A device for routine studies of nuclear track annealing in mineral grains

Abstract

For studies of annealing of nuclear tracks in common rock-forming minerals, we have devised a simple heating system that provides a highly stable hot environment characterized by a large temperature gradient. The temperature can be maintained at the desired values within ± 2°C over a period of several months. The system allows placing of samples at eight different temperature points in the temperature range of 350–550°C in a single setting. This range essentially encompasses the entire temperature range normally used in laboratory track annealing of mineral grains with annealing duration of a few minutes to a couple of months. Lower as well as higher temperatures and different ranges are possible by changing the material used for the heating system and its geometry. However, for annealing at high temperature (600–1000°C), and for short duration (1–10 min) we found that it is more convenient to heat samples in the appropriate region of the cone of a large gas flame. We present, as an example, results of cosmic-ray track annealing studies in hypersthene grains from the Johnstown meteorite. The simplicity and reproducibility of the technique allows an in-depth study of annealing characteristics of different minerals. An annealing model based of our results will be presented elsewhere.