Elution of recoiled fragments from fission tracks by chemical etching

Abstract

Polycarbonate films, which were exposed to fission fragments, were treated with different etching reagents. It was found that a dilute alcoholic solution of strong base gave an outstandingly higher etching rate than any aqueous solution. Etching with the alcoholic solution could conveniently be performed at room temperature. The etching rates by methanol solutions of the organic base R 4NOH, KOH, and NaOH were in the ratio of 4:2:1. The rates were found to be independent of aliphatic chain length of alcohols between methyl and amyl. When polycarbonate film irradiated from a fission source through 1 cm air was treated with 1 M KOH in methanol for 20 min, ca. 80% of the heavy fragments of uranium were leached out, whereas most of the light ones still remained in the target. Heavy atoms make shorter tracks than light ones according to their fission recoil energy and it appears that the elution rate depends only on the range of the fragments in the film. The difference in the formations of heavy and light tracks could be observed continuously when the etching was performed under a microscope.