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Just Accepted manuscripts are peer-reviewed and accepted for publication. They are posted online prior to technical editing formatting for publication and author proofing.
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, Available online ,
doi: 10.11884/HPLPB202638.250283
Abstract:
Background Purpose Methods Results Conclusions
Slots are critical weak scattering sources in stealth aircraft design, significantly influencing Radar Cross Section (RCS). Existing simulation and measurement models often fail to capture true weak scattering behavior, as it is difficult to isolate slot scattering from the low-RCS background.
This study aims to accurately quantify the RCS contribution of weak slots by separating their scattering effect from the background structure, establish relationships between slot dimensions and RCS, and develop a fast estimation method for various slot configurations.
Using the electric field vector superposition principle, a cancellation technique was applied to extract slot scattering from the background. A fast multi-target scatterer accumulation method was developed to predict scattering from single straight slots, arrays, and bent slots. Simulations and experiments were conducted for validation.
The cancellation technique effectively isolated slot scattering, revealing clear RCS-dimension correlations. The fast estimation method agreed well with detailed simulations and experimental measurements across different slot types.
The proposed approach offers an effective tool for designing and optimizing aircraft structures such as skin joints and apertures. It enables efficient RCS evaluation of weak scattering sources, enhancing stealth performance assessment capability.
, Available online ,
doi: 10.11884/HPLPB202638.250362
Abstract:
Background Purpose Methods Results Conclusions
The rapid development of high-power microwave application technology presents significant challenges for the reliability and installability of pulsed power drivers.
The design methodology of a compact, lightweight Tesla-type pulsed power driver based on high-energy-density liquid dielectric Midel 7131 and a dual-width pulse-forming line (PFL) is introduced.
There was a key breakthrough in the miniaturization of the integrated Tesla transformer and PFL assembly. Through optimization of the electrical length of the short pulse transmission line and its impedance matching characteristics, longstanding challenges associated with conventional single-cylinder PFLs and extended transmission lines using transformer oil dielectrics have been effectively resolved. A high-elevation, high-vacuum oil impregnation technique was developed for the Tesla transformer, successfully mitigating partial discharge in oil-paper insulation systems and thereby enhancing the power rating and operational reliability of the PFL.
The developed pulsed power driver delivers a peak output power of 20 GW, a pulse duration of 50 ns, a pulse flat-top fluctuation of less than 2%, and a maximum repetition rate of 50 Hz. The system has demonstrated stable operation over continuous one-minute durations, accumulating approximately 200 000 pulses with consistent performance. The driver’s overall dimensions are 4.0 m(L)×1.5 m (W)×1.5 m (H), with a total mass of approximately 5 metric tons.
Compared to the conventional 20 GW Tesla-type pulsed power generator, this driver has achieved significant improvements in power density and miniaturization.
, Available online ,
doi: 10.11884/HPLPB202638.250123
Abstract:
Background Purpose Methods Results Conclusions
Owing to its unique miniaturized structure, real-time frequency tuning capability, and broad-spectrum microwave output characteristics, the gyromagnetic nonlinear transmission line (GNLTL) exhibits considerable application potential in the development of small-scale solid-state high-power microwave sources. This has driven the need for in-depth exploration of its circuit characteristics and parameter influences to optimize its performance.
This study aims to derive the analytical expression of solitons in the GNLTL equivalent circuit, construct a reliable equivalent circuit model of GNLTL, and systematically clarify the influence mechanism of key circuit parameters on its output characteristics.
Firstly, the analytical expression of solitons in the GNLTL equivalent circuit was obtained through theoretical deduction. Secondly, an equivalent circuit model of GNLTL was established using circuit simulation methods. Finally, the influence mechanism of key circuit parameters on the output characteristics of GNLTL was systematically investigated based on the constructed model.
The results show that the saturation current and initial inductance of the nonlinear inductor have a decisive effect on the nonlinear characteristics of the circuit: when these two parameters are small, the leading edge of the output pulse is not fully steepened and is accompanied by oscillating waveforms; increasing them improves the steepening degree of the pulse leading edge, indicating a positive correlation between these two parameters and circuit nonlinearity. Additionally, enhanced nonlinearity of the equivalent circuit leads to a decrease in output frequency; saturation current, saturation inductance, initial inductance, and capacitance per stage all show a negative correlation with the output microwave frequency.
The findings of this study clarify the relationship between key circuit parameters and the nonlinear characteristics as well as output frequency of GNLTL, thereby providing theoretical and simulation references for the design and performance analysis of gyromagnetic nonlinear transmission lines.
, Available online ,
doi: 10.11884/HPLPB202638.250067
Abstract:
Background Purpose Methods Results Conclusions
Neutron nuclear data are crucial for fundamental research in nuclear physics, providing essential information for nuclear science and engineering applications. Advanced high-current accelerator neutron sources serve as the foundation for nuclear data measurements. The neutron converter target is a key component of such high-current accelerator neutron sources. Under intense particle beam bombardment, the heat dissipation of the neutron converter target is a critical factor limiting the neutron yield and operational stability.
This study aims to address the insufficient heat dissipation capacity of traditional gas targets by designing a novel dynamic gas target system. By optimizing the structure of the gas target chamber to form an active cooling circulation loop, it seeks to solve the cooling problem within the confined space of the gas target chamber.
First, a conceptual design of the gas target system and chamber structure was conducted. The Target software was then used to analyze the energy straggling of incident ions caused by the metal window and the gas itself. Numerical simulations of the thermal environment inside the gas target chamber were performed. The heat source was dynamically loaded based on gas density by coupling with SRIM calculations of the heating power. The gas flow patterns within the target chamber under different beam currents and inlet velocities were analyzed.
The energy straggling calculations show that the contribution from the gas is very small, with the metal window being the primary source of energy straggling for incident ions. The simulation results indicate that as the beam current increases, the heating power rises gradually, while the density in the heated region decreases rapidly. Increasing the inlet flow velocity enhances the heat dissipation capacity and reduces the density drop effect caused by beam heating.
The comprehensive performance evaluation demonstrates that this dynamic gas target system can achieve a neutron yield of up to 5.2×1012 n/s at a beam current of 10 mA. The results prove that the novel dynamic gas target system effectively improves heat dissipation performance, contributes to obtaining a higher neutron yield, and ensures operational stability under high-current application scenarios.
, Available online ,
doi: 10.11884/HPLPB202638.250252
Abstract:
Background Purpose Methods Results Conclusions
High-power femtosecond fiber lasers are essential tools for advanced applications in ultrafast science, precision manufacturing, and nonlinear optics. However, achieving hundred-watt-level output while maintaining high beam quality and short pulse duration remains challenging due to nonlinear effects and transverse mode instabilities.
This work aims to develop a high-power femtosecond fiber laser system based on chirped-pulse amplification (CPA), using rod-type photonic crystal fiber as the gain medium, to achieve hundred-watt-level output with high efficiency and stable beam quality.
The system adopts a rod-type photonic crystal fiber as the main amplifier. Backward pumping combined with double-pass amplification in a single rod fiber is implemented to enhance pump-to-signal conversion efficiency. Nonlinear effects are mitigated by employing a large mode area fiber, short gain length, and proper chirped-pulse management. A double-grating compressor is used for final pulse compression.
The amplifier achieves a pump-to-signal conversion efficiency exceeding 60%. The system delivers pulses with a central wavelength of 1033 nm, a repetition rate of 1 MHz, a single-pulse energy of 162 μJ, and a pulse duration of 233 fs. The output beam ellipticity is better than 95%. The overall pump-to-compressed-signal efficiency reaches 54%.
The demonstrated system achieves high repetition rate, high average power, and ultrashort pulse duration simultaneously, providing a novel and practical scheme for hundred-watt-level femtosecond fiber lasers. This approach offers new opportunities for applications requiring stable, high-brightness ultrafast sources.
, Available online ,
doi: 10.11884/HPLPB202638.250257
Abstract:
Background Purpose Methods Results Conclusions
Space solar arrays, as a crucial part of satellite power systems, are essential for maintaining normal satellite operation. Their large surface area and complex insulation structure make them highly vulnerable to strong external electromagnetic fields. High-power microwaves (HPM), with their wide bandwidth, high power, and rapid action, can readily damage such structures. Therefore, investigating the HPM coupling effects on space solar arrays is of significant importance.
This study investigates the electric field coupling of space solar cell array samples under high-power microwave exposure.
Using a representative solar cell array structure and layout as a reference, this study constructs a three-dimensional model under high-power microwave irradiation and examines the coupling behavior of the array under varying excitation source parameters, including frequency, polarization direction, incidence angle and so on.
（1）Within the frequency range of 2–18 GHz, vertically polarized S-band microwave irradiation is most likely to induce discharge damage to the solar cell array, with the induced electric field at the triple junction in cell string gaps being much higher than that at interconnect gaps. (2) Under microwave irradiation, the solar cell samples exhibit intense transient electric fields; in the case of vertical polarization, the induced field is mainly concentrated in the cell string gaps, near the busbars, and along the cell edges. (3) The steady peak of the induced electric field at the triple junction decreases with increasing microwave incidence angle and increases with higher microwave power density. (4) The rise and fall times of the microwave pulse have no significant effect on the induced electric field magnitude. (5) The electric field in the space around the cell string gap gradually decreases from the gap center toward the outer region.
The findings of this study provide valuable references for the electromagnetic protection design of space solar cell arrays.
