Nuclear Track Detection最新文献

Various reasons are analysed for finding values of the geometry factor G in fission track dating (i.e. the ratio of track density in an “external” to that in an “internal” surface) to be greater than the “ideal” value of 0.5. It is shown that revelation of “new” tracks by prolonged etching is a minor effect, and that the effects of the minimum observable track length and differing distributions of etched track length in different surfaces are the major causes of values of G ≫ 0.5. It is also shown experimentally that with modern equipment, which allows tracks of ∼0.5 μm length to be resolved, it is possible to obtain values of G ∼ 0.5, and the use of this “ideal” value introduces little error in the final analysis. The behaviour of some other geometry ratios is also discussed.

The olivine etchant, boiling WN solution, has been tested at three particular values of pH (7.6, 8.0 and 8.4) for various etch times up to 7 hr on externally produced fission tracks in specific crystallographic planes. Evidence has been found for systematic anisotropies in fission-track revelation in certain planes. These anisotropies reflect marked differences in the bulk etching rates for the various planes, which are found to be in the proportions 5:4:2 for the ab, bc and ac planes, respectively. Lower apparent etching efficiencies, in the range 37–77% relative to muscovite mica, have been found in some planes than would seem reasonable from critical angle considerations.

Distributions of projected lengths, full lengths, depth projections and inclination angles of fission tracks emerging from thick layers of dielectrics are calculated. Results are compared with experimental distributions for the (0001) plane of apatite crystals, for different annealing rates. Special attention is paid to error sources common to similar methods. These results seem to imply that certain errors in age correction methods based on the length distributions ought to be considered.

In this paper a study on the spark counting of etch-holes of α-particle tracks recorded on 13 μm strippable cellulose nitrate track detectors (Kodak-Pathé LR-115 films) is described. Results for the counting characteristics as a function of etching and irradiation parameters are given. Applications of the spark counting technique to α-radiograms obtained by the (p, α) nuclear reaction and soil-radon exhalation measurements are presented.

The response of some polymer nuclear track detectors to high-energy neutrons of E_max=680 MeV produced by a proton synchrocyclotron is determined. The studies are carried out with two types of cellulose nitrates and polycarbonates; the detectors are etched by usual chemical etching, one of them electrochemically. The detection efficiencies obtained are of the order of 10^-6-10^-5 tracks per perpendicular-incident neutron.

An electrochemical etching (ECE) device is described in which four plastic detectors, pre-irradiated with normally-incident fission fragments, can be simultaneously etched. Optimization of the applied field strength and frequency for etched spots in all detectors is examined. The results of automatic scanning of etched detectors using a Joyce-Loebl double-beam microdensitometer are also reported.

Systematic annealing experiments on fission tracks in epidote, under standardized etching conditions, have been carried out to obtain the correction curve. The corrected fission track ages of epidotes from the Sausar group, Madhya Pradesh (India), coupled with their annealing characteristics help to evaluate the cooling history of Sausar belt. A comparative study of the annealing properties of epidote minerals shows a similar behaviour. The mean values of fission fragment range for induced fission ²³⁵U, uranium concentration and activation energy determined are 10.9 μm, 4×10^-6 g/g and 2.0 eV, respectively.