Near-earth orbit neutron and gamma ray detector group, detection device and detection method

Abstract

The disclosure provides a low-orbit neutron and gamma-ray detector group, a detection device and a detection method. The detection device is a small-volume, small-mass, low-power and high-speed neutron / gamma spectrometer based on a multi-layer single / dual sensitive area Si detector and a cadmium zinc telluride (CZT) detector array. The neutron / gamma spectrometer can be carried on a small satellite as an independent load to measure thermal neutrons, fast neutrons below 20 MeV and gamma rays. The cooperation between different layers of the detector group in the detection device forms multiple anticoincidence groups, improving the accuracy of energy spectrum inversion. The detection method proposes a pile discarding algorithm, thereby avoiding the interference caused by signal overlap and improving the system resolution of the entire neutron / gamma spectrometer.

Description

Technical Field

[0001] This invention relates to the field of radiation detection technology, and in particular to a near-Earth orbit neutron and gamma-ray detector array, detection equipment, and detection method. Background Technology

[0002] The radiation belts near low Earth orbit contain galactic cosmic rays, high-energy solar particles, and various derivative secondary particles, creating an extremely complex radiation environment. Detecting neutrons and gamma rays in low Earth orbit helps to gain a deeper understanding of space science issues, such as space station environmental monitoring, the origin of particles in the low Earth orbit radiation belts, and the physical phenomena related to high-energy solar particles.

[0003] Commonly used detectors for measuring nuclear radiation include gas discharge detectors, scintillator detectors, and semiconductor detectors. Gas discharge detectors have relatively low energy resolution, high operating voltage, and difficulty distinguishing between different energies of radiation, making them unsuitable for spectral detection. Scintillator detectors can detect various types of charged and neutral particles, offering high detection efficiency and good temporal resolution, but suffer from poor spatial resolution and high energy consumption. Semiconductor detectors offer advantages such as low noise, low leakage current, high detection efficiency, and high energy resolution. They exhibit different response characteristics to ionizing radiation and can reflect the dose of radiation in human tissue or water through the conversion coefficient. However, monolithic semiconductor detectors cannot effectively determine LET values ​​and dose equivalents; therefore, silicon-based detectors with telescope structures have been proposed, designed, and widely used. However, silicon-based detectors are typically large and consume significant electrical energy during operation. Summary of the Invention

[0004] To address the aforementioned issues, this invention proposes a near-Earth orbit neutron and gamma-ray detector array, detection equipment, and detection method. The detection equipment is a small-volume, low-mass, low-power, high-speed neutron / gamma-ray spectrometer designed based on a multi-layered single / dual-sensitive region Si detector and a cadmium zinc telluride (CZT) detector array. The neutron / gamma-ray spectrometer can be carried as an independent payload on a small satellite to measure thermal neutrons, fast neutrons below 20 MeV, and gamma rays. The coordination between different layers of the detector array forms multiple anti-coincidence sets, improving the accuracy of energy spectrum inversion. The detection method proposes a stacking-drop algorithm to avoid interference caused by signal overlap, thereby improving the overall system resolution of the neutron / gamma-ray spectrometer.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a near-Earth orbit neutron and gamma-ray detector array, comprising 15 detectors stacked sequentially, specifically including:

[0007] The first and fifteenth detectors are single-sensitivity CZT detectors used to detect gamma rays;

[0008] The second detector is a single-sensitive-area Si detector, used to identify the direction of particle injection.

[0009] The third, fourth, and fifth detectors constitute the first anti-coincidence detection group, which consists of two single-sensitive region Si detectors and a first dual-sensitive region Si detector with a LiF coating in between. The twelfth, thirteenth, and fourteenth detectors have the same structure as the first anti-coincidence detection group, and are also wrapped with a Gd layer to form the second anti-coincidence detection group. Both the first and second anti-coincidence detection groups are used to detect thermal neutrons.

[0010] The fifth, sixth, seventh, and eighth detectors constitute the third anti-coincidence detection group, which consists of a single-sensitive region Si detector, a second dual-sensitive region Si detector, a first dual-sensitive region Si detector, and a single-sensitive region Si detector, respectively. The eighth, ninth, tenth, and eleventh detectors constitute the fourth anti-coincidence detection group, which consists of a single-sensitive region Si detector, a first dual-sensitive region Si detector with an HDPE coating, a second dual-sensitive region Si detector, and a single-sensitive region Si detector, respectively. The fifth to eleventh detectors are used to detect fast neutrons.

[0011] Preferably, the sensitive layer of the single-sensitive region CZT detector has a side length of 35 mm and a nominal thickness of 5 mm;

[0012] The sensitive layer of the single-sensitive region Si detector has a side length of 35 mm and a nominal thickness of 650 μm.

[0013] The outer sensitive layer of the first dual-sensitive region Si detector has a side length of 35 mm, the inner sensitive region has a side length of 25 mm, and the thickness is nominally 300 μm.

[0014] The outer sensitive layer of the second dual-sensitive region Si detector has a side length of 35 mm, the inner sensitive region has a side length of 25 mm, and the thickness is nominally 650 μm.

[0015] Preferably, the anti-coincidence detector group is used to remove interference from charged particles.

[0016] Preferably, the fourth detector containing the LiF coating is used to record the count of signals generated by the reaction of neutrons with LiF in all energy ranges;

[0017] The Gd layer of the second anti-coincidence detector group is used to absorb thermal neutrons, and the thirteenth detector is used to record the count of signals generated by the reaction of neutrons other than thermal neutrons with LiF.

