Abstract: Background: The investigation of the material damage state is very important for industrial application. Most mechanical damage starts with a change in the microstructure of the material. Positron annihilation techniques are very sensitive probes for detecting defects and damage on an atomic scale in materials, which are of great concern in the engineering applications. Additionally they are apparatus of non-destruction, high-sensitivity and easy-use. Purpose: Our goal is to develop a system to exploit new non-destructive testing (NDT) methods using positron annihilation spectroscopy, a powerful tool to detect vacancy-type defects and their chemical environment. Methods: A positron NDT system was designed and constructed by modifying the "sandwich structure" of sample-source-sample in conventional Doppler broadening and positron lifetime spectrometers. Doppler broadening and positron lifetime spectra of a single sample can be measured and analyzed by subtracting the contribution of a reference sample. Results: The feasibility and reliability of positron NDT system have been tested by analyzing nondestructively deformation and damage caused by mechanical treatment or by irradiation of metal alloys. This system can be used for detecting defects and damage in thick or large-size samples, as well as for measuring the two-dimension distribution of defects in portable, sensitive, fast way. Conclusion: Positron NDT measurement shows changes in real atomic-scale defects prior to changes in the mechanical properties, which are detectable by other methods of NDT, such as ultrasonic testing and eddy current testing. This system can be developed for use in both the laboratory and field in the future.

Key words: Positron annihilation, Non-destructive testing (NDT), Defect