Wide-energy liquid flicker counting device

Abstract

The utility model provides a wide-energy liquid flicker counting device, which comprises a photomultiplier module, a signal adjusting module, a logarithm converter module, a comparator module and a counter module. According to the wide-energy liquid flicker counting device provided by the utility model, the gradual compression principle is utilized, the amplification factor is reduced along with the increase of the input energy intensity, and the amplitude of an output signal is increased on year-on-year basis along with the logarithm increase of the amplitude of the input signal, so that the dynamic input range can be greatly improved, and meanwhile, the continuous change of the output signal is ensured; the device is simple in structure design, can realize dynamic energy range input measurement from a few keV to dozens of MeV without additionally adding a complex feedback circuit and a control circuit, and can effectively control and reduce the cost.

Description

Technical Field

[0001] The utility model relates to the technical field of nuclear radiation measurement, in particular to a wide energy liquid scintillation counting device. Background Art

[0002] In the nuclear radiation measurement equipment industry, it is always necessary to perform statistical counting of radiation energy in order to evaluate the radioactivity of samples. Liquid scintillation counting is a method that mainly detects radioactivity in liquids, hereinafter referred to as liquid scintillation counting. Since the different radiation energy ranges of the measured samples are also different, there are low-energy nuclide samples and high-energy nuclide samples, ranging from a few tenths of keV to tens of MeV or even wider, so the wider energy detection range allows the equipment to measure more different types of samples, and can also be used to identify different nuclides. This wide energy liquid scintillation counting method collects the radiation energy of the sample through a photomultiplier tube and converts it into a voltage signal, and then compresses and converts the voltage signal through a logarithmic converter. The compressed and converted signal is compared with a threshold to determine whether it is a valid count, and finally a counter is used for counting. This counting method has the advantages of enhancing equipment performance, reducing the complexity of system design, making the system more stable, and improving detection efficiency.

[0003] Traditional liquid scintillation counting uses linear amplification followed by threshold comparison to determine the count. Linear amplification refers to a fixed amplification method. Due to the voltage limit of the threshold comparison part, the output voltage range is always fixed. When the amplification factor is fixed, there will be a fixed energy input range. For example, if the voltage limit output is 0.1~2V, and the fixed amplification factor is set to 1000, the input signal range will only be 0.1~2mv. At this time, the corresponding energy range may be only a few tenths of keV to more than ten KeV. This energy input range is relatively narrow. Once the input energy exceeds this range, it will not correspond to the output voltage. Traditional liquid scintillation counting requires the design of an amplification adjustment circuit to meet the energy range requirements of different samples. Before measuring the sample, the amplification factor needs to be adjusted according to the energy range of the sample. The wider the range required for this method, the more adjustment circuits are required. This method belongs to static energy range adjustment. The disadvantages of the traditional liquid scintillation counting method are obvious. Because of its small dynamic range, it cannot be directly used for unknown sample source measurement. It can only be measured by determining the range through tedious tests and then determining the appropriate amplification factor. The system design is relatively complex.

[0004] In order to deal with the problem of narrow dynamic range of traditional liquid scintillation counting methods, most liquid scintillation counters and liquid scintillation spectrometers are currently improved by adopting a piecewise linear amplification system design. Piecewise linear amplification refers to segmenting the output signal according to the output signal feedback, and different segments correspond to different amplification factors to improve the dynamic range of the input signal. Therefore, the more segments there are, the wider the energy range that can be measured. The disadvantages of the piecewise linear amplification method are also obvious. Each segment requires more hardware circuits as support. The more segments there are, the more complex the circuit is. Moreover, if the segmentation is unreasonable, there will be a large output signal jump at the segmentation point, resulting in edge jitter in the threshold comparison part, which is not conducive to the stability of the system and directly affects the detection efficiency. Summary of the invention

[0005] In order to address the deficiencies in the prior art, the utility model provides a wide-energy liquid scintillation counting device, which utilizes the principle of progressive compression to reduce the amplification factor as the input energy intensity increases, and the amplitude of the output signal increases year-on-year with the logarithm of the input signal amplitude, thereby greatly improving the dynamic input range, which can be easily increased to more than 80dB, while ensuring the continuous change of the output signal. The structural design is simple, and there is no need to add complex feedback circuits and control circuits, so that dynamic energy range input measurement from a few tenths of keV to tens of MeV can be achieved, effectively controlling and reducing costs.

