Self-adaptive passing rate lanthanum bromide energy spectrum measuring device and method

Abstract

The invention relates to a self-adaptive passing rate lanthanum bromide energy spectrum measuring device and method. The device comprises a dose rate monitoring unit, an analog switch control unit and a charge sensitive pre-amplification circuit. The dose rate monitoring unit monitors the environmental dose rate in real time, and the analog switch control unit automatically adjusts the resistance Rf in the charge-sensitive pre-amplification circuit according to the monitored dose rate, thereby changing the signal attenuation time tau, and ensuring that the pulse signal duration is shortened under the high dose rate so as to improve the passing rate. And meanwhile, relatively long signal decay time is kept at a low dosage rate so as to ensure high energy resolution. The measurement method relates to real-time monitoring of the dose rate and dynamic adjustment of the resistor Rf so as to adapt to pulse signal processing requirements in different dose rate environments.

Description

Technical Field

[0001] The invention relates to an adaptive pass rate lanthanum bromide spectrum measuring device, belonging to the technical field of nuclear spectrum measurement. Background Art

[0002] At present, low-energy pulse energy-resolved measurement technology is developing rapidly and plays an irreplaceable role in many fields. In some cases, pulse energy-resolved measurement devices may need to work in an environment with a high dose rate.

[0003] In the prior art, lanthanum bromide crystals are often used as probes for portable gamma nuclide identification instruments due to their ultrafast light decay time and excellent energy resolution. However, at present, lanthanum bromide spectrometers operate at a maximum dose rate of 100uSv / h. A higher count rate will cause the system to become clogged and unable to work properly. In this case, due to the high dose rate and long pulse signal duration, the pass rate of the pulse energy resolution measurement device is likely to be too low, thus affecting the experimental efficiency.

[0004] With the further development of nuclear technology, high-activity sources are used more frequently. When faced with the measurement of high-activity sources, traditional measurements cannot achieve composite number identification. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide an adaptive pass rate lanthanum bromide spectrum measurement device and method to solve the problem that the lanthanum bromide detection system cannot work normally under high dose rate.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions: The present invention provides an adaptive pass rate lanthanum bromide spectrum measuring device, comprising: a dose rate monitoring unit, used to monitor the dose rate in the measurement environment; an analog switch control unit, connected to the dose rate monitoring unit through an FPGA chip, used to automatically switch the state of the analog switch according to the dose rate, so as to control the resistor R in the charge sensitive preamplifier circuit. f The charge sensitive preamplifier circuit is connected to the analog switch control unit to adjust the resistance R f The size of can change the signal decay time τ = R f ×C f , thereby reducing the pulse signal duration at high dose rates, improving the pulse throughput rate, and maintaining a longer signal decay time at low dose rates to ensure high energy resolution; The FPGA chip obtains the count of the dose rate monitoring unit every second, controls the state of the analog switch according to the count rate, and realizes the resistor R fDynamic adjustment, the use of FPGA chips enables the control unit to quickly respond to dose rate changes, which is suitable for dynamic environments that require real-time adjustment of measurement parameters.

[0007] Furthermore, the dose rate monitoring unit may be a GM tube, a semiconductor dosimeter or a plastic scintillator dosimeter.

[0008] Furthermore, the dose rate monitoring unit is a GM tube, which is used to monitor the dose rate of the surrounding environment in real time and convert the nuclear pulse into a trigger signal. The FPGA obtains the count of the GM tube every second and adjusts the analog switch according to the count rate: When the count rate is lower than a certain threshold, it is considered that the dose rate is low, and the analog switch is placed in a low resistance conduction state to achieve high energy resolution measurement; When the count rate is higher than a certain threshold, it is considered that the dose rate is high, and the analog switch is placed in a large resistance on state to achieve pulse high pass rate measurement.

