Fusion impurity control

Gruen, D. M., Vepfek, S., and Wright, R. B. Plasma-Materials Interactions and Impurity Control in Magnetically Confined Thermonuclear Fusion Machines. 89, 45-105 (1980). 

X-ray fluorescence can be used to analyse all types of samples. Its applications are numerous, whether in research and development or in quality control of production. Initially, X-ray fluorescence was used in industries that treat metals of primary fusion or alloys and, more generally, in the mineral industry (for use one ceramics, cements, steel, glass, etc.). Because of the ease of use of common X-ray fluorescence instruments, its scope of application has expanded into other areas the photographic industry and semi-conductors (for impurity control in silicon chips), the petroleum industry, geology, paper mills, gas analyses (such as nitrogen), toxicology and environmental applications (dust, fumes from combustion, heavy metals, and dangerous materials in waste such as Pb, As, Cr, Cd, etc.). 

Plasma-Materials Interactions and Impurity Control in Magnetically Confined Thermonuclear Fusion Machines ... 

The previous discussion has shown that plasma impurities present a complex set of problems whose solution is crucial to the successful operation of fusion reactors. The many and often subtle factors that govern plasma-materials interactions are still only partially understood. Consequently, the methods used today to control impurities are to a degree empirical in nature and cannot yet be precisely defined. It is likely that in the end a variety of approaches will be used to keep plasma impurities at minimal levels. The techniques are conveniently divided into divertor and non-divertor methods. The latter depend on modifications of one sort or another of the composition or structure of the surfaces facing the plasma. As will be seen in Sect. 6.5., meth-... 

The control of impurity release and transport requires a better understanding of the complex phenomena of plasma-wall interactions including the processes occuring in the scrape-off layer in the limiter shadow. In order to establish the feasibility of suggested solutions such as divertors or surface modifications, experiments have to be performed not only in the laboratory but also in-situ in fusion devices. The latter... 

Lithium aluminate, LiAlsOg with the inverse spinel structure, is a material with possible applications in ceramic blankets for thermal control of fusion reactors. Li and Li NMR has been used to measure the spin-lattice relaxation of lithium in this compound (Stewart et al. 1995). The results indicate that Li relaxes most significantly through interactions with paramagnetic impurities, whereas Li relaxes much more strongly through dipole-dipole interactions. 

Vitreous silica has a unique set of properties. It is produced either from natural quartz by fusion or, if extreme purity is required, by chemical vapor deposition or via a sol-gel routes. Depending on the manufacturing process, variable quantities impurities are incorporated in the ppm or ppb range, such as Fe, Mg, Al, Mn, Ti, Ce, OH, Cl, and F. These impurities and radiation-induced defects, as well as complexes of impurities and defects, and also overtones, control the UV and IR transmittance. In the visible part of the spectrum, Rayleigh scattering from thermod)uiamically caused density fluctuations dominates. Defects are also responsible for the damage threshold under radiation load, and for fluorescence. The refractive index n and the absorption... 

V-alloy development efforts have been made for apphcation to fusion reactors in the condition of maintaining the low activation properties. These requirements involved limitation of the alloy element selection and necessity of precise control of impurities to ppm level which can have a long-life radioactivity, such as Mb, Mo,... 

---