[0006] The utility model adopts a technical solution to solve the technical problem: a wide energy liquid scintillation counting device is provided, including a photomultiplier tube module, a signal adjustment module, a logarithmic converter module, a comparator module and a counter module, wherein:

[0007] The photomultiplier tube module is used to collect the light signal generated by the scintillation fluid being excited when the nuclides in the measurement sample generate nuclear radiation and convert the light signal into an electrical signal;

[0008] The signal adjustment module is used to extract effective signals from electrical signals, and its signal input end is connected to the signal output end of the photomultiplier tube module;

[0009] The logarithmic converter is used to compress and amplify the effective signal to obtain an amplified voltage signal, and its signal input end is connected to the signal output end of the signal adjustment module;

[0010] The comparator module is used to compare the amplified voltage signal with the set threshold voltage signal and output a level signal, and its signal input end is connected to the signal output end of the logarithmic converter module;

[0011] The counter module is used for counting the level signal, and its signal input end is connected with the signal output end of the comparator module.

[0012] The signal adjustment module includes an isolation capacitor, an operational amplifier and a feedback resistor, wherein one end of the isolation capacitor is connected to the signal output end of the photomultiplier tube module, the other end of the isolation capacitor is grounded through a grounding resistor and connected to the in-phase input end of the operational amplifier, the inverting input end of the operational amplifier is connected to the output end of the operational amplifier through a feedback resistor, and the output end of the operational amplifier is the signal output end of the signal adjustment module.

[0013] The logarithmic converter module includes a coupling capacitor resistor circuit, a logarithmic amplifier, an intercept adjustment resistor circuit and a slope adjustment resistor circuit, wherein the coupling capacitor resistor circuit is connected to the signal output end of the signal adjustment module, and the output end of the logarithmic amplifier is the signal output end of the logarithmic converter module.

[0014] The comparator module includes a comparator, a feedback resistor, a voltage regulator and a pull-up resistor, wherein the inverting input of the comparator is connected to the signal output of the logarithmic converter module, the non-inverting input of the comparator is connected to the output of the comparator through a feedback resistor and a voltage regulator in series, the output of the comparator is grounded through a pull-up resistor, and the output of the comparator is the signal output of the comparator module.

[0015] The comparator module is connected to the threshold setting circuit.

[0016] The threshold setting module includes an adjustable resistor, and the threshold setting module is connected to the non-inverting input terminal of the comparator module.

[0017] The photomultiplier tube module, the signal adjustment module, the logarithmic converter module, the comparator module and the counter module are connected in series through resistors respectively.

[0018] The beneficial effects of the utility model based on its technical solution are:

[0019] (1) The utility model utilizes the principle of progressive compression to reduce the amplification factor as the input energy intensity increases, and the amplitude of the output signal increases year-on-year as the logarithm of the input signal amplitude increases. The counting formula is Vo=Vs*lg(Vi / Vx) (Vo is the output, Vs is the slope, Vi is the input, and Vx is the intercept). This can greatly improve the dynamic input range, which can be easily increased to more than 80dB, while ensuring the continuous change of the output signal, so that the device has the ability to amplify small signals and can extract more signals in the low energy area, thereby achieving the effect of improving detection efficiency.

[0020] (2) The output signal of the utility model has a one-to-one correspondence with the input signal, so there will be no jump in the output signal. No other adjustments are required for measuring different nuclides, and the edge jump can be prevented from affecting the counting.

[0021] (3) The utility model can still maintain a wide range of energy dynamic input performance at high frequencies, and can still measure samples with strong radioactivity and high activity, thus avoiding the rapid change of energy that introduces noise that affects the detection efficiency.

[0022] (4) The utility model has a simple structural design and does not require additional feedback circuits and control circuits to achieve input measurement in a dynamic energy range of a few tenths of keV to tens of MeV. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention is a schematic diagram of module connection of a wide energy liquid scintillation counting device.

