A spatial neutron detection energy discrimination device and method

Abstract

The application provides a space neutron detection energy discrimination device and method, and belongs to the technical field of neutron detection.The application comprises a plastic scintillator, a photomultiplier tube, a first charge measurement chip, a second charge measurement chip, a first operational amplifier and analog-to-digital conversion chip, a second operational amplifier and analog-to-digital conversion chip and an FPGA chip; the plastic scintillator interacts with incident neutrons to generate neutron scattered fluorescence and neutron capture fluorescence; the neutron scattered fluorescence and the neutron capture fluorescence are amplified and converted by the photomultiplier tube to form a neutron signal; the first charge measurement chip and the second charge measurement chip are used for collecting the neutron signal; the collected neutron signal is transmitted to the FPGA chip after being processed by the first operational amplifier and analog-to-digital conversion chip and the second operational amplifier and analog-to-digital conversion chip.The application reduces overall power consumption and mass, is simple in process, safe and reliable, has strong environmental adaptability, and is very suitable for deep space exploration tasks limited in mass and function.

Description

Technical Field

[0001] This invention belongs to the field of neutron detection technology, specifically relating to a space neutron detection energy identification device and method. Background Technology

[0002] Space environment neutron detection technology is of great significance for space radiation protection and the search for water resources on planetary surfaces. Existing space environment neutron detection technologies often rely on helium-3 proportional counters or complex readout electronics, which place high demands on the weight, power consumption, and manufacturing process of the detectors, making them unsuitable for deep space exploration applications with significant technological limitations. Summary of the Invention

[0003] This invention addresses the shortcomings of existing technologies by providing a space neutron detection energy identification device and method. By using a boron-doped plastic scintillator and a photomultiplier tube as detection units, coupled with two charge measurement chips, an operational amplifier, and an analog-to-digital converter chip, and employing parallel acquisition and pulse interval measurement methods, this invention achieves neutron detection and energy measurement functions in the space environment.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] In a first aspect, the present invention provides a space neutron detection energy identification device, comprising: a plastic scintillator, a photomultiplier tube, a first charge measurement chip, a second charge measurement chip, a first operational amplifier and analog-to-digital converter chip, a second operational amplifier and analog-to-digital converter chip, and an FPGA chip; the plastic scintillator interacts with incident neutrons, and the generated neutron dispersion fluorescence and neutron capture fluorescence are amplified and converted by the photomultiplier tube to form a neutron signal; the first charge measurement chip and the second charge measurement chip are used to collect the neutron signal, and the collected neutron signal is processed by the first operational amplifier and analog-to-digital converter chip and the second operational amplifier and analog-to-digital converter chip respectively and then transmitted to the FPGA chip.

[0006] Optionally, the plastic scintillator is a boron-doped plastic scintillator of model EJ254.

[0007] Optionally, the photomultiplier tube is an R3886A phototube.

[0008] Optionally, the first charge measurement chip and the second charge measurement chip are IDE3381 chips.

[0009] Optionally, it also includes a high-voltage power supply module, wherein the FPGA chip controls the high-voltage power supply module to provide voltage to the photomultiplier tube.

[0010] In a second aspect, the present invention provides a method for identifying the energy of a space neutron detector, employing the space neutron detector energy identification device as described in the first aspect, comprising the following steps:

[0011] The first charge measurement chip receives a neutron signal and generates a trigger. The FPGA chip receives the trigger signal from the first charge measurement chip and controls the second charge measurement chip to detect subsequent neutron signals.

[0012] If the second charge measurement chip receives a neutron signal within a set time t1, it is considered that the neutron signal cannot be distinguished from the neutron signal received by the first charge measurement chip, the acquisition operation of the two charge measurement chips is terminated, and the two charge measurement chips are recharged to the initial state and wait for a neutron signal again.

[0013] If the second charge measurement chip does not receive a neutron signal within the set time t1, the amplitude of the neutron signal received by the first charge measurement chip is detected as follows:

[0014] ① If the amplitude exceeds the preset threshold, the neutron signal received by the first charge measurement chip is considered to be incorrect. The acquisition operation of the two charge measurement chips is terminated, and the two charge measurement chips are recharged to the initial state and wait for the neutron signal again.

[0015] ② If the amplitude does not exceed the preset threshold, and the second charge measurement chip receives a neutron signal and triggers within the set time t2, then the dual-pulse acquisition process is entered. The FPGA chip controls the first operational amplifier and analog-to-digital converter chip corresponding to the first charge measurement chip to acquire the neutron dispersion signal, and controls the second operational amplifier and analog-to-digital converter chip corresponding to the second charge measurement chip to acquire the neutron capture signal. If the second charge measurement chip does not receive a neutron signal within the set time t2, then the single-pulse acquisition process is entered. The FPGA chip only controls the first operational amplifier and analog-to-digital converter chip corresponding to the first charge measurement chip to acquire the neutron capture signal.

