RU65660U1 - GAMMA SPECTROMETER - Google Patents

Abstract

The utility model relates to measuring technique and is intended to measure the energy spectra of gamma radiation. The objective of the utility model is to create a gamma spectrometer with increased sensitivity while reducing the likelihood of overlapping two or more pulses. The essence of the utility model is that the gamma spectrometer contains at least two scintillators, for each of which the spectrometer contains a photomultiplier, the output of each photomultiplier is connected through its measuring amplifier to the corresponding input of the analyzer, the number of outputs of each analyzer is N, where N is the number gamma spectrometer channels, the gamma spectrometer contains N adders, while the number of inputs of each adder is equal to the number of scintillators, and each output of each analyzer is connected to the input the house of the corresponding adder, the outputs of the adders are the outputs of the gamma spectrometer. The outputs of the first to Nth adders can be connected to the inputs of the serial channel adapter, the output of which is the output of a digital data channel.

Description

The utility model relates to measuring technique and is intended to measure the energy spectra of gamma radiation.

Known scintillation spectrometer [1, C.28, Fig. 13], containing a scintillator, a photomultiplier, a preamplifier, a linear amplifier, a differential amplitude analyzer, a conversion circuit, a counter. A disadvantage of the known spectrometer is insufficient accuracy, insufficient sensitivity and insufficient noise immunity to the noise of the photomultiplier. In addition, the measurement process is lengthy because to obtain the spectrum, it is necessary to conduct many measurements with various settings of the amplitude analyzer.

The closest and selected as a prototype is a scintillation spectrometer [2], in which these disadvantages are partially eliminated. The scintillation spectrometer contains a scintillator, two photomultipliers fed from a high voltage source, two discriminators, a comparison circuit, two pulse shape analyzers, a valve, two electronic timers, and a multi-channel analyzer. At the same time, the comparison circuit provides the opening of the gate and the resolution of the arrival of pulses to the input of the multichannel analyzer only if the pulses coming from two photomultipliers coincide. The pulse shape analyzers also ensure that the valve opens only if the pulse shapes coincide with the given shape. This provides increased noise immunity, and a multichannel analyzer allows you to obtain a radiation spectrum without reconfiguring any elements of the spectrometer circuit.

The disadvantage of the prototype is the lack of sensitivity at a given measurement time. This drawback can be eliminated by increasing the size of the scintillator crystal. At the same time, a larger number of gamma quanta fall on the crystal over the same period of time, however, this increases the likelihood that two or more gamma quanta can fall on the crystal at the same or close intervals of time, which will lead to superposition of pulses, due to light emissions in the scintillator by individual quanta,

summation of their amplitudes and the impossibility of separating these pulses in the analyzer, which leads to a distortion of the measurement results of the spectral characteristics of gamma radiation. In addition, scintillators with large crystals are difficult to manufacture and are expensive.

The objective of the utility model is to create a gamma spectrometer with increased sensitivity while reducing the likelihood of overlapping two or more pulses.

The essence of the utility model is that the gamma spectrometer contains at least two scintillators, for each of which the spectrometer contains a photomultiplier, the output of each photomultiplier is connected through its measuring amplifier to the corresponding input of the analyzer, the number of outputs of each analyzer is N, where N is the number channels of the gamma spectrometer, the gamma spectrometer contains N adders, while the number of inputs of each adder is equal to the number of scintillators, and each output of each analyzer is connected to the input the house of the corresponding adder, the outputs of the adders are the outputs of the gamma spectrometer.

The outputs of the first to Nth adders can be connected to the inputs of the serial channel adapter, the output of which is the output of a digital data channel.

The essence of the utility model is illustrated by drawings, on which are presented:

figure 1 is a structural diagram of a gamma spectrometer;

figure 2 - structural diagram of the analyzers (the first embodiment);

figure 3 is a structural diagram of analyzers (second embodiment);

In the drawings indicated:

1 ₁ - the first scintillator;

1 _M - _Mth scintillator;

2 ₁ - the first photomultiplier;

2 _M - M-th photomultiplier;

3 ₁ - the first source of high voltage;

3 _M - M-th source of high voltage;

4 ₁ - the first measuring amplifier;

4 _M - M-th measuring amplifier;

5 ₁ - the first analyzer;

5 _M - M-th analyzer;

6 ₁ - the first adder;

6 ₂ - second adder;

6 _N - N-th adder;

7 - unit for determining the maximum amplitude;

8 ₁ - the first threshold block;

8 _N - Nth threshold block;

9 ₁ - the first counter;

9 _N - N-th counter;

10 - analog-to-digital Converter;

11 - block determining the highest value;

12 - block determining the end of the pulse;

13 is a storage device.