[0018] The thermal neutron flux in orbit is obtained by dividing the count difference between the fourth and thirteenth detectors by the detection efficiency.

[0019] Preferably, the sixth and seventh detectors are used to detect signals generated by galactic cosmic rays or other secondary neutrons;

[0020] The ninth and tenth detectors are used to detect the recoil proton signal generated by neutrons in near-Earth orbit passing through the high-density polyethylene conversion layer.

[0021] Under anti-coincidence conditions, the energy spectrum of the recoil proton is obtained by subtracting the total energy spectra of the ninth and tenth detectors from that of the sixth and seventh detectors.

[0022] In a second aspect, the present invention provides a near-Earth orbit neutron and gamma ray detection device, comprising a rectangular outer shell, a front end plate, a data acquisition plate, and a near-Earth orbit neutron and gamma ray detector assembly as described in the first aspect.

[0023] The data acquisition board is communicatively connected to the detector group and the front-end board, and is used to provide analog and digital power; it includes an FPGA chip, a level conversion chip, a CAN chip, an eMMC, a gigabit Ethernet PHY chip, a universal asynchronous transceiver chip, and an ADC chip.

[0024] The front-end board is communicatively connected to the detector group and includes a preamplifier circuit composed of an ASIC chip and discrete components; the ASIC chip is used to collect neutrons, and the preamplifier circuit is used to collect gamma rays; the front-end board is used to receive particle signals transmitted by the detector group and convert them into voltage pulses.

[0025] The housing includes multiple mounting holes for securing it to a load.

[0026] Preferably, multiple fixed supports are provided inside the outer casing to connect to each side, in order to ensure the stability of the detection equipment.

[0027] Thirdly, the present invention provides a method for detecting neutrons and gamma rays in near-Earth orbit, based on the near-Earth orbit neutron and gamma ray detection device described in the second aspect, comprising:

[0028] After the detection device is powered on, the data acquisition board is initialized;

[0029] Once configured, the system enters acquisition mode and begins acquisition. The ADC internally converts the acquired random voltage pulses, and the resulting digital signal is cached in the DDR along with the corresponding trigger time. Then, a signal accumulation and discard algorithm is used to determine if there are any accumulated signals. If there are accumulated signals, they will be labeled with different frame formats and stored in the EMMC. If an upload command is received from the CAN interface, the data stored in the EMMC will be uploaded to the satellite via Ethernet. The satellite host will upload the data when it lands at the ground station.

[0030] Preferably, the initialization of the data acquisition board further includes: detecting whether the peripheral circuit is normal; if no configuration signal is received from the satellite or the configuration is abnormal, relevant telemetry data will be sent to the satellite.

[0031] Preferably, the stacking and discarding algorithm is as follows:

[0032] The rise time of a single-particle pulse is It is in the nanosecond range, and the molding time is... When set to 10 µs, the fast amplifier output pulse, after passing through the fast discriminator, will generate a pulse with a width of [value missing]. rectangular wave, The rise time of a single-particle pulse is less than 1. When two consecutive particles enter the detector, causing signal buildup, two signals with a width of [missing information] will be generated at the fast discriminator output, i.e., the TF pin of the CPRE10-32. A rectangular wave, when the spacing between two rectangular waves... Less than the total molding time When signal accumulation is detected, the accumulated signals are stored in the EMMC in different frame formats to achieve the function of discarding accumulated signals.

[0033] Compared with the prior art, the beneficial effects of this disclosure are as follows:

[0034] To address the issues of large size, high power consumption, low resolution, and inability to achieve high throughput in current spectrometers using scintillator detectors, this application proposes a small-volume, low-mass, low-power, and high-speed neutron / gamma spectrometer based on a single / dual sensitive region Si detector and a cadmium zinc zinc telluride (CdZnTe, CZT) detector array. The neutron / gamma spectrometer is intended to be carried as an independent payload on a small satellite.

[0035] Simultaneously, a stacking and discarding algorithm was proposed, and an FPGA program was designed to meet the configuration, readout timing, data processing, storage, and interface requirements of the CPCE10-32. Finally, to verify the design goals of the neutron / gamma spectrometer, its basic performance was tested, including its operation at a standard radiation source. , , The energy spectrum under irradiation was analyzed, and a host computer interface was designed to observe the changes in the energy spectrum in real time and compare them with the simulation results of Geant4.

[0036] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0037] The accompanying drawings, which form part of this disclosure, are used to provide a further understanding of this disclosure. The illustrative embodiments of this disclosure and their descriptions are used to explain this disclosure and do not constitute a limitation thereof.

[0038] Figure 1 The following are the detector package dimensions provided in Embodiment 1 of this disclosure: (a) is the package dimension of a single-sensitive area detector; (b) is the package dimension of a dual-sensitive area detector.

