Email alert
RSSCurrent Articles
Recommend Articles
column
Display Method:
2024,
36: 1-2.
2024,
36: 043001.
doi: 10.11884/HPLPB202436.230375
Abstract:
In this article, the development of strong electromagnetic protection technology is reviewed in response to the strong electromagnetic environmental threats and protection reinforcement requirements faced by electronic information equipment in complex electromagnetic countermeasures environments, and the development prospects of strong electromagnetic system level comprehensive protection are proposed. Strong electromagnetic protection is a technical means to ensure that electronic information equipment is not damaged or destroyed in a strong electromagnetic environment. This paper analyzes the current focus and difficulties of electromagnetic protection from the coupling pathway of electromagnetic waves, and then analyzes and summarizes the development status of front door protection technology from three aspects: limiter technology, frequency filtering technology, and energy selection protection technology. Finally, the new electromagnetic protection technology is prospected from two aspects of new shielding materials and protective devices, and the system level electromagnetic protection is summarized from three aspects of integrated front and rear door protection, integrated field and road protection, and multi domain joint protection, which provides support for the electromagnetic protection reinforcement design of electronic information equipment in complex electromagnetic environment.
In this article, the development of strong electromagnetic protection technology is reviewed in response to the strong electromagnetic environmental threats and protection reinforcement requirements faced by electronic information equipment in complex electromagnetic countermeasures environments, and the development prospects of strong electromagnetic system level comprehensive protection are proposed. Strong electromagnetic protection is a technical means to ensure that electronic information equipment is not damaged or destroyed in a strong electromagnetic environment. This paper analyzes the current focus and difficulties of electromagnetic protection from the coupling pathway of electromagnetic waves, and then analyzes and summarizes the development status of front door protection technology from three aspects: limiter technology, frequency filtering technology, and energy selection protection technology. Finally, the new electromagnetic protection technology is prospected from two aspects of new shielding materials and protective devices, and the system level electromagnetic protection is summarized from three aspects of integrated front and rear door protection, integrated field and road protection, and multi domain joint protection, which provides support for the electromagnetic protection reinforcement design of electronic information equipment in complex electromagnetic environment.
2024,
36: 043002.
doi: 10.11884/HPLPB202436.230338
Abstract:
Aiming at the problem that the layout design of air-terminations in multiple lightning rod systems relies too much on engineering experience, based on the principle of least cost, an optimization model for the layout of air-terminations in multiple lightning rod systems is established by taking height and installation position of the air-terminations as the optimization variables. An optimization method for the layout of multiple air-terminations based on the genetic algorithm is proposed. The effectiveness of the proposed optimization method is verified by typical design cases. The results show that the deviation of the height and position of the air-terminations obtained by this method is not more than 0.29 m. All the preset objects to be protected can be completely covered within the protection range of the multiple lightning rod systems, and the minimum distance between the protected objects and the boundary of the protection range is not more than 0.71 m, which can fully meet the needs of engineering applications.
Aiming at the problem that the layout design of air-terminations in multiple lightning rod systems relies too much on engineering experience, based on the principle of least cost, an optimization model for the layout of air-terminations in multiple lightning rod systems is established by taking height and installation position of the air-terminations as the optimization variables. An optimization method for the layout of multiple air-terminations based on the genetic algorithm is proposed. The effectiveness of the proposed optimization method is verified by typical design cases. The results show that the deviation of the height and position of the air-terminations obtained by this method is not more than 0.29 m. All the preset objects to be protected can be completely covered within the protection range of the multiple lightning rod systems, and the minimum distance between the protected objects and the boundary of the protection range is not more than 0.71 m, which can fully meet the needs of engineering applications.
2024,
36: 043003.
doi: 10.11884/HPLPB202436.230261
Abstract:
The shielding effectiveness of a miniature unmanned aerial vehicle (UAV) has a significant impact on its ability to resist strong external electromagnetic interference. An equivalent method based on a large-scale model is employed to overcome the difficulties of measurement performed inside an extremely small space. In this method, the original miniature UAV is enlarged in proportion with scaling factor n and then a large-scale model is obtained. The shielding effectiveness of the large-scale model can be measured by existing mature instruments and test method. Then, the shielding effectiveness of the original model is obtained according to the relationship between the two models. On this basis, two typical miniature UAVs, i.e., a loitering munition and a quad-rotor UAV, are modeled and simulated. It is validated that the shielding effectiveness of the original model at the frequency f is equal to that of the large-scale model at the frequency\begin{document}$ {f_1} = f/n $\end{document} ![]()
![]()
The shielding effectiveness of a miniature unmanned aerial vehicle (UAV) has a significant impact on its ability to resist strong external electromagnetic interference. An equivalent method based on a large-scale model is employed to overcome the difficulties of measurement performed inside an extremely small space. In this method, the original miniature UAV is enlarged in proportion with scaling factor n and then a large-scale model is obtained. The shielding effectiveness of the large-scale model can be measured by existing mature instruments and test method. Then, the shielding effectiveness of the original model is obtained according to the relationship between the two models. On this basis, two typical miniature UAVs, i.e., a loitering munition and a quad-rotor UAV, are modeled and simulated. It is validated that the shielding effectiveness of the original model at the frequency f is equal to that of the large-scale model at the frequency
2024,
36: 043004.
doi: 10.11884/HPLPB202436.230267
Abstract:
As the battlefield environment becomes increasingly complex, especially in high-confrontation environments, it poses a great threat to all types of existing equipment. This article designs a C-band radar receiver protector, which adopts the structural design of inflatable microwave switch tube + waveguide coaxial conversion, innovatively integrates the solid-state limiter chip into the waveguide coaxial convertor, while the limiting chip adopts a cascaded form to increase the power of the microstrip limiter. With a power resistance of over 10 MW and a response time of less than 5 ns, the protector is not only used for receiver protection during radar transmission, but also can cope with external electromagnetic interference and high-power microwave attacks.
As the battlefield environment becomes increasingly complex, especially in high-confrontation environments, it poses a great threat to all types of existing equipment. This article designs a C-band radar receiver protector, which adopts the structural design of inflatable microwave switch tube + waveguide coaxial conversion, innovatively integrates the solid-state limiter chip into the waveguide coaxial convertor, while the limiting chip adopts a cascaded form to increase the power of the microstrip limiter. With a power resistance of over 10 MW and a response time of less than 5 ns, the protector is not only used for receiver protection during radar transmission, but also can cope with external electromagnetic interference and high-power microwave attacks.
2024,
36: 043005.
doi: 10.11884/HPLPB202436.230246
Abstract:
In view of the characteristics of many electromagnetic interference measurement parameters, measurement points and measurement conditions in complex electromagnetic environment and large-scale systems, the traditional sweeping frequency-domain measurement method has practical problems such as high cost and being time-consuming. This paper proposes a multi-channel time-domain rapid measurement and signal calculation method for low-frequency electromagnetic interference, and a multi-channel time-domain rapid measurement system for low-frequency electromagnetic interference is developed. The experimental results show that the proposed measurement, calculation method and the developed measurement system can accurately obtain the low frequency electromagnetic interference characteristics of complex electromagnetic environment and large-scale system, and the measurement speed is fast and the cost is low.
