RU1803896C - Method of gamma spectrometry and gamma spectrometer - Google Patents

Abstract

i Use: in various areas of the national economy, for example, mining, metallurgy, and geology. SUMMARY OF THE INVENTION: to reduce signal miscalculations with increased integrated loading of the spectrometric trust and to simplify the apparatus, pulse amplitudes are converted to a n-bit digital code selectively in the specified energy intervals of the full gamma spectrum by their preliminary amplitude selection, and then after transmission over the communication line, the digital codes are inversely converted to analog signals, while the energy and spectral intensities of gamma rays are determined by amplitude selection of the reconverted piecewise-continuous spectrum of analog signals. In terms of the device: into a recording unit, consisting of gamma-ray detectors connected in series with a high-voltage power supply unit, a linear amplifier, an amplitude detector or integrator, buffer RAM and a n-bit analog-to-digital converter (ADC), output a cascade connected to a communication line, an analysis and processing unit, a parallel-to-serial code converter, random access memory, four differential channels and an OR logical element are introduced, and an analysis and processing unit The network includes a serially connected linear signal amplifier, a serial to parallel conversion unit, a digital-to-analog converter, and n differential channels, for example 4, as well as a single-shot and an automatic gain control system. 2 s.p. f-ly, 2 ill. ate with oo o CJ 00 o o

Description

The invention relates to measuring technique, namely to methods and apparatus for studying the spectral composition of gamma radiation of various physical drives and can be used in mining, metallurgy, geology, in particular, in geophysical surveys in wells.

The aim of the invention is to increase the accuracy of measurements by reducing the miscalculation of signals with increased integrated loading of the spectrometric path.

The essence of the spectrometric method is as follows. Light scintillations of gamma rays are converted into

electrical pulses with an amplitude proportional to the energy of the original gamma-quantum, then convert the spectrum of amplitudes of the electrical pulses into a digital bit code. In order to increase the accuracy of measurements, the conversion of the amplitude of the pulses to an n-bit digital code is carried out selectively in the specified energy intervals of the full gamma spectrum by preliminary amplitude selection. Then, after transmission over an extended communication line, the digital codes are inversely converted to analog signals, and the energy and spectral intensities of gamma quanta are determined by amplitude selection of the reconverted piecewise-continuous spectrum of analog signals.

For the practical implementation of the method, a gamma spectrometer is proposed comprising a recording part and an analysis and processing unit connected by a communication line. The recording unit consists of a detector

gamma rays, the input of which is connected to

first line of communication, and the output through a series-connected first linear amplifier v. an amplitude detector is connected to an input of a buffer memory device, the output of which is connected to the input of an n-bit digital converter, as well as an output stage connected to the first communication line.

The proposed gamma spectrometer differs from the known gamma spectrometers in that a parallel code into serial, random access memory, differential channel block and logical 4-input OR element are inserted into the recording unit. The information outputs of the analog-to-digital converter are connected via random access memory via the inputs of the parallel-to-serial code converter, the output connected to the input of the output stage. The inputs of all comparators are connected to the output of the buffer memory, and the outputs of the first and second comparators of each differential channel are connected respectively to the first and second inputs of the anti-coincidence circuit, the output of each of which is connected via a 4-input logical element OR to the control input of an analog digital converter.

The analysis and processing unit of the gamma spectrometer contains a second linear amplifier, the output of which is connected to the input

5

0

5

0

5 0 5 0 5

a serial to parallel converter, the information inputs of which are connected to the inputs of the digital-to-analog converter (DAC). The readiness of the serial code to parallel converter, the output of the digital-analog converter through the first and third differential channels is connected to the first or third inputs of the information processing unit, through the fourth differential channel to the first input of the automatic gain control unit and through the fifth differential channel - with the second input of the said automatic gain control unit, the output of which is connected with a second link. The output of the information processing unit is connected to the registrar.

In FIG. 1 is a functional diagram of a device implementing the proposed method; in FIG. 2 is a functional diagram of a differential channel.