, Available online ,
doi: 10.11884/HPLPB202638.250070
Abstract:
Background Purpose Methods Results Conclusions
Optical manipulation based on integer-order vortex beams is widely used in nanotechnology, yet their discrete nature restricts continuous and precise transverse control of nanoparticles.
This study aims to overcome this limitation by proposing a novel approach using fractional-order vortex beams (FVBs), with the goal of achieving continuous and precise transverse optical trapping and manipulation of nanoparticles.
We developed a vector diffraction model to characterize the focal field of FVBs, revealing it as a coherent superposition of integer-order modes with a highly asymmetric weight distribution. Additionally, an optical force model was established to analyze the trapping behavior of spherical nanoparticles. Theoretical calculations and Langevin dynamics simulations were employed to evaluate the three-dimensional trapping stability and multi-degree-of-freedom manipulation capability.
The transverse trapping position exhibits a linear dependence on the fractional topological charge. By continuously tuning the topological charge, nanoparticles can be displaced precisely and continuously in the transverse plane with sub-wavelength accuracy—a capability not achievable with conventional integer-order vortex beams. Simulations further confirm the stability of the three-dimensional trap and the feasibility of coordinated multi-degree-of-freedom manipulation.
This work demonstrates that fractional-order vortex beams offer a superior alternative for high-precision optical manipulation. They provide a powerful and novel technique for applications in microfluidics, nanofabrication, and lab-on-a-chip devices.
, Available online ,
doi: 10.11884/HPLPB202638.250256
Abstract:
Background Purpose Methods Results Conclusions
In the fields of high-power microwaves and pulse compression, compared with exponentially decaying microwave pulses, flat-top output has core advantages such as reducing the maximum transient surface field of the structure and enhancing system stability. Therefore, it has significant technical significance and application value.
The purpose of this study is to develop a new method for power doubling that generates a flat-topped output and to observe its benefits through simulation experiments.
The research analyzes the energy storage process and the power gain and flat-top output width after input inversion based on the scattering matrix theory, and conducts simulation experiments using CST.
The simulation experiment results show that its power gain is more than 5.7 times, the flat top width is 80 ns, the waveform is gentle, and the power capacity can reach 160 MW.
Compared with the existing technology, this design has a simple structure, compact volume and convenient processing and maintenance, providing a new solution for the stable output of high-power microwave energy and the research of two-stage pulse compression systems.
, Available online ,
doi: 10.11884/HPLPB202638.250174
Abstract:
Background Purpose Methods Results Conclusions
Accurate identification of radionuclides is the key to improving the level of radioactivity monitoring.
To further enhance the performance of radionuclide identification, a method combining Convolutional Neural Network (CNN) and Recurrent Neural Network (RNN) for radionuclide identification has been studied.
Gamma-ray spectra data of eight single and mixed radioactive nuclides were collected using a sodium iodide spectrometer, and a large number of gamma-ray spectral training data were generated by calculating the probability density of gamma photons at different energy levels and using random sampling methods, followed by normalization of the data. The CNN was then used to extract feature vectors from the input spectral data, and these extracted feature vectors were fed into the RNN for training, with the final radionuclide classification results being output by the activation function.
To verify the accuracy of the CNN-RNN method in identifying radionuclides, a comparative analysis was conducted with the radionuclide identification method based on Convolutional Neural Network (CNN) and Long Short-Term Memory Neural Network (LSTM), and the results showed that the LSTM spectral model achieved a recognition accuracy rate of over 97.5% for single nuclides and over 92.31% for mixed nuclides on the test set, while the CNN and CNN-RNN spectral models achieved a recognition accuracy rate of 100% for single nuclides and recognition rates of over 92.95% and 97.44% for mixed nuclides.
respectively, indicating that the CNN-RNN method performs better in gamma-ray spectral identification of radioactive nuclides, Compared with neural network models trained only on real - measured data, incorporating augmented data can improve the training efficiency and generalization ability of the models.
, Available online ,
doi: 10.11884/HPLPB202638.250178
Abstract:
Background Purpose Methods Results Conclusions
Different applications require lasers of different wavelengths, and Raman laser is one of effective methods to expand spectral range of lasers. Raman lasers have advantages of high conversion efficiency, excellent beam quality, excellent scalability and wide range coverage etc. However, the cumbersome size of Raman cell (especially the long length of Raman cell) deteriorates the application of Raman laser. To reduce the length of Raman cell, a short-focus lens is required, and this would lead laser-induced breakdown (LIB).
To realize miniaturization of Raman laser devices while suppressing LIB, this work proposed a method to modulate the pump laser into a Bessel beam to achieve stimulated Raman frequency conversion using an axicon. The goal is to achieve high photon conversion efficiency (PCE) and beam quality in a compact system.
By the comparison of intensity at focus and depth of focus of f = 0.5 m focal lens and axicon, axicon with bottle angle of 2° could effectively reduce laser intensity at focus and increase the depth of focus. In this work, a pulsed 1064 nm laser was used as pump source, pressurized methane was used as Raman medium, and axicon with bottle angle of 2° was used to focus pump laser. Pressure of methane, pump laser divergence angles and diameter of pump beam were optimized to achieve the maximum conversion efficiency.
In 3.5 MPa methane and 366 mJ energy of 1064 nm pump laser, 128 mJ forward Raman laser at 1543 nm was generated; the corresponding photon conversion efficiency was 50.7%, and higher output energy and conversion efficiency were expected under higher pressure and at higher pump energy. By blocking the central rounded apex of the axicon, the Raman laser pulse energy of 97 mJ can still be retained with the beam quality β=2.19. An experiment verified that the Raman cell can be designed to be 0.4 m without damaging the window. Based on the results of multiple experiments, it can be inferred that the Raman cell can be further shortened to 0.3 m without sacrificing the conversion efficiency. By axially translating the axicon within an extended cell, the forward/backward Stokes light ratio became tunable.
This study demonstrates the viability of Bessel beams for compact, high-efficiency gaseous Raman lasers. The conical wavefront pumping strategy mitigate LIB risks and enable system miniaturization, offering a promising pathway for practical applications.
, Available online ,
doi: 10.11884/HPLPB202638.250184
Abstract:
Background Purpose Methods Results Conclusions
The output switch is an essential part of the electromagnetic pulse simulator, and the switch gap directly affects the waveform characteristics of the electric field generated by the simulator. The single-polarity electromagnetic pulse simulator can adjust the switch gap by an external motor, but the bipolar electromagnetic pulse simulator cannot use the method due to the influence of mechanical structure and high voltage insulation.
This study aims to investigate a gas-driven method to achieve precise regulation of the switch gap in a bipolar electromagnetic pulse simulator.
Firstly, the basic structure of the gas remote adjustment system is proposed, which takes the cylinder as the actuator and connects with the outer cavity body through air pipe. Secondly, based on the structure, the mathematical model of the switch gap adjustment system is established. Thirdly, in view of the disadvantage of slow gas driving response, a switch gap control method combining trajectory planning and PIDA control method is proposed; Finally, the effectiveness of this method is verified by using Matlab simulation software.
Simulation results of the whole regulation process can be seen that when the switch gap is moved from 0 mm to the desired 30 mm, the process tracking error of the switch gap is less than 3.5 mm, and the final error is less than 0.5 mm.
This paper proposes a gas-driven switch gap adjustment method,which can achieve fast and accurate adjustment of the switch electrode gap, and a single adjustment can be within 200s, with an adjustment error of less than 0.5 mm. This method is of great significance for the engineering construction of electromagnetic pulse simulators.
, Available online ,
doi: 10.11884/HPLPB202638.250181
Abstract:
Background Purpose Methods Results Conclusions
The surface flashover in SF6 under nanosecond pulses involves complex physical processes, and accurately predicting the surface flashover voltage of insulating media in such environments constitutes a critical challenge for the design of high-voltage pulsed power equipment and the evaluation of insulation reliability. Compared with traditional AC or DC voltages, the extremely short rise time and high amplitude of nanosecond pulses lead to significant space charge effects and distinct discharge development mechanisms, thereby posing severe challenges to prediction models based on classical theories. In recent years, with the rapid improvement of computer computing power and breakthroughs in artificial intelligence algorithms, data-driven machine learning methods have demonstrated great potential in solving complex nonlinear insulation problems.
Targeting this specific challenge under nanosecond pulses, this paper selects four algorithms, including support vector machine (SVM), multi-layer perceptron (MLP), random forest (RF), and extreme gradient boosting (XGBoost), to train and predict flashover voltage data under different experimental conditions within the multi-scale distance range of 15 mm to 500 mm.
First, external operating conditions such as electric field distribution, voltage waveform, and gas pressure were parametrically extracted and characterized. The Pearson correlation coefficient was employed to conduct a correlation analysis on the aforementioned characteristic parameters, and ultimately 22 feature quantities were screened out as the model inputs. Subsequently, the Bayes hyperparameter optimization algorithm was utilized to perform hyperparameter optimization for four types of algorithms, and the 10-fold cross-validation method was adopted to select the optimal hyperparameter combination for each algorithm. After that, the sample training set was input into the four algorithms for training, and each algorithm was validated on the test set.
The four algorithms demonstrated overall good performance. Among them, Random Forest (RF) and XGBoost exhibited excellent performance on the training set but poor performance on the validation set, which is likely a manifestation of overfitting in ensemble learning and indicates weak generalization ability. Support Vector Machine (SVM) achieved relatively outstanding performance on both the training set and the validation set. Furthermore, the generalization performance of the SVM and XGBoost algorithms was validated using data outside the sample dataset. The results showed that SVM yielded better prediction outcomes on the data outside the sample dataset.