In view of the characteristics of many electromagnetic interference measurement parameters, measurement points and measurement conditions in complex electromagnetic environment and large-scale systems, the traditional sweeping frequency-domain measurement method has practical problems such as high cost and being time-consuming. This paper proposes a multi-channel time-domain rapid measurement and signal calculation method for low-frequency electromagnetic interference, and a multi-channel time-domain rapid measurement system for low-frequency electromagnetic interference is developed. The experimental results show that the proposed measurement, calculation method and the developed measurement system can accurately obtain the low frequency electromagnetic interference characteristics of complex electromagnetic environment and large-scale system, and the measurement speed is fast and the cost is low.
2024,
36: 043006.
doi: 10.11884/HPLPB202436.230327
Abstract:
Strong electromagnetic pulse can be coupled into vehicle engine management system (EMS) through external cables, causing interference and even damage to EMS equipment. Electromagnetic protection components can provide support for vehicle EMS protection design. This article takes vehicle EMS as the research object, comprehensively considers EMS equipment and its external connecting cables, establishes an electromagnetic simulation model of EMS equipment, and conducts simulation research on the port coupling characteristics of cables of different lengths and the induced current on the surface of EMS metal shell. Based on protective circuit simulation, an electromagnetic protection component applied to vehicle EMS equipment was designed. The simulation results show that the protection component can limit the 5 kV electromagnetic pulse to the maximum peak amplitude of 18 V, and the protection efficiency reaches 48 dB. Adding the protection component to the EMS cable interface can effectively improve the reliability in strong electromagnetic environment, which has certain reference significance for the electromagnetic protection design of the vehicle platform control system.
Strong electromagnetic pulse can be coupled into vehicle engine management system (EMS) through external cables, causing interference and even damage to EMS equipment. Electromagnetic protection components can provide support for vehicle EMS protection design. This article takes vehicle EMS as the research object, comprehensively considers EMS equipment and its external connecting cables, establishes an electromagnetic simulation model of EMS equipment, and conducts simulation research on the port coupling characteristics of cables of different lengths and the induced current on the surface of EMS metal shell. Based on protective circuit simulation, an electromagnetic protection component applied to vehicle EMS equipment was designed. The simulation results show that the protection component can limit the 5 kV electromagnetic pulse to the maximum peak amplitude of 18 V, and the protection efficiency reaches 48 dB. Adding the protection component to the EMS cable interface can effectively improve the reliability in strong electromagnetic environment, which has certain reference significance for the electromagnetic protection design of the vehicle platform control system.
2024,
36: 043007.
doi: 10.11884/HPLPB202436.230320
Abstract:
To solve the problem that the aviation Engine Electronic Controller (EEC) is easily disturbed by high-intensity radiation field (HIRF) interference, the plane wave irradiation simulation is performed to simulate the interference effect of HIRF on the EEC through the software CST for the modeling of the EEC. The simulation results show that HIRF can be coupled into the EEC and the electric field strength increases significantly at the resonance frequency. Conducting EEC radiated susceptibility tests at 400 MHz-4 GHz, the test results show that the EEC failure frequency points are 2.40 GHz and 3.84 GHz, the susceptive module is the analog input and output module, The EEC failure frequency is close to the resonance frequency, and the EEC failure is related to the cavity resonance. The wave-absorbing material is mounted inside the EEC and simulation is carried out, and the simulation results show that the wave-absorbing material can effectively suppress the resonance electromagnetic interference, and the results of the study can provide a theoretical basis and reference for the HIRF protection of the EEC.
To solve the problem that the aviation Engine Electronic Controller (EEC) is easily disturbed by high-intensity radiation field (HIRF) interference, the plane wave irradiation simulation is performed to simulate the interference effect of HIRF on the EEC through the software CST for the modeling of the EEC. The simulation results show that HIRF can be coupled into the EEC and the electric field strength increases significantly at the resonance frequency. Conducting EEC radiated susceptibility tests at 400 MHz-4 GHz, the test results show that the EEC failure frequency points are 2.40 GHz and 3.84 GHz, the susceptive module is the analog input and output module, The EEC failure frequency is close to the resonance frequency, and the EEC failure is related to the cavity resonance. The wave-absorbing material is mounted inside the EEC and simulation is carried out, and the simulation results show that the wave-absorbing material can effectively suppress the resonance electromagnetic interference, and the results of the study can provide a theoretical basis and reference for the HIRF protection of the EEC.
2024,
36: 043008.
doi: 10.11884/HPLPB202436.230272
Abstract:
In this paper, a typical backdoor coupled target is constructed, and the echo characteristics of the target are simulated from two dimensions of time domain and frequency domain. It is found that amplitude pits can be observed in the echo frequency domain waveform when the aperture-cavity structure of the target is strongly coupled, and the echo time domain waveform when the aperture-cavity structure is strongly coupled is bimodal, which is obviously different from the non-strongly coupled echo. By changing the size and shape of the backdoor coupled target, the characteristic law of the echo signal is verified by simulation.
In this paper, a typical backdoor coupled target is constructed, and the echo characteristics of the target are simulated from two dimensions of time domain and frequency domain. It is found that amplitude pits can be observed in the echo frequency domain waveform when the aperture-cavity structure of the target is strongly coupled, and the echo time domain waveform when the aperture-cavity structure is strongly coupled is bimodal, which is obviously different from the non-strongly coupled echo. By changing the size and shape of the backdoor coupled target, the characteristic law of the echo signal is verified by simulation.
2024,
36: 043009.
doi: 10.11884/HPLPB202436.230358
Abstract:
To recover the missing frequency information in optical-frequency-comb-based down-converted signal receiving, this paper introduces a frequency recovering method based on frequency-phase-mapping. An optical time delay line is used to generate a certain time delay and it builds a frequency-phase-mapping between signal’s frequency and down-converted component’s phase, which can be acquired by data processing. Thus, the frequency can be calculated through the measurable phase and certain time delay. Then, this paper analyzes parameters such as time delay on frequency recovery, estimates the limit requirements of this method for the uncertainty of phase measurement, and finally gives the setting strategy of key parameters in the specific implementation of this method. The number of signals under test is theoretically unlimited as long as the down-converted components are not aliased. Compared to related works, this method has better performance in multi-signals recovery, because its expense in time consumption and data processing is nearly constant as the number of signals increases.
To recover the missing frequency information in optical-frequency-comb-based down-converted signal receiving, this paper introduces a frequency recovering method based on frequency-phase-mapping. An optical time delay line is used to generate a certain time delay and it builds a frequency-phase-mapping between signal’s frequency and down-converted component’s phase, which can be acquired by data processing. Thus, the frequency can be calculated through the measurable phase and certain time delay. Then, this paper analyzes parameters such as time delay on frequency recovery, estimates the limit requirements of this method for the uncertainty of phase measurement, and finally gives the setting strategy of key parameters in the specific implementation of this method. The number of signals under test is theoretically unlimited as long as the down-converted components are not aliased. Compared to related works, this method has better performance in multi-signals recovery, because its expense in time consumption and data processing is nearly constant as the number of signals increases.
