Positron Annihilation Spectroscopy (PAS) techniques can be utilized as a sensitive probe of defects in materials. Studying these microscopic defects is very important for a number of industries in order to predict material failure or structural integrity. We have been developing gamma‐induced pair‐production techniques to produce positrons in thick samples ( ∼4–40 g/cm2, or ∼0.5–5 cm in steel). These techniques are called ‘Accelerator‐based Gamma‐induced Positron Annihilation Spectroscopy’ (AG‐PAS). We have begun testing the capabilities of this technique for imaging of defect densities in thick structural materials. As a first step, a linear accelerator (LINAC) was employed to produce photon beams by stopping 15 MeV electrons in a 1 mm thick tungsten converter. The accelerator is capable of operating with 30–60 ns pulse width, up to 200 mA peak current at 1 kHz repetition rate. The highly collimated bremsstrahlung beam impinged upon our steel tensile specimens, after traveling through a 1.2 m thick concrete wall. Annihilation radiation was detected by a well‐shielded and collimated high‐purity germanium detector (HPGe). Conventional Doppler broadening spectrometry (DBS) was performed to determine S, W and T parameters for our samples.
Engineering Science and Materials | Materials Science and Engineering | Mechanical Engineering | Other Engineering Science and Materials
Copyright American Institute of Physics. Used with permission.
Wells, D. P.,
Roy, A. K.
Doppler Broadening Analysis of Steel Specimens Using Accelerator Based In Situ Pair Production.
AIP Conference Proceedings, 1099
American Institute of Physics.