Positron lifetime measurements by proton capture

A positron lifetime spectroscopy (PLS) technique was developed using coincident gamma rays induced by proton capture. Proton capture in some light elements induce coincident MeV gamma rays, allowing positron lifetime to be measured. One gamma quantum provides a start signal for the positron lifetime spectrometer, whereas the other gamma quantum bombards the sample under investigation, generating a positron inside it through pair production. The stop signal is obtained from the detection of one of the two 511 keV photons emitted from positron annihilation with the sample electrons. This new technique can extend PLS, which is a powerful tool to identify the size and concentration of defects, to thick materials and a broad range of applications. It also eliminates the source contribution from the measured spectra, which may lead to the identification of more defect types in a sample. (C) 2005 American Institute of Physics.