[0024] Figure 2 The present invention is a schematic diagram of the signal processing flow of a wide energy liquid scintillation counting device.

[0025] Figure 3 The present invention is a circuit connection diagram of a wide energy liquid scintillation counting device.

[0026] In the figure: 10-photomultiplier tube module, 20-signal adjustment module, 30-logarithmic converter module, 40-comparator module, 50-counter module, 21-isolation capacitor, 22-grounding resistor, 23-operational amplifier, 24-feedback resistor, 31-coupling capacitor resistor circuit, 32-logarithmic amplifier, 33-intercept adjustment resistor circuit, 34-slope adjustment resistor circuit, 41-comparator, 42-voltage regulator, 43-feedback resistor, 44-pull-up resistor, 45-threshold setting circuit, 46-adjustable resistor. DETAILED DESCRIPTION

[0027] The utility model is further described below in conjunction with the accompanying drawings and embodiments.

[0028] The utility model provides a wide energy liquid scintillation counting device, referring to Figure 1 , including a photomultiplier tube module 10, a signal adjustment module 20, a logarithmic converter module 30, a comparator module 40 and a counter module 50, wherein:

[0029] The photomultiplier tube module is used to collect the light signal generated by the scintillation fluid being excited when the nuclides in the measurement sample generate nuclear radiation and convert the light signal into an electrical signal;

[0030] The signal adjustment module is used to extract effective signals from electrical signals, and its signal input end is connected to the signal output end of the photomultiplier tube module;

[0031] The logarithmic converter is used to compress and amplify the effective signal to obtain an amplified voltage signal, and its signal input end is connected to the signal output end of the signal adjustment module;

[0032] The comparator module is used to compare the amplified voltage signal with the set threshold voltage signal and output a level signal, and its signal input end is connected to the signal output end of the logarithmic converter module;

[0033] The counter module is used for counting the level signal, and its signal input end is connected with the signal output end of the comparator module.

[0034] Reference Figure 2 The measurement sample contains radioactive nuclides and scintillating liquid. When the nuclides emit nuclear radiation, they will stimulate the light emitted by the scintillating liquid. The light signal collected by the photomultiplier tube represents a nuclear decay. The light signal is converted into an electrical signal after passing through the photomultiplier tube. The electrical signal is adjusted by differential isolation to extract the effective signal, and then compressed and amplified by the logarithmic amplifier to obtain an amplified voltage signal. The comparator then compares it with the set threshold voltage signal to output a level signal. The counter counts the level signal to complete the liquid scintillator counting process.

[0035] Reference Figure 3 , the utility model can be implemented by the following specific circuit:

[0036] The photomultiplier tube input signal is an electrical signal converted from the photomultiplier tube after absorbing light. The useful part of the signal is separated by a differential isolation signal adjustment circuit.

[0037] The signal adjustment module includes an isolation capacitor 21, an operational amplifier 23 and a feedback resistor 24, wherein one end of the isolation capacitor is connected to the signal output end of the photomultiplier tube module, the other end of the isolation capacitor is grounded through a grounding resistor 22, and is connected to the in-phase input end of the operational amplifier, the inverting input end of the operational amplifier is connected to the output end of the operational amplifier through a feedback resistor, and the output end of the operational amplifier is the signal output end of the signal adjustment module. When the signal passes through the logarithmic conversion circuit, the signal can be converted to between 1 and 3.3V.

[0038] The logarithmic converter module includes a coupling capacitor resistor circuit 31, a logarithmic amplifier 32, an intercept adjustment resistor circuit 33 and a slope adjustment resistor circuit 34, wherein the coupling capacitor resistor circuit is connected to the signal output end of the signal adjustment module, and the output end of the logarithmic amplifier is the signal output end of the logarithmic converter module.

[0039] The comparator module includes a comparator 41, a feedback resistor 43, a voltage regulator 42 and a pull-up resistor 44, wherein the inverting input of the comparator is connected to the signal output of the logarithmic converter module, the non-inverting input of the comparator is connected to the output of the comparator through a feedback resistor and a voltage regulator in series, the output of the comparator is grounded through a pull-up resistor, and the output of the comparator is the signal output of the comparator module. The signal after logarithmic conversion is compared with a set threshold value by the comparator, and a low level is output if it exceeds the threshold value, and a high level is maintained if it does not exceed the threshold value.

