SU563057A1 - Device for determining element composition of substance - Google Patents

Description

increasing the accuracy and sensitivity of the analysis.

The goal is achieved according to the invention by introducing into the device for determining the elemental composition of the substance an additional retarder-reflector, in the cavity of which all the elements of the known device are located on the same axis, with the linear dimensions of the cavity of the reflector retarder in all directions not less than half and not more than two distances neutron source and y-ray detector.

In the proposed device, the sample is located directly near the detector, which ensures maximum collection of γ-quanta of radiation capture to the detector, and the detector with the sample is removed from the source placed in the moderator at a distance necessary to reliably protect the detector from direct radiation from the source.

Due to the diffusion reflection of neutrons from the walls of the moderating mirror and the absence of absorption of thermal neutrons in the cavity, there is a uniform distribution of sex-thermal neutrons with the same density both in the location of the moderator with the source and in the area of the sample. With the optimal dimensions of the cavity of the retarder, retarder, retarder, and the distance between the source and the detector, the maximum accuracy and sensitivity of the analysis is achieved at a given neutron source power.

PA drawing shows schematically the proposed device for determining the elemental composition of samples of a substance.

Isotope source 1 neutron,

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for example, the Cf isotope is placed in a Plexiglas moderator 2. A cone-shaped bismuth filter 3 closes the detector 4 from the y and neutron radiation from the moderator. Filter 5 from the L i isotope prevents the penetration of thermal neutrons into the detector. From soft, scattered construction materials jy-quanta, the detector is closed by a bismuth screen b, which is a hollow cylinder with upper and lower covers. Inside this screen is placed a cassette 7 with sample 8 of the analyte weighing up to several kilograms. The cassette has a double-wall cup and is planted directly on a lithium filter, which ensures the best collection of JJ quanta from the sample to the detector. A retarder-reflector 9 made of Plexiglas or reactor graphite, which is a hollow cylinder with upper and lower covers, forms a cavity 10. In this cavity, a moderator with a neutron source, a bismuth filter, a bismuth screen with a sample and thermal neutron detector.

A comparison of the γ-radiation spectra of radiation capture of thermal neutrons in a sample containing titanium, obtained using the known and proposed devices, shows that the proposed device only due to its distinguishing features provides a big gain in accuracy and sensitivity of the analysis. For example, the accuracy and sensitivity-determination of titanium on the 342 keV line provided by the proposed device is more than 4 times better achieved using a known device. This means that the specified accuracy of determining this element is achieved by using the proposed device for a time that is more than 16 times less than when using a known device.

Claims (1)

Invention Formula Device for determining the elemental composition of a substance containing a neutron source, a Stimulator, a fast neutron filter, a thermal neutron filter, an ambient γ-radiation detector, and a cassette for the test substance, which are different in that, in order to increase the sensitivity and accuracy of the analysis, it is additionally equipped with a moderator; the reflector, in the cavity of which all the indicated elements of the device are placed on the same axis, and the linear dimensions of the cavity of the retarder-reflector in all directions are not less than half and not more than two distances to the source chnikom and neutron radiation detector.