Associated with the spectroscopic studies of high temperature plasma, a spatial resolution is of great importance with time resolution. An application for spatial- and time-resolved spectrum in x-ray region is required to obtain significant information concerning the profile of electron temperature, impurity transport, and the profile of non-thermal electrons generated with electron cyclotron heating. An assembly of Pulse Height Analyzer (PHA) has been designed and constructed to investigate the profiles of continuum and line spectra in LHD. The assembly is equipped with a scanning system which makes it possible to estimate the radial profile of x-ray spectrum. The scanning system basically consists of a diaphragm which is flipped by a linear-motion mechanism. With the system the sight line of the PHA is scanned to the radial direction of LHD. The most specific feature of the assembly is that the inversion of a line integrated spectrum to a radial profile is possible. In the present research a radial profile of x-ray spectrum has been successfully obtained with a spatial resolution of a few centimeters [1]. In the case of line spectrum the radial profiles of K_α lines emitted from Ar, Ti, Cr, and Fe have been obtained. Especially, the line profile of Ar has been estimated with a time resolution of 25 msec. The time resolved profile reflects diffusion coefficient and convective velocity of Ar. The line integrated continuum from 3 keV to 25 keV has been successfully inverted to a radial profile. From the result a radial profile of electron temperature has been estimated. In the present report it is demonstrated that experimental results obtained from the assembly satisfy the characteristic demands of transport studies, radial profile of electron temperature, and high energy electron.

References