3-D confocal microscopy of etched nuclear tracks in CR-39.

ABSTRACT

Solid State Nuclear Track Detectors (SSNTD's) are used in a wide range of applications such as Geological Dating, Environmental Sciences (radon), life Sciences (Radiobiology, Dosimetry...), as well as Nuclear and Astro-Physics. In order to be observable under a microscope, the nanometric latent damaged trails due to the slowing down of charged particles into the SSNTD have to be specifically etched. In our laboratory, we are studying this chemical action and propose models that enable simulations to be performed. In the literature, the basic model uses two distinct etch-rates that are considered constant, VB; the Bulk and VT the Track etch-rate. A little bit more sophisticated and realistic, a model with a variable track etch-rate was established, taking into account the variation of energy deposition along the particle's trajectory. Up to now, the known methods used for determining the response function of CR-39 are very time consuming and strenuous. The method we present here is based on the use of the confocal microscope, which provides three-dimensional track images. The obtained set of 3-D co-ordinates can be treated mathematically, giving, in the framework of the two etch-velocity model, the response function. With this new approach, tracks are analysed one by one; response functions are obtained for each track and can be compared to fundamental characteristics of the charged Particle-Matter interactions. Moreover, the method we propose is applied semi-automatically and could easily be automated in the near future.