[0009] Furthermore, in the charge sensitive preamplifier circuit, the capacitor C f Used to integrate the charge, through V=Q / C f , we can know the maximum value of charge converted into voltage, R f Used to discharge C f The charge in the capacitor; when a certain number of counts are accumulated, the position of the full energy peak is calculated and compared with the database to realize nuclide identification.

[0010] The present invention also provides an adaptive pass rate lanthanum bromide spectrum measurement method, which uses the above-mentioned adaptive pass rate lanthanum bromide spectrum measurement device to monitor the dose rate in the measurement environment; according to the dose rate, the state of the analog switch is automatically switched to control the resistor R in the charge sensitive preamplifier circuit. f The size of the resistor R f The size of the change signal decay time τ = R f ×C f , thereby reducing the pulse signal duration at high dose rates and improving the pulse throughput rate, and maintaining a longer signal decay time at low dose rates to ensure high energy resolution.

[0011] Compared with the prior art, the present invention has the following beneficial effects: 1. The adaptive pass rate lanthanum bromide spectrum measuring device of the present invention automatically adjusts the resistance R in the charge sensitive preamplifier circuit f The size of the pulse transmission rate can be improved while maintaining high energy resolution in different dose rate environments, effectively solving the problem of low pulse transmission rate and decreased energy resolution in traditional nuclear energy spectrum measurement under high dose rate environment. It can significantly improve the accuracy and efficiency of measurement and provide strong technical support for research and application in related fields.

[0012] 2. The present invention reduces the pulse duration by switching the time decay constant, changes the pulse pass rate of the lanthanum bromide detector, provides the scintillator pulse pass rate, and realizes the energy spectrum recognition under high dose rate. The invention is suitable for portable direct reading equipment, does not require the operator to manually select the working state, and the equipment can realize automatic measurement mode conversion according to the ambient dose rate.

[0013] 3. The method of the present invention not only improves the efficiency of nuclear energy spectrum measurement, but also ensures the accuracy of measurement results under different dose rate environments. It is suitable for a wide range of fields such as nuclear energy spectrum research, nuclear material analysis, and nuclear safety monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a circuit block diagram of the adaptive pass rate lanthanum bromide spectrum measuring device of the present invention; Figure 2 This is a circuit block diagram of a typical scintillator detector; Figure 3 It is a block diagram of a charge sensitive preamplifier circuit; Figure 4 It is the charge sensitive preamplifier voltage waveform. DETAILED DESCRIPTION

[0016] The technical solution of the present invention is clearly and completely described below in conjunction with the embodiments and the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. It is usually described and shown in the drawings herein that the components can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments provided in the drawings is not intended to limit the scope of protection claimed, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0017] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0018] like Figure 1As shown, the present invention provides an adaptive pass rate lanthanum bromide spectrum measuring device, including a dose rate monitoring unit (GM tube) for monitoring the dose rate in the measurement environment; an analog switch control unit, connected to the dose rate monitoring unit (GM tube) through an FPGA chip, for automatically switching the state of the analog switch according to the dose rate, so as to control the resistor R in the charge sensitive preamplifier circuit. f The charge sensitive preamplifier circuit is connected to the analog switch control unit to adjust the resistance R f The size of can change the signal decay time τ = R f ×C f , thereby reducing the pulse signal duration at high dose rates and improving the pulse throughput rate, and maintaining a longer signal decay time at low dose rates to ensure high energy resolution.

[0019] The FPGA chip obtains the count of the dose rate monitoring unit every second, controls the state of the analog switch according to the count rate, and realizes the resistor R f Dynamic adjustment, the use of FPGA chips enables the control unit to quickly respond to dose rate changes, which is suitable for dynamic environments that require real-time adjustment of measurement parameters.

[0020] In specific implementation, the dose rate monitoring unit can be a GM tube, a semiconductor dosimeter or a plastic scintillator dosimeter, the scintillator detector can be a lanthanum bromide crystal detector or a silicon photomultiplier tube detector, the optical signal amplification component can be a photomultiplier tube or an avalanche photodiode, and the FPGA controls the analog switch control unit to control the analog switch state according to the counting rate of the dose rate monitoring unit to achieve dynamic adjustment of the resistor Rf.