[0039] Figure 2 This is a schematic diagram of a basic anti-coincidence detector arrangement provided in Embodiment 1 of this disclosure;

[0040] Figure 3 This is a schematic diagram of a near-Earth orbit neutron and gamma-ray detector array provided in Embodiment 1 of this disclosure;

[0041] Figure 4 This is a perspective view of the casing of a near-Earth orbit neutron and gamma-ray detection device according to Embodiment 2 of this disclosure;

[0042] Figure 5 This is a single-channel logic block diagram of the CPRE10-32 chip provided in Embodiment 2 of this disclosure;

[0043] Figure 6 This is a hardware structure diagram of a near-Earth orbit neutron and gamma-ray detection device provided in Embodiment 2 of this disclosure;

[0044] Figure 7 This is a method for detecting neutrons and gamma rays in near-Earth orbit provided in Embodiment 3 of the present disclosure;

[0045] Figure 8 This is a schematic diagram of the stacking and discarding algorithm provided in Embodiment 3 of this disclosure;

[0046] Figure 9 This is a flowchart of the stacking and discarding algorithm provided in Embodiment 3 of this disclosure;

[0047] Figure 10 The energy spectrum obtained by irradiating a 35 mm diameter Si detector with an α source is provided in an embodiment of this disclosure;

[0048] Figure 11The host functional spectrum of the Si detector being tested is provided in the embodiments of this disclosure;

[0049] Figure 12 The system energy resolution of the Si detector irradiated by the radiation source provided in the embodiments of this disclosure;

[0050] Figure 13 Provided for the embodiments of this disclosure The energy spectrum irradiated by the CZT detector;

[0051] Figure 14 Provided for the embodiments of this disclosure System energy resolution for irradiating the CZT detector;

[0052] Figure 15 Provided for the embodiments of this disclosure The energy spectrum irradiated by the CZT detector;

[0053] Figure 16 Tests provided for embodiments of this disclosure Irradiate the upper-level functional spectrum of the CZT detector;

[0054] Figure 17 Provided for the embodiments of this disclosure , Neutron / gamma spectrometer calibration curves irradiated with CZT detector;

[0055] Figure 18 Provided for the embodiments of this disclosure Verification diagram by comparing with Geant4 energy spectrum;

[0056] Figure 19 Provided for the embodiments of this disclosure Verification diagram by comparing the energy spectrum with Geant4. Detailed Implementation

[0057] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0058] Example 1

[0059] Si semiconductor detectors have low density, low leakage current, and high energy resolution, making them widely used in particle detection. CZT detectors overcome the thickness limitation of Si detectors through advanced manufacturing processes, and their gamma-ray detection efficiency is typically several times that of Si detectors. Therefore, this embodiment uses a Si detector as the neutron detector in the detector group and a CZT detector as the gamma-ray detector.

[0060] like Figure 1 As shown, this embodiment designs a single-sensitive area detector and a dual-sensitive area detector to meet the detection requirements. Specifically, it includes:

[0061] A single-sensitive region CZT detector with a sensitive layer side length of 35 mm and a nominal thickness of 5 mm;

[0062] A single-sensitive region Si detector with a sensitive layer side length of 35 mm and a nominal thickness of 650 μm;

[0063] The first dual-sensitivity Si detector has an outer sensitive layer with a side length of 35 mm, an inner sensitive region with a side length of 25 mm, and a nominal thickness of 300 μm.

[0064] The second dual-sensitivity Si detector has an outer sensitive layer with a side length of 35 mm, an inner sensitive region with a side length of 25 mm, and a nominal thickness of 650 μm.

[0065] For neutron detection in space, the radiation environment in which the detector operates is complex, with both charged particles and neutrons present. Therefore, anti-coincidence detectors are needed to remove interference from charged particles. A combination structure of anti-coincidence detectors is shown below. Figure 2 As shown, the upper and lower detectors have larger areas, while the middle detector has a smaller area. The red area represents the neutron conversion layer. Anti-coincidence means that if detectors A or C produce a signal at the same moment, it proves that the signal at that moment is a charged particle, and therefore the signal from detector B at that moment is removed.

[0066] To improve detection efficiency and remove the influence of charged particles, a near-Earth orbit neutron and gamma-ray detector array is formed by arranging the single-sensitive region detector and the dual-sensitive region detector, as well as the anti-coincidence method.

[0067] Considering the varying number of charged particles in different test environments, if the detected radiation environment contains a large number of charged particles, resulting in a signal-to-noise ratio that cannot be maintained for over 90% of the anti-coincidence solid angle range, a single-sensitive region detector design cannot meet the requirements. Therefore, this embodiment employs a dual-sensitive region detector to further increase the range of the anti-coincidence solid angle.

[0068] like Figure 3 As shown, the detector array comprises 13 Si semiconductor detectors in the middle section and 2 CZT detectors on either side, totaling 15 detectors stacked sequentially. The gamma-ray detection section uses 2 detectors, the thermal neutron detection section uses an anti-coincidence detector array consisting of 6 detectors and a Gd shielding layer, and the fast neutron detection section uses 7 detectors to detect thermal neutrons, fast neutrons below 20 MeV, and gamma rays. The specific arrangement is as follows:

[0069] (1) Gamma-ray detection section

[0070] The first and fifteenth detectors are single-sensitivity CZT detectors used to detect gamma rays.

[0071] In this embodiment, the second detector is a single-sensitive-area Si detector, used to identify the direction of particle injection.

[0072] In this embodiment, since neutrons are uncharged and cannot interact with particles in the semiconductor detector, it is necessary to indirectly detect neutrons by detecting secondary particles generated after neutrons interact with atomic nuclei. This embodiment proposes to use the nuclear reaction method to detect neutrons, that is, to add a LiF and HDPE conversion layer to the detector so that neutrons can undergo nuclear reactions with atomic nuclei in the conversion layer.

[0073] (2) Thermal neutron detection section

[0074] The third to fifth detectors constitute the first anti-coincidence detection group. The third and fifth detectors are single-sensitive region Si detectors, and the fourth detector is a neutron conversion layer, specifically a first dual-sensitive region Si detector containing a LiF coating.