[0016] Optionally, after all acquisition processes are completed, the FPGA chip controls the two charge measurement chips to wait for a set time t3 before re-entering the observation mode to wait for new neutron signals.

[0017] Optionally, after all acquisition processes are completed, the acquired data is recorded in the internal memory according to time information, and the acquired data is summarized into an energy spectrum according to numerical information.

[0018] Optionally, the set time t1 is 400 ns, t2 is 5 μs, and t3 is at least 25.6 μs.

[0019] Optionally, the preset threshold is 2.5 MeV.

[0020] The beneficial effects of this invention are as follows: This invention utilizes the different proportions of elastic scattering and nuclear reactions between neutrons of different energies and detector materials, creatively employing multiple charge measurement chips to collect photoelectric signals from different reaction outputs in parallel. By utilizing the differences in signal intervals and amplitudes, neutron energy can be identified. The advantages of this invention are: 1. It avoids the use of complex detector materials, using only boron-doped plastic scintillators, which are adaptable to the space detector application environment, avoiding complex shockproof and thermal control requirements; 2. It avoids the use of complex electronic readout systems for signal waveform discrimination, reducing system power consumption and weight, and improving system reliability; 3. By comparing signals at different time intervals, accidental coincidences can be effectively screened out during energy spectrum accumulation, improving the accuracy of neutron identification. To meet the scientific needs of space neutron detection, this invention achieves up to 8-channel neutron signal measurement functions, enabling independent and correlation detection of 8 channels, satisfying scientific research requirements. Compared to traditional neutron measurement schemes, the device of this invention has lower overall power consumption and weight, simpler manufacturing process, greater safety and reliability, and stronger environmental adaptability, making it highly suitable for deep space exploration missions with limited mass and functionality. Attached Figure Description

[0021] Figure 1 This is a structural diagram of a space neutron detection energy identification device.

[0022] Figure 2 This is the timing diagram of the charge measurement chip.

[0023] Figure 3 Control system workflow diagram. Detailed Implementation

[0024] The invention will now be described in further detail with reference to the accompanying drawings.

[0025] Example 1

[0026] This embodiment proposes a space neutron detection energy identification device, the structure of which is shown in the attached diagram. Figure 1 It consists of four parts: a plastic scintillator, a photomultiplier tube, two charge measurement chips and corresponding operational amplifiers and analog-to-digital converter chips, an FPGA chip (acquisition and control system), and a data transmission circuit. The functions of each part are as follows:

[0027] The plastic scintillator is EJ254, manufactured by EJ Company in the United States. This plastic scintillator has a boron doping ratio of 5% by mass. 10 The boron isotope content is 1% of the crystal mass, and the operating temperature range is -60℃ to +60℃. Slow neutrons can react with the scintillator... 10The boron isotope undergoes a capture reaction, depositing the full 2.34 MeV energy. Fast neutrons can be moderated by the plastic scintillator and undergo a capture reaction after an average of approximately 2.7 μs. In this device, for 2.5 MeV fast neutrons, the volume of the plastic scintillator should not be less than a 50 mm * 50 mm * 50 mm cube; otherwise, the fast neutron moderation efficiency will be significantly reduced.

[0028] The photomultiplier tube is a 1.5-inch tube manufactured by Hamamatsu Corporation of Japan, model R3886A. This phototube operates at 1250V, with an operating temperature range of -30℃ to +50℃, and can withstand 100g of impact and 20g of random vibration. It converts fluorescent photons emitted by a plastic scintillator into electronic signals, which are then used for readout acquisition by subsequent charge measurement chips and peripheral circuits. The phototube has a sensitive wavelength of 420nm, matching the emission wavelength of the selected plastic scintillator, EJ454. The phototube size should not be less than half the length of the light-emitting surface of the plastic scintillator; otherwise, significant light reception loss will occur.

