Bremsstrahlung Based Positron Annihilation Spectroscopy for Material Defect Analysis

The Idaho Accelerator Center (IAC) has developed new techniques for Positron Annihilation Spectroscopy (PAS) using highly penetrating γ‐rays to create positrons inside the material via pair production. γ‐Ray induced positron annihilation spectroscopy can provide highly penetrating probes for material characterization and defect analysis. Bremsstrahlung beams from small, pulsed electron Linacs (6 MeV) have been used to bombard the materials to generate positrons, which annihilate with the material electrons emitting 511 keV radiation. We have also synchronized bremsstrahlung pulses with laser irradiation pulses to study dynamic structural changes in material. In addition, we have developed another method using (p,γ) reactions from a 2 MeV proton beam, which induce coincident γ‐rays to perform positron life‐time spectroscopy. We have showed the feasibility of extending PAS into thick samples and a wide variety of materials and industrial applications.