[0075] The twelfth to fourteenth detectors constitute the second anti-coincidence detection group. The twelfth and fourteenth detectors are single-sensitive region Si detectors, and the thirteenth detector is a neutron conversion layer, specifically a first dual-sensitive region Si detector containing a LiF coating. Unlike the first anti-coincidence detection group, the twelfth to fourteenth detectors are also wrapped with a Gd shielding layer.

[0076] Both the first and second anticoincidence detector groups are used to detect thermal neutrons.

[0077] In this embodiment, among the six detectors in the first and second anti-coincidence detector groups, the third, fifth, twelfth, and fourteenth detectors have larger areas. As anti-coincidence detectors, they can remove a large amount of charged particle signals through anti-coincidence. Furthermore, a 1 mm thick Gd film is wrapped around the twelfth, thirteenth, and fourteenth detectors to absorb thermal neutrons. Therefore, it possesses… The fourth detector with the coating can detect neutrons across the entire energy range. The counting of signals generated by the reaction occurs, while the thirteenth detector in the second anticoincidence detector group, which is wrapped in Gd, mainly records the signals of neutrons other than thermal neutrons. The count of signals generated by the reaction, and the thermal neutron flux in the orbit, can be obtained by dividing the count difference between the two detectors by the detection efficiency, etc.

[0078] (3) Fast neutron detection section

[0079] The fifth to eighth detectors constitute the third anti-coincidence detection group. The fifth detector is a single-sensitive region Si detector, the sixth detector is a second dual-sensitive region Si detector, the seventh detector is a first dual-sensitive region Si detector, and the eighth detector is a single-sensitive region Si detector.

[0080] The eighth to eleventh detectors constitute the fourth anti-coincidence detection group. The eighth detector is a single-sensitive region Si detector, the ninth detector is a first dual-sensitive region Si detector with HDPE coating, the tenth detector is a second dual-sensitive region Si detector, and the eleventh detector is a single-sensitive region Si detector.

[0081] The third and fourth anti-coincidence detector groups share a single Si detector, while the fifth to eleventh detectors are used to detect fast neutrons.

[0082] In this embodiment, the sixth and seventh detectors can detect signals generated by galactic cosmic rays or other secondary neutrons, while the ninth and tenth detectors can detect recoil proton signals generated by neutrons in near-Earth orbit passing through a high-density polyethylene (HDPE) conversion layer. Therefore, under anti-coincidence conditions, the energy spectrum of the recoil protons can be obtained by subtracting the total energy spectra of the ninth and tenth detectors from those of the sixth and seventh detectors. This symmetrical structure can effectively reduce the influence of background signals on the measurement and improve the accuracy of neutron energy spectrum inversion.

[0083] The near-Earth orbit neutron and gamma-ray detector array provided in this embodiment uses a total of 13 Si detectors and 2 CZT detectors. The Si detectors are used in conjunction with the nuclear reaction method to detect neutrons. LiF and high-density polyethylene are used as neutron conversion layers and the detectors are stacked and arranged. The influence of charged particles can be removed by anti-coincidence. The CZT detectors are used to detect gamma rays with a maximum deposition energy of 1.3 MeV.

[0084] Example 2

[0085] This embodiment provides a near-Earth orbit neutron and gamma-ray detection device, the three-dimensional perspective view of which is shown below. Figure 4 As shown, it includes a rectangular outer shell, a front end plate, a data acquisition plate, and a near-Earth orbit neutron and gamma-ray detector array as described in Embodiment 1.

[0086] In this embodiment, the outer casing measures 93mm × 87mm × 93mm, and the flatness of the mounting surface is 0.1 / 100 mm × 100 mm. The outer casing has four φ3 mounting holes for fixing to the load, forming a Faraday cage with the satellite casing. Fixing brackets connect the sides of the outer casing to provide support and ensure the stability of the detection equipment. All outer casing and fixing brackets are made of aluminum alloy.

[0087] The casing contains two PCBs: the lower one is the front-end board with a preamplifier circuit composed of ASIC and discrete components, and the upper one is the data acquisition board with FPGA, EMMC, ADC, Gigabit Ethernet and various power supplies required.

[0088] The data acquisition board is communicatively connected to the detector group and the front-end board, and is used to provide analog and digital power.

[0089] In this embodiment, the data acquisition board provides the analog and digital power required by the entire system. The data acquisition board uses an FPGA as the core control chip and is equipped with a level conversion chip, a CAN chip, an eMMC, a Gigabit Ethernet PHY chip, a Universal Asynchronous Receiver / Transmitter (UART) chip, and an ADC chip.

[0090] In this embodiment, the ASIC chip on the front-end board is powered by a single 5V power supply, while the FPGA's HR Bank does not support 5V signal input. To achieve a higher dynamic range, the single-ended signal in the ASIC interacts with the FPGA through a level conversion chip. In the communication interface, the CAN protocol is responsible for transmitting commands, the Ethernet interface is used for data transmission, and the UART interface is used for communication with the host computer during testing.

[0091] The front-end board is communicatively connected to the detector group and includes a preamplifier circuit composed of an ASIC chip and discrete components; the ASIC is used to collect neutrons, and the preamplifier circuit is used to collect gamma rays; the front-end board is used to receive particle signals transmitted by the detector group and convert them into voltage pulses.

[0092] Preferably, the ASIC chip used in this embodiment is the CPRE10-32 chip.

