Positron annihilation - a special technique in non-destructive materials testing

The annihilation radiation of positrons and electrons (i.e. a γ-ray pair travelling in opposite directions), which forms at defects in the crystal lattice, can be used for non-destructive materials testing. It is particularly suitable for the determination of plastic deformations, which occur during the initial phase of fatigue defects or at stress concentration points, above all if the examinations are to be performed at points with poor access. The basic principles of this method and its use to date with heat-treated steels are discussed in the report. (orig.)