2024,
36: 043010.
doi: 10.11884/HPLPB202436.230321
Abstract:
With the increasing complexity of the electromagnetic environment, the threats posed of electromagnetic weapons to electronic equipment are becoming increasingly serious. As a sensitive integrated electronic device, the optoelectronic system is coupled with high-power electromagnetic pulse energy. This can disrupt the normal operation of the optoelectronic system, especially when it lacks sufficient electromagnetic protection. To clarify the high-power microwave coupling process of typical optoelectronic systems including barrel type, side window type, multi-window type under different irradiation conditions, simulations and analyses are conducted. The characteristics of high-power microwave coupling in optoelectronic systems and their constraints are extracted. The necessity and urgency of protecting reinforcing optoelectronic systems with high-power microwave are verified. For addressing the issue of weak high-power microwave protection ability in optoelectronic systems, the simulation analysis verifies the effectiveness of reinforcing transparent electromagnetic protection windows for high-power microwave. The study focuses in the method of electromagnetic gap protection and reinforcement, which is based on the support step and the conductive side wall. The key parameters of the installation structure for the gap coupling leakage of transparent electromagnetic protection windows are analyzed, and a method of non-electric contact assembly gap high-power microwave protection and reinforcement method is proposed. When the length of the gap protection structure is 6 mm, the average high-power microwave protection efficiency of the 0.2−4 GHz optoelectronic system increases by 4.51 dB. The study provides theoretical guidance and specific solutions for enhancing the high-power microwave protection capability of optoelectronic systems.
With the increasing complexity of the electromagnetic environment, the threats posed of electromagnetic weapons to electronic equipment are becoming increasingly serious. As a sensitive integrated electronic device, the optoelectronic system is coupled with high-power electromagnetic pulse energy. This can disrupt the normal operation of the optoelectronic system, especially when it lacks sufficient electromagnetic protection. To clarify the high-power microwave coupling process of typical optoelectronic systems including barrel type, side window type, multi-window type under different irradiation conditions, simulations and analyses are conducted. The characteristics of high-power microwave coupling in optoelectronic systems and their constraints are extracted. The necessity and urgency of protecting reinforcing optoelectronic systems with high-power microwave are verified. For addressing the issue of weak high-power microwave protection ability in optoelectronic systems, the simulation analysis verifies the effectiveness of reinforcing transparent electromagnetic protection windows for high-power microwave. The study focuses in the method of electromagnetic gap protection and reinforcement, which is based on the support step and the conductive side wall. The key parameters of the installation structure for the gap coupling leakage of transparent electromagnetic protection windows are analyzed, and a method of non-electric contact assembly gap high-power microwave protection and reinforcement method is proposed. When the length of the gap protection structure is 6 mm, the average high-power microwave protection efficiency of the 0.2−4 GHz optoelectronic system increases by 4.51 dB. The study provides theoretical guidance and specific solutions for enhancing the high-power microwave protection capability of optoelectronic systems.
2024,
36: 043011.
doi: 10.11884/HPLPB202436.230249
Abstract:
To meet the requirements of MV/m intensity pulse electric field measurement, a single optical path type small volume broadband pulse electric field measurement system based on integrated optics is designed and developed. Based on electro-optical effect and electro-optic modulation principle, the amplitude and frequency response transfer function of the measuring system is established, the reception characteristics of the integrated optical probe are analyzed, the relationship between its sensitivity and bandwidth with the length of the waveguide is derived. The pure optical non-metallic single-optical waveguide structure is designed, and a method of adjusting the measurement sensitivity using crystal width is proposed, which raised the designed half-wave electric field more than 3 times. The passive probe size is less than 20 mm×10 mm×5 mm, the theoretical bandwidth is more than 4 GHz, and the maximum measurement range is more than 1.2 MV/m. The developed measurement system has applications in the fields of high-altitude electromagnetic pulse (HEMP), lightning (LEMP) and pulsed power technology.
To meet the requirements of MV/m intensity pulse electric field measurement, a single optical path type small volume broadband pulse electric field measurement system based on integrated optics is designed and developed. Based on electro-optical effect and electro-optic modulation principle, the amplitude and frequency response transfer function of the measuring system is established, the reception characteristics of the integrated optical probe are analyzed, the relationship between its sensitivity and bandwidth with the length of the waveguide is derived. The pure optical non-metallic single-optical waveguide structure is designed, and a method of adjusting the measurement sensitivity using crystal width is proposed, which raised the designed half-wave electric field more than 3 times. The passive probe size is less than 20 mm×10 mm×5 mm, the theoretical bandwidth is more than 4 GHz, and the maximum measurement range is more than 1.2 MV/m. The developed measurement system has applications in the fields of high-altitude electromagnetic pulse (HEMP), lightning (LEMP) and pulsed power technology.
2024,
36: 043012.
doi: 10.11884/HPLPB202436.230367
Abstract:
Aiming at the problem of high reflection and poor low-frequency radiation performance of TEM horn antenna, the simulation optimization design is carried out. The low frequency compensation methods of end loading resistance and back loading resistance are analyzed by using time domain analysis method, and the structural parameters such as the size of the TEM horn antenna and the apex angle of the plate are optimized. The peak field strength and pulse width of the radiation field are improved by using the end crimping structure. According to the simulation results, TEM horn antenna with length of 2.5 m, the included angle of the plates of 45° and antenna plate apex angle of 45° is developed. The simulation results are verified by the measurement of the new antenna. The results show that the loading resistance can effectively reduce the reflection, and the peak field strength and pulse width of the back loading resistance are higher than that of the end loading resistance, and the effect of 4 resistors in parallel loading is better. The radiation performance of the antenna can be improved by appropriately increasing the antenna length, the apex angle of the plate and the included angle between two plates. The research results provide a reference for the application of TEM horn antenna in the radiation nuclear electromagnetic pulse test system.
Aiming at the problem of high reflection and poor low-frequency radiation performance of TEM horn antenna, the simulation optimization design is carried out. The low frequency compensation methods of end loading resistance and back loading resistance are analyzed by using time domain analysis method, and the structural parameters such as the size of the TEM horn antenna and the apex angle of the plate are optimized. The peak field strength and pulse width of the radiation field are improved by using the end crimping structure. According to the simulation results, TEM horn antenna with length of 2.5 m, the included angle of the plates of 45° and antenna plate apex angle of 45° is developed. The simulation results are verified by the measurement of the new antenna. The results show that the loading resistance can effectively reduce the reflection, and the peak field strength and pulse width of the back loading resistance are higher than that of the end loading resistance, and the effect of 4 resistors in parallel loading is better. The radiation performance of the antenna can be improved by appropriately increasing the antenna length, the apex angle of the plate and the included angle between two plates. The research results provide a reference for the application of TEM horn antenna in the radiation nuclear electromagnetic pulse test system.
2024,
36: 043013.
doi: 10.11884/HPLPB202436.230237
Abstract:
PIN diodes are critical devices for preventing damage from strong electromagnetic signals. Accurately predicting the temperature rise curve of the PIN diode has important guiding significance for selecting protective devices. Machine learning-based methods can effectively predict the characteristics of devices. However, the temperature rise characteristic curve of the PIN diode contains strong nonlinearity and small fluctuations, and traditional machine learning methods cannot predict accurately. To accurately predict the temperature rise characteristic curve of PIN diodes, this paper proposes a prediction method that combines variational mode decomposition (VMD) and autoencoder to decompose the temperature rise characteristics into sub-signals, which include high-frequency fluctuations, intermediate quantities, and low-frequency trend quantities. Then an autoencoder is used to predict each component. Finally, the predicted values of the components are added together, so as to accurately predict the temperature rise characteristic curve of the PIN diode. By comparing with various machine learning methods, it is verified that combining VMD decomposition can effectively improve prediction accuracy, and the advantage of autoencoder in fitting characteristic curves is also verified.