SVM achieved high prediction accuracy on the training set, test set, and data outside the sample dataset, making it more suitable for the insulation design of electromagnetic pulse simulation devices.
, Available online ,
doi: 10.11884/HPLPB202638.250187
Abstract:
Airborne Synthetic Aperture Radar (SAR) is vulnerable to continuous wave (CW) interference in complex electromagnetic environments, leading to significant degradation in imaging quality. Its susceptibility to front-door coupling electromagnetic effects is a critical concern. This study aims to systematically investigate the impact patterns and physical mechanisms of single-frequency CW interference on airborne SAR imaging through equivalent injection experiments. It further seeks to establish a robust evaluation method for interference effects. Equivalent injection testing was employed to simulate CW interference susceptibility. The interference effect was evaluated using a composite SAR image quality factor integrating the Pearson Correlation Coefficient (PCC), Structural Similarity Index (SSIM), and Peak Signal-to-Noise Ratio (PSNR). Detailed analysis of the radio frequency (RF) front-end response and Analog-to-Digital Converter (ADC) behavior under interference was conducted. Significant interference effects were observed when the interfering frequency fell within the receiver's hardware passband (8.5-9.5 GHz) and the Jammer-to-Signal Ratio reached 15 dB. While the RF front-end exhibited no significant nonlinearity, the interference induced a nonlinear response specifically within the internal Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) of the ADC sampling chip. This nonlinearity generated additional DC components and harmonics, identified as the fundamental physical cause of characteristic interference stripes and overall SAR image quality degradation. The generation of DC offsets and harmonic distortion within the ADC's MOSFET circuitry is the root physical mechanism behind SAR image degradation under CW interference within the specified band and JSR threshold. This research provides a solid theoretical foundation for designing electromagnetic interference (EMI) countermeasures in airborne SAR systems, thereby enhancing their robustness and imaging capability in challenging complex electromagnetic environments.
Airborne Synthetic Aperture Radar (SAR) is vulnerable to continuous wave (CW) interference in complex electromagnetic environments, leading to significant degradation in imaging quality. Its susceptibility to front-door coupling electromagnetic effects is a critical concern. This study aims to systematically investigate the impact patterns and physical mechanisms of single-frequency CW interference on airborne SAR imaging through equivalent injection experiments. It further seeks to establish a robust evaluation method for interference effects. Equivalent injection testing was employed to simulate CW interference susceptibility. The interference effect was evaluated using a composite SAR image quality factor integrating the Pearson Correlation Coefficient (PCC), Structural Similarity Index (SSIM), and Peak Signal-to-Noise Ratio (PSNR). Detailed analysis of the radio frequency (RF) front-end response and Analog-to-Digital Converter (ADC) behavior under interference was conducted. Significant interference effects were observed when the interfering frequency fell within the receiver's hardware passband (8.5-9.5 GHz) and the Jammer-to-Signal Ratio reached 15 dB. While the RF front-end exhibited no significant nonlinearity, the interference induced a nonlinear response specifically within the internal Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) of the ADC sampling chip. This nonlinearity generated additional DC components and harmonics, identified as the fundamental physical cause of characteristic interference stripes and overall SAR image quality degradation. The generation of DC offsets and harmonic distortion within the ADC's MOSFET circuitry is the root physical mechanism behind SAR image degradation under CW interference within the specified band and JSR threshold. This research provides a solid theoretical foundation for designing electromagnetic interference (EMI) countermeasures in airborne SAR systems, thereby enhancing their robustness and imaging capability in challenging complex electromagnetic environments.
, Available online ,
doi: 10.11884/HPLPB202638.250248
Abstract:
Background Purpose Methods Results Conclusions
Pulse step modulation (PSM) high-voltage power supply is widely used in the heating systems of the Experimental Advanced Superconducting Tokamak (EAST). This power supply adopts a modular topology, where the high output voltage is generated by superimposing the outputs of multiple independent DC power modules. In conventional designs, input over-voltage and under-voltage protection for each power module is achieved by installing individual voltage sensors across the input capacitors.
However, this method requires a large number of voltage sensors, which significantly increases system monitoring costs and complicates the hardware detection circuitry. To address these limitations, this study aims to develop a sensorless voltage measurement (SVM) method capable of estimating the input voltage of each power module using only a single voltage sensor on the output side.
This paper first introduces the circuit topology of the PSM high-voltage power supply and provides a detailed analysis of its control strategy. Building on this foundation, a novel sensorless voltage detection technique is proposed to estimate the input voltage of each power module. The method utilizes only one voltage sensor installed at the output side of the PSM high-voltage power supply to collect voltage signals, from which the input voltages of individual modules are derived through algorithmic processing.
To validate the proposed method, a model was constructed and tested based on the RT-LAB real-time simulation platform. Experimental results demonstrate that the SVM technique can effectively estimate input voltages, thereby confirming the feasibility of the proposed method.
The study concludes that the SVM method not only reduces the number of required sensors and associated costs but also simplifies the system architecture while maintaining reliable module-level voltage monitoring. The findings provide valuable insights for the design of modular power supplies in large-scale experimental setups and suggest potential applications in other multi-module power electronic systems.
, Available online ,
doi: 10.11884/HPLPB202638.250112
Abstract:
Background Purpose Methods Results Conclusions
Envelope instabilities and halo formation are critical challenges limiting beam quality in space-charge-dominated beams of low-energy superconducting proton linear accelerators. The dynamic evolution of focusing parameters during acceleration and the intrinsic role of double-period focusing structures in the low-energy region in these phenomena remain insufficiently explored.
This study aims to systematically investigate the influence of dynamically evolving focusing parameters on envelope instabilities, reveal the relationship between double-period focusing structures and halo formation, and achieve localized breakthroughs of the zero-current phase advance σ0 beyond 90° while optimizing beam quality.
A theoretical model was established via the second-order even-mode expansion of the Vlasov–Poisson equations. Multiple evolution schemes were designed, and multi-particle simulations were performed on low-energy proton beams (normalized RMS emittance: 0.2–0.4 π·mm·mrad). The particle–core model was used to compare halo formation mechanisms between quasi-periodic and double-period structures, with two-dimensional and three-dimensional models verifying key findings.
For weak space-charge effects (high η), σ0 can exceed 90° without degrading beam quality; strong space-charge effects (low η) induce resonances and emittance growth, especially in doublet structures. Double-period structures cause envelope instability even with σ0 < 90° per cell, being more prone to halo formation via the 2∶1 resonance. Longitudinal beam size variations alter core charge density (a new halo mechanism), and higher-order resonances contribute significantly. The number of short-period cells (N) correlates inversely with resonance probability.
Dynamic focusing parameters and double-period structures strongly affect envelope instabilities and halo formation. The 2∶1 resonance and longitudinal-transverse coupling are key halo mechanisms. σ0 breakthrough beyond 90° is feasible under weak space-charge conditions, and increasing N reduces resonance risk. These findings provide theoretical and numerical support for beam quality optimization in low-energy superconducting proton linac.
, Available online ,
doi: 10.11884/HPLPB202638.250171
Abstract:
Background Purpose Methods Results Conclusions
The use of high-power lasers for Wireless Power Transmission (WPT) in space-based solar power stations poses a potential risk to orbiting spacecraft. Misalignment or system failures could cause the laser beam to irradiate a spacecraft's solar array, potentially inducing discharge phenomena that threaten the spacecraft's safety. Existing research has primarily focused on the thermal damage effects of lasers on solar arrays, while studies on the characteristics of laser-induced discharge remain insufficient.
This study aims to systematically investigate the influence of two key laser parameters, energy and wavelength, on the discharge characteristics of spacecraft solar arrays. The goal is to reveal the underlying mechanisms of laser-induced discharge, thereby providing a theoretical and experimental basis for the safe application of high-power laser wireless energy transmission technology.
The mechanism of laser-induced solar array discharge was analyzed based on laser-induced plasma theory and discharge mechanisms within the Low Earth Orbit (LEO) plasma environment. Guided by this theoretical framework, the experimental parameters for the laser-induced spacecraft solar array discharge test were determined. The experiment analyzed the probability of discharge induced by a 532 nm laser at different energy levels and acquired discharge duration data. Probability-time distribution curves were established, and the probability functions for discharge duration under different laser energies were obtained by fitting with a double Poisson distribution. Furthermore, a comparative study was conducted on the peak discharge current and the duration probability functions induced by 532 nm and 266 nm wavelength lasers at the same energy level.
The experimental results demonstrate that higher laser energy leads to a greater probability of induced discharge and longer discharge durations. Shorter laser wavelengths result in a lower discharge threshold and induce discharge events with higher peak currents. The discharge risk parameter increases significantly with shorter wavelength and higher energy.
Laser energy and wavelength are critical factors affecting the discharge risk of solar arrays. Short-wavelength, high-energy lasers pose a greater threat to solar array safety. The findings of this study provide important guidance for selecting laser parameters in WPT systems and for designing protective measures for solar arrays.
