Enhancement of Track Etching Rates in Charged Particle-irradiated Plastics by a Photo-oxidation Effect

Abstract

THE use of appropriate etching solutions to reveal the paths of charged particles in irradiated insulating materials¹ is a technique of increasing importance in several disciplines ranging from nuclear physics and space exploration to geology and archaeology (for reviews see ref. 2). Among the variety of dielectric solids useful for track-etching applications are plastic films, notably the cellulosics and polyesters, which are acutely sensitive to a variety of energetic charged particles^3,4. The responsiveness of plastic particle detectors derives from the dramatic increase in chemical reactivity of the damaged area along the particle track. The etching rate along the track is generally 10³ to 10⁴ times that for the bulk polymer^2–4. We report that exposure of a charged particle-bombarded polycarbonate film to ultraviolet energy in an oxygen atmosphere causes a significant acceleration in the etching rate for the damage region along a track, permitting immediate processing and analysis of the sample. Two approaches were utilized in this study of the sensitization of track etchability in polycarbonate film by this photo-oxidative treatment.