[0029] The charge measurement chip uses the IDE3381 chip manufactured by IDEAS, Norway. This chip features 16 channels of phototube or photodiode input and independent processing capabilities, with a minimum signal triggering time of 50ns and a signal shaping capability of 50ns. The chip can accept either positive or negative charge signals and can adapt to different operating modes, such as dual output with anode capacitor distribution or dual output with anode electrode bonding. (See attached...) Figure 2 As shown, during parallel operation, since the neutron dispersion signal appears first, followed by the neutron capture signal within a 0-5µs timeframe, the first charge measurement chip responsible for neutron dispersion signal processing should directly convert the first input signal and send a trigger signal to the control system. The second charge measurement chip responsible for neutron capture signal processing does not process the first input signal until the control system receives a trigger signal from the neutron dispersion signal and notifies the second charge measurement chip responsible for capture signal conversion to begin waiting for the neutron capture signal. Subsequent neutron signals are then treated as neutron capture signals and converted by the second charge measurement chip responsible for neutron capture signal processing. If no neutron capture signal is received within 5µs, it is considered that the first charge measurement chip responsible for neutron dispersion signal processing has acquired the neutron capture signal. This embodiment achieves the simultaneous processing and acquisition of neutron dispersion and neutron capture signals by using two chips in parallel.

[0030] The operational amplifier (op-amp) and analog-to-digital converter (ADC) chips amplify and convert the signal output from the charge measurement chip into a digital signal for subsequent data storage and transmission. The op-amp and ADC chips are directly controlled by the acquisition system, with the acquisition circuit triggered by the corresponding charge measurement chip trigger signal. When the acquisition system receives a trigger signal from the first charge measurement chip, it controls the corresponding op-amp and ADC chips to perform signal conversion; similarly, when the acquisition system receives a trigger signal from the second charge measurement chip, it controls the corresponding op-amp and ADC chips to perform signal conversion. (See attached...) Figure 2 The analog-to-digital conversion circuit operates for approximately 4 µs. During this period, the corresponding charge measurement chip cannot function and process new neutron signals.

[0031] Programmable logic chips (FPGAs) are responsible for controlling various parts of the entire system, such as high-voltage power supplies, charge measurement chips, and analog-to-digital converters, and are also responsible for the external interfaces of the entire system.

[0032] When a neutron enters the plastic scintillator of the detector, it interacts with the scintillator to produce neutron dispersion or neutron capture fluorescence. After the fluorescence is generated, it is amplified and converted by a photomultiplier tube to form an electrical signal, which enters the charge measurement chip. Two charge measurement chips process the neutron dispersion signal and the neutron capture signal respectively to identify the energy of the incident neutron. Subsequent operational amplifiers, analog-to-digital converters, and FPGA chips realize the acquisition, storage, and transmission of the signal to the actual user.

[0033] Example 2

[0034] Based on the space neutron detection energy identification device proposed in the embodiments, this embodiment further proposes a space neutron detection energy identification method. The FPGA chip responsible for acquisition and control needs to be based on the attached... Figure 3 The control logic is as follows:

[0035] 1. When the acquisition system receives a trigger signal from the first charge measurement chip, the control system begins to control the second charge measurement chip to detect the subsequent neutron signal.

[0036] 2. If the second charge measurement chip receives a neutron signal and triggers within 400ns, it is considered that the signal cannot be distinguished from the first signal. At this time, all processing and acquisition operations should be terminated, the invalid data counter should be incremented by 1, and both charge measurement chips should be recharged to the initial state and wait for the neutron signal again.

[0037] 3. If the second charge measurement chip does not receive a neutron signal and trigger within 400ns, the signal amplitude of the first charge measurement chip will be detected. If the amplitude exceeds the threshold of 2.5MeV, the first signal is considered not to be a neutron signal. At this time, all processing and acquisition operations should be terminated, the large signal counter should be incremented by 1, and both charge measurement chips should be recharged to the initial state to wait for a neutron signal again.

[0038] 4. If the signal from the first chip does not exceed the limit, and the second charge measurement chip receives a neutron signal and triggers within 5µs, then the dual-pulse acquisition process begins. The neutron dispersion signal is acquired by the operational amplifier and analog-to-digital converter chip corresponding to the first charge measurement chip, and the neutron capture signal is acquired by the operational amplifier and analog-to-digital converter chip corresponding to the second charge measurement chip.

[0039] 5. If the second charge measurement chip does not receive a neutron signal and trigger within 5µs, the single-pulse acquisition process begins. The acquisition system only controls the operational amplifier and analog-to-digital converter chip corresponding to the first charge measurement chip to acquire the neutron capture signal.

[0040] 6. Regardless of which acquisition process is completed, the acquisition control system should control the two charge measurement chips to wait for 25.6 μs before re-entering the observation mode to wait for a new neutron signal.

[0041] After the data acquisition and control system completes the above process, it can record the acquired data in the internal memory according to the time information, and simultaneously summarize the acquired data into an energy spectrum according to the numerical information. When an external data request is sent, the recorded event information and energy spectrum data are sent to the external user.