[0093] The CPRE10-32 (Charge Pulse Readout Electronics) is a 32-channel general-purpose readout chip designed for pulse signal readout of particle (nuclear) detectors. It features energy and time readout capabilities, low noise, and low power consumption. Equipped with convenient readout control logic, it can easily implement various readout schemes such as sparse, proximity, and full-channel. The chip's native amplification factor is suitable for semiconductor particle detectors without multiplication effects, such as Si-PIN and CZT. By employing a smaller gain within the chip or an external charge distribution structure, it can also be used with detectors that have a certain gain.

[0094] The single-channel logic block diagram of the CPRE10-32 chip is as follows: Figure 5As shown, each channel of the chip includes a charge-sensitive preamplifier, a filter shaping circuit, a peak detection and hold circuit, and a timing circuit. The held energy information is sent to the analog output bus by the readout control logic for the ADC to read; the timing information within the channel is held by the quadrature timing peak hold circuit and sent to the analog bus. This chip is being used for the first time after tape-out in this embodiment.

[0095] By performing functional verification and performance testing on this chip, such as Figure 5 As shown, when a charge signal is input to the chip, it first passes through a charge-sensitive preamplifier, which converts the charge signal into a voltage signal. Then, it passes through a pole-zero cancellation circuit, and a differential amplifier is used to amplify the signal. The amplified signal is then input to the slow-forming and fast-forming circuits. The signal is compared to a configured threshold voltage. For anodic signals, the voltage is greater than the threshold voltage; for cathodic signals, it is less than the threshold voltage. In this case, the comparator outputs a valid signal indicating channel triggering, allowing the signal to be read. Simultaneously, the signal passes through a peak hold circuit, which stores the peak voltage value for later reading. Controlled by a digital signal, the voltage in the peak hold circuit is output to the chip's analog output bus. This voltage signal is then converted from analog to digital by an ADC to obtain the data for this nuclear radiation event signal.

[0096] Figure 5 This demonstrates the signal flow in a single channel. In a multi-channel scenario, it expands the functionality of most circuits. The trigger signals from multiple channels are output via an OR relationship; when the comparator output of one channel is valid, the overall output trigger signal is valid. During multi-channel triggering, the signal peak values ​​of each trigger channel are stored in their respective peak-holding circuits. Controlled by digital signals, these peak values ​​are sequentially output to the analog output bus on the rising edge of each clock signal.

[0097] Since both Si and CZT detectors are semiconductor detectors, the current pulses output by these detectors are extremely short in duration and have very low energy, which can be considered as charge signals. These signals cannot be detected directly, so a very high-gain operational amplifier is required to convert the input charge signal into a voltage pulse.

[0098] In this embodiment, because the CZT detector's gamma-ray detection efficiency is several orders of magnitude higher than that of the Si detector with a neutron conversion layer, under the same energy level and the same number of neutrons and gamma rays, the CZT detector will detect several times, or even tens of times, more neutrons than the Si detector. However, since all channels of the ASIC only output to one set of analog buses, connecting the CZT detector to the ASIC would occupy its bandwidth and reduce neutron detection efficiency. Therefore, the preamplifier provided in Chinese invention patent CN118311640A—"Single-channel signal analysis system and method applicable to multiple radiation detectors"—is used to complete the gamma-ray acquisition.

[0099] The overall architecture of the front-end board and data acquisition board is as follows: Figure 6 As shown, the front-end board and data acquisition board are connected via a flexible flat cable (FCC). The signals on the FFC cable include Low Voltage Differential Signaling (LVDS) signals, power supplies, and single-ended signals. Compared to traditional TTL and CMOS interfaces, LVDS signals utilize differential signal transmission, driven by a 3.5 mA constant current source and returned via a 100 Ω resistor at the termination. Therefore, the signal swing is only 350 mV, while the data rate can reach hundreds of Mbit / s, significantly reducing power consumption during communication. Furthermore, the use of differential signals can greatly reduce common-mode interference. The single-ended signals include the analog output of the amplifier circuit and the analog output of the CPRE10-32 microcontroller, the clock signal configuring the CPRE10-32, and the digital signal for triggering the output.

[0100] In this embodiment, both the front-end board and the data acquisition board have four φ3 mounting holes that are tightly coupled to the outer casing by metal screws.

[0101] The maximum total weight of the near-Earth orbit neutron and gamma-ray detection device provided in this embodiment is 800 g, and the final assembled total weight is 688 g. This embodiment uses a CPRE10-32 chip to read out particle signals from 13 Si detectors. This chip has 32 channels and a peak time of 200 ns. All channels are connected to the single-ended output pin DIRECTOUT of the analog readout bus. The amplifier circuit is used to read out gamma-ray signals from two CZT detectors. An FPGA is used as the core of the data acquisition system to configure the ASIC, readout, and set thresholds for the amplifier circuit. The analog signals read out by the CPRE10-32 and the amplifier circuit are converted into digital signals by a high-speed ADC. The detection device communicates with the satellite host via two CAN channels and a gigabit Ethernet. One CAN channel is the main control line, and the other is a backup. Data from the detection device is uploaded to the satellite host via gigabit Ethernet on the PS side.