[0040] The comparator module is connected to the threshold setting circuit 45. The threshold setting module includes an adjustable resistor 46, and the threshold setting module is connected to the non-inverting input terminal of the comparator module.

[0041] The photomultiplier tube module, the signal adjustment module, the logarithmic converter module, the comparator module and the counter module are respectively connected in series through resistors to improve the stability of the circuit.

[0042] The utility model provides a wide energy liquid scintillation counting device, which utilizes the principle of progressive compression to reduce the amplification factor as the input energy intensity increases, and the amplitude of the output signal increases year-on-year as the logarithm of the input signal amplitude increases, thereby greatly improving the dynamic input range and ensuring the continuous change of the output signal. The structure design is simple, and no complex feedback circuit and control circuit are required to realize input measurement in the dynamic energy range of a few tenths of keV to tens of MeV, thereby effectively controlling and reducing costs.

Claims

1. A wide energy liquid scintillation counting device, comprising a photomultiplier tube module (10), characterized in that: It also includes a signal adjustment module (20), a logarithmic converter module (30), a comparator module (40) and a counter module (50), wherein: The photomultiplier tube module is used to collect the light signal generated by the scintillation fluid being excited when the nuclides in the measurement sample generate nuclear radiation and convert the light signal into an electrical signal; The signal adjustment module is used to extract effective signals from electrical signals, and its signal input end is connected to the signal output end of the photomultiplier tube module; The logarithmic converter is used to compress and amplify the effective signal to obtain an amplified voltage signal, and its signal input end is connected to the signal output end of the signal adjustment module; The comparator module is used to compare the amplified voltage signal with the set threshold voltage signal and output a level signal, and its signal input end is connected to the signal output end of the logarithmic converter module; The counter module is used for counting the level signal, and its signal input end is connected with the signal output end of the comparator module.

2. The wide energy liquid scintillation counting device according to claim 1, characterized in that: The signal adjustment module comprises an isolation capacitor (21), an operational amplifier (23) and a feedback resistor (24), wherein one end of the isolation capacitor is connected to the signal output end of the photomultiplier tube module, the other end of the isolation capacitor is grounded via a grounding resistor (22) and connected to the in-phase input end of the operational amplifier, the inverting input end of the operational amplifier is connected to the output end of the operational amplifier via the feedback resistor, and the output end of the operational amplifier is the signal output end of the signal adjustment module.

3. The wide energy liquid scintillation counting device according to claim 1, characterized in that: The logarithmic converter module comprises a coupling capacitor resistor circuit (31), a logarithmic amplifier (32), an intercept adjustment resistor circuit (33) and a slope adjustment resistor circuit (34), wherein the coupling capacitor resistor circuit is connected to the signal output end of the signal adjustment module, and the output end of the logarithmic amplifier is the signal output end of the logarithmic converter module.

4. The wide energy liquid scintillation counting device according to claim 1, characterized in that: The comparator module comprises a comparator (41), a feedback resistor (43), a voltage regulator (42) and a pull-up resistor (44), wherein the inverting input end of the comparator is connected to the signal output end of the logarithmic converter module, the non-inverting input end of the comparator is connected to the output end of the comparator via the feedback resistor and the voltage regulator in series, the output end of the comparator is grounded via the pull-up resistor, and the output end of the comparator is the signal output end of the comparator module.

5. The wide energy liquid scintillation counting device according to claim 1, characterized in that: The comparator module is connected to the threshold setting circuit (45).

6. The wide energy liquid scintillation counting device according to claim 4 or 5, characterized in that: The threshold setting module comprises an adjustable resistor (46), and the threshold setting module is connected to the non-inverting input terminal of the comparator module.

7. The wide energy liquid scintillation counting device according to claim 1, characterized in that: The photomultiplier tube module, the signal adjustment module, the logarithmic converter module, the comparator module and the counter module are connected in series through resistors respectively.

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