Measurement of diffusion coefficients in solids by the short-lived radioactive beam of 8Li

As an effort to effectively use the short-lived radioactive ion beams to be available in near future at Tokai Radioactive Ion Accelerator Complex, we have developed a radiotracer method for diffusion studies in solids. A test experiment has been performed to measure the diffusion coefficients of Li in the sample of LiAl compound, by using the α-emitting radiotracer of 8Li (T 1/2 = 0.84 s). The yields of α-particles emitted from diffusing 8Li primarily implanted in the sample have been measured as a function of time under a recurrent time sequence; the implantation of 8Li for 1.5 s (beam-on) and subsequent diffusion for 4.5 s (beam-off). We have found that the time-dependent yields of the α-particles could be used as a measure of the diffusivity of the tracer in a none-destructive way. By taking into account the experimental conditions, we have simulated the time-dependent α-particle yields for various diffusion coefficients and compared with the experimental ones in order to extract the diffusion coefficients of Li in the sample. The process of the simulations and the comparisons is discussed