[0021] Furthermore, the dose rate monitoring unit is a GM tube. The use of the GM tube ensures the real-time and accuracy of dose rate monitoring, and is suitable for scenarios that require rapid response to dose rate changes, such as nuclear facility safety monitoring and radiation protection assessment. It is used to monitor the dose rate of the surrounding environment in real time, convert nuclear pulses into trigger signals, and the FPGA obtains the count of the GM tube every second and adjusts the analog switch according to the count rate: When the count rate is lower than a certain threshold, it is considered that the dose rate is low, and the analog switch is placed in a low resistance conduction state to achieve high energy resolution measurement; When the count rate is higher than a certain threshold, it is considered that the dose rate is high, and the analog switch is placed in a large resistance on state to achieve pulse high pass rate measurement.

[0022] In one embodiment, the dose rate monitoring unit is a semiconductor dosimeter, which is used to monitor the dose rate of the surrounding environment in real time. The semiconductor dosimeter has high sensitivity and energy response range, and is suitable for fields such as nuclear medical imaging and industrial non-destructive testing that require high accuracy of dose rate monitoring.

[0023] In another embodiment, the dose rate monitoring unit is a plastic scintillator dosimeter, which is used to monitor the dose rate of the surrounding environment in real time. The plastic scintillator dosimeter can provide dose rate monitoring in a wide energy range, and is suitable for application scenarios such as environmental radiation monitoring and nuclear accident emergency response that need to cover multiple radiation types.

[0024] like Figure 2 As shown in the figure, the light from the scintillator detector is amplified by the photomultiplier tube, and then the pulse amplitude is measured by the multi-channel analyzer. The charge-sensitive preamplifier circuit is used to convert the charge signal into a voltage signal, and then the analog switch is controlled by the FPGA chip. The use of photomultiplier tubes can significantly increase the amplification of light signals and is suitable for occasions that require high-sensitivity detection, such as cosmic ray detection, particle physics experiments, etc.

[0025] In a specific implementation, the scintillator detector may also be a lanthanum bromide crystal detector. Lanthanum bromide crystal detectors have excellent energy resolution and fast response time, and are suitable for high-energy physics experiments, nuclear medicine positron emission tomography (PET), and other occasions that require high-precision energy measurement.

[0026] like Figure 3 As shown, in the charge sensitive preamplifier circuit, the capacitor C f Used to integrate the charge, through V=Q / C f , we can know the maximum value of charge converted into voltage, R f Used to discharge C f The charge in the capacitor. When a certain number of counts are accumulated, the position of the full energy peak is calculated and compared with the database to achieve nuclide identification.

[0027] Depend on Figure 4 It can be seen that its voltage waveform conforms to the exponential decay law and satisfies V=V 0e-t / τ, where τ is the decay time of the signal, τ=R f ×C f . When the signal decay time is longer, the signal takes longer to return to the baseline, and the subsequent signal will accumulate on the previous signal, causing the signal to be deformed. However, when the signal is longer and no accumulation occurs, the energy resolution is better. At low doses, the better the energy resolution, the more obvious the full energy peak, and the stronger the radionuclide identification ability.

[0028] The present invention also provides an adaptive pass rate lanthanum bromide spectrum measurement method, which uses the above-mentioned adaptive pass rate lanthanum bromide spectrum measurement device to monitor the dose rate in the measurement environment; according to the dose rate, the state of the analog switch is automatically switched to control the resistor R in the charge sensitive preamplifier circuit. f The size of the resistor R f The size of the change signal decay time τ = R f ×Cf , thereby reducing the pulse signal duration at high dose rates and improving the pulse throughput rate, and maintaining a longer signal decay time at low dose rates to ensure high energy resolution.

