QUANTITATIVE SPECTROSCOPY OF X-RAY-LINES AND CONTINUA IN TOKAMAKS

Crystal and synthetic multilayer diffractors, deployed either as flat Bragg reflectors, or curved, as in the Johann configuration, are used to study the spectrum of COMPASS-D and other tokamaks in the wavelengt h region of 1-100 Angstrom, In this article, we concentrate on the mea surement of absolute photon fluxes and the derivation of volume emissi vities of the lines and continua in the x-ray region. The sensitivitie s of these instruments to absolute photon flux have been constructed a b initio from the individual component efficiencies, including publish ed values of the diffractor reflectivities, which have been checked or supplemented by measurements using a double-axis goniometer or from l ine branching ratios. For those tokamak plasmas, where the elemental a bundances and effective ion charge are documented, the x-ray continuum intensity itself has been used as a calibration source to derive abso lute instrument sensitivity, in reasonable agreement with the nb initi o method. In the COMPASS-D Tokamak, changes id the effective ion charg e state, Z(eff), have been derived for different operating conditions, from the absolute intensity of the continuum at similar to 4 Angstrom . From the radiances of the line emission, changes in the absolute lev el of impurities following ''boronization'' of the vacuum vessel have also been documented. (C) 1997 American Institute of Physics.