SU785821A1 - Analogue computer of logging gamma-spectrometer - Google Patents

Description

(54) ANALOG ACCOUNT DETERMINING CAROTTING DEVICE The invention relates to radiometric equipment for the separate determination of the concentration of natural radioactive elements in place of occurrence and can be used in geological prospecting organizations in the composition of logging gamma spectrometers with three independent differential channels. A known counter-solving device is known for separately determining the concentration of uranium, thorium and potassium in geological formations. The device is part of a gamma-ray spectrometer with five measuring differential channels with adjacent energy windows and is switched on at the output of integrators of differential channels. Its action consists in algebraic addition of direct currents, coming from integrators, and issuing signals that are analogous to the concentrations of U.Th.K and the total pulse count flj. However, the accuracy of determining their concentration is insufficient. GAMMA-SPECTROMETER A well-known analog counting / deciding device for determining cone; The concentration of uranium, thorium and potassium is included in the composition of the logging gamma spectrometer, which includes a downhole tool and three independent measuring differential kangsha | j2. Each of the measuring channels contains a differential discriminator tuned to the selection of pulses of appropriate amplitude and a counting rate meter. The calculator includes buffer amplifiers and output cascades designed to algebraically sum the output voltages of counting rate meters built on operational amplifiers. The input of each of the buffer amplifiers is supplied with a DC signal voltage (t1, 2 or 3 - the number of the differential channel) from the corresponding meter of the count rate, proportional to the average frequency of pulses N in the differential channel. The output stages through a system of resistors are connected to the buffer amplifiers in such a way that the DC signal at their output is the analog of the concentration of the nth

radioactive element by automatically solving equations

 -1 - i a. -. ,)

L and ,, .- R; of, - (2)

X | - RA, (3)

where., Poison are the coefficients taking into account the fraction of the radiation of the following: radioactive elements in the differential KaHajie tuned to the energy line of the gamma spectrum of the main element.

However, the known device does not provide for. Changing the measurement ranges for the concentrations of radioactive elements, therefore, for small concentrations, the error in obtaining their data is unacceptably high because of the inaccuracy of the analog indicator devices, and for large ones it becomes impossible due to an overrun of indicators.

The use of individual frequency-transducers in each differential kan / 1e does not allow independent range switching. Therefore, with an increased concentration of one of the radioactive elements, accurate registration of other elements becomes impossible. ,

The known device does not provide for a change in the constant time of the computational decisive scheme, This causes a large statistical error in the registration of clarke concentrations of radioactive elements and the low productivity of logging at high concentrations.

The aim of the invention is to improve the measurement accuracy.

This is achieved by the fact that in a device containing n pulse normalizers, n frequency-current converters and coolers made on the integrating circuits and one-action amplifiers, the inputs of the frequency-current converters are connected to the outputs of the corresponding pulse normalizers, and their outputs to the inputs of the corresponding summators , while the inputs of the corresponding pulse normalizers are interconnected.

The drawing shows a schematic diagram of the device

The device includes counting triggers 1.1 + 1.7 in a microcircuit version, which, together with transHCTOpaMii 2.1-2.7 and variable resistors 3.1-3.7, form the normalizers of the amplitude of differential discriminator pulses, the dosimeter or 4.14.7 capacitors peak diode semiconductor, which form frequency-current transducers, as well as integrated circuit circuits, connected between inverting inputs to output a of operational amplifiers 5, 6, 7, and consisting of these capacitors 8-10 and resistor 7

Pins 11.1-11.5, 12.1-12.5 and 13.1-13.5 The choice of the required resistor is made by the switches 14-16 of the range.

A trigger 1.1 is connected to the output of the first differential discriminator tuned to the energy of gamma rays in the Region of 1.46 meV (the 40 K isotope line, triggers 1,2,1,4, and 1.7 to the output of the second discriminator tuned to energy 1.75 meV / line of the family U), triggers 1,3,1,5 and 1,6 to the output of the third discriminator tuned to energy in the region of 2.62 meV (line of the family Th), First Integrating Circuit (capacitor 8 and one of the resistors 11.1-11.5) through the system of diodes, the dosage of the capacitor 4.14, 3, the variable resistors 3.1-3.3 and the corresponding holes Pulse amplitude amplifiers are connected to the outputs of three differential discriminators, the diodes being switched on in such a way that pulses are supplied to the capacitor 8 from the first and third discriminators in negative polarity, and from the second in positive polarity. The second integrated circuit (capacitor 9 and one of the resistors 12.1-12.5) is similarly connected to the outputs of two differential diskrik / Matorov (second and third). The pulses from the second discriminator are fed to the capacitor 9 in negative polarity, and from three pins in positive . The inclusion of the third integrating circuit (capacitor 10 and one of the resistors 13.1-13.5) is the same as the second, with the only difference that due to the corresponding diode connection, the pulses from the third discriminator enter the circuit in negative polarity t and from the second in positive.