PIN diodes are critical devices for preventing damage from strong electromagnetic signals. Accurately predicting the temperature rise curve of the PIN diode has important guiding significance for selecting protective devices. Machine learning-based methods can effectively predict the characteristics of devices. However, the temperature rise characteristic curve of the PIN diode contains strong nonlinearity and small fluctuations, and traditional machine learning methods cannot predict accurately. To accurately predict the temperature rise characteristic curve of PIN diodes, this paper proposes a prediction method that combines variational mode decomposition (VMD) and autoencoder to decompose the temperature rise characteristics into sub-signals, which include high-frequency fluctuations, intermediate quantities, and low-frequency trend quantities. Then an autoencoder is used to predict each component. Finally, the predicted values of the components are added together, so as to accurately predict the temperature rise characteristic curve of the PIN diode. By comparing with various machine learning methods, it is verified that combining VMD decomposition can effectively improve prediction accuracy, and the advantage of autoencoder in fitting characteristic curves is also verified.
2024,
36: 043014.
doi: 10.11884/HPLPB202436.230345
Abstract:
Conducting material shielding effectiveness testing in complex electromagnetic environments of reverberation chambers has become a key technology for accurately evaluating the electromagnetic protection ability of materials. To study the performance of the boundary deformation mutual coupling reverberation chamber shielding effectiveness testing system, experiments were conducted to verify the dynamic range, electric field distribution characteristics, and uncertainty. The results show that: in actual testing, a test result less than 60 dB is considered a reliable test value; the standard deviation of the electric field in both the transmitting and receiving reverberation chambers is less than 3 dB within the testing frequency range, fully meeting the uniformity requirements of the reverberation chamber; especially, the standard deviation of the spatial electric field in the receiving reverberation chamber is all less than 2 dB, and the uniformity is excellent; the expanded uncertainty of the testing system is 5.90 dB, which can be used as a material shielding effectiveness testing platform.
Conducting material shielding effectiveness testing in complex electromagnetic environments of reverberation chambers has become a key technology for accurately evaluating the electromagnetic protection ability of materials. To study the performance of the boundary deformation mutual coupling reverberation chamber shielding effectiveness testing system, experiments were conducted to verify the dynamic range, electric field distribution characteristics, and uncertainty. The results show that: in actual testing, a test result less than 60 dB is considered a reliable test value; the standard deviation of the electric field in both the transmitting and receiving reverberation chambers is less than 3 dB within the testing frequency range, fully meeting the uniformity requirements of the reverberation chamber; especially, the standard deviation of the spatial electric field in the receiving reverberation chamber is all less than 2 dB, and the uniformity is excellent; the expanded uncertainty of the testing system is 5.90 dB, which can be used as a material shielding effectiveness testing platform.
2024,
36: 043015.
doi: 10.11884/HPLPB202436.230384
Abstract:
An analysis of lightning standards is made for military and civil aircraft platforms, subsystems, and equipment both domestically and internationally, detailing the applicable areas, waveform requirements, and testing configurations for each test item for both direct and indirect lightning effects. Based on the existing domestic lightning design verification standards and shortcomings in testing, suggestions are proposed to improve the compatibility between testing equipment and testing verification technology, expand the field of military standard testing, and unify the requirements of the same service and platform. Through presenting the lightning design verification standards and testing for military airborne platforms, equipment, and subsystems, the analysis provides design index references for relevant product designers and testers to clarify the design requirements and verification requirements for lightning protection, thus to achieve targeted goals and improve design cost-effectiveness.
An analysis of lightning standards is made for military and civil aircraft platforms, subsystems, and equipment both domestically and internationally, detailing the applicable areas, waveform requirements, and testing configurations for each test item for both direct and indirect lightning effects. Based on the existing domestic lightning design verification standards and shortcomings in testing, suggestions are proposed to improve the compatibility between testing equipment and testing verification technology, expand the field of military standard testing, and unify the requirements of the same service and platform. Through presenting the lightning design verification standards and testing for military airborne platforms, equipment, and subsystems, the analysis provides design index references for relevant product designers and testers to clarify the design requirements and verification requirements for lightning protection, thus to achieve targeted goals and improve design cost-effectiveness.
2024,
36: 043016.
doi: 10.11884/HPLPB202436.230119
Abstract:
Aiming at the problems of low recognition accuracy and poor timeliness of existing radar emitter signal recognition methods under the condition of low SNR, this paper proposes a radar emitter signal recognition method based on compressed residual network. Using Choi-Williams distribution for reference, the time-domain signal is converted into a two-dimensional time-frequency image, which improves the effectiveness of signal essential feature extraction. According to the characteristics of the application scenario, it selects the “compression” range of convolutional neural networks (CNN), and builds a compression residual network to automatically extract image features and identify. The simulation results show that compared with other advanced models, the proposed method can reduce the running time of signal recognition by about 88%, and the average recognition rate of 14 radar emitter signals is at least 5% higher when the signal-to-noise ratio is −14 dB. This paper provides an efficient intelligent recognition method of radar emitter signal, which has potential engineering application prospects.
Aiming at the problems of low recognition accuracy and poor timeliness of existing radar emitter signal recognition methods under the condition of low SNR, this paper proposes a radar emitter signal recognition method based on compressed residual network. Using Choi-Williams distribution for reference, the time-domain signal is converted into a two-dimensional time-frequency image, which improves the effectiveness of signal essential feature extraction. According to the characteristics of the application scenario, it selects the “compression” range of convolutional neural networks (CNN), and builds a compression residual network to automatically extract image features and identify. The simulation results show that compared with other advanced models, the proposed method can reduce the running time of signal recognition by about 88%, and the average recognition rate of 14 radar emitter signals is at least 5% higher when the signal-to-noise ratio is −14 dB. This paper provides an efficient intelligent recognition method of radar emitter signal, which has potential engineering application prospects.
2024,
36: 043017.
doi: 10.11884/HPLPB202436.230383
Abstract:
Due to extensive electromagnetic radiation or interference, the rapid detection and location of electromagnetic interference sources in a large space has become a hot issue to be studied urgently. Electromagnetic imaging technology can visually display the location of radiation sources and solve the problem of rapid detection and localization of electromagnetic interference sources. However, the existing reflector electromagnetic imaging system is bulky and cannot meet the requirements of airborne, vehicle-mounted, UAV and other application platforms. To address this issue, this paper studies the structure and imaging characteristics of Luneburg lens, designs a large field-of-view Luneburg lens electromagnetic imaging (EMI) system, and realizes rapid identification and location of EMI with the advantages of large field of view, wide bandwidth and high resolution. In this paper, the parameters of the 300 mm Luneburg lens with spherical core are calculated, the E-field intensity distribution of the 4～18GHz is simulated, and the space invariant imaging characteristics of Luneburg lens and its super-resolution algorithm are verified. The paper finally compares the volume, field of view, source number and resolution of the parabolic reflector electromagnetic imaging system and the Luneburg lens electromagnetic imaging system. The results demonstrate the superiority of the system proposed in this paper, achieving a large field of view with azimuth and elevation angles of 40° at the same resolution.
Due to extensive electromagnetic radiation or interference, the rapid detection and location of electromagnetic interference sources in a large space has become a hot issue to be studied urgently. Electromagnetic imaging technology can visually display the location of radiation sources and solve the problem of rapid detection and localization of electromagnetic interference sources. However, the existing reflector electromagnetic imaging system is bulky and cannot meet the requirements of airborne, vehicle-mounted, UAV and other application platforms. To address this issue, this paper studies the structure and imaging characteristics of Luneburg lens, designs a large field-of-view Luneburg lens electromagnetic imaging (EMI) system, and realizes rapid identification and location of EMI with the advantages of large field of view, wide bandwidth and high resolution. In this paper, the parameters of the 300 mm Luneburg lens with spherical core are calculated, the E-field intensity distribution of the 4～18GHz is simulated, and the space invariant imaging characteristics of Luneburg lens and its super-resolution algorithm are verified. The paper finally compares the volume, field of view, source number and resolution of the parabolic reflector electromagnetic imaging system and the Luneburg lens electromagnetic imaging system. The results demonstrate the superiority of the system proposed in this paper, achieving a large field of view with azimuth and elevation angles of 40° at the same resolution.
