The ion- and atom-driven transport of deuterium in Nb under the influence of surface impurities

Atom- as well as ion-driven permeation behavior of deuterium in Nb was stud ied experimentally The measurements were performed under two different vacu um conditions which resulted in contrasting surface compositions: one resul ted in a surface rich in carbon (C) after atom beam irradiation and the oth er rich in sulfur (S) which was unaffected by the irradiation. The result o f permeation measurements revealed that when the specimen surface was cover ed by sulfur the deuterium permeation rate weakly depended on the temperatu re, whereas when the surface was rich in carbon and oxygen it tended to dec rease sharply for temperatures below similar to 700 K. (C) 1999 Elsevier Sc ience B.V. All rights reserved.