, Available online ,
doi: 10.11884/HPLPB202638.250182
Abstract:
Achieving high-efficiency and high-power operation under low magnetic fields is an important development trend for high-power microwave sources. In order to enhance the efficiency of high-power microwave source under low guiding magnetic fields, a high-efficiency coaxial dual-mode relativistic Cherenkov oscillator (RCO) under a low guiding magnetic field is proposed. The RCO works in both coaxial quasi-TEM mode and TM01 mode and realizes high-efficiency output in low magnetic field (＜0.4 T). In particle-in-cell simulation, when the guiding magnetic field is only 0.35 T, the RCO achieves a microwave output of 3 GW with a beam-wave conversion efficiency of 40%. At the same time, aiming at the RF breakdown phenomenon in the experiment, the power capacity is improved by increasing the number of slow wave structure periods, which is verified by both simulation and experiment. In the experiment, under a magnetic field of 0.37 T, the output power is 2.85 GW with a pulse width of 57 ns and conversion efficiency of 34%. The experimental results obtained under the low magnetic field provide strong support for the development of miniaturization of high-power microwave systems.
Achieving high-efficiency and high-power operation under low magnetic fields is an important development trend for high-power microwave sources. In order to enhance the efficiency of high-power microwave source under low guiding magnetic fields, a high-efficiency coaxial dual-mode relativistic Cherenkov oscillator (RCO) under a low guiding magnetic field is proposed. The RCO works in both coaxial quasi-TEM mode and TM01 mode and realizes high-efficiency output in low magnetic field (＜0.4 T). In particle-in-cell simulation, when the guiding magnetic field is only 0.35 T, the RCO achieves a microwave output of 3 GW with a beam-wave conversion efficiency of 40%. At the same time, aiming at the RF breakdown phenomenon in the experiment, the power capacity is improved by increasing the number of slow wave structure periods, which is verified by both simulation and experiment. In the experiment, under a magnetic field of 0.37 T, the output power is 2.85 GW with a pulse width of 57 ns and conversion efficiency of 34%. The experimental results obtained under the low magnetic field provide strong support for the development of miniaturization of high-power microwave systems.
, Available online ,
doi: 10.11884/HPLPB202638.250204
Abstract:
Background Purpose Methods Results Conclusions
The PFN-Marx pulse driver with millisecond charging holds significant potential for achieving lightweight and miniaturized systems. To ensure its long-life, stable, and reliable operation, the development of a triggered gas gap switch represents a key technological challenge.
This study aims to address issues related to the large dispersion in operating voltage and rapid erosion of the trigger electrode under millisecond charging conditions.
Based on the operating mechanism of the corona-stabilized switch, a corona-based gas-triggered switch was developed. Investigations were conducted on its structural design, electrostatic field simulation, trigger source development, operational voltage range, time delay, and jitter characteristics. These efforts resolved the problem of frequent self-breakdown or trigger failure under millisecond charging.
Experimental results demonstrate that, using SF6 as the working gas at a pressure of 0.6 MPa, the maximum operating voltage of the triggered switch reaches 90 kV. Under conditions of 84 kV operating voltage, 20 Hz repetition frequency, 500 pulses per burst, and without gas replacement, the switch was tested continuously for 100,000 pulses. Only one self-breakdown incident occurred during this period, resulting in a self-breakdown rate of less than 0.01‰.
The triggered switch developed in this study meets the design requirements and effectively resolves the instability issues under millisecond charging conditions, thereby providing a foundation for future engineering applications.
, Available online ,
doi: 10.11884/HPLPB202638.250176
Abstract:
Background Purpose Methods Results Conclusions
Global Navigation Satellite System (GNSS) compatible receiver antennas—integrating multiple global navigation constellations—feature more complex front-door radio frequency (RF) channel architectures than single-constellation GPS antennas. High power microwave (HPM) effect research on GNSS compatible antennas with complex RF front-end were rarely seen.
To investigate the GNSS compatible antenna HPM effects, radiation experiments on a type of GNSS-compatible receiver antenna were carried out, a customized characterization approach was designed to analyze the damaged antennas and identify the specific failed components within the complex RF front-end.
The RF front-end structure of the antenna was analyzed, revealing a design with two separate RF channels (around 1.25 GHz and 1.6 GHz), each with a dedicated first-stage low-noise amplifier (LNA), followed by shared second and third-stage LNAs. The performance of these components was characterized employing a customized “hot measurement” setup, which using a vector network analyzer incorporating a test antenna and a DC blocker.
The measurements pinpointed the failure to the first-stage LNA (Q6) of the RF channel corresponding to the HPM source frequency of 1.6 GHz. This specific component showed significant degradation or complete failure. In contrast, the first-stage LNA (Q4) of the other channel (～1.25 GHz) and the shared subsequent amplifier stages (Q2 and Q1) remained unaffected. The root cause was confirmed by replacing the damaged Q6 LNA, which successfully restored the antenna’s full functionality.
This work demonstrates that in a multi-channel RF front-end, HPM effects can be highly localized, selectively damaging the first-stage amplifier of the channel cover the HPM frequency while sparing other sections. The findings provide valuable insights into the HPM vulnerability of complex RF systems and offer a reference methodology for related effect analysis.
, Available online ,
doi: 10.11884/HPLPB202638.250018
Abstract:
Background Purpose Methods Results Conclusions
Field-programmable gate array (FPGA)-based time-to-digital converters (TDCs) have been extensively employed for high-precision time interval measurements, in which picosecond-level resolution is often required. Among existing approaches, the delay-line method remains widely used, while the system clock frequency and the delay chain design are recognized as the primary factors affecting resolution and linearity.
The objective of this study is to develop a multi-channel FPGA-TDC architecture that integrates multiphase clocking with delay-line interpolation, thereby lowering the operating frequency, improving linearity, and reducing hardware resource utilization, while maintaining high measurement resolution.
A two-stage interpolation scheme was introduced, where fine time measurement cells were implemented through the combination of multiphase clocks and shortened delay chains. This configuration mitigates the accumulation of nonlinearity in the delay elements and reduces the scale of thermometer-to-binary encoders, resulting in decreased logic overhead. The proposed TDC was implemented on a Xilinx ZYNQ-7035 device, and its performance was evaluated within a measurement range of 0–16000 ps.
The experimental evaluation demonstrated that a time resolution better than 4 ps was achieved. The measured differential nonlinearity (DNL) was in the range of −1 least significant bit (LSB) to +7 LSB, while the integral nonlinearity (INL) ranged from −2 LSB to +14 LSB. Compared with conventional architectures, the proposed scheme shortens the delay chain length by several times at the same operating frequency, and achieves lower frequency with the same chain length.
The proposed two-stage interpolation architecture not only enhances resolution and linearity but also significantly reduces logic resource consumption, demonstrating strong application potential.
, Available online ,
doi: 10.11884/HPLPB202638.250155
Abstract:
Background Purpose Methods Results Conclusions
Currently, the bias power supplies in high-voltage electron beam welders, both domestically and internationally, are suspended at a negative high voltage. The output voltage regulation is achieved by sampling the operating current in the high-voltage power circuit. The sampled current signal undergoes multi-stage conversion before being sent to the bias power supply, which then adjusts its output voltage based on the feedback current. This adjusted output voltage, in turn, alters the current in the high-voltage circuit. Since the bias power supply is an inverter-based power source, its response and adjustment cycles are relatively long, and precise step-wise regulation is challenging. Consequently, this leads to significant beam current ripple, poor stability, and inadequate beam current reproducibility, failing to meet the requirements of precision welding for beam current stability and low fluctuation.
This paper aims to develop a bias power supply with an adjustable DC output voltage ranging from −100 V to −2 kV, featuring low voltage ripple and high voltage stability. The bias power supply can be connected in series within the high-voltage circuit, enabling rapid adjustment and precise control of the operating beam current through a fast closed-loop feedback control system. Additionally, the bias power supply must operate reliably during load arcing of the electron gun.
The design incorporates absorption and protection methods to address the issue of electron gun load arcing damaging the bias power supply. By connecting the bias power supply in series within the high-voltage circuit and feeding back the operating current in the bias power supply loop, the output voltage (bias cup voltage) is adjusted. The bias cup voltage adaptively regulates according to the beam current magnitude, achieving real-time rapid tracking and fine control of the operating beam current.
A bias power supply was developed with an adjustable DC output voltage from −100 V to −2 kV, featuring a ripple voltage of ≤0.1% across the entire voltage range, voltage stability better than 0.1%, and an output current greater than 3 mA. When applied to a −150 kV/33 mA high-voltage electron beam welder, it achieved a beam current ripple of ±0.19%, beam current stability better than ±5 μA, and beam current reproducibility of ±0.04%.
Based on the methods of absorption, protection, and adaptive regulation of the bias cup voltage according to the beam current magnitude, a novel bias power supply for high-voltage electron beam welders has been successfully developed. This solution addresses the issues of large beam current ripple, poor stability, and inadequate reproducibility in high-voltage electron beam welding, providing an effective approach for high-stability, precision-controllable welding.
, Available online ,
doi: 10.11884/HPLPB202638.250238
Abstract:
Background Purpose Method Results Conclusions
Accurately simulating the gas-solid coupled heat transfer in high-temperature pebble-bed reactors is challenging due to the complex configuration involving tens of thousands of fuel pebbles. Conventional unresolved CFD-DEM methods are limited in accuracy by their requirement for coarse fluid grids, whereas fully resolved simulations are often prohibitively expensive.
This study aims to develop a semi-resolved function model suitable for fine fluid grids to enable accurate and efficient coupled thermal-fluid simulation in pebble beds.
A Gaussian kernel-based semi-resolved function was introduced to smooth physical properties around particles and compute interphase forces via weighted averaging. The key parameter, the dimensionless diffusion time, was optimized through comparison with Voronoi cell analysis. The model was implemented in an open-source CFD-DEM framework and validated against both a single-particle settling case and a fluidized bed experiment.