As scintillators 1 ₁ , ..., 1 _M, from the first to the Mth, for example, NaJ (Ti) crystals can be used. The crystal sizes are selected based on minimizing the probability of superposition of pulses at the output of the photomultiplier caused by the hit of two gamma quanta simultaneously in one scintillator. The sensitivity of the spectrometer is ensured by an increase in the number of scintillators (the desired total crystal volume is provided).

The analyzers 5 ₁ , ..., 5 _M from the first to the Mth are devices that separate the pulses arriving at their inputs depending on the maximum amplitude (belonging to the maximum amplitude of the pulse to a given range) of each pulse and separately calculate the pulses, maximum whose amplitudes correspond to a given range of amplitudes.

The analyzers 5 ₁ , ..., 5 _M from the first to the Mth can be implemented as follows (figure 2). Each analyzer 5 ₁ , ..., 5 _M from the first to the Mth contains a block 7 for determining the maximum amplitude, N threshold blocks 8 ₁ , ..., 8 _N , N counters 9 ₁ , ..., 9 _N. In this case, the input of the analyzer 5 ₁ , ..., 5 _M is the input of the amplitude maximum determining unit 7, the output of which is connected to the inputs of all threshold blocks 8 ₁ , ..., 8 _N from the first to the Nth, the outputs of which are connected to the inputs corresponding counters 9 ₁ , ..., 9 _N from the first to the Nth.

The analyzers 5 ₁ , ..., 5 _M from the first to the _Mth can also be implemented as follows (figure 3). Each analyzer 5 ₁ , ..., 5 _M from the first to the _Mth contains an analog-to-digital converter 10, a block 11 for determining the highest value, a block 12 for determining the end of the pulse, a storage device 13, while the input

the analog-to-digital converter 10 is the input of the analyzer, and the output of the analog-to-digital converter 10 is connected to the inputs of the block 11 for determining the highest value and the block 12 for determining the end of the pulse, the output of the block for determining the highest value 11 is connected to the input of the address (A) of the storage device 13, and the output block 12 determine the end of the pulse is connected to the incremental ("+1") input of the storage device 13 and the reset reset (s) of the block 11 determining the highest value. The analog-to-digital converter 10 has a built-in restart circuit. The storage device 13 has N cells and N outputs. At each output of the storage device 13, a value stored in the corresponding cell is output. When a pulse arrives at the input of an analog-to-digital converter 10, a digital signal is generated at its output, which is fed to the inputs of the block 11 for determining the highest value and block 12 for determining the end of the pulse. Block 11 determining the largest value remembers and holds at its output a value that is the largest of the values received at its input during the time since the reset. Block 11 determining the highest value can be made in the form of a register and a digital comparator, while one input of the digital comparator is the input of block 11 for determining the highest value and is connected to the input of the register, and the second input of the digital comparator is connected to the output of the register, the output of the digital comparator is connected to the entrance of the register gate. The register reset input is the reset input of the highest value determining unit 11. If the value received at the input of the unit for determining the highest value is greater than the value located in the register, the digital comparator generates a signal at its output, which is fed to the input of the register strobe and the new value is written to the register. Block 12 determining the end of the pulse generates a signal at its output when the value at its input becomes less than the highest value by a predetermined value. Block 12 determine the end of the pulse contains a circuit similar to that of block 11 for determining the highest value and a digital comparator. Also, the end-of-pulse determination unit 12 may use the value generated by the highest value determination unit 11. In this case, the pulse end determination unit 12 has a second input connected to the output of the highest value determination unit 11. The signal from the output of the end of pulse determination unit 12 is supplied to the incremental ("+1") input of the storage device 13, and the cell of the storage device 13, whose address is equal to the value received at the input of the address (A) from the output of the unit for determining the highest value. At

further lowering the value at the input of the pulse end determination unit 12 and reaching the set value, this unit takes a signal at its output. On the negative edge of the signal at the output of the pulse end determination unit 12 and, accordingly, at the reset input (c) of the highest value determination unit 11, the register of the highest value determination unit 11 is reset.

