Development of a dual purpose synthetic quartz oscillator/emergency dosimeter

Abstract

In the event of large scale public radiation exposures, a means of rapid personal radiation dosimetry would provide a valuable tool for environmental and human health protection as well as for possible criminal investigations (in the event of terrorist dirty bombs). This thesis describes a method of sensitizing synthetic quartz oscillators, found in many timekeeping devices such as watches and cellular phones, to function as radiation dosimeters. Experiments on the sensitization of synthetic quartz crystals from watch oscillators were performed by subjecting the quartz to thermal treatments in the range of 200°C to 800°C. The lengths of treatments ranged from numerous one hour cycles to week-long single anneal treatments and combinations of the two. All treatments were designed to mimic factors that are known to cause sensitization in geologic quartz grains (Botter-Jensen, Larsen et al., 1995). The greatest sensitization was observed in crystals treated to 800°C for one week and then subjected to two series of heating, irradiation, and optical exposures. These crystals were able to recover doses as low as 0.5 Gray at an error within 10% of the delivered dose. This work is the first stage of development for creating dual purpose quartz oscillator-dosimeters which could be used in watches, cellular phones, clocks, and nearly all equipment requiring a timekeeping component. In the future, experiments should be conducted to show definitively that crystals still function as 32.768 kHz oscillators after annealing and that oscillators trap charge while in operation.