DEFECT ACCUMULATION UNDER CASCADE DAMAGE CONDITIONS

There is now ample evidence from both experimental and computer simula tion studies that in displacement cascades not only intense recombinat ion takes place but also efficient clustering of both self-interstitia l atoms (SIAs) and vacancies. The size distributions of the two types of defects produced in cascades are not only different but this differ ence is also temperature dependent because of the different thermal st abilities of SIA and vacancy clusters. This asymmetry in the productio n of SIAs and vacancies has been termed ''production bias''. In the pr esent paper, the basic physics of the defect reactions kinetics associ ated with the specific features of cascade damage is described, with e mphasis on asymmetries between SIA and vacancy type defects concerning their production, stability, mobility and interactions with other def ects. Defect accumulation under cascade damage conditions is discussed in terms of this reaction kinetics taking into account cluster produc tion, dissociation, migration and annihilation at extended sinks. Micr ostructural features which are characteristic of cascade damage and ca nnot be explained in terms of the conventional single defect reaction kinetics are emphasized, in particular the heterogeneous microstructur al evolution at low doses and the dose and temperature dependence of s welling.