2024,
36: 043018.
doi: 10.11884/HPLPB202436.230186
Abstract:
With the development of networks such as mobile communications, Internet of Things (IoT), V2X (meaning Vehicle to everything, including Vehicle to Vehicle and Vehicle to Infrastructure), and Industrial Internet of Things (IIoT), the electromagnetic environment is becoming increasingly complex, illegal electronic devices are also increasing day by day, and there are severe coupling and intermodulation of various signals, which bring difficulties to the identification of leaked signal types. This paper proposes a leakage signal classification and recognition method based on fused features. Comprehensively utilizing high-dimensional feature extraction methods and graphical dimensionality reduction characterization methods, and combining with deep learning models such as residual networks and feature fusion analysis methods, the method can distinguish more comprehensively multiple types of electromagnetic leakage signals. The features method has with high robustness against noise and good interpretability, and can support the intelligent detection engineering application of radiation sources based on electromagnetic signal type recognition.
With the development of networks such as mobile communications, Internet of Things (IoT), V2X (meaning Vehicle to everything, including Vehicle to Vehicle and Vehicle to Infrastructure), and Industrial Internet of Things (IIoT), the electromagnetic environment is becoming increasingly complex, illegal electronic devices are also increasing day by day, and there are severe coupling and intermodulation of various signals, which bring difficulties to the identification of leaked signal types. This paper proposes a leakage signal classification and recognition method based on fused features. Comprehensively utilizing high-dimensional feature extraction methods and graphical dimensionality reduction characterization methods, and combining with deep learning models such as residual networks and feature fusion analysis methods, the method can distinguish more comprehensively multiple types of electromagnetic leakage signals. The features method has with high robustness against noise and good interpretability, and can support the intelligent detection engineering application of radiation sources based on electromagnetic signal type recognition.
2024,
36: 043019.
doi: 10.11884/HPLPB202436.230380
Abstract:
A Grad-CAM based visualizing method for important regions is proposed for the interpretability of RF fingerprint extraction and deep learning models of time-domain pulse signal samples. The impact of important regions on RF fingerprint recognition results is analyzed through multiple mask tests of important regions. Based on signal samples of 10 emitters, the test results of two ResNet models with different layers are compared. It is found that the proposed method can distinguish different types of signals and present individual differences. Analysis shows that this method can detect important regional localization differences when different emitters send the same signal, and can visually reflect the spatial distance of RF fingerprint characteristics, as well as the differences in feature representation and fingerprint localization accuracy of different models; At the same time, it is found that masks for important areas are more prone to false predictions, which proves the existence of RF fingerprints related to time-frequency characteristics in specific signals, and can assist in visualizing key points that affect the recognition of RF fingerprint samples.
A Grad-CAM based visualizing method for important regions is proposed for the interpretability of RF fingerprint extraction and deep learning models of time-domain pulse signal samples. The impact of important regions on RF fingerprint recognition results is analyzed through multiple mask tests of important regions. Based on signal samples of 10 emitters, the test results of two ResNet models with different layers are compared. It is found that the proposed method can distinguish different types of signals and present individual differences. Analysis shows that this method can detect important regional localization differences when different emitters send the same signal, and can visually reflect the spatial distance of RF fingerprint characteristics, as well as the differences in feature representation and fingerprint localization accuracy of different models; At the same time, it is found that masks for important areas are more prone to false predictions, which proves the existence of RF fingerprints related to time-frequency characteristics in specific signals, and can assist in visualizing key points that affect the recognition of RF fingerprint samples.
2024,
36: 043020.
doi: 10.11884/HPLPB202436.230302
Abstract:
Optical down-conversion technology can simultaneously down-convert all electromagnetic signals within a wide frequency band to the low-frequency range for reception, and is a new type of fast reception technology for broadband electromagnetic environments. However, the obtained optical down-conversion signal contains multiple signals with unknown number of sources and different bandwidths. Existing signal separation methods need to know the number of source signals and cannot simultaneously separate narrowband and broadband signals. To achieve automatic separation of optical down-conversion signals, a method for optical down-conversion signal separation based on VMD adaptive mode recombination is proposed. By using spectral segmentation factors and spectral envelope detection, the VMD over decomposition modes of optical down-conversion signals are automatically recombined and signal recombination modes are extracted, achieving the separation of optical down-conversion signals. For optical down-conversion signals containing ordinary pulse signals, WCDMA signals, and linear frequency modulation pulse signals, this method can automatically separate the three types of signals, and the similarity coefficients with the original signal are all higher than 0.97. The experimental results show that the method proposed in this paper does not need to know the number of source signals when separating optical down-conversion signals, and can simultaneously separate multiple source signals with different bandwidths.
Optical down-conversion technology can simultaneously down-convert all electromagnetic signals within a wide frequency band to the low-frequency range for reception, and is a new type of fast reception technology for broadband electromagnetic environments. However, the obtained optical down-conversion signal contains multiple signals with unknown number of sources and different bandwidths. Existing signal separation methods need to know the number of source signals and cannot simultaneously separate narrowband and broadband signals. To achieve automatic separation of optical down-conversion signals, a method for optical down-conversion signal separation based on VMD adaptive mode recombination is proposed. By using spectral segmentation factors and spectral envelope detection, the VMD over decomposition modes of optical down-conversion signals are automatically recombined and signal recombination modes are extracted, achieving the separation of optical down-conversion signals. For optical down-conversion signals containing ordinary pulse signals, WCDMA signals, and linear frequency modulation pulse signals, this method can automatically separate the three types of signals, and the similarity coefficients with the original signal are all higher than 0.97. The experimental results show that the method proposed in this paper does not need to know the number of source signals when separating optical down-conversion signals, and can simultaneously separate multiple source signals with different bandwidths.
2024,
36: 043021.
doi: 10.11884/HPLPB202436.230303
Abstract:
The cognitive bias is an objective existence of cognitive electronic warfare. Based on the method of dynamic gaming, this paper investigates the approach to modeling radar countermeasure with the cognitive bias caused by the incomplete information and the measuring error in the cognitive radar countermeasure. It adopts the anti-jamming improvement factors of radar and the jamming payoff factors of jammer to calculate the utilities of both adversarial parties. Thereafter, the dynamic radar countermeasure model is setup with the perfect Bayesian equilibrium. The influence of cognitive bias on gaming result is further analyzed. The results of simulation test validate the effectiveness of the proposed method.
The cognitive bias is an objective existence of cognitive electronic warfare. Based on the method of dynamic gaming, this paper investigates the approach to modeling radar countermeasure with the cognitive bias caused by the incomplete information and the measuring error in the cognitive radar countermeasure. It adopts the anti-jamming improvement factors of radar and the jamming payoff factors of jammer to calculate the utilities of both adversarial parties. Thereafter, the dynamic radar countermeasure model is setup with the perfect Bayesian equilibrium. The influence of cognitive bias on gaming result is further analyzed. The results of simulation test validate the effectiveness of the proposed method.
