Investigation by slow positron beam of defects in CLAM steel induced by helium and hydrogen implantation

Hydrogen and helium ion beams delivering different doses are used in the ion implantation, at room temperature, of China Low Activation Martensitic (CLAM) steel and the induced defects studied by Doppler broadening of gamma-rays generated in positron annihilation. Defect profiles are analysed in terms of conventional S and W parameters, measures of relative contributions of low and high-momentum electrons in the annihilation peak, as functions of incident positron energies E up to 30 keV. The behaviours of the S–E, W–E and S–W plots under different implantation doses indicate clearly that the induced defect size has obvious variation with depth, taking values that interpolate between surface and bulk values, and depend mainly on helium ion fluences. The S–W plot indicates that two types of defects have formed after ion implantation.