[0042] To improve fast neutron discrimination capability and reduce the rate of random coincidence events mixed into the system, the acquisition and control system, in addition to acquiring dual-signal events within the range of 400 ns to 5 μs, also acquires dual-signal events within the range of 20 μs to 25.6 μs. By subtracting the dual-signal events within the range of 20 μs to 25.6 μs from the dual-signal events within the range of 400 ns to 5 μs when summarizing the energy spectrum events, the fast neutron discrimination capability can be effectively improved.

[0043] This embodiment uses a boron-doped plastic scintillator, combined with subsequent dual-pulse identification and acquisition functions in electronics, effectively achieving the identification of different neutron energies and avoiding the need for complex processes in the space environment. 3 He proportional counter or 6The Li glass detector avoids the need for complex, high-power electronics chips for waveform discrimination. It can achieve neutron detection and energy discrimination for eight probes while keeping the total detector mass below 10 kg and total power consumption no more than 5 W. Through simulation and actual calibration tests, it demonstrates a discrimination capability exceeding 81% for 700 keV fast neutrons.

[0044] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for identifying the energy of space neutron detection, wherein the space neutron detection energy identification device comprises a plastic scintillator, a photomultiplier tube, a first charge measurement chip, a second charge measurement chip, a first operational amplifier and analog-to-digital converter chip, a second operational amplifier and analog-to-digital converter chip, and an FPGA chip; the plastic scintillator interacts with incident neutrons, and the generated neutron scattered fluorescence and neutron captured fluorescence are amplified and converted by the photomultiplier tube to form a neutron signal; the first charge measurement chip and the second charge measurement chip are used to collect the neutron signal, and the collected neutron signal is processed by the first operational amplifier and analog-to-digital converter chip and the second operational amplifier and analog-to-digital converter chip respectively before being transmitted to the FPGA chip; Its features are, Includes the following steps: The first charge measurement chip receives a neutron signal and generates a trigger. The FPGA chip receives the trigger signal from the first charge measurement chip and controls the second charge measurement chip to detect subsequent neutron signals. If the second charge measurement chip receives a neutron signal within a set time t1, it is considered that the neutron signal cannot be distinguished from the neutron signal received by the first charge measurement chip, the acquisition operation of the two charge measurement chips is terminated, and the two charge measurement chips are recharged to the initial state and wait for a neutron signal again. If the second charge measurement chip does not receive a neutron signal within the set time t1, the amplitude of the neutron signal received by the first charge measurement chip is detected as follows: ① If the amplitude exceeds the preset threshold, the neutron signal received by the first charge measurement chip is considered to be incorrect. The acquisition operation of the two charge measurement chips is terminated, and the two charge measurement chips are recharged to the initial state and wait for the neutron signal again. ② If the amplitude does not exceed the preset threshold, and the second charge measurement chip receives the neutron signal and triggers within the set time t2, then the dual-pulse acquisition process is entered. The FPGA chip controls the first operational amplifier and analog-to-digital converter chip corresponding to the first charge measurement chip to acquire the neutron dispersion signal, and controls the second operational amplifier and analog-to-digital converter chip corresponding to the second charge measurement chip to acquire the neutron capture signal. If the second charge measurement chip does not receive a neutron signal within the set time t2, the single-pulse acquisition process is entered. The FPGA chip only controls the first operational amplifier and analog-to-digital converter chip corresponding to the first charge measurement chip to acquire the neutron capture signal.

2. The energy identification method for space neutron detection as described in claim 1, characterized in that: The plastic scintillator is a boron-doped plastic scintillator of model EJ254.

3. The energy identification method for space neutron detection as described in claim 1, characterized in that: The photomultiplier tube used is a phototube of model R3886A.

4. The energy identification method for space neutron detection as described in claim 1, characterized in that: The first charge measurement chip and the second charge measurement chip are both IDE3381 chips.

5. The energy identification method for space neutron detection as described in claim 1, characterized in that: It also includes a high-voltage power supply module, through which the FPGA chip controls the high-voltage power supply module to provide voltage to the photomultiplier tube.

6. The energy identification method for space neutron detection as described in claim 1, characterized in that: After all acquisition processes are completed, the FPGA chip controls the two charge measurement chips to wait for a set time t3 before re-entering the observation mode to wait for new neutron signals.

7. The energy identification method for space neutron detection as described in claim 1, characterized in that: After all acquisition processes are completed, the acquired data is recorded in the internal memory according to the time information, and the acquired data is summarized into an energy spectrum according to the numerical information.

8. The energy identification method for space neutron detection as described in claim 1, characterized in that: The set time t1 is 400 ns, t2 is 5 μs, and t3 is at least 25.6 μs.

9. The energy identification method for space neutron detection as described in claim 1, characterized in that: The preset threshold is 2.5 MeV.

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