2024,
36: 043022.
doi: 10.11884/HPLPB202436.230236
Abstract:
A field-circuit co-simulation model of a two-stage PIN limiter was built to explore the influence of high-power microwave signal parameters on the temperature distribution of the limiter. The simulation results indicate that the increase in microwave pulse amplitude or frequency can expand the PIN diode's high-temperature region inside the two-stage PIN limiter towards the P-region. Compared with the frequency, the amplitude of the microwave pulse has a more significant impact on the temperature distribution of the PIN limiter.
A field-circuit co-simulation model of a two-stage PIN limiter was built to explore the influence of high-power microwave signal parameters on the temperature distribution of the limiter. The simulation results indicate that the increase in microwave pulse amplitude or frequency can expand the PIN diode's high-temperature region inside the two-stage PIN limiter towards the P-region. Compared with the frequency, the amplitude of the microwave pulse has a more significant impact on the temperature distribution of the PIN limiter.
2024,
36: 043023.
doi: 10.11884/HPLPB202436.230276
Abstract:
The high-speed switching of power devices such as MOSFETs and IGBT switches in power conversion systems will generate high amplitude and broadband electromagnetic interference (EMI), which is the most common and unavoidable EMI for electric vehicles. At the same time, interconnecting cables are the carrier of signals and energy transmitted by electrical devices, the antenna effect of cables is the main pathway for EMI radiation propagation, and is one of the main sources of system electromagnetic compatibility (EMC) problems. To analyze the electromagnetic coupling between the high-voltage power conversion system and the low-voltage control system, this paper takes the pulse width modulation (PWM ) wave generated by the IGBT as the EMI source, and uses the actual cable as the analysis object to construct a high and low voltage harness crosstalk model. The simulation analysis analyzes the near-end crosstalk voltage of multiple types of low voltage cable under different conditions of cable spacing and ground distance, obtains the anti-interference performance of low-voltage cables, thus provides guidance for the wiring of the system cable harness.
The high-speed switching of power devices such as MOSFETs and IGBT switches in power conversion systems will generate high amplitude and broadband electromagnetic interference (EMI), which is the most common and unavoidable EMI for electric vehicles. At the same time, interconnecting cables are the carrier of signals and energy transmitted by electrical devices, the antenna effect of cables is the main pathway for EMI radiation propagation, and is one of the main sources of system electromagnetic compatibility (EMC) problems. To analyze the electromagnetic coupling between the high-voltage power conversion system and the low-voltage control system, this paper takes the pulse width modulation (PWM ) wave generated by the IGBT as the EMI source, and uses the actual cable as the analysis object to construct a high and low voltage harness crosstalk model. The simulation analysis analyzes the near-end crosstalk voltage of multiple types of low voltage cable under different conditions of cable spacing and ground distance, obtains the anti-interference performance of low-voltage cables, thus provides guidance for the wiring of the system cable harness.
2024,
36: 043024.
doi: 10.11884/HPLPB202436.230273
Abstract:
Using 3D MC code and PIC code, model of electromagnetic pulse (SGEMP) generated in the cavity system radiated by SG-facility is calculated. The simulated results show that the intensity of electric field could be 2.2 MV/m and magnetic field be 0.8×10−3 T under irradiation of the bremsstrahlung X-ray point source with full width at half maximum 2.9 ns, average energy 10.3 keV produced by SG-facility irradiating the end of cylinder cavity. The electric field is mainly axial and the magnetic field is primarily azimuthal. Both electric field and magnetic field are concentrated near the emitting surface, with the pulsed DC field being predominant and the amplitude of the AC radiation field being relatively smaller, at the level of kV/m. The effect of fluence on SGEMP is also studied, showing that higher fluence leads to faster axial variation of the electric field and larger proportion of the AC radiation field.
Using 3D MC code and PIC code, model of electromagnetic pulse (SGEMP) generated in the cavity system radiated by SG-facility is calculated. The simulated results show that the intensity of electric field could be 2.2 MV/m and magnetic field be 0.8×10−3 T under irradiation of the bremsstrahlung X-ray point source with full width at half maximum 2.9 ns, average energy 10.3 keV produced by SG-facility irradiating the end of cylinder cavity. The electric field is mainly axial and the magnetic field is primarily azimuthal. Both electric field and magnetic field are concentrated near the emitting surface, with the pulsed DC field being predominant and the amplitude of the AC radiation field being relatively smaller, at the level of kV/m. The effect of fluence on SGEMP is also studied, showing that higher fluence leads to faster axial variation of the electric field and larger proportion of the AC radiation field.
2024,
36: 043025.
doi: 10.11884/HPLPB202436.230299
Abstract:
Based on the object-oriented C++ language, a 3D cylindrical coordinate conformal grid generation program is developed. The conformal grid generation of beam-field interaction(BFI) device discretizing is performed, providing integral line and face elements for Particle-in-Cell simulation algorithm. By defining the basic elements of the three-dimensional cylindrical coordinate grid system, including grid step-size, grid index, guardian grid layer and bounding box, the spatial information of the model can be converted into the information of the cylindrical coordinate grid information necessary for numerical calculation. The grid cells on-axis should be specially treated so as to maintain the consistency of the particle-in-cell algorithm between the axial grid and the non-axial grid. The discrete boundary points on the model subsurface and on the model edge were attained by ray-tracing algorithm. Meanwhile, the vertices of the model were obtained by topological relations. Topological information and cylindrical coordinate grid information of the two types of boundary points and model vertices were recorded, then the basic grid elements were coupled with the boundary point information, finally the model was reconstructed in the discrete grid system. Taking the relativistic magnetron for example, using the conformal grid generation technique proposed in the paper to discretize the model, the transparent cathode, anode, and resonant cavity structures of the magnetron can be identified.
Based on the object-oriented C++ language, a 3D cylindrical coordinate conformal grid generation program is developed. The conformal grid generation of beam-field interaction(BFI) device discretizing is performed, providing integral line and face elements for Particle-in-Cell simulation algorithm. By defining the basic elements of the three-dimensional cylindrical coordinate grid system, including grid step-size, grid index, guardian grid layer and bounding box, the spatial information of the model can be converted into the information of the cylindrical coordinate grid information necessary for numerical calculation. The grid cells on-axis should be specially treated so as to maintain the consistency of the particle-in-cell algorithm between the axial grid and the non-axial grid. The discrete boundary points on the model subsurface and on the model edge were attained by ray-tracing algorithm. Meanwhile, the vertices of the model were obtained by topological relations. Topological information and cylindrical coordinate grid information of the two types of boundary points and model vertices were recorded, then the basic grid elements were coupled with the boundary point information, finally the model was reconstructed in the discrete grid system. Taking the relativistic magnetron for example, using the conformal grid generation technique proposed in the paper to discretize the model, the transparent cathode, anode, and resonant cavity structures of the magnetron can be identified.
2024,
36: 043026.
doi: 10.11884/HPLPB202436.230370
Abstract:
To analyze the electromagnetic environmental effects of composite shell platforms in strong electromagnetic environments such as nuclear electromagnetic pulses, we have obtained an equivalent calculation method of the finite-difference time-domain method in dealing with weakly conducting thin-layer dielectric materials based on the integral form of the Maxwell-Amper theorem. The thin layer model can be appropriately thickened while proportionally reducing its conductivity when the equivalent wavelength of the medium is larger than the model thickness. The electromagnetic coupling characteristics of the model before and after parameter equivalence are essentially the same. This method can reduce the computational effort by increasing the grid step size. In addition, this method does not require changing the time step format of the traditional finite-difference time-domain method and does not affect the stability of the calculation. Numerical experiments, such as the examples using infinitely large thin plates, thin spherical layers, and electromagnetic coupling of unmanned aerial vehicles with thin shells, have shown that it has good applicability to the electromagnetic coupling simulation of thin-shell platforms containing weakly conducting materials with millimeter thickness in nuclear electromagnetic pulse environments.