The recording unit includes a gamma-ray detector connected in series with a high-voltage power supply unit 1, a linear amplifier 2, an amplitude detector or integrator 3, a buffer memory (BCD) 4, and an analog-to-digital converter (ADC)

5. random access memory

6. a parallel-to-serial converter 7, an output stage 8, as well as a block of differential channels 9 and a 4-input element OR 10, the input of the block of differential channels 9 is connected to the output of the buffer memory, and the output through the logic element IL AND 10 to the control input of the ADC 5.

The analysis and processing unit contains a serially connected input amplifier 11, a serial to parallel converter 12, a digital-to-tax converter 13, five differential channels 14, 15, 16, 17 and 18, the outputs of which are connected to the processing unit 19, as well as an automatic gain control 20 and one-shot 21. The output of the first communication line 22 is connected to the high voltage power supply unit of the gamma-ray detector 1. The one-shot 21 is connected to the gate input of the DAC 13 and the input to the output Ready b serial to parallel conversion lock 12.

Differential channels, of which there are four in the recording part (block 7) and five in the analysis block (14, 15, 16,

17, 18) are made according to the identical circuit shown in Fig. 2.

The differential channel circuit consists of a comparator of the upper 23 and lower 24 levels, the outputs of which are connected to two corresponding inputs of the anti-coincidence circuit 25. The outputs of the anti-coincidence circuit of the recording part 25 through four input logic element OR 10 are connected to the control input of the ADC 5, and the inputs of all comparators are connected to the output of the buffer memory 4.

The device operates as follows.

The electric pulse coming from the output of the gamma-ray detector 1 is amplified by a linear amplifier 2 and then fed to an amplitude detector 3, the output of which is a signal with a flat top and amplitude proportional to the energy of the original gamma-quantum. The signal duration is 3-5 microseconds. Further, this signal enters the buffer memory 4, which is the same amplitude detector. The output of the latter generates an identical pulse in amplitude, but with a longer duration (20-40 μs), intended for subsequent coding in the ADC and amplitude selection in the differential channel block 9. The use of an amplitude detector in combination with a buffer memory allows equalization statistically distributed signals in time and thereby reduce the Miscalculations during transmission over long lines of communication by about half. From the output of the buffer memory 4, the signals simultaneously arrive at the input of the ADC 5 and the block of differential channels 9. The conversion of the analog signals of the ADC to a digital one-bit code is carried out upon receipt of an enable pulse from the output of the logic element OR 10. This is possible only in the case if the signal amplitude is between the lower and upper levels of one of the pairs (four pairs are provided in this device), there are four different differential channels. In this way, selective digital coding of information signals belonging to predetermined energy regions of the original gamma-ray spectrum is achieved. From the output of the ADC 5, the digital code is recorded in RAM 6, due to which there is a secondary equalization with the signalistics of the density, eliminating further miscalculations in the transmission of information over the communication line. Extraction

of digital codes from RAM is reached by a signal. Readiness from output. End of conversion of a block for converting a parallel code into a serial one,

coming to read RAM input. Read on RAM b The word is converted into a serial code with a total duration of 200-250 microseconds. (with 8 bit coding), amplified by power

the output stage 8 and enters the communication line 22. With a digital code duration of 200 microseconds, the device allows transmitting without miscalculations up to 5000 W s, which corresponds to about 20-40 thousand W s

full gamma spectrum. The digital codes coming in via the communication line 22 are reconstructed from the level using a linear amplifier 11, and then they are input to the serial conversion unit

code in parallel 12 and further to the inputs of the digital-to-analog converter (DAC) 13. Output The readiness of the converter unit 12 is connected to the gate input of the DAC through a single-shot 20, which ensures the end of the conversion of the digital code into an analog signal. The duration of the analog output signal is accordingly determined by the duration of the single-shot pulse. DAC output

analog signals are applied to the inputs of identical differential channels 14, 15, 16, 17, 18, by which amplitude selection of the transmitted and reconverted piecewise-continuous gamma spectrum is carried out. Further, from the outputs of the first 3 differential channels, the information flows to the processing unit 21, which can be made in the form of a calculating and solving device that implements the required calculation algorithm by hard logic or another type of computer. In particular, in the spectrometry of natural gamma radiation, the calculation of potassium, uranium and

Tories based on hardware solutions to systems of 3 equations of the following form:

fifty

q (K) anm + ai2N2 + aisNs

g (U) 32lNl + 322N2 + 323N3

g (Th) asiNi + aza # + assNs where g (K), g (U), g (Th) are potassium, uranium, and tori, respectively;

Ni, N2, N3 — counting rates along the channel of potassium (1.46 MeV), uranium (1.78 MeV), tori (2.62 MeV);

aij are the constant spectral coefficients determined in graded ore models.

