Radioactive aerosol continuous monitor based on digital multiple channels

Abstract

The utility model relates to the technical field of nuclear radiation detection, and provides a digital multichannel radioactive aerosol continuous monitor, which is characterized in that gas extracted from an environment to be detected by an air pump of the monitor passes through a sampling loop and radioactive aerosol particles are filtered and accumulated by a filter; the aerosol detector right facing the filter paper detects alpha and beta particles emitted by the aerosol accumulated on the filter paper to form a nuclear pulse signal, and the nuclear pulse signal is sent to the digital multichannel for energy spectrum data processing and then is used for a rear-end signal processing unit to calculate a radioactive activity concentration value. According to the utility model, the processing and analysis of the nuclear pulse and the processing of the nuclear information are completed by adopting the digital multi-channel based on the FPGA and the system on chip thereof, and the collection and analysis processing of the nuclear pulse can be completed by only one FPGA; the digital multi-channel system based on the FPGA system-on-chip can effectively simplify the system framework, reduce the size and the weight, and improve the anti-interference capability and the system stability.

Description

TECHNICAL FIELD

[0001] The utility model relates to nuclear radiation detection technology field, concretely relates to a kind of based on digital multiway's radioactive aerosol continuous monitor. BACKGROUND

[0002] The method of nuclear energy spectrum measurement is widely used in nuclear radiation detection technology field due to its precise and efficient characteristics. By analyzing the energy spectrum, the type and content of the nuclides contained in the measured object can be obtained. Continuous radioactive aerosol monitor needs to analyze and measure the activity concentration of α and β particles in the air, and if necessary, it also needs to distinguish typical artificial α nuclide species for decision-making in accident state. By analyzing the energy spectrum, the type and content of the nuclides contained in the measured object can be obtained, so the multi-channel pulse amplitude analysis spectrometer is an important method for continuous monitoring of radioactive aerosol.

[0003] Constrained by the development of ADC and digital signal processor, the traditional nuclear spectrometer based on multi-channel pulse amplitude analysis is mostly an analog nuclear spectrometer characterized by sampling and holding the peak value of analog pulse signal and AD conversion. The commonly used radioactive aerosol monitoring equipment is also based on the above measurement method. Due to the use of analog devices susceptible to electromagnetic interference, in order to make the equipment work normally in complex electromagnetic environment, special shielding protection mechanism is used outside the equipment, which increases the complexity of the system and the volume and weight of the equipment. At the same time, the measurement accuracy is relatively poor. SUMMARY

[0004] The utility model aims at overcoming the above-mentioned deficiencies in the prior art, and provides a kind of based on digital multiway's radioactive aerosol continuous monitor, which uses a kind of digital multiway based on FPGA and its on-chip system to complete the processing and analysis of nuclear pulse and the processing of nuclear information. Only one FPGA can complete the collection and analysis of nuclear pulse, and this digital multiway system based on FPGA on-chip system can effectively simplify the system architecture, reduce the volume and weight, improve the anti-interference ability and system stability.

[0005] The utility model discloses a kind of radioactive aerosol continuous monitoring instruments based on digital multi-channel, including aerosol detector, preamplifier circuit, automatic paper mechanism, digital multi-channel, signal processing unit, air pump and sampling loop, the air pump of monitoring instrument extracts gas from the environment to be measured, radioactive aerosol particles are filtered and accumulated by filter in sampling loop, α and β particles emitted by aerosol detector on filter paper accumulated are detected, form nuclear pulse signal, after energy spectrum data processing is sent to digital multi-channel, and backend signal processing unit calculates radioactivity concentration value, the digital multi-channel includes high-speed ADC, pulse waveform acquisition module, nuclear pulse digitizing shaping sampling module, nuclear pulse generation module, high-speed DAC, memory and peripheral equipment.

[0006] The utility model discloses a kind of radioactive aerosol continuous monitoring instruments based on digital multi-channel, including aerosol detector, preamplifier circuit, automatic paper mechanism, digital multi-channel, signal processing unit, air pump and sampling loop, the air pump of monitoring instrument extracts gas from the environment to be measured, radioactive aerosol particles are filtered and accumulated by filter in sampling loop, α and β particles emitted by aerosol detector on filter paper accumulated are detected, form nuclear pulse signal, after energy spectrum data processing is sent to digital multi-channel, and backend signal processing unit calculates radioactivity concentration value, the digital multi-channel includes high-speed ADC, pulse waveform acquisition module, nuclear pulse digitizing shaping sampling module, nuclear pulse generation module, high-speed DAC, memory and peripheral equipment.

[0007] In the above technical scheme, the pulse waveform acquisition module in digital multi-channel stores nuclear pulse collected by high-speed ADC after detector generates into memory, for artificial data analysis.

