Change in the sensitivity of PM-355 track detectors for protons after long-term storage

Changes in the sensitivity function due to fading of the tracks in CR-39/PM-355 detectors stored over a 9 - year period have been studied using protons in the energy range 0.2-6 MeV. The irradiated and non-irradiated detectors were stored in air at room temperature in the absence of light. The track diameters were found to decrease as time passed from the detector exposure to etching. The bulk etch rate VB is not affected by ageing effects and remains almost constant over a nine year period of storage. The sensitivity function V = VT/VB represents a small loss of sensitivity with storage time (about 1-2% per year).