Gamma-spectral logging becomes the leading method of studying wells in the search and exploration of radioactive ore deposits and a wide range of other minerals, as well as in the documentation of wells in order to compile and refine the geologic section.

Serially produced radiometric and nuclear geophysical spectrometers with rare exceptions contain one or two measuring differential channels, which complicates research and does not provide high labor productivity. As experience of geophysical works shows, radiometric spectrometer should have at least three independent differential channels, nuclear geophysical spectrometer - three-four, and sometimes more channels.

Gamma-spectral logging to separately determine the concentrations of natural radioactive elements emerged and formed in the USSR as a new radiometric method in the mid-60s. Thanks to the works mainly of the radiometric laboratory of the LGI, this method is widely recognized and successfully applied in prospecting and exploration of radioactive ore deposits. Its main advantages over geologic sampling of well cores are in efficiency, cost-effectiveness and the ability to fully investigate the well regardless of the core yield ...

The effective mass attenuation coefficients of gamma ray attenuation of radioactive ores have close values for the integral spectrum measured by the NaI(Tl) scintillator in a standard screen, and for the energy windows used in gamma-ray spectral logging and ore sampling ...

The logging gamma-spectrometer developed and tested by us contains three counting-resolving channels providing continuous recording of gamma equivalent concentrations of U, Tb and K, and an integral channel. The counting-resolving channels can be used in the mode of continuous or discrete recording of the average pulse frequency in specified energy windows ...

The most promising method of sampling of uranium-thorium ores, which allows separate determination of uranium and thorium, is the gamma-spectral method in modification of measurements of the difference effect of radiation. The principle of such sampling is considered earlier...

The development of gamma-spectral methods for in situ sampling of complex uranium-thorium ores and the associated increase in the amount of information obtained requires the development of accelerated methods of interpretation of measurement results. The proposed counting and solving device allows to increase approximately twice the productivity of gamma-spectral measurements processing in comparison with the usual nomographic method, is characterized by universality, high reliability and long service life.

Continuous recording of equivalent contents of radioactive elements instead of registration of count rates in differential channels during gamma-spectral measurements allows to quickly obtain information on the distribution of elements in the studied object and simplify the processing and interpretation of results. This method is used for search gamma-spectral surveys in motion. We have used continuous recording of uranium (by radium) and thorium contents in gamma-spectral logging at the site of two-component uranium-thorium ores.

The electronic energy scale stabilization circuit is a device that monitors the photopeak of a gamma ray repeater. The basis of the scheme are two adjacent differential channels with the same window width, tuned, respectively, to the left and right branches of the photopeak of the reference source. At the output of both differential channels is placed a comparison circuit and an actuator...

The different spectral composition of gamma radiation of uranium and thorium ores determines the specificity of taking into account the attenuation of radiation in casing pipes and washing fluid when interpreting gamma-spectral logging diagrams.

Gamma-spectrometry is increasingly used in the sampling of uranium-thorium ores. It is based on measurements of pulse count rate in the optimal for uranium and thorium areas of the gamma-radiation spectrum. One of the main conditions ensuring high accuracy of sampling is the correct choice of gamma-spectrometer energy windows. This question arises most acutely at creation of spectrometric equipment with small size of scintillators in connection with low speed of counting of pulses in narrow energy windows, recommended usually in the literature.

As it is known, a significant part of the error of uranium and thorium content determination by gamma-spectral method is a statistical error. Unfavorable conditions of measurement are formed first of all for scintillators of small size. So, to provide with NaJ(Tl) crystals, 18x30 mm, the error of U and Th determination not more than 10% in ores with the content of these elements 0,03%, the measurement exposure should be about 10 min. If, however, when calculating the content of U and Th from gamma-spectral data to use not the count rate of pulses, and the area of gamma-spectral logging diagrams recorded by the recorder or built on the results of point measurements in the optimal energy intervals of the gamma-spectrum, the error in determining the area of the curve is relatively small even with a small exposure measurement of the count rate of pulses.

Semiconductor diodes and triodes are widely used in the practice of geophysical instrumentation, which allow to significantly increase the efficiency, reduce the size and weight of the equipment. However, semiconductor devices, having high performance qualities, at the modern level of production technology are characterized by a scatter of parameters. Therefore, when designing critical nodes of equipment it is necessary to select diodes and especially triodes according to their electrical properties. The most complete idea about amplifying properties of transistors gives the analysis of their output characteristics. Since the process of taking characteristics by points is labor-intensive, there are devices that allow visual observation of the output characteristics of transistors on the oscilloscope screen. Such devices are made in the USSR and abroad in various modifications depending on the range of solved tasks and the required accuracy of observations. Relatively universal units have a complex electronic circuit, simpler ones, as a rule, provide the possibility of only qualitative assessment of amplifying properties of transistors ...