[0008] In the above technical scheme, the nuclear pulse digitizing shaping sampling module in digital multi-channel obtains peak energy information of waveform and stores into memory after a series of operations such as second-order difference filter and trapezoidal filter and baseline deduction after high-speed ADC collects nuclear pulse waveform generated by detector.

[0009] In the above technical scheme, nuclear pulse generation module is provided, and nuclear pulse waveform stored in memory is formed into energy spectrum data by amplitude controller, time and amplitude scanning module and output control module, and then sent to backend signal processing unit.

[0010] The utility model discloses a kind of radioactive aerosol continuous monitoring instruments based on digital multi-channel, and compared with prior art, has the following beneficial effects:

[0011] 1.A digital multi-channel based on FPGA and its system on chip as core carries out sampling analysis to the pulse waveform generated by aerosol detector, obtains energy spectrum data.Compared with conventional analog nuclear spectrometer, volume and weight can be reduced, and measurement accuracy can be improved.

[0012] 2. Digital multichannel performs time and amplitude analysis during the digital shaping and sampling of nuclear pulses. It uses second-order differential filtering and trapezoidal filtering to reduce errors caused by potential fluctuations in the nuclear pulse baseline, thereby improving the accuracy and reliability of data measurement.

[0013] 3. Digital multi-channel sampling and control parameters can be adjusted externally to match the waveform characteristics of the detector signal. At the same time, the dual buffering mechanism allows the buffering of pulse waveforms, the external transmission of pulse waveform data, and the processing of data by the processor to be carried out in parallel, thereby maximizing the system throughput and reducing the processor utilization. Attached Figure Description

[0014] Figure 1 This is a block diagram of the aerosol monitoring system of this utility model.

[0015] Figure 2 This is a schematic diagram of the nuclear pulse digital shaping and sampling module of this utility model.

[0016] Figure 3 This is a schematic diagram of the core pulse waveform acquisition module in this utility model.

[0017] Figure 4 This is a schematic diagram of the nuclear pulse generation module in this utility model. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0019] like Figure 1 As shown, the aerosol monitor in this embodiment consists of a sampling circuit, an aerosol detector, a signal processing unit, and a digital multichannel system. The sampling circuit extracts gas from the environment under test, filters out radioactive aerosol particles, and the aerosol detector, positioned directly opposite the filter paper, detects the α and β particles emitted by the accumulated aerosols on the filter paper, generating nuclear pulse signals. These signals are then sent to the digital multichannel system for energy spectrum data processing, which is then used by the back-end signal processing unit to calculate the radioactivity concentration value. The digital multichannel system comprises a high-speed ADC, a pulse waveform acquisition module, a nuclear pulse digital shaping and sampling module, a nuclear pulse generation module, a high-speed DAC, a memory, and peripherals. The pulse waveform acquisition module acquires the nuclear pulses generated by the high-speed ADC acquisition detector and stores them in the memory for data analysis. The nuclear pulse digitization and shaping sampling module obtains the peak energy information of the nuclear pulse waveform generated by the high-speed ADC acquisition detector through a second-order differential filter, a trapezoidal filter, and baseline subtraction, and stores it in the memory. The nuclear pulse generation module sends the energy spectrum data of the nuclear pulse waveform stored in the memory to the back-end signal processing unit through an amplitude controller, a time and amplitude scanning module, and an output control module.

[0020] As shown in Figure 2 The nuclear pulse digital shaping sampling module includes a second-order differential filter, a trapezoidal filter, a threshold comparator, a baseline deduction module, and a peak extraction module. The exponentially decaying signal output by the high-speed ADC circuit is sent to the second-order differential filter and the trapezoidal filter for processing. The second-order differential filter performs second-order differential processing on the input signal, and the amplitude of the signal is compared with a specific threshold value through the threshold comparator. When the amplitude of the signal is greater than the threshold value, the zero-crossing detection module is enabled. When the zero-crossing detection module is enabled, it performs zero-crossing detection on the output signal of the second-order differential filter and generates a trigger signal at the zero-crossing point. The trapezoidal filter converts the input exponential pulse signal into a trapezoidal signal. To eliminate the influence of baseline drift, the baseline value is estimated and deducted. The peak extraction module performs peak sampling on the trapezoidal signal after the baseline is filtered out. The sampling point of the peak sampling is the delay of the trigger output by the zero-crossing detection module. The delay time can be set through software, so that it is at the midpoint of the flat top region of the trapezoidal signal. The peak energy information obtained by sampling is stored in the internal memory of the FPGA.

