurements can automatically be repeated with time resolution from 0.1 to 2 µs. The display of these time-resolved line profiles has been accomplished by means of electronic circuit. An example of application to a transient plasma is shown.

INTENSITY CALIBRATION OF MONOCHROMATORS IN VACUUM ULTRAVIOLET WAVELENGTH REGION

Abstract Intensity calibration of a grazing incidence monochromator and a normal incidence monochromator is reported. A grazing incidence monochromator with 2 m, 600 grooves/mm, platinum coated grating at an angle of incidence of 86° and with a sodium salicylate sensitized photomultiplier has been calibrated for absolute intensity at several points in the wavelength region of 100 — 750 a by the atomic branching ratio method. It has a structure in the resulting sensitivity curve. A normal incidence monochromator of the in-plane Eagle mounting with 1.5 m, 1200 grooves/mm grating and a sodium salicylate sensitized photomultiplier has been calibrated in the wavelength region of 740 — 2300 a by the double monochromator method and 1100 — 1650 a by the molecular braching ratio method. The two results are compared.