The outputs of the fourth and fifth differential channels 17, 18 are connected to the input of the automatic gain control system 20, operating, for example, on the principle of comparing the counting rates in two adjacent energy regions selected symmetrically on the slopes of the photopeak of the reference source. The unbalance signal is converted to a constant voltage, which is transmitted through the communication line to the high voltage power supply unit of the gamma-ray detector, changing it in one direction or another. This provides a constant signal level required for the stable operation of the entire device and especially the differential channels of the recording part. The reference voltage of the DAC 13 and the differential channels 14-18 is set from a single stabilized power source. Due to this, the dynamic range of signal amplitudes at the output of the DAC corresponds exactly to the level range of the differential channels 14-18. This eliminates the use of an additional amplifier at the output of the DAC, which inevitably destabilizes the operation of the device.

Thus, the proposed gamma spectrometry method and device for its implementation can significantly (5-10 times) reduce the miscalculations of information signals and, accordingly, increase the accuracy of spectral flux measurements by at least 2-3 times. An increase in accuracy compared to analog transmission of information is achieved by improving the energy resolution of the spectrometric path by eliminating the influence of the cable.

Claims (2)

1. The method of gamma spectrometry, which consists in converting light scintillations of gamma rays into electrical pulses with an amplitude proportional to the energy of the original gamma quantum, then converting the spectrum of amplitudes of the electrical pulses into a digital n-bit code, characterized in that, for the purpose of increasing the accuracy of measurements by reducing miscalculations of signals with increased integrated loading of the spectrometric path, the conversion of the pulse amplitude to a n-digit digital code is carried out selectively in predetermined energy ranges full gamma spectrum by the amplitude of provisional selection, then after the transmission of an elongated link is carried out inverse transform digital codes into analog signals, with In this case, the energy and spectral intensities of gamma rays determine the path of the amplitude selection of the reconverted piecewise continuous spectrum analog signals. 2. A gamma spectrometer comprising a recording unit consisting of a gamma-ray detector, the output of which is connected through a series-connected first linear amplifier and amplitude detector to the input of a buffer storage device, the output of which is connected to the input of an n-bit analog-digital a converter, an output stage connected to the first communication line, an analysis and processing unit, the input of the detector being connected to the first communication line, characterized in that a parallel converter is introduced into the recording unit Yelnia 0 code in a serial, random access memory, block of differential channels (each of which contains the first and second comparators, respectively, of the upper and lower levels and 5 is an anti-coincidence circuit), a logical four-input IL element AND, while the information outputs of the analog-to-digital converter are connected via random access memory to the inputs of the parallel to serial converter, the output is connected to the output stage input, the inputs of all comparators are connected to the output of the buffer memory, and the outputs The 5 first and second comparators of each differential channel are connected respectively to the first and second inputs of the anti-coincidence circuit, the output of each of which, respectively, through a four-input logic element OR is connected to the control input of the analog-to-digital converter, the analysis and processing unit contains a second linear amplifier whose output is connected to the input of the serial-to-parallel code converter, the information inputs of which are connected to the inputs of the digital-to-analog converter, to the gating input, which is connected via a single-vibrator than the output. Ready of the serial to serial converter, the digital-to-analog converter output is connected to the first or third inputs through the first-third differential channels 5 information processing unit, through the fourth differential channel - with the first input of the automatic gain control unit, and through the fifth differential channel - with the second input of the said automatic gain control unit, the output of which the output of the information processing unit is connected to the second line communication connected to the recorder. FIG. 2 Editor T. Kupr kova Compiled by E. Sharipo Tehred M. Morgenthal Proofreader S.Jusco