Track registration and retention characteristics of natural quartz and its synthetic counterpart Vitreosil [fused silica) have been studied. Tests have been carried out at high temperatures (200-1000°C) and the detectors subjected to intense y-ray fields of up t o 250 MRads, with a view to establishing their suitability for high temperature in-core neutron fluence measurements. Both the major crystallographic axes of natural quartz reveal registration efficiencies of the order of unity showing little or no anisotropy when etched in boiling 65% NaOH, although superficial etching anisotropy of the track openings is highly evident. Whereas quartz shows residual tracks of fssion fragments at "95OoC, in both the major axes, tracks in vitreosil anneal out at 65OoC. Annealing studies of the track ranges have not established preferential annealing relative to either axes, and the measurements of the reaction rates have yielded probable activation energies for annealing of 3.83 eV, and 0.85 eV for quartz and vitreosil respectively. Natural quartz can therefore be used as a neutron monitor in the extreme conditions of temperature and background radiation of the reactor core.
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