[0102] Example 3

[0103] like Figure 7 As shown, this embodiment provides a method for detecting neutrons and gamma rays in near-Earth orbit, based on the detection equipment provided in Embodiment 2. The method includes: after the detection equipment is powered on, it initializes the data acquisition system and checks whether the peripheral circuits are normal. If no configuration signal is received from the satellite or the configuration is abnormal, relevant telemetry data is sent to the satellite. After configuration is complete, it enters the acquisition mode and performs acquisition. The ADC internally converts the acquired random voltage pulses, and the resulting digital signal is cached in the DDR along with the corresponding trigger time. Then, a signal accumulation and discard algorithm is used to determine if there are accumulated signals. If there are accumulated signals, they are marked with different frame formats and stored in the EMMC. If an upload command is received from the CAN interface, the data stored in the EMMC is uploaded to the satellite via Ethernet. The satellite host uploads the data when landing at the ground station.

[0104] In this specific embodiment, after the detection device is powered on, it first initializes each module, including serial port initialization and ADC initialization. When initialization is normal, the device works normally and begins CPRE configuration; when the device malfunctions, the indicator light flashes as a reminder.

[0105] The CPRE single-channel configuration is performed sequentially: channel selection, preamplifier feedback capacitor and resistor selection, main amplifier gain selection, pole-zero phase cancellation function selection, slow shaping time selection, reference voltage selection, fast and slow DAC threshold selection, and fast and slow trigger enable selection.

[0106] Repeat the above process until all 32 channels are configured. Then enable the peak hold function and prepare for signal readout.

[0107] Since the readout signal is an analog signal, it needs to be sampled and converted into a digital readout using an ADC. Because the 32 channels have parallel input and serial output, a FIFO buffer and data splitting are required. After splitting, two operations are performed simultaneously: determining the particle type and distinguishing between accumulation and non-accumulation. When signal accumulation is detected, the data is stored in a different format; otherwise, the data is stored directly. Finally, the data is uploaded to the host computer.

[0108] Because particle signals are random, signal accumulation can occur in the slow-forming output voltage pulses at high count rates. If this accumulated signal is not processed, the system resolution of the neutron / gamma spectrometer will decrease. Therefore, an accumulation discarding algorithm is needed to remove the accumulated signal. A schematic diagram of the accumulation discarding algorithm is shown below. Figure 8 As shown.

[0109] The rise time of a single-particle pulse is Typically in the nanosecond (ns) range, molding time In this embodiment, the value is set to 10µs. After the fast amplifier output pulse passes through the fast discriminator, it will generate a pulse with a width of [value missing]. rectangular wave, The rise time of a single-particle pulse is less than 1. When two consecutive particles enter the detector, causing signal buildup, two signals with a width of [missing information] will be generated at the fast discriminator output, i.e., the TF pin of the CPRE10-32. A rectangular wave, when the spacing between two rectangular waves... Less than the total molding time When signal accumulation is detected, the accumulated signals are stored in the EMMC in different frame formats to achieve the accumulation discarding function. The flowchart of the signal accumulation discarding algorithm is as follows: Figure 9 As shown.

[0110] The shaping time, or time constant (τ), is an important parameter in the filter shaping circuit, which defines the time characteristics of the circuit's response to the input signal.

[0111] Shaping time typically refers to the time required for a circuit to reach 63.2% of its final steady-state value. In physics and engineering, shaping time more specifically describes the exponential response time of a first-order linear dynamic system. For a first-order RC filter, the shaping time τ is determined by the product of the resistance R and the capacitance C, i.e., τ = R × C.

[0112] In nuclear instruments and radiation detectors, filtering and shaping circuits are used to convert the raw signal (typically a fast pulse) output by the detector into a slower signal that is easier to measure and analyze. This slower signal is generally easier to digitize and can reduce the effects of noise, thus improving the signal-to-noise ratio.

[0113] The choice of build time depends on specific application requirements, including signal characteristics, required time resolution, and measurement accuracy. Shorter build times can provide faster response but may sacrifice some signal quality; while longer build times can provide better signal quality but slower response.

[0114] The shaping time is obtained by measuring the time span of the waveform output by the main amplifier using an oscilloscope. As can be seen, the value can be adjusted based on the resistance and capacitance.

[0115] To verify the performance of the detector group and detection equipment provided by the present invention, the detector and the entire system of the neutron / gamma spectrometer were tested using α and γ radiation sources. The α radiation source was used to test the readout performance of the Si detector and ASIC, and the γ radiation source was used to test the readout performance of the CZT detector and the amplifier circuit.

[0116] (1) α-radiation source testing and charged particle energy resolution testing

[0117] To verify the performance of the Si detector and the charged particle energy resolution, an irradiation test was conducted on a neutron / gamma spectrometer using Americium-241. The nuclide symbol for Americium-241 is [symbol missing]. Its half-life is 432.2 years. It is an alpha radiator, and during its decay, it releases three sets of alpha particles, as well as gamma rays and X-rays of a certain energy. The α source generated by the radioactive source irradiates the detector. Because α particle rays cannot penetrate multiple detectors, testing only one detector can yield the results. The energy spectrum is as follows Figure 10 As shown, blue represents the data without the stacking and discarding algorithm, and red represents the energy spectrum after the stacking and discarding control algorithm. (Host computer test) The energy spectrum of the Si detector is shown below. Figure 11 .

[0118] During testing, the measurement system was not evacuated; therefore, the α particles reacted with the air, causing a change in energy. Currently, only... An alpha radiation source cannot be used to calibrate the neutron / gamma spectrometer. This energy spectrum only verifies whether the entire neutron / gamma spectrometer system is functioning correctly. Figure 10 Gaussian fitting was performed on the source data to obtain the relative energy resolution of the entire system. The system energy resolution of a Si detector irradiated by a radioactive source is as follows: Figure 12 As shown, in The system energy resolution under radiation source irradiation is 4.6%.

