Hydrogen Trapping Studies in Fusion First Wall Materials
Hydrogen trapping in the first wall of fusion reactors is one of the most serious materials problems facing the designers of magnetic confinement devices. The release of this trapped hydrogen from the near surface region of the first wall during a tokamak discharge has been shown to play a major role in the hydrogen fueling of today's plasmas, while trapped hydrogen isotopes will directly influence the on-site tritium inventory and the structural properties of future D-T reactors. This paper summarizes the laboratory ion implantation sttidies on the hydrogen trapping characteristics of first wall materials. Emphasis is placed on the near term materials problems associated with austenitic stainless steels that are currently in use in magnetic confinement devices. Hydrogen trapping experiments involving more exotic first wall structural and coating materials are briefly reviewed.
The spatial distribution of ions implanted into solids subject to diffusion and surface sputtering
Abstract The depth distributions of ions implanted into solids is evaluated : heoretically for the situation where, following implantation and degradation to rest, each ion can diffuse in the solid whilst simultaneously the surface of the solid is eroded via the sputtering process. Time dependent and equilibrium solutions of the depth distribution or concentration profiles and the total quantities of trapped atoms are determined for cases where (a) the surface is a perfectly transparent boundary for diffusing ions, allowing immediate escape by diffusion only, and (b) the escape of diffusing ions takes place by surface erosion only, the diffusion rate becoming zero at the surface. Two methods of approach for situation (a) are examined-the Laplace transformation technique of the defining partial differential equation and a novel image method. Solutions are compared with earlier work and shown to correspond where appropriate.
Modified Diaphragm Pressure Gauge for Corrosive Gases
The Booth‐Cromer diaphragm gauge has been modified to use a linear variable differential transformer to detect the position of the diaphragm. The sensitivity of the unit is 0.01 mm Hg. The ruggedness and simplicity of the original gauge are retained.