Voronoi cell analysis determined the optimal diffusion time to be 0.6. Exceeding this value over-smoothens the spatial distribution and obscures local bed features. The single particle settling case demonstrated excellent agreement with experimental terminal velocities under various viscosities. The fluidized bed simulation successfully captured porosity distribution and the relationship between fluid velocity and particle density, consistent with experimental data. Application to HTR-10 pebble bed thermal-hydraulics showed temperature distributions aligning well with the SA-VSOP benchmark.
The proposed semi-resolved function model effectively overcomes the grid size limitation of traditional CFD-DEM, accurately capturing interphase forces in sub-particle-scale grids. It provides a high-precision and computationally viable scheme for detailed thermal-fluid analysis in advanced pebble-bed reactors.
, Available online ,
doi: 10.11884/HPLPB202638.250243
Abstract:
Background Purpose Methods Results Conclusions
The traditional Monte-Carlo (MC) method faces an inherent trade-off between geometric modeling accuracy and computational efficiency when addressing real-world irregular terrain modeling.
This paper proposes a fast MC particle transport modeling method based on irregular triangular networks for complex terrains, addressing the technical challenge of achieving adaptive and efficient MC modeling under high-resolution complex terrain scenarios.
The methodology consists of three key phases: First, high-resolution raster-format terrain elevation data are processed through two-dimensional wavelet transformation to precisely identify abrupt terrain variations and extract significant elevation points. Subsequently, the Delaunay triangulation algorithm is employed to construct TIN-structured terrain models from discrete point sets. Finally, the MCNP code's "arbitrary polyhedron" macrobody definition is leveraged to establish geometric planes, with Boolean operations applied to synthesize intricate geometric entities, thereby realizing rapid automated MC modeling for high-resolution complex terrains.
Results demonstrate that the proposed method accurately reproduces terrain-induced effects on radiation transport, achieving high-fidelity simulations while significantly compressing the number of cells and enhancing computational efficiency.
This methodology represents a novel approach for large-scale radiation field modeling under complex terrain constraints, demonstrating broad applicability to MC particle transport simulations in arbitrary large-scale complex terrain scenarios.
, Available online ,
doi: 10.11884/HPLPB202638.250049
Abstract:
Background Purpose Methods Results Conclusions
The motion and trapping of high-energy charged particles in the radiation belts are significantly influenced by the structure of Earth's magnetic field. Utilizing different geomagnetic models in simulations can lead to varying understandings of particle loss mechanisms in artificial radiation belts.
This study aims to simulate and compare the trajectories and loss processes of 10 MeV electrons injected at different longitudes and L-values under the centered dipole, eccentric dipole, and International Geomagnetic Reference Field (IGRF) models, to elucidate the influence of geomagnetic field models on particle trapping and loss, particularly within the South Atlantic Anomaly (SAA) region.
The particle loss processes during injection were simulated using the MAGNETOCOSMIC program within the Geant4 Monte Carlo software. Simulations were conducted for 10 MeV electrons at various longitudes and L-values. The trajectories, loss cone angles, and trapping conditions were analyzed and compared among the three geomagnetic models.
The centered dipole model yielded relatively regular and symmetric electron drift trajectories. asymmetry was observed in the eccentric dipole model. The IGRF model produced the most complex and irregular trajectories, best reflecting the actual variability of Earth's magnetic field. Regarding the relationship between loss cone angle and L-value, the IGRF model exhibited the largest loss cone angles, indicating the most stringent conditions for particle trapping. Furthermore, injection longitude significantly influenced loss processes, with electrons approaching the center of the SAA being most susceptible to drift loss.
The choice of geomagnetic model critically impacts the simulation of particle dynamics in artificial radiation belts. The IGRF model, offering the most detailed field representation, predicts the strictest trapping conditions and most realistic loss patterns, especially within the SAA. These findings enhance the understanding of particle trapping mechanisms and are significant for space environment research and applications.
, Available online ,
doi: 10.11884/HPLPB202638.250209
Abstract:
Background Purpose Methods Results Conclusions
Gyrotron traveling wave tube (Gyro-TWT) is a vacuum electronic device with broad application prospects. Magnetron injection gun (MIG) is one of the core components of gyro-TWT, and its performance directly determines the success or failure of gyro-TWT. From the current research results on MIGs at home and abroad, it can be seen that the working voltage and current of existing MIGs are mostly low, and the velocity spread is generally high, which cannot meet the requirements of future megawatt-class gyro-TWT for MIG.
In order to meet the requirement for MIG with high voltage, high current, and low electron beam velocity spread in the development of megawatt-class high-power gyro-TWT, this paper presents a novel design scheme for a single anode electron gun.
The novel electron gun scheme introduces a curved cathode structure to reduce the velocity spread of the electron beam, while effectively increasing the cathode emission band area and reducing the cathode emission density.
The results of PIC simulation show that under the working conditions of 115 kV and 43 A, the designed electron gun has a transverse to longitudinal velocity ratio of 1.05, a velocity spread of 1.63%, and a guiding center radius of 3.41 mm. The thermal analysis results indicate that the MIG can heat the cathode to 1050 ℃ at a power of 76 W.
The simulation and thermal analysis results indicate that the designed MIG meets the design expectations and satisfies the requirements of high voltage, high current, and low electron beam velocity spread for megawatt level gyro-TWT.
, Available online ,
doi: 10.11884/HPLPB202537.250150
Abstract:
Background Purpose Methods Results Conclusions
High power GaN-based blue diode lasers have wide application prospects in industrial processing, copper material welding, 3D printing, underwater laser communication and other technical fields. The Chip On Submount (COS unit) packaged in the heat sink is a kind of single component that can be applied to the fabrication of high power GaN-based blue diode lasers. The device has the advantages of low thermal resistance and small size.
However, due to the low reliability of this device, the industrial application of this COS single component in high power GaN-based blue diode lasers is still limited to a certain extent, and its performance degradation factors need to be studied.
In this paper, based on the optical microscopy、scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) the degradation factors of high power blue light COS components were studied.
Finally, the experimental study and analysis show that the performance degradation factors of blue light diode laser chip are mainly related to GaN matrix material defects, cavity surface surplus deposition and photochemical corrosion factors, and through experiments, it is compared that high power blue light COS single component can improve its reliability by hermetic packaging and provide a reference for the subsequent engineering application of high power blue COS units.
Finally, experimental research and analysis indicate that the performance degradation factors of high-power blue laser diodes (LDs) are primarily related to defects in the GaN substrate material, foreign matter deposition on the cavity surface, and photochemical corrosion factors. Comparative experiments further reveal that the threshold current growth rate of LDs with gas sealing (～0.14 mA/h) is lower than that of non-gas-sealed LDs (～0.27 mA/h). This demonstrates that gas-sealed packaging of high-power blue LD COS unit devices can enhance their reliability.
, Available online ,
doi: 10.11884/HPLPB202537.250038
Abstract:
Background Purpose Methods Results Conclusions
To enhance the performance of the next-generation X-ray free electron laser (XFEL), a photocathode RF gun capable of providing the required high-quality electron beam with a small emittance has been a significant research objective. In comparison to the conventional L-band or S-band RF gun, the C-band RF gun features a higher acceleration gradient above 150 MV/m and the ability to generate a small-emittance beam. Low-emittance electron beams are critical for enhancing XFEL coherence and brightness, driving demand for advanced RF gun designs. For a bunch charge of 100 pC, a normalized emittance of less than 0.2 mm.mrad has been expected at the gun exit.
This paper presents the design of an emittance measurement device, which can accurately measure such a small emittance at the C-band RF gun exit to ensure beam quality for XFEL applications.
To achieve the desired accuracy, the primary parameters —slit width, slit thickness, and beamlet-drift length—have been systematically optimized through numerical simulations using Astra and Python based on the single-slit-scan method. Dynamic errors, including motor displacement and imaging resolution, were quantified to ensure measurement reliability.
The evaluations indicate that the measurement error of 95% emittance is less than 5%, employing a slit width of 5 μm, a slit thickness of 1 mm, and a beamlet-drift length of 0.11 m under dynamic conditions.
This optimized emittance measurement device supports precise beam quality characterization for XFELs, offering potential for further advancements in electron beam diagnostics.
, Available online ,
doi: 10.11884/HPLPB202537.250019
Abstract:
Background Purpose Methods Results Conclusions
Fiber laser coherent beam combining technology enables high-power laser output through precise phase control of multiple laser channels. However, factors such as phase control accuracy, optical intensity stability, communication link reliability, and environmental interference can degrade system performance.
This study aims to address the challenge of anomaly detection in phase control for large-scale fiber laser coherent combining by proposing a novel deep learning-based detection method.
First, ten-channel fiber laser coherent combining data were collected, system control processes and beam combining principles were analyzed, and potential anomalies were categorized to generate a simulated dataset. Subsequently, an EMA-Transformer network model incorporating a lightweight Efficient Multi-head Attention (EMA) mechanism was designed. Comparative experiments were conducted to evaluate the model's performance. Finally, an eight-beam fiber laser coherent combining experimental setup was established, and the algorithm was deployed using TensorRT for real-time testing.
The proposed algorithm demonstrated significant improvements, achieving approximately 50% higher accuracy on the validation set and a 2.20% enhancement on the test set compared to ResNet50. In practical testing, the algorithm achieved an inference time of 2.153 ms, meeting real-time requirements for phase control anomaly detection.
The EMA-Transformer model effectively addresses anomaly detection in fiber laser coherent combining systems, offering superior accuracy and real-time performance. This method provides a promising solution for enhancing the stability and reliability of high-power laser systems.