To analyze the electromagnetic environmental effects of composite shell platforms in strong electromagnetic environments such as nuclear electromagnetic pulses, we have obtained an equivalent calculation method of the finite-difference time-domain method in dealing with weakly conducting thin-layer dielectric materials based on the integral form of the Maxwell-Amper theorem. The thin layer model can be appropriately thickened while proportionally reducing its conductivity when the equivalent wavelength of the medium is larger than the model thickness. The electromagnetic coupling characteristics of the model before and after parameter equivalence are essentially the same. This method can reduce the computational effort by increasing the grid step size. In addition, this method does not require changing the time step format of the traditional finite-difference time-domain method and does not affect the stability of the calculation. Numerical experiments, such as the examples using infinitely large thin plates, thin spherical layers, and electromagnetic coupling of unmanned aerial vehicles with thin shells, have shown that it has good applicability to the electromagnetic coupling simulation of thin-shell platforms containing weakly conducting materials with millimeter thickness in nuclear electromagnetic pulse environments.
2024,
36: 043027.
doi: 10.11884/HPLPB202436.230245
Abstract:
Near-ground nuclear explosion fallout consists of radioactive particles of different particle size, and its motion has a large spatial and temporal scales. For the problem how to simulate the atmospheric γ ionizing radiation environment of the near-ground explosion fallout, in this paper, firstly, the mechanism analysis of atmospheric gamma radiation is carried out, the no-wind conditions are set up, and the theoretical model of fallout gamma radiation is established. Secondly, the corresponding numerical difference and integration algorithms are introduced and proposed. Finally, the simulation example of the radioactivity and radiative dose rate in the atmosphere of the 1000 kt Nevada near-ground explosion is given, a certain summary of the temporal and spatial evolution patterns of the radiation environment and the comparison of the results are accomplished, and the comparison reveals that the present model is able to calculate the theoretical maximum of the atmospheric radiation dose rate while ensuring the consistency of the activity results.
Near-ground nuclear explosion fallout consists of radioactive particles of different particle size, and its motion has a large spatial and temporal scales. For the problem how to simulate the atmospheric γ ionizing radiation environment of the near-ground explosion fallout, in this paper, firstly, the mechanism analysis of atmospheric gamma radiation is carried out, the no-wind conditions are set up, and the theoretical model of fallout gamma radiation is established. Secondly, the corresponding numerical difference and integration algorithms are introduced and proposed. Finally, the simulation example of the radioactivity and radiative dose rate in the atmosphere of the 1000 kt Nevada near-ground explosion is given, a certain summary of the temporal and spatial evolution patterns of the radiation environment and the comparison of the results are accomplished, and the comparison reveals that the present model is able to calculate the theoretical maximum of the atmospheric radiation dose rate while ensuring the consistency of the activity results.
2024,
36: 043028.
doi: 10.11884/HPLPB202436.230372
Abstract:
This study aims to address the issue of the rapidly increasing quantity of space debris by investigating the feasibility of active debris removal by strong electromagnetic irradiation. A multi-layer insulation structure was employed as a typical model for hazardous space debris, and feasibility validation experiments were conducted in a complex physical environment incorporating multiple environmental factors under strong electromagnetic irradiation in the S-band and vacuum conditions. The experimental results demonstrate that, in a vacuum environment at the order of 10−3 Pa, strong electromagnetic pulses interact with the multi-layer insulation structure, triggering discharge phenomena and generating plasma, accompanied by changes in macroscopic dynamic characteristics. Through observation and analysis, possible physical processes were explored, including strong field breakdown leading to point discharge in materials, surface flashover causing mesh discharge and coating to damage, particle absorption of microwave energy resulting in material deformation or expansion, as well as plasma ablation leading to material destruction. This study provides important technical support for the active removal of hazardous space debris using strong electromagnetic irradiation.
This study aims to address the issue of the rapidly increasing quantity of space debris by investigating the feasibility of active debris removal by strong electromagnetic irradiation. A multi-layer insulation structure was employed as a typical model for hazardous space debris, and feasibility validation experiments were conducted in a complex physical environment incorporating multiple environmental factors under strong electromagnetic irradiation in the S-band and vacuum conditions. The experimental results demonstrate that, in a vacuum environment at the order of 10−3 Pa, strong electromagnetic pulses interact with the multi-layer insulation structure, triggering discharge phenomena and generating plasma, accompanied by changes in macroscopic dynamic characteristics. Through observation and analysis, possible physical processes were explored, including strong field breakdown leading to point discharge in materials, surface flashover causing mesh discharge and coating to damage, particle absorption of microwave energy resulting in material deformation or expansion, as well as plasma ablation leading to material destruction. This study provides important technical support for the active removal of hazardous space debris using strong electromagnetic irradiation.
2024,
36: 043029.
doi: 10.11884/HPLPB202436.230373
Abstract:
Monte Carlo method was used to study the shielding characteristics of ship compartments in early nuclear radiation scenarios. Using early gamma radiation as a radiation source, the mass attenuation coefficients of three commonly used materials, HSLA-80, 5456Al, and FDCL-3B, for ship bodies were measured. A simulated cabin model was established based on the geometric structure of the ship, and Gaussian broadening method was used to fit the detector's energy spectrum. The absorption energy spectrum of the NaI detector inside the cabin under gamma radiation was obtained, and compared with experimental results in the literature, thus verified the reliability of the calculation model and results. On this basis, using the gamma protection coefficient as the evaluation index, considering two scenarios of radioactive isotopes (single energy point sources) and early gamma radiation (surface sources with energy distribution), the spatial distribution characteristics of gamma radiation shielding in simulated cabins were calculated and analyzed. The results show that the protection coefficient of the simulated cabins for different radioactive isotopes was different, with a maximum difference of 6.74 times (Cd-109 and Cs-137); The protection coefficient varies in different positions of the cabin. The gamma radiation dose at the front end of the cabin is relatively high, while the gamma radiation dose at the corners is relatively low, with a difference of 35%; The protection coefficient is related to the incident angle of gamma irradiation. Compared with normal incidence, the simulated cabin has a higher gamma radiation protection coefficient for oblique 45° incidence, which can be improved by 43%.
Monte Carlo method was used to study the shielding characteristics of ship compartments in early nuclear radiation scenarios. Using early gamma radiation as a radiation source, the mass attenuation coefficients of three commonly used materials, HSLA-80, 5456Al, and FDCL-3B, for ship bodies were measured. A simulated cabin model was established based on the geometric structure of the ship, and Gaussian broadening method was used to fit the detector's energy spectrum. The absorption energy spectrum of the NaI detector inside the cabin under gamma radiation was obtained, and compared with experimental results in the literature, thus verified the reliability of the calculation model and results. On this basis, using the gamma protection coefficient as the evaluation index, considering two scenarios of radioactive isotopes (single energy point sources) and early gamma radiation (surface sources with energy distribution), the spatial distribution characteristics of gamma radiation shielding in simulated cabins were calculated and analyzed. The results show that the protection coefficient of the simulated cabins for different radioactive isotopes was different, with a maximum difference of 6.74 times (Cd-109 and Cs-137); The protection coefficient varies in different positions of the cabin. The gamma radiation dose at the front end of the cabin is relatively high, while the gamma radiation dose at the corners is relatively low, with a difference of 35%; The protection coefficient is related to the incident angle of gamma irradiation. Compared with normal incidence, the simulated cabin has a higher gamma radiation protection coefficient for oblique 45° incidence, which can be improved by 43%.