The analyzers 5 ₁ , ..., 5 _M from the first to the _Mth can have one common analog-to-digital converter. At the same time, this analog-to-digital converter is multi-channel. Block 11 determining the highest value, block 12 determining the end of the pulse, the storage device 13 can be made in the form of a programmable logic matrix or microcontroller, and on one programmable logic matrix (one microcontroller) can be implemented Block 11 determining the highest value, block 12 for determining the end of the pulse , storage device 13 of several analyzers. On the same programmable logic matrix (microcontroller) adders 6 ₁ , ..., 6 _N from the first to the Nth can be implemented.

The outputs of the adders 6 ₁ , ..., 6 _N from the first to the Nth can be connected to the inputs of the serial channel adapter, the output of which is the output of a digital data channel, for example, the output of the RS-232 or RS-485 interface. At the same time, it is possible to exchange data between a gamma spectrometer and a consumer computing device of the information received by the gamma spectrometer, which allows for the automatic and automated processing of this information.

Gamma spectrometer works as follows.

Gamma quanta of various energies cause light emission by scintillators 1 ₁ , ..., 1 _M from the first to the _Mth . Light radiation is detected by photomultipliers 2 ₁ , ..., 2 _M from the first to the _Mth and electrical pulses are formed at the outputs of the photomultipliers 2 ₁ , ..., 2 _M from the first to the _Mth , whose maximum amplitude is proportional to the energy of the received gamma quanta. The signals from the outputs of the photomultipliers 2 ₁ , ..., 2 _M from the first to the _{Mth are} amplified by the corresponding amplifiers 4 ₁ , ..., 4 _M from the first to the _Mth arrive at the inputs of the analyzers 5 ₁ , ..., 5 _M respectively, from the first to the Mth. Each analyzer 5 ₁ , ..., 5 _M, from the first to the _Mth , separates the pulses depending on the value of their maximum amplitude across N channels and counts the pulses for each channel for a given time (measurement time). At the outputs of the analyzers 5 ₁ , ..., 5 _M from the first to the _Mth

digital signals about the number of received pulses with a maximum amplitude corresponding to the amplitude range for a given channel. These digital signals for each channel from the outputs of all analyzers 5 ₁ , ..., 5 _M from the first to the _Mth go to the inputs from the first to the _{Mth of the} corresponding adders 6 ₁ , ..., 6 _N from the first to N- where the sum of the pulses of a given maximum range is the amplitude of all the analyzers, that is, the number of pulses caused by gamma rays trapped in all scintillators.

As a result of using the utility model, a gamma spectrometer was created, which has a high sensitivity, which allows to reduce the measurement time or to increase the accuracy at a given measurement time. At the same time, the technologically complex and expensive manufacture of large single crystals is not required.

The presented drawings and description make it possible to manufacture a gamma spectrometer using known materials and element base, which characterizes the utility model as industrially applicable.

BIBLIOGRAPHY

1. Vartanov N.A., Samoilov P.S. Practical scintillation gamma spectrometry methods.

2. US patent No. 4914300, IPC G01T 1/20, 04/03/1990.

Claims (2)

1. A gamma spectrometer containing at least two scintillators, for each of which the spectrometer contains a photomultiplier, the output of each photomultiplier is connected through its measuring amplifier to the corresponding input of the analyzer, the number of outputs of each analyzer is N, where N is the number of channels of the gamma spectrometer, The gamma-ray spectrometer contains N adders, while the number of inputs of each adder is equal to the number of scintillators, and each output of each analyzer is connected to the input of the corresponding adder, the outputs of sum Ator are outputs a gamma spectrometer. 2. The gamma spectrometer according to claim 1, characterized in that the outputs of the first adders through the Nth are connected to the inputs of the serial channel adapter, the output of which is the output of a digital data channel.