Articles in press have been peer-reviewed and accepted, which are not yet assigned to volumes /issues, but are citable by Digital Object Identifier (DOI).
Display Method:
, Available online ,
doi: 10.11884/HPLPB202638.250113
Abstract:
Background Purpose Methods Results Conclusions
Electromagnetic pulse welding (EMPW) is an emerging solid-state welding technology. Its application in connecting power conductors and terminals can effectively enhance joint reliability. However, EMPW joints exhibit unbonded intermediate zones, and their tensile performance requires improvement, which severely restricts the application of EMPW technology in power conductor connections.
To address this, this paper proposes a split field shaper structure to further improve the bonding performance of electromagnetic pulse welded joints.
To validate the effectiveness of the proposed split field shaper structure, this paper combines equivalent circuit analysis, finite element simulation models, and mechanical property testing of experimental specimens to demonstrate the efficacy of the proposed method.
Theoretical analysis of both the split and traditional field shaper provides the basis for the split field shaper structure design. Finite element simulation models reveal the influence patterns of the field shaper structure on the electromagnetic and motion parameters of the joint deformation zone. Mechanical property tests validated the split field shaper’s enhancement of joint bonding performance. Experimental results demonstrate that, compared to the integrated field shaper, joints prepared using the segmented field shaper exhibit a 22.73% increase in tensile performance and a 2.68 mm extension in the total weld length.
The proposed split field shaper successfully enhances joint mechanical properties relative to conventional field shapers while maintaining overall dimensional consistency.
, Available online ,
doi: 10.11884/HPLPB202638.250166
Abstract:
Background Purpose Methods Results Conclusions
System-generated electromagnetic pulse (SGEMP) arises from electromagnetic fields produced by photoelectrons emitted from spacecraft surfaces under intense X-ray or γ -ray irradiation. Cavity SGEMP, a critical subset of SGEMP, involves complex interactions within enclosed structures. While scaling laws have been established for external SGEMP, their applicability to cavity SGEMP remains debated due to photon spectrum distortion caused by variations in cavity wall thickness and other factors.
This study aims to validate the applicability of SGEMP scaling laws to cavity SGEMP by proposing a canonical transformation method that maintains constant wall thickness. The goal is to provide a theoretical basis for analyzing cavity SGEMP mechanisms and designing laboratory-scale experiments.
A cylindrical cavity model with an aluminum wall was irradiated by a laser-produced plasma X-ray source. Numerical simulations were performed using a 3D particle-in-cell (PIC) code under two conditions: an original model and a 10×scaled-up model. Key parameters, including grid size and time steps, were scaled according to the derived laws. The wall thickness was kept constant to avoid photon spectrum distortion. Simulations compared electric fields, magnetic fields, charge densities, and current distributions between the two models.
The original and scaled-up models exhibited identical spatial distributions of electromagnetic fields and charge densities. Specific validation results include: Peak electric fields decreased from 2.0 MV/m (original) to 200 kV/m (scaled-up); peak magnetic fields reduced from 0.8×10−3 T (original) to 0.8×10−4 T (scaled-up); and charge densities maxima dropped from 6.0×10−3 /m3 to 6.0×10−5 /m3. Waveform shapes for currents and fields remained unchanged across models. These results all adhere to the scaling laws.
The scaling laws for SGEMP are validated for cavity SGEMP when wall thickness remains unchanged. This work provides a universal theoretical tool for cavity SGEMP studies and reliable scaling criteria for laboratory experiments.
, Available online ,
doi: 10.11884/HPLPB202638.250185
Abstract:
Background Purpose Methods Results Conclusions
Gyrotron traveling-wave tubes (gyro-TWTs), based on the electron cyclotron maser mechanism, are extensively utilized in critical military domains such as high-resolution millimeter-wave imaging radar, communications, and electronic countermeasures. Experimental observations indicate that when the cathode magnetic field exceeds a specific range, the electron beam bombardment of the tube wall occurs.
This study aims to reduce damage risks to the electron gun during experiments, provide guidance for identifying optimal operating points in experimental testing of Ka-band second-harmonic large-orbit gyrotron traveling wave tube (gyro-TWT).
This paper introduces the formation theory of large-orbit electron guns and analyzes the motion of electron beams in non-ideal CUSP magnetic fields. Using CST Particle Studio and E-Gun software modeled and simulated the electron gun. The effects of magnetic fields, operating voltage, and beam current on the quality and trajectories of large-orbit electron beams were investigated.
As the absolute value of the cathode magnetic field increases, both the velocity ratio and the Larmor radius increase, while the velocity spread decreases. With an increase in voltage, the velocity ratio decreases, and the Larmor radius drops to a minimum at a certain point before rising again. Variations in current have limited impact on the Larmor radius and the transverse-to-longitudinal velocity ratio; however, the electron-wave interaction efficiency reaches its maximum at the optimal operating current.
The study demonstrates that excessively low operating voltage leads to high transverse-to-longitudinal velocity ratios and electron back-bombardment phenomena, which detrimentally affect the cathode. Therefore, within this voltage range (20–40 kV), the power supply voltage should be increased promptly. Conversely, excessively high reverse magnetic fields at the cathode result in an oversized electron cyclotron radius, causing beam-wall bombardment and gun damage. To prevent electron beam bombardment of the tube wall, the cathode magnetic field should not exceed 0.0085 T.
, Available online ,
doi: 10.11884/HPLPB202638.250194
Abstract:
The Low Energy High Intensity High Charge State Heavy Ion Accelerator Facility (LEAF) is a national scientific instrument developed by the Institute of Modern Physics, Chinese Academy of Sciences, to provide high-current, high-charge-state, full-spectrum low-energy heavy ion beams for interdisciplinary studies. To meet research needs in nuclear astrophysics, atomic and molecular physics, and nuclear materials, LEAF offers tunable energies from 0.3 to 0.7 MeV/u and supports continuous-wave acceleration for ions with with a mass-to-charge ratio ranging from 2−7. This paper presents an overview of the construction progress, key design parameters, and operational performance of the facility, summarizing recent achievements and outlining future development goals. The paper introduces the system architecture—comprising the 45 GHz superconducting ECR ion source FECR, RFQ, IH-DTL, and terminal beamlines—and describes beam commissioning and diagnostic approaches. LEAF has successfully achieved stable acceleration of multi-species, high-charge-state heavy ion beams with intensities up to 1 emA. It has delivered more than13000 h of beam time, realized efficient operation of “cocktail”multi-ion beams, and established a high-current, low-energy-spread 12C2+ beamline for precise reaction measurements in the Gamow window. These results verify LEAF’s excellent beam quality and operational reliability. Planned upgrades—including an extended energy tuning range and triple-ion beam capability—will further enhance its role as a frontier platform for experimental studies in nuclear astrophysics and radiation effects in advanced materials.
The Low Energy High Intensity High Charge State Heavy Ion Accelerator Facility (LEAF) is a national scientific instrument developed by the Institute of Modern Physics, Chinese Academy of Sciences, to provide high-current, high-charge-state, full-spectrum low-energy heavy ion beams for interdisciplinary studies. To meet research needs in nuclear astrophysics, atomic and molecular physics, and nuclear materials, LEAF offers tunable energies from 0.3 to 0.7 MeV/u and supports continuous-wave acceleration for ions with with a mass-to-charge ratio ranging from 2−7. This paper presents an overview of the construction progress, key design parameters, and operational performance of the facility, summarizing recent achievements and outlining future development goals. The paper introduces the system architecture—comprising the 45 GHz superconducting ECR ion source FECR, RFQ, IH-DTL, and terminal beamlines—and describes beam commissioning and diagnostic approaches. LEAF has successfully achieved stable acceleration of multi-species, high-charge-state heavy ion beams with intensities up to 1 emA. It has delivered more than
, Available online ,
doi: 10.11884/HPLPB202638.250148
Abstract:
Background Purpose Methods Results Conclusions
Backward stimulated Raman scattering (SRS) and backward stimulated Brillouin scattering (SBS) are two major laser-plasma instabilities that influence the laser-target energy coupling efficiency in inertial confinement fusion (ICF). Hot electrons excited by SRS can preheat the fuel. Their nonlinear competition determines the effectiveness of laser-plasma coupling and thus the performance of laser-driven fusion. In realistic laser fusion conditions, the electron distribution often deviates from a Maxwellian due to strong laser heating, leading to nonthermal effects such as the Langdon effect. Additionally, ion-ion collisions in multispecies plasmas such as CH can alter the damping and dispersion of ion acoustic waves.
This study aims to investigate the impact of the Langdon effect and ion-ion collisions on the competition between SRS and SBS in CH plasma, particularly focusing on their respective reflectivities under varying plasma conditions.
Five-wave coupling equations describing the nonlinear interactions among the pump laser, scattered light, Langmuir wave, and ion acoustic wave were numerically solved. A super-Gaussian electron distribution function was employed to incorporate the Langdon effect, while ion-ion collision effects were included through modifications to the ion susceptibility. The dispersion relations and damping characteristics of both electron plasma waves (EPWs) and ion acoustic waves (IAWs) were analyzed in detail.
The results reveal that the Langdon effect notably reduces Landau damping of EPWs and modifies the dispersion relation of SRS, enhancing its growth rate. Simultaneously, ion-ion collisions increase IAW damping and shift the SBS dispersion curve, weakening its instability. These combined effects lead to a dominance of SRS over SBS at lower electron densities, altering the overall backscattering reflectivity spectrum in laser fusion plasma.