2024,
36: 043030.
doi: 10.11884/HPLPB202436.230275
Abstract:
As a kind of high power microwave generator, the plasma relativistic microwave generators (PRMGs) have the virtues of wideband high power microwave output and fine frequency tunability. Thus PRMG is very useful for a wide variety of applications. The beam-wave interaction region in the PRMG is generally a cylindrical metal waveguide with preformed annular plasma. The dispersion characteristics of the operating slow plasma wave TM01 mode (called as P-TM01 mode below) in the interaction region are critical to the output properties. Therefore, the dispersion characteristics and field distributions of the P-TM01 mode in a cylindrical waveguide loaded with annular plasma beam is studied numerically using the all electromagnetic PIC (Particle-in-Cell) code. Variation trends of the dispersion characteristics and the field distributions of the P-TM01 mode with the density np, radial thickness Δrp and radial position rp of the plasma beam, the intensity of the guiding magnetic field Bz and the radius of the waveguide rw are obtained. Simulation results show that: (1) Both np and Δrp affect the dispersion characteristics markedly and the frequency of the P-TM01 mode increases with the increasing of either np or Δrp at the same axial wave number kz. (2) Variations of rp, rw or Bz have very slight influence on the dispersion in the interested range. It is indicated that one can choose relatively larger dimensions of the waveguide for larger power capacity and lower guiding magnetic field for compactness if necessary. (3) The basic features of the field distributions of the P-TM01 mode will not change with the variations of the above mentioned physical parameters. But with the increasing of axial mode number and kz, the electromagnetic energy will be trapped inside the plasma beam gradually and no effective beam-wave interaction will happen in the end. Therefore, it is suggested to choose the operating point with relatively small kz for the efficient operation of PRMG.
As a kind of high power microwave generator, the plasma relativistic microwave generators (PRMGs) have the virtues of wideband high power microwave output and fine frequency tunability. Thus PRMG is very useful for a wide variety of applications. The beam-wave interaction region in the PRMG is generally a cylindrical metal waveguide with preformed annular plasma. The dispersion characteristics of the operating slow plasma wave TM01 mode (called as P-TM01 mode below) in the interaction region are critical to the output properties. Therefore, the dispersion characteristics and field distributions of the P-TM01 mode in a cylindrical waveguide loaded with annular plasma beam is studied numerically using the all electromagnetic PIC (Particle-in-Cell) code. Variation trends of the dispersion characteristics and the field distributions of the P-TM01 mode with the density np, radial thickness Δrp and radial position rp of the plasma beam, the intensity of the guiding magnetic field Bz and the radius of the waveguide rw are obtained. Simulation results show that: (1) Both np and Δrp affect the dispersion characteristics markedly and the frequency of the P-TM01 mode increases with the increasing of either np or Δrp at the same axial wave number kz. (2) Variations of rp, rw or Bz have very slight influence on the dispersion in the interested range. It is indicated that one can choose relatively larger dimensions of the waveguide for larger power capacity and lower guiding magnetic field for compactness if necessary. (3) The basic features of the field distributions of the P-TM01 mode will not change with the variations of the above mentioned physical parameters. But with the increasing of axial mode number and kz, the electromagnetic energy will be trapped inside the plasma beam gradually and no effective beam-wave interaction will happen in the end. Therefore, it is suggested to choose the operating point with relatively small kz for the efficient operation of PRMG.
2024,
36: 043031.
doi: 10.11884/HPLPB202436.230248
Abstract:
In response to the possible breakdown phenomenon of high-power microwave in atmospheric transmission, our study focuses on the first breakdown delay pulse number in pulse sequences. It is found that it is closely related to seed electrons, pulse breakdown probability, and microwave field strength. Microwave field strength can indirectly affect the pulse breakdown probability and delay pulse number through seed electrons. A method is proposed to estimate the critical field strength of microwave breakdown using the number of delayed pulses, and the microwave critical field strength is defined as the breakdown threshold when the probability of pulse breakdown is greater than a certain value. In this paper, the estimation formula of pulse impulse breakdown probability is derived, and the performance of the estimator is analyzed. Then, the experimental verification is carried out using the S band microwave atmospheric breakdown simulation device. The experimental results show that, within a certain range, the number of pulse delays for repetitive frequency microwave pulse breakdown is only inversely proportional to the seed electron generation rate and pulse width, and can be used to estimate the probability of pulse breakdown, thereby giving the critical field strength for breakdown.
In response to the possible breakdown phenomenon of high-power microwave in atmospheric transmission, our study focuses on the first breakdown delay pulse number in pulse sequences. It is found that it is closely related to seed electrons, pulse breakdown probability, and microwave field strength. Microwave field strength can indirectly affect the pulse breakdown probability and delay pulse number through seed electrons. A method is proposed to estimate the critical field strength of microwave breakdown using the number of delayed pulses, and the microwave critical field strength is defined as the breakdown threshold when the probability of pulse breakdown is greater than a certain value. In this paper, the estimation formula of pulse impulse breakdown probability is derived, and the performance of the estimator is analyzed. Then, the experimental verification is carried out using the S band microwave atmospheric breakdown simulation device. The experimental results show that, within a certain range, the number of pulse delays for repetitive frequency microwave pulse breakdown is only inversely proportional to the seed electron generation rate and pulse width, and can be used to estimate the probability of pulse breakdown, thereby giving the critical field strength for breakdown.
2024,
36: 043032.
doi: 10.11884/HPLPB202436.230101
Abstract:
The relativistic electron beam can hit the target with a high injection rate under the ideal paramagnetic environment, but in reality, due to the influence of the environment, the transmission direction of the relativistic electron beam may deviate from the geomagnetic field at a small angle, thus the Larmor precession will be generated by the action of the geomagnetic field, which affects the target aiming of the electron beam as well as the amount of the injection to the target. In this paper, based on the two-dimensional sheet relativistic electron beam, taking the paramagnetic relativistic electron beam and the beam with 3° angle deviation from the magnetic field as two cases, through the simulation of the propagation of the bunches, we analyze and study the effect of different transmission distance on the bunch to target rate in paramagnetic environment, as well as that of the 3° deviation from the magnetic field on the amount of injection in the propagation process, thus to provide data for reference in the prediction of relativistic electron beam-to-target rate and target aiming.
The relativistic electron beam can hit the target with a high injection rate under the ideal paramagnetic environment, but in reality, due to the influence of the environment, the transmission direction of the relativistic electron beam may deviate from the geomagnetic field at a small angle, thus the Larmor precession will be generated by the action of the geomagnetic field, which affects the target aiming of the electron beam as well as the amount of the injection to the target. In this paper, based on the two-dimensional sheet relativistic electron beam, taking the paramagnetic relativistic electron beam and the beam with 3° angle deviation from the magnetic field as two cases, through the simulation of the propagation of the bunches, we analyze and study the effect of different transmission distance on the bunch to target rate in paramagnetic environment, as well as that of the 3° deviation from the magnetic field on the amount of injection in the propagation process, thus to provide data for reference in the prediction of relativistic electron beam-to-target rate and target aiming.
