Estimation of lattice defect density by positron annihilation lifetime measurement in a short time

Abstract

The possibility of on-site and nondestructive inspection of lattice defects, such as those caused by metal fatigue, through positron annihilation lifetime measurement has been investigated by simulation. In such inspection of defects, short-time measurement is essential. Therefore, it is important to extract as much as possible information on lattice defects from positron annihilation data with large statistical errors. To extract this information, a master curve representing two-dimensional change of the "mean" positron lifetime (τ m ) and the starting time shift (ΔT 0 ) with positron trapping rate (proportional to defect density) was obtained in advance. ΔT 0 and τm were determined by single-component analysis of the positron lifetime spectrum, taking account of the source component. Then, the trapping rate was estimated by specifying a corresponding position on the master curve, which is based on the interpolation of ΔT 0 and τm , obtained by short-time measurement of about one minute. The result of the investigation elucidated that the trapping rate can be sufficiently estimated.