Positron annihilation lifetime spectroscopy is a sensitive probe of vacancies and voids in materials. This nondestructive measurement technique can identify the presence of specific defects in materials at the part-per-million level. Recent experiments by Asoka-Kumar et al. have identified two lifetime components in aged plutonium samples-a dominant lifetime component of around 182 ps and a longer lifetime component of around 350-400 ps. This second component appears to increase with the age of the sample and accounts for only about 5 percent of the total intensity in 35-year-old plutonium samples.
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