Use of the D-D reaction to locate deuterium implanted in metals

Abstract

A method, based on observing the energy spectra of the tritons and protons from the D-D reaction, is used to measure the distribution with depth of deuterium implanted in metals. The deuterium profile is observed either during implantation, using the primary D+ beam to initiate the reaction, or following implantation using a reduced integrated D+ flux to probe the distribution. Preliminary studies have been made with copper, gold, silver, zinc and aluminium targets using probe and implantation energies of a few hundred keV and a range of target temperature. The method is illustrated with reference to the particular case of 200 keV deuterons and a copper target. The protons and tritons are observed at 60° in the laboratory using a silicon surface barrier detector. The calculations are made using an assumed energy loss for deuterons in the metal target, the kinematics and known energy dependence of the D-D reaction cross section, and published energy loss data for tritons and protons. The dynamics of the deuterium build-up during implantation are found to depend markedly on the target temperature. Two striking features, especially evident with targets above room temperature, are the rapid build-up of a high concentration of deuterium in a narrow layer at the target surface and the movement of deuterium against the reverse concentration gradient at the deeper edge of this surface layer. A migration of deuterium away from the surface is observed on cooling an implanted copper target.