[0029] The method of the present invention not only improves the efficiency of nuclear energy spectrum measurement, but also ensures the accuracy of measurement results under different dose rate environments, and is applicable to a wide range of fields such as nuclear energy spectrum research, nuclear material analysis, and nuclear safety monitoring.

[0030] The analog switch control is realized by FPGA chip, which obtains the count of dose rate monitoring unit every second, controls the state of analog switch according to the count rate, and realizes the resistance R f Dynamic adjustment. The real-time control capability of the FPGA chip enables the nuclear energy spectrum measurement device to respond quickly to changes in dose rate. It is suitable for dynamic environments that require real-time adjustment of measurement parameters, such as nuclear reactor operation status monitoring and radiation environment assessment after a nuclear explosion, which improves the adaptability of the device and the accuracy of measurement.

[0031] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the technical solution. Those skilled in the art should understand that those modifications or equivalent substitutions of the technical solution of the present invention that do not depart from the purpose and scope of the technical solution should be included in the scope of the claims of the present invention.

Claims

1. An adaptive through rate lanthanum bromide spectrum measuring device, characterized in that: include: Dose rate monitoring unit, used to monitor the dose rate in the measurement environment; The analog switch control unit is connected to the dose rate monitoring unit through the FPGA chip, and is used to automatically switch the state of the analog switch according to the dose rate to control the resistor R in the charge sensitive preamplifier circuit. f The charge sensitive preamplifier circuit is connected to the analog switch control unit to adjust the resistance R f The size of can change the signal decay time τ = R f ×C f , thereby reducing the pulse signal duration at high dose rates, improving the pulse throughput rate, and maintaining a longer signal decay time at low dose rates to ensure high energy resolution; The FPGA chip obtains the count of the dose rate monitoring unit every second, controls the state of the analog switch according to the count rate, and realizes the resistor R f Dynamic adjustment, the use of FPGA chips enables the control unit to quickly respond to dose rate changes, which is suitable for dynamic environments that require real-time adjustment of measurement parameters.

2. The adaptive pass rate lanthanum bromide spectrum measuring device according to claim 1, characterized in that: The dose rate monitoring unit may be a GM tube, a semiconductor dosimeter or a plastic scintillator dosimeter.

3. The adaptive pass rate lanthanum bromide spectrum measuring device according to claim 1, characterized in that: The dose rate monitoring unit is a GM tube, which is used to monitor the dose rate of the surrounding environment in real time and convert the nuclear pulse into a trigger signal. The FPGA obtains the count of the GM tube every second and adjusts the analog switch according to the count rate: When the count rate is lower than a certain threshold, it is considered that the dose rate is low, and the analog switch is placed in a low resistance conduction state to achieve high energy resolution measurement; When the count rate is higher than a certain threshold, it is considered that the dose rate is high, and the analog switch is placed in a large resistance on state to achieve pulse high pass rate measurement.

4. The adaptive pass rate lanthanum bromide spectrum measuring device according to claim 1, characterized in that: In the charge sensitive preamplifier circuit, the capacitor C f Used to integrate the charge, through V=Q / C f , we can know the maximum value of charge converted into voltage, R f Used to discharge C f The charge in the capacitor; when a certain number of counts are accumulated, the position of the full energy peak is calculated and compared with the database to realize nuclide identification.

5. An adaptive through rate lanthanum bromide spectrum measurement method, characterized in that: The adaptive pass rate lanthanum bromide spectrum measuring device according to any one of claims 1 to 4 is used to monitor the dose rate in the measurement environment; according to the dose rate, the state of the analog switch is automatically switched to control the resistor R in the charge sensitive preamplifier circuit. f The size of the resistor R f The size of the change signal decay time τ = R f ×C f , thereby reducing the pulse signal duration at high dose rates and improving the pulse throughput rate, and maintaining a longer signal decay time at low dose rates to ensure high energy resolution.

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