[0021] As shown in Figure 3 The nuclear pulse waveform acquisition module includes a trigger control module, a redundant data buffer area, and a buffer controller. The trigger control module can start the acquisition of a frame of pulse waveform through an external trigger signal. The external trigger signal can be triggered by software or by the zero-crossing detection in the nuclear pulse digital shaping sampling module. The pulse waveform buffering method uses a double-buffering mechanism, that is, the trigger control module alternately writes pulse waveform data into two buffer areas. When one buffer completes the storage of a frame of waveform data, the nuclear pulse waveform acquisition module sends an interrupt request to the processor. At this time, the processor starts the DMA controller to transfer the pulse waveform data from the buffer area inside the nuclear pulse waveform acquisition module to the external interface controller and to the signal processing unit. The entire transmission process is completed by the DMA controller without the intervention of the CPU. In addition, if a new external trigger occurs during the transmission process, the trigger controller will cache the pulse waveform data to the other buffer. This double-buffering mechanism allows the caching of pulse waveform, the external transmission of pulse waveform data, and the processing of data by the processor to be performed in parallel, thereby maximizing the throughput of the system and reducing the processor occupancy.

[0022] As shown in Figure 4As shown, the nuclear pulse generation module mainly comprises a memory, an amplitude controller, a time and amplitude scanning module and an output control module. The memory is used for storing the nuclear pulse waveform written by the processor; the amplitude controller is used for adjusting the nuclear pulse amplitude scale size, and the adjustment parameter can be set through the processor; the time and amplitude scanning module reads the pulse waveform in the memory at a certain time frequency, and outputs to the output control module at a certain amplitude scale. The output control module finally outputs the pulse waveform to the DAC in a level protocol compatible with the external DAC.

[0023] The contents not described in detail in the specification belong to the prior art known to those skilled in the art.

[0024] Those skilled in the art can easily understand that the above only describes the preferred embodiments of the present application, and is not intended to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A digital multi-channel based continuous monitoring instrument for radioactive aerosols, comprising an aerosol detector, a preamplifier, an automatic paper feeding mechanism, a digital multi-channel, a signal processing unit, a pumping unit and a sampling loop, characterized in that: The sampling circuit extracts gas from the environment to be measured, filters and accumulates radioactive aerosol particles through a filter, detects alpha and beta particles emitted by the accumulated aerosol on the filter paper through an aerosol detector opposite the filter paper, forms nuclear pulse signals, and sends the signals to a digital multichannel for energy spectrum data processing, and then sends the signals to a backend signal processing unit for calculation of radioactivity concentration value. ​ 2. The digital multichannel based continuous monitoring of radioactive aerosols according to claim 1, characterized in that: The nuclear pulse digital shaping sampling module includes a second-order difference filter, a trapezoidal filter, a threshold comparator, a baseline deduction module, and a peak extraction module. The exponential decay signal output by the high-speed ADC circuit is sent to the second-order difference filter and the trapezoidal filter for processing. The second-order difference filter performs second-order difference processing on the input signal, compares the amplitude with a specific threshold value through the threshold comparator, and enables the zero-crossing detection module when the amplitude is greater than the threshold value. When the zero-crossing detection module is enabled, the output signal of the second-order difference filter is subjected to zero-crossing detection, and a trigger signal is generated at the zero-crossing point. The trapezoidal filter converts the input exponential pulse signal into a trapezoidal signal. To eliminate the influence of baseline drift, the baseline is deducted by an estimated baseline value. The peak extraction module samples the peak value of the trapezoidal signal after filtering the baseline. The sampling point of the peak value is the delay of the trigger output by the zero-crossing detection module. The delay time can be set through software, so that the midpoint of the flat top region of the trapezoidal signal is reached. The peak energy information obtained by sampling is stored in the internal memory of the FPGA.

3. The digital multichannel based continuous radon aerosol monitor according to claim 1, characterized in that: The nuclear pulse waveform acquisition module comprises a trigger control module, a redundant data buffer area and a buffer controller, a frame of pulse waveform is started to be acquired through an external trigger signal, the external trigger signal can be triggered through software or through zero detection in the nuclear pulse digital shaping sampling module, the pulse waveform buffer method adopts a double buffer mechanism, that is, the trigger control module writes pulse waveform data into two buffer areas alternately, when one buffer completes storage of a frame of waveform data, the nuclear pulse waveform acquisition module sends an interrupt request to the processor, at this time the processor starts the DMA controller to transmit the pulse waveform data from the buffer area inside the nuclear pulse waveform acquisition module to the external interface controller and to the signal processing unit, the whole transmission process is completed by the DMA controller, in addition, if a new external trigger is generated during the transmission process, the trigger controller will cache the pulse waveform data to another buffer.

4. The digital multichannel based continuous radon aerosol monitor according to claim 1, characterized in that: The nuclear pulse generation module comprises a memory, an amplitude controller, a time and amplitude scanning module and an output control module, the memory is used to store the nuclear pulse waveform written by the processor, the amplitude controller is used to adjust the nuclear pulse amplitude scale, the adjustment parameter can be set through the processor, the time and amplitude scanning module reads the pulse waveform in the memory at a certain time frequency and outputs to the output control module at a certain amplitude scale, the output control module finally outputs the pulse waveform to the DAC in a level protocol compatible with the external DAC.

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