Anticipated X-ray and VUV spectroscopic data from ITERwith appropriate diagnostic instrumentation

Abstract

The radiation characteristics of anticipated sample elements, from H through W, in the International Thermonuclear Experimental Reactor (ITER) have been modelled using the diffusion equilibrium model SANCO for the ion concentrations coupled with the spectral signature of the ions, throughout the X-ray and VUV regions (0.1–100 keV), using the Atomic Data and Analysis Structure population code and database, ADAS. The spectral signature varies greatly depending on whether the viewing line-of-sight (LOS) encompasses the divertor and (or) core regions of the plasma volume. Bound–bound transitions required for line profile analyses of nonfuel core ions can locally dominate the continuum spectrum in the 0.1–10 keV region at acceptably low elemental concentrations. While the background continuum is the main source of noise in the line profile analyses, the intensity and features of the continuum when divided into many spectral bands covering 0.1–100 keV are themselves powerful diagnostics of the plasma composition, Zeff, and the electron temperature. The spectral signature of the divertor LOSs where 1 < Te < 300 eV is dominated typically and exclusively by lines in the XUV–VUV region, restricted in the case of W to λ > 40 Å. Appropriate instrumentation, relying on imaging Bragg reflectors and diffractors and position-sensitive energy-resolving detectors, is designed to cover the full spatial extent of the core plasma. Estimates of the core signal/noise based on experience with tritium experiments on the Joint European Torus indicates substantial signal levels with tolerable neutron-induced noise and component degradation. The divertor diagnostics make use of a suite of aspheric diffraction grating spectrometers designed to measure impurity ion influxes and are essential for plasma control. The EBIT could be conceived as a neutron-free adjunct facility to the ITER spectroscopic programme. At its simplest level, it provides standards for instrument performance and for the spectroscopic signature of selected ions subjected to electronic and atomic collisions over a wide range of ITER-relevant impacting energies.PACS Nos.: 52.58.Lq, 52.55.Fa, 52.70–m, 52.25.Vy, 87.64.Gb