[0119] (2) Gamma radiation source and gamma ray energy resolution test

[0120] To verify the performance and energy resolution of the CZT (CdZnTe) detector, irradiation tests were conducted on the CZT detector using two nuclides, cesium-137 and cobalt-60. The nuclide symbol for cesium-137 is... Its half-life is 30.17 years. After emitting 512 keV beta rays, it transforms into . It undergoes isomorphic transition decay, with a γ energy of 662 keV. Commonly used for gamma-ray energy resolution testing of systems. The gamma rays produced by the radiation source irradiate the CZT detector, and after processing by the stacking and discarding algorithm, the following can be obtained: The energy spectrum is as follows Figure 13 As shown, the blue data represents the data without the stacking and discarding algorithm, while the red data represents the energy spectrum after the stacking and discarding control algorithm.

[0121] Will Figure 13 The processed data is then fitted with a Gaussian scheme to obtain the relative energy resolution of the entire system. The system energy resolution of a CZT detector irradiated by a radioactive source is as follows: Figure 14 As shown: The system energy resolution is 2.8% under radiation source irradiation.

[0122] To calibrate the system, the CZT detector was irradiated with cobalt-60. The nuclide symbol for cobalt-60 is... Its half-life is 5.27 years. Similarly, β decay produces gamma rays with energies of 1173 keV and 1333 keV. (Using...) The gamma rays produced by the radiation source irradiate the CZT detector, and after processing by the stacking and discarding algorithm, the following can be obtained: The energy spectrum is as follows Figure 15 As shown, blue represents the data without the stacking and discarding algorithm, and red represents the energy spectrum after the stacking and discarding control algorithm. The energy spectrum of the CZT detector irradiated by the host computer is shown in the figure. Figure 16 .

[0123] (3) Spectrometer calibration and Geant4 energy spectrum verification

[0124] The above (1) and (2) have been tested using a neutron / gamma spectrometer with two different gamma nuclides, namely (1) and (2). , The gamma-ray calibration was performed based on the three full-energy peaks of the radioactive source: 662 keV, 1173 keV, and 1333 keV. , Neutron / gamma spectrometer calibration curves irradiated with the CZT detector are as follows: Figure 17 As shown.

[0125] After normalizing the data obtained from the Geant4 simulation, it was compared and verified with the energy spectrum measured by the neutron / gamma spectrometer. Geant4 simulated... , Energy spectra of the two nuclides. The comparison and verification diagram with the Geant4 energy spectrum is shown below. Figure 18 As shown.

[0126] Depend on Figure 18 It can be seen that the neutron / gamma spectrometer detected 137 C S The positions of the full-energy peak and the Compton plateau remained consistent. Similarly, the peaks measured by the neutron / gamma spectrometer... 60 The Co spectrum was compared and verified with the spectrum simulated by Geant4. 60 The comparison and verification graph of the energy spectra of Co and Geant4 is shown below. Figure 19 As shown.

[0127] Depend on Figure 19 It can be seen that the neutron / gamma spectrometer detected The positions of the full-energy peak and the Compton plateau remain consistent. This indicates that the neutron / gamma spectrometer is functioning normally and the stacking and discarding algorithm is working well, meeting design expectations.

[0128] This invention tested the basic performance, power consumption, interface functions, and energy resolution of the α and γ radiation sources of the first neutron / γ spectrometer. Finally, the information read... , The energy spectrum was compared and verified with that simulated by Geant4 software. The main purpose was to verify whether the frequency performance, baseline, linearity, count rate, and energy resolution of the ASIC chip CPRE10-32 and the amplifier circuit met the design expectations. The ASIC achieved a count rate greater than 60 kHz with a detection efficiency greater than 95%, and a linearity greater than 0.998 in the system's linear region. The amplifier circuit achieved a count rate greater than 100 kHz with a detection efficiency greater than 98%, and a linearity greater than 0.999. After applying the stacking-dropout algorithm... The system energy resolution of the Si detector irradiated by the radiation source was improved from 7.8% to 4.6%. The system energy resolution under CZT detector irradiation with a radioactive source was improved from 4.8% to 2.8%. The interface and storage functions of the neutron / gamma spectrometer were tested. Simultaneously, Geant4 software was used to... , The simulation results were normalized and compared with the tested energy spectrum. The comparison showed that the position of the full-energy peak and the energy and position of the Compton platform were consistent with the simulation results. This invention tested the communication speed of the CAN interface and Gigabit Ethernet, and tested the read / write speed of the EMMC memory in the neutron / gamma spectrometer. All tests met the design expectations.

[0129] The steps or modules involved in Embodiments 2 and 3 above correspond to those in Embodiment 1. For specific implementation details, please refer to the relevant description section of Embodiment 1. The above descriptions are merely preferred embodiments of the present invention and are not intended to limit the invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A near-Earth orbit neutron and gamma-ray detector array, characterized in that, It includes 15 detectors stacked sequentially, specifically: The first and fifteenth detectors are single-sensitivity CZT detectors used to detect gamma rays; The second detector is a single-sensitive-area Si detector, used to identify the direction of particle injection. The third, fourth, and fifth detectors constitute the first anti-coincidence detection group, which consists of two single-sensitive region Si detectors and a first dual-sensitive region Si detector with a LiF coating in between. The twelfth, thirteenth, and fourteenth detectors have the same structure as the first anti-coincidence detection group, and are also wrapped with a Gd layer to form the second anti-coincidence detection group. Both the first and second anti-coincidence detection groups are used to detect thermal neutrons. The fifth, sixth, seventh, and eighth detectors constitute the third anti-coincidence detection group, which consists of a single-sensitive region Si detector, a second dual-sensitive region Si detector, a first dual-sensitive region Si detector, and a single-sensitive region Si detector, respectively. The eighth, ninth, tenth, and eleventh detectors constitute the fourth anti-coincidence detection group, which consists of a single-sensitive region Si detector, a first dual-sensitive region Si detector with an HDPE coating, a second dual-sensitive region Si detector, and a single-sensitive region Si detector, respectively. The fifth to eleventh detectors are used to detect fast neutrons.

