A practical procedure is proposed to standardize etching degrees for materials having different critical angles. Assuming that Vq and Vt are constant through the etching process, the increase of the track densities is considered to be proportional to the enlargement in the maximum track width. The density observable at time (Tt) after the saturation is given by ρt = ρηo cos2 θ + ηs (dρ/dW)Ws + (dρ/dW)(Wt - Ws), were ρ is the 'true' track density for a reference material, θ is the critical ange η0 the optical counting efficiency for tracks intersecting the original surface, ηs that for tracks revealed by bulk etching from the start of the saturation time, and Ws and Wt the maximum track widths at times of the saturation (Ts) and (Tt). The sum of the former two is equal to the saturated density (ρs), and the last to the additional density after the saturation. The etching index at time (Tt) after the saturation is defined as the ratio of ρt to ρ cos2 θ: EIt = ρt/[(ρs - ηs(dρ/dW)Ws)/ ηo]. The counting efficiency for latent tracks (ηs) can be evaluated by integrating (dρ/dW) from W = 0 to Ws, taking into account consideration the appearance of the bulk etched tracks, and can also be calculated when the track geometry is assumed. It must be stressed that this efficiency is unchangeable by the resolving power of microscopes used. On the other hand, ηo would be greatly affected by the resolving power in most cases, and cannot be logically evaluated because it is the product of two kinds of obscure factors: η1 for track length correction and ηu for many other unknowns. However, the former will be roughly given by ηo = Wr/R, where Wr is the resolving power measured separately, or estimated by the minimum track width which corresponds to just after the incubation period on the line tied to the origin and Wt. R is the etchable track length. In conclusion, using the available value of ρ cos2 θ, objective comparison of track densities is possible, because it depends essentially not on the etching efficiency only, but also the resolving power of microscopes used.
|Number of pages||2|
|Journal||Nuclear Tracks and Radiation Measurements|
|Publication status||Published - 1990|
|Event||Proceedings of the 6th International Fission Track Dating Workshop - Besancon, Fr|
Duration: Sep 5 1988 → Sep 9 1988
All Science Journal Classification (ASJC) codes