Both the Langdon effect and ion-ion collisions play crucial roles in reshaping the nonlinear dynamics of SRS and SBS. Their influence must be considered in predictive models of laser-plasma interactions. These findings provide insight into optimizing plasma parameters for improved control of backscatter instabilities in inertial confinement fusion experiments.
, Available online ,
doi: 10.11884/HPLPB202638.250271
Abstract:
Background Purpose Methods Results Conclusions
In recent years, reflectarray antennas have received significant attention and research in the high-power microwave field due to their low profile, conformability, and spatial feed characteristics. Multi-frequency reflectarray antennas can share the same antenna plane while providing differentiated beam steering at different frequencies, resulting in greater system platform adaptability. However, these antennas commonly face the challenges of limited power handling capacity and low aperture efficiency.
This paper aims to propose a phase synthesis method for high-power, dual-band reflectarray antennas, which enhances their power handling capacity and aperture efficiency. This approach is universally applicable to the design of multi-frequency reflectarray antennas.
The proposed phase synthesis method incorporates reference phase optimization and screening threshold techniques. It takes into account the reflected phase and electric field intensity of the antenna elements under different incident wave conditions. This approach effectively increases power capacity and aperture efficiency.
We designed an improved reflectarray antenna element and applied the proposed phase synthesis method to a dual-band reflectarray antenna design. A 27×27 array operating at 4.3 GHz and 10.0 GHz achieved aperture efficiencies of 67.37% and 48.69%, respectively, with a power capacity of hundreds of megawatts in a vacuum environment.
The proposed phase synthesis method has been successfully validated, proving its effectiveness in designing high-performance, high-power, dual-frequency, and multi-frequency reflectarray antennas.
, Available online ,
doi: 10.11884/HPLPB202537.250138
Abstract:
Background Purpose Methods Results Conclusions
High-power microwave (HPM) pulses, which can interfere with or damage electronic components and circuits, have attracted considerable research interest in recent years. Aperture coupling represents a primary mechanism for such pulses to penetrate shielded metallic enclosures, significantly affecting the electromagnetic compatibility and resilience of electronic systems. Although substantial studies have focused on shielding effectiveness and resonant behaviors, the spatial distribution of coupling parameters—particularly the extent of strongly coupled regions within the cavity—remains inadequately investigated. This paper proposes a quantitative metric termed “the coverage rate of strong-coupled region” to better evaluate HPM backdoor coupling effects.
The objective is to systematically examine the influence of key HPM waveform parameters on this coverage rate within a representative metallic cavity.
A three-dimensional simulation model of a rectangular metallic cavity with an aperture was developed using the finite-difference time-domain (FDTD) method. The internal field distribution was monitored via an array of electric field probes. Numerical simulations were performed to assess the effects of various HPM parameters, including frequency, pulse width, the pulse rise time, and polarization angle, on the coverage of strongly coupled regions.
The coverage rate was markedly higher at the cavity’s inherent resonant frequencies than at non-resonant frequencies. Increasing the pulse width led to a saturation of coverage beyond a specific threshold. Variations in polarization angle from horizontal to vertical considerably enhanced the coverage, with vertical polarization yielding the maximum value. Superimposing multiple resonant frequencies effectively compensated for weakly coupled areas, further increasing the overall coverage. In contrast, the pulse rise time had a negligible effect on the coverage rate. The proposed the coverage rate of strong-coupled region effectively addresses the practical dilemma wherein strong local coupling does not necessarily lead to significant system-level effects.
This metric provides a quantitative basis for optimizing the alignment between sensitive components and highly coupled zones. Frequency and polarization are identified as decisive parameters for enhancing coupling effectiveness, while pulse width and multi-frequency excitation can be utilized to achieve more uniform and robust coupling coverage. These findings offer valuable guidance for the design and assessment of HPM protection measures and electromagnetic compatibility analysis.
Display Method:
2025, 37: 122001.
doi: 10.11884/HPLPB202537.250066
Abstract:
Background Purpose Methods Results Conclusions
Surface defects on optical components in high-power solid-state laser systems seriously impair the system’s operational stability and laser output performance. However, precise detection of such defects under few-shot conditions remains a critical challenge, as limited training data often restricts the generalization ability of detection models and creates an urgent need for high-performance defect detection methods adapted to this scenario.
To address this issue, this study aims to design and propose an enhanced detection method dubbed ICFNetV2, which is developed based on the existing ICFNet. Its core goal is to improve the accuracy and generalization of optical component surface defect detection under few-shot scenarios.
ICFNetV2 integrates data augmentation techniques with deep residual networks: Its framework adopts a synergistic design of residual connection mechanisms and decoupled channel convolution operations to construct a 34-layer cascaded network—this structure mitigates gradient decay during deep network training and enhances cross-layer feature transmission efficiency. The network also incorporates spatial dropout layers and implements a data preprocessing pipeline encompassing random rotation, mirror flipping, and Gaussian noise injection, which expands the training dataset to 9 times its original size. Additionally, ablation studies were conducted to verify the efficacy of each individual network module.
Experimental results demonstrate that the optimized ICFNetV2 achieves a classification accuracy of 97.4% for three typical defect types, representing a 0.7% improvement over the baseline ICFNet model.
In conclusion, ICFNetV2 effectively enhances defect detection performance under few-shot conditions through architectural optimization and data augmentation. The validation from ablation studies and the observed accuracy gains confirm the effectiveness of its key modules, providing a reliable solution for surface defect detection of optical components in high-power solid-state laser systems and offering reference value for similar few-shot detection tasks.
2025, 37: 123001.
doi: 10.11884/HPLPB202537.250338
Abstract:
Background Purpose Methods Results Conclusions
As the low-altitude economy industry accelerates, low-altitude security has attracted increasing attention. High-power microwave (HPM) is one of the important means to address the security threats posed by non-cooperative unmanned aerial vehicles (UAVs).
As a type of high-power electromagnetic pulse, ultra-wideband high-power microwave (UWB-HPM) can attack the electronic information systems of non-cooperative UAVs through “front-door” or “back-door” coupling, resulting in effects such as interference, disruption, damage, and burnout.
We propose a new concept of on-wafer high-power microwave on wafer (HPM on-wafer), which integrates energy storage capacitors, high-power optically controlled semiconductor switches, and antennas on a single semiconductor wafer with a thickness of 0.5 mm and a diameter of 0.15 m.
The unit of HPM on-wafer achieves an ultra-wideband high-power microwave output with a radiation factor of 20 kV.
Experiments show that based on this integrated HPM on-wafer unit, the communication link of a consumer-grade UAV at a distance of 10 m is cut off and the UAV loses flight control. By arranging and combining the basic units of HPM on wafer, modular expansion can be realized to form ultra-wideband high-power microwave systems of different scales, which can meet the requirement of achieving the intended strike effect on different platforms.
2025, 37: 123002.
doi: 10.11884/HPLPB202537.250149
Abstract:
Background Purpose Methods Results Conclusions
The high peak power and wide spectral characteristics of high-power radar may cause unintended interference to communication systems operating in adjacent frequency bands.
This study aims to clarify the effects of key LFM waveform parameters on interference mechanisms and to describe their governing patterns.
A closed-loop injection platform based on software-defined radio (SDR) was developed to inject synthesized LFM waveforms into a QPSK receiver. Error vector magnitude (EVM) serves as the performance metric, while pulse width, pulse period, and chirp bandwidth are varied systematically under fixed duty-cycle constraints.
Results indicate that increasing the duty cycle significantly raises the EVM value, although its growth moderates beyond a 30% duty cycle. Under constant duty cycles, pulse-period variations show negligible influence on EVM. As chirp bandwidth increases from 1 MHz to 3 MHz, the EVM decreases from −10.5 dB to −19.8 dB, a reduction of 9.3 dB, but remains nearly constant with further bandwidth expansion to 10 MHz.
These findings offer critical insights into radar-communication spectrum coexistence and anti-interference system design, while confirming the effectiveness of SDR-based platforms for investigating high-power microwave (HPM) interference effects.
2025, 37: 123003.
doi: 10.11884/HPLPB202537.250160
Abstract:
Background Purpose Methods Results Conclusions
Traveling-wave tubes (TWTs) are widely applied in radar, imaging, and military systems owing to their excellent amplification characteristics. Miniaturization and integration are critical to the future of TWTs, with multi-channel slow-wave structures (SWSs) forming the foundation for their realization in high-power vacuum electronic devices.
To provide design insights for multi-channel TWTs and simultaneously enhance their output power, a W-band folded-waveguide TWT with dual electron beams and H-plane power combining was proposed.
Three-dimensional electromagnetic simulations in CST were conducted to verify the high-frequency characteristics, electric field distribution, and amplification performance of the proposed SWS, thereby confirming the validity of the design.
Results indicate that the designed TWT achieves a transmission bandwidth of 10 GHz. With an electron beam voltage of 17.9 kV and a current of 0.35 A, the output power reaches 450 W at 94 GHz, corresponding to an efficiency of 7.18% and a gain of 23.5 dB. Moreover, under fixed beam voltage and current, the TWT delivers over 200 W output power across 91–99 GHz, with a 3 dB bandwidth of 91–98.5 GHz. The particle voltage distribution after modulation further validates the mode analysis.
These results demonstrate the feasibility of compact dual-beam power-combining structures and provide useful guidance for the design of future multi-channel TWTs.
