Measurement of self-diffusion in solids by neutron activation of masked samples

A nonuniform distribution of a radioactive tracer was produced within a glass specimen by partially masking it with Cd and irradiating it with thermal neutrons. The calculated distribution of the tracer in the given geometry agreed reasonably well with the measured distribution. The latter, in turn, served as the initial condition for a self‐diffusion experiment which gave results consistent with previous studies. This technique avoids problems associated with interfaces in conventional diffusion couples.