The device works as follows

In the potassium counter channel, electrical pulses from the first second and third differential discriminators with frequencies N, N and Nj, respectively, arrive at triggers 1.1–1.3, which convert THEIR into a signal, such as a square wave. Transistors 2.1-2.3 at the output of the triggers operate in the key mode, which allows stabilizing the amplitude of the signals.

The formed signals are removed from the engines of variable resistors 3.1–3.3 and through the metering capacitors 4.1–4.3 and the diode system are fed to the integrated circuits, and the pulses from the first and third discriminators (17 and 19) bring negative charges to the capacitor the pulses from the second discriminator (18) are positive. At steady state, the output voltage

amplifier 5 is determined by the average value of the frequency of the pulses 17.18, 19, the amount of electricity transmitted by each pulse into the integration circuit, and the resistance of the leakage resistor selected from 11.1-11.5 by switch 14.

The amount of electricity transmitted by the pulses into the integrated circuit depends on the capacity of the metering capacitors 4.1–4.3 and is smoothly adjusted by resistors 3.1–3.3 in the process of tuning the circuit. As a result, the voltage at the channel output is found to be analogous to the concentration in the rocks and ores surrounding the radiation detector.

The leakage resistor 11.1 has g shimal resistance, therefore when turning on the switch 14 to the upper position according to the scheme, the calculating decanter has the maximum sensitivity and width of the range. When the position of the switch 14 changes, the width of the range increases by as many times as the resistance of the resistor connected to the capacitor 8 is less than the resistance of the resistor 11.1. Simultaneously with the change of the ranges automatically from the constant ten, the time of the integrating contour is constant, each time acquiring the optimum value. . . The switching of ranges in the potassium channel occurs independently and does not affect the parameters of other counting channels. The uranium and thorium counting channels operate similarly to the potassium channel with the only difference that the integrating circuits only receive pulses from the second and third differential discriminators 18 and 19 with a medium frequency and corresponding polarity. The channel is tuned by resistors 3.4-3.7 in such a way that the voltage at the output of amplifiers b and 7 is analogous to the concentration of V and Th in rocks. Switching ranges in constant time is done by switches 15 and 16 as well as in the potassium channel. The use of the proposed analog computing device as part of the logging gamma spectrometer makes it possible to continuously record on the chart tape both clarke and ore concentrations of radioactive elements in the gamma-spectral well logging process, will increase the productivity of work and will bring the accuracy of the results to the requirements for laboratory analysis of powder samples for U.Th and K.

The behavior of labor productivity is determined as follows. To obtain high-quality logging results, the following conditions must be met: Vf 150 cm / h, where V is the logging speed, m / h; t is the time constant of the recorder, p. As shown by calculations, confirmed by work experience, for ore intervals, the value of C can be reduced by a factor of 8–10 compared with the mines. Therefore, for intervals with a high proactive

The logging speed and, consequently, the productivity of work can be 8–10 times less than the prototype device set up to study rocks with low radioactivity.

five

Compared with a logging spectrometer without a counteraction device, the proposed invention will reduce the time spent on processing diagrams of tape ribbons of 5 or more

Claims (2)

0 times. Analog counting device of a logging gamma spectrometer containing pulse normalizers, n frequency-current transducers, adders are made of integrating circuits and operational amplifiers, in order to improve the accuracy of measurements, the inputs of frequency-current transducers are connected to the outputs of the corresponding conductors, pulse normalizers, and their outputs to the inputs of the corresponding adders, while the inputs of the corresponding pulse normalizers are combined between oboy Sources of information taken into account in the examination of 1, US Patent 3976878, CL, 2SO-253, 1976. 2. The patent of USL 3940610, class 250-253, 1976 (prototype).