RADIAL PROFILES OF 2P-1S HELIUM-LIKE OXYGEN LINES MEASURED FROM THE COMPACT HELICAL SYSTEM USING A VACUUM CRYSTAL SPECTROMETER

The Vacuum crystal spectrometer (Johann type; RAP crystal) has been de signed and developed to measure soft x-ray lines in the vicinity of 20 Angstrom. A photodiode array and a two-stage multichannel plate were used as a detector. Radial profiles of heliumlike oxygen Lines were su ccessfully obtained from NBI plasmas in the compact helical system wit h a spectral resolution of 525 (= lambda/Delta lambda). The radial pro file in the intensity ratio of Y(P-3(1) --> S-1(0)) to W(P-1(1) --> S- 1(0)) was also obtained. The intensity ratio among 2l-1l' transitions of the heliumlike oxygen are calculated as a function of the electron temperature and the electron temperature profile was obtained from the ratio. The obtained electron temperature was compared with one from a Thomsom scattering measurement. As a result, the comparison showed a good agreement. (C) 1997 American Institute of Physics.