Lexan plastic prints: How are they formed?

Abstract

Lexan plastic prints are formed when a rock section is irradiated, with a sheet of plastic held against it, in a predominantly thermal neutron flux. The print texture is made up of varying densities of tiny etch pits, which are formed when the plastic is chemically etched after irradiation. The pits are formed from short trails caused by the passage of either α-particles or recoil ions from the rock material. Observed pit densities are correlated with the mineral phases producing them, and calculations of the elemental concentration of B, Li and O required to produce them are made. The present ideas of the print formation are compared with a previous suggestion that they are produced by recoiling OH ions.