2. The near-Earth orbit neutron and gamma-ray detector array as described in claim 1, characterized in that, The sensitive layer of the single-sensitive region CZT detector has a side length of 35 mm and a nominal thickness of 5 mm. The sensitive layer of the single-sensitive region Si detector has a side length of 35 mm and a nominal thickness of 650 μm. The outer sensitive layer of the first dual-sensitive region Si detector has a side length of 35 mm, the inner sensitive region has a side length of 25 mm, and the thickness is nominally 300 μm. The outer sensitive layer of the second dual-sensitive region Si detector has a side length of 35 mm, the inner sensitive region has a side length of 25 mm, and the thickness is nominally 650 μm.

3. A near-Earth orbit neutron and gamma-ray detector array as described in claim 1, characterized in that, The anti-coincidence detector group is used to remove interference from charged particles.

4. A near-Earth orbit neutron and gamma-ray detector array as described in claim 1, characterized in that, The fourth detector, which includes a LiF coating, is used to record the count of signals generated by the reaction of neutrons with LiF in all energy ranges. The Gd layer of the second anti-coincidence detector group is used to absorb thermal neutrons, and the thirteenth detector is used to record the count of signals generated by the reaction of neutrons other than thermal neutrons with LiF. The thermal neutron flux in orbit is obtained by dividing the count difference between the fourth and thirteenth detectors by the detection efficiency.

5. A near-Earth orbit neutron and gamma-ray detector array as described in claim 1, characterized in that, The sixth and seventh detectors are used to detect signals generated by galactic cosmic rays or other secondary neutrons; The ninth and tenth detectors are used to detect the recoil proton signal generated by neutrons in near-Earth orbit passing through the high-density polyethylene conversion layer. Under anti-coincidence conditions, the energy spectrum of the recoil proton is obtained by subtracting the total energy spectra of the ninth and tenth detectors from that of the sixth and seventh detectors.

6. A near-Earth orbit neutron and gamma-ray detection device, characterized in that, It includes a rectangular outer shell, a front end plate, a data acquisition plate, and a near-Earth orbit neutron and gamma-ray detector assembly as described in any one of claims 1-5; The data acquisition board is communicatively connected to the detector group and the front-end board, and is used to provide analog and digital power; it includes an FPGA chip, a level conversion chip, a CAN chip, an eMMC, a gigabit Ethernet PHY chip, a universal asynchronous transceiver chip, and an ADC chip. The front-end board is communicatively connected to the detector group and includes a preamplifier circuit composed of an ASIC chip and discrete components; the ASIC chip is used to collect neutrons, and the preamplifier circuit is used to collect gamma rays; the front-end board is used to receive particle signals transmitted by the detector group and convert them into voltage pulses. The housing includes multiple mounting holes for securing it to a load.

7. The near-Earth orbit neutron and gamma-ray detection device as described in claim 6, characterized in that, Multiple fixed supports are installed inside the outer casing to connect to each side, ensuring the stability of the detection equipment.

8. A method for detecting neutrons and gamma rays in near-Earth orbit, based on the near-Earth orbit neutron and gamma ray detection device as described in claim 6, characterized in that, include: After the detection device is powered on, the data acquisition board is initialized; Once configured, the system enters acquisition mode and begins acquisition. The ADC internally converts the acquired random voltage pulses, and the resulting digital signal is cached in the DDR along with the corresponding trigger time. Then, a signal accumulation and discard algorithm is used to determine if there are any accumulated signals. If there are accumulated signals, they will be labeled with different frame formats and stored in the EMMC. If an upload command is received from the CAN interface, the data stored in the EMMC will be uploaded to the satellite via Ethernet. The satellite host will upload the data when it lands at the ground station.

9. The method for detecting neutrons and gamma rays in near-Earth orbit as described in claim 8, characterized in that, The initialization of the data acquisition board also includes: checking whether the peripheral circuits are normal; if no configuration signal is received from the satellite or the configuration is abnormal, relevant telemetry data will be sent to the satellite.

10. A method for detecting neutrons and gamma rays in near-Earth orbit as described in claim 8, characterized in that, include: The stacking and discarding algorithm is as follows: The rise time of a single-particle pulse is It is in the nanosecond range, and the molding time is... When set to 10 µs, the fast amplifier output pulse, after passing through the fast discriminator, will generate a pulse with a width of [value missing]. rectangular wave, The rise time of a single-particle pulse is less than 1. When two consecutive particles enter the detector, causing signal buildup, two signals with a width of [missing information] will be generated at the fast discriminator output, i.e., the TF pin of the CPRE10-32. A rectangular wave, when the spacing between two rectangular waves... Less than the total molding time When signal accumulation is detected, the accumulated signals are stored in the EMMC in different frame formats to achieve the function of discarding accumulated signals.

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