2025, 37: 123004.
doi: 10.11884/HPLPB202537.250080
Abstract:
Background Purpose Methods Results Conclusions
There is currently little research on the choice of the effective workspace of large split vertically polarized electromagnetic pulse (EMP) simulator with distributed terminators.
The purpose of this reasearch is to obtain the distribution characteristics of the peak-value of electric field’s vertical component (called “field peak-value”) inside large simulators.
Based on an example of selecting the effective workspace of this type of simulator, two typical planes were chosen as test planes. Then, the influences of the maximum width, the maximum height, and the maximum width of the upper plate’s void on (normalized) field peak-value distribution characteristics on the two test planes were studied and analyzed based on parallel finite-difference time-domain (FDTD) method.
The results show that, field peak-values increase on the two test planes, as the simulator’s maximum width is wider, maximum height is lower, and maximum width of the upper plate’s void is smaller. The field peak-value uniformity along the simulator’s width direction becomes better as the simulator’s maximum width increases; The field peak-value uniformity along the simulator’s height direction becomes better, but slightly deteriorates along the simulator’s width direction, as the simulator’s maximum height increases; The field peak-value uniformity along the simulator’s width direction becomes better, but deteriorates along the simulator’s height direction, as the maximum width of the upper plate’s void increases.
When selecting an effective workspace in practical experiments, it is necessary to select the appropriate size-parameters of the simulator according to the field peak-values required by the effect experiment and the actual size of the effector, combined with the engineering practice.
2025, 37: 123005.
doi: 10.11884/HPLPB202537.250285
Abstract:
Background Purpose Methods Results Conclusions
With the rapid development of microsatellite platforms such as CubeSats, microwave plasma thrusters have become ideal for orbit maintenance and attitude control due to their high specific impulse, no electrode ablation, compact structure, and flexible working fluid. However, the thrust of such thrusters (at the 1000 W power level) is usually in the millinewton range, and its accurate measurement is crucial for performance verification. Existing thrust measurement schemes require at least 50 cm of space, conflicting with the extreme spatial constraint of 18 cm×16 cm in the current laboratory vacuum chamber; traditional indirect measurement also requires 2−3 parameters, increasing experimental complexity.
This study aims to address the spatial limitation of the vacuum chamber, develop miniaturized thrust measurement schemes, establish a complete testing system including direct mechanical measurement and indirect parameter estimation, and verify the effectiveness and feasibility of these methods for ground testing of thrusters.
Four thrust measurement methods were developed: 1) Modified NH-2 electronic push-pull force gauge (2 N range, 0.001 N resolution) with a 5.5 cm metal target and 3D-printed bracket; 2) Pendulum thrust meter using an eddy current displacement sensor (2 mV/μm sensitivity) to measure small displacements, with force analysis under small angles (<10°); 3) Thrust calculation based on resonant cavity gas temperature (measured by WRe26 thermocouple, 0−1800 ℃ range) using adiabatic process and ideal gas equations; 4) Thrust calculation based on resonant cavity pressure (measured by a precision pressure gauge) via derived formulas. Experiments used a 1500 W 2.45 GHz magnetron microwave source with helium as the working fluid, conducted under cold gas (microwave off) and discharge (microwave on) conditions.
In cold gas experiments, thrust increased almost linearly with helium flow; push-pull force gauge and pendulum data were highly consistent, while temperature- and pressure-based calculated values were higher. In discharge experiments, thrust still increased with flow (though slower at high flow), specific impulse remained stable (with a slight drop at high flow), and temperature- and pressure-based values showed better consistency. All four methods performed well within the 0−600 mN thrust range, with indirect methods consistent with direct measurements.
The four methods effectively solve the spatial constraint issue. Direct measurements (push-pull force gauge, pendulum) are effective, and indirect calculations (temperature, pressure) are feasible. The modular design is particularly suitable for CubeSats, providing reliable, low-cost, and easy-to-implement solutions for micro thruster performance verification and optimization, with promising application prospects.
2025, 37: 124001.
doi: 10.11884/HPLPB202537.250114
Abstract:
Background Purpose Methods Results Conclusions
Neutral beam injection (NBI) systems are critical to fusion research and require precise control and monitoring of negative ion sources. Existing solutions often have limitations in terms of development efficiency and adaptability.
This study aims to design and implement a cost-effective, highly scalable NBI control and monitoring system for negative ion sources. The system is specifically designed to address the inherent issues of traditional NI-PXIe hardware and LabVIEW-FPGA architectures, such as lengthy development cycles, high hardware costs, and limited scalability.
A modular control solution is proposed, utilizing a domestically produced PXIe platform, a Linux real-time system, and the Qt5.9 framework. By replacing imported components with locally sourced hardware and leveraging optimizations in the Linux real-time kernel, precise control is achieved. A multi-threaded control program is developed using C++ object-oriented programming to enhance system flexibility and overcome scalability limitations.
Experimental verification confirmed that the system achieved microsecond-level synchronisation accuracy. Compared with traditional methods, this solution has significant advantages in scalability and control accuracy, meeting all experimental requirements for time-sensitive operations in negative ion source NBI.
The Qt-based system successfully addresses the limitations of traditional NBI control architectures in terms of cost and scalability. By adopting localized hardware, Linux real-time system, and modular C++ design, the system provides reliable performance for complex ion source experiments. This approach establishes a flexible framework that can adapt to further enhancements in future NBI systems.
2025, 37: 124002.
doi: 10.11884/HPLPB202537.250161
Abstract:
Background Purpose Methods Results Conclusions
The fast orbit feedback (FOFB) system of the high energy photon source (HEPS) has been developed for the beam orbit control in its storage ring. It mainly consists of beam position monitors (BPMs), the algorithms of fast orbit controller (FOC) and fast correction units. To support HEPS commissioning, we have developed a high-performance signal generator to complete the simulation of beam signals.
The developed signal source includes four output ports with independently adjustable signal amplitudes and synchronous triggers. Its goal is to simulate the timing signals, and enable the simulation output of BPM signals under real beam conditions in the laboratory without beam, with the advantages of simple structure, low cost and high repeatability.
The core of the signal source is an FPGA board. Firstly, a 250 MHz clock signal with a 25% duty cycle was generated by the PLL and directly routed through the MRCC pin. After completing the impedance matching, the RF signal was processed via differential circuit to obtain the required simulated beam signals. Then, the required signals were amplified using the RF amplifier. After the 1∶4 power division, beam signals with four adjustable amplitudes output channels were finally acquired. The trigger signal was supplied directly from the FPGA I/O pins configured for LVCMOS33 operation at 3.3 V, to meet the required LVTTL of BPM electronics.
Based on the beam current characteristics of the HEPS storage ring, we tested the beam signal simulation performance of HEPS storage ring with a frequency of 220 kHz and different patterns during the experiment. In addition, the simulation performance of the single trigger signal and BEPCII collision zone with a frequency of 1.21 MHz has also been tested. The test results showed that the developed signal source could simulate the beam signal well and meet the design requirements. Then, we tested the pattern dependence of HEPS BPM electronics with this signal source. The results showed that there was no pattern dependence effect in the HEPS BPM electronics used in this experiment.
This signal generator could be used to assist in the logical design and correctness of DBPM, to debug the data transmission and control logic between the DBPM and FOFB, and to test the latency of the FOFB system. Based on this system, the debugging difficulty of BPM and FOFB systems could be reduced and accelerate the deployment of the FOFB system.
2025, 37: 124003.
doi: 10.11884/HPLPB202537.250023
Abstract:
Background Purpose Method Result Conclusions
Shenzhen Superconducting Soft X-Ray Free Electron Laser (S3FEL) is a facility newly proposed by Institute of Advanced Science Facilities, Shenzhen (IASF). The linear accelerator based on a TESLA-type superconducting RF cavity is used to obtain a high-repetition-frequency and high-gradient field. The cryomodule is the most challenging core part of the S3FEL device and ultra-high vacuum differential system is located at the module beam pipe outlet, which is used to realize the transition from cryomodule to ambient temperature section. The vacuum interlock protection is required for the differential system to protect the superconducting RF cavity in cryomodule from emergencies.
This study aims to analyze the transient process of rapid protection.
The traditional fast closing valve protection process is only calculated according to the gas molecular rate. In this paper, the finite element method and the Monte Carlo method are used in this paper.
The transient pressure distribution results of sensor-fast closing valve section show that setting the sensor 8—10 m away from the fast closing valve can provide sufficient buffer reaction time.
The differential system analyses show that the pressure here reaches 10−5 Pa within 2 s when the gate valve is completely closed, corresponding to a leakage size of 0.5 mm, which still maintains a high-vacuum environment and meets the working requirements of ion pumps. This work provides an important theoretical basis for the S3FEL.
2025, 37: 124004.
doi: 10.11884/HPLPB202537.250263
Abstract:
Background Purpose Methods Results Conclusions
High-resolution industrial computed tomography (CT) is crucial for the non-destructive testing (NDT) of critical components, particularly in the aerospace industry where high-density materials are common. The Rhodotron accelerator, with its micro-focus capability, offers a hardware advantage for achieving high spatial resolution over traditional linear accelerators. However, its potential is severely hampered when inspecting large, high-density workpieces. The strong X-ray attenuation leads to projection data with a very low signal-to-noise ratio (SNR), causing conventional reconstruction algorithms to either produce noisy images or oversmooth critical details, thereby limiting the system’s effective resolution.
This study aims to develop and validate a reconstruction algorithm capable of overcoming the low-SNR challenge inherent in Rhodