No abstract

No 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, Z eff and the electron temperature. The spectral signature of the divertor LOSs where 1 < T e < 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.Résumé : Les caractéristiques anticipées dans ITER d'échantillons allant de H à W ont été modélisées à l'aide du modèle d'équilibre de diffusion SANCO pour les concentrations ioniques, couplé à la signature spectrale des ions, sur l'ensemble des domaines X et VUV (0.1-100 keV), en utilisant le programme de population et la banque de données ADAS. La signature spectrale varie beaucoup, selon que la ligne de visée (LOS) comprend l'écorceur et/ou le coeur du volume de plasma. Les transitions entre états liés, requises pour l'analyse du profil de raie des ions non combustibles du coeur, peuvent dominer largement le spectre continu dans le domaine 0.1-10 keV aux faibles concentrations acceptables des éléments. Alors que le continu du fond est la principale source de bruit dans l'analyse du profil de raie, l'intensité et les caractéristiques du continuum lorsque divisé en plusieurs bandes spectrales couvrant 0.1-100 keV, ...

The formation of local regions of the high-temperature, high-pressure plasma, 'hot-spots', in a vacuum spark is studied using X-ray spectroscopy and holography. Measurements of the dimensions of the hot-spots, of the absolute flux of radiation and of the spectral composition of the X-ray emission, have been analysed to give order-of-magnitude values for the local electron density, temperature and plasma lifetime. It appears that the plasma pressure is >or approximately=107 atm and that the formation of the hot spots requires intense heating rates more commonly associated with focused laser beams, i.e. >or approximately=1015 W cm-3. It is probable that in the vacuum spark electron beams are responsible for plasma heating. Possible mechanisms for concentrating energy deposition in localised regions are discussed.

No abstract

The wavelengths of the 1s2s2p-1s 2 2s and 1s2p 2 -1s 2 2p transitions in Ar 15+ have been measured using a crystal spectrometer and an electron beam ion trap. These spectral lines are satellites to the n = 2 resonance lines of He-like Ar 16+ and play an important diagnostic role in high-temperature plasmas directed toward fusion research. The results of these measurements are compared with a number of different theoretical results, demonstrating the relative accuracy of these theoretical approaches.

No abstract

Light from the Joint European Torus (JET) tokamak is relayed by optical fibers to detectors outside the biological shield, where personnel access is unrestricted. This arrangement, which is described in detail, will permit routine recording during the intense neutron emission associated with the production of D–T plasmas—scheduled for 1989. The diagnostic has been in routine use since JET began operation in mid-1983. A selection of results obtained is presented. The likely degradation in fiber performance, due to irradiation, during the D–T phase of the program is assessed. Methods of overcoming the problems due to induced absorption are presented.