The desired output from a gamma-ray logging system in mining applications is an accurate log of the quantitative distribution of radioelements with depth along the borehole. However, the measured log is not the desired output, but it may be visualized as the desired output modified by a series of low-pass filters of various characteristics. These filters can be related to the distance interval over which each count is made (or the analog ratemeter time constant), the detector length, and the 'geologic impulse response' (the response of a point detector to an infinitesimally thin layer of ore of a known grade). In effect, this means that the response due to thin beds is lower than expected, and the resolution will be reduced. An understanding of the nature and properties of these filters will aid in the proper evaluation of the log.To optimize the accuracy and resolution of quantitative uranium (or other radioelement) determinations, especially in thin beds and complex sequences, it is necessary to keep the counting interval short, and to compensate for the effect of the geologic impulse response. Although the effect of the geologic impulse response may be removed in any of several ways, the use of a simple inverse convolution operator as described here allows the data to be processed on-line, essentially in real time, using a microprocessor or portable minicomputer.

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