The detection of latent nuclear particle tracks in some common minerals with conventional TEM

Abstract

Although the first direct photographs of nuclear particle tracks in solids were obtained using a TEM (1), the tendency of the tracks to fade in natural micas under the electron beam, as well as the difficulty of preparing suitably thin samples, resulted in the use of optical and scanning electron microscopy to observe chemically enlarged (etched) tracks in the study of lunar soils and gas-rich meteorites in the early 1970's. However, the possibility of useful applications for conventional (100 kV) TEM in the examination of latent tracks was seldom mentioned.More recently, the emphasis on the study of submicron-sized grains in extraterrestrial materials research has made feasible the use of conventional TEM for ultrastructural studies without the complications of, or need for, ion thinning techniques (e.g. 3, & 4). In the process, many of the minerals examined have shown that latent fission-fragment tracks are easily observed with conventional TEM. The tracks, usually introduced by spontaneous fission from a “thin” Cf2 5 2source, appear to exhibit “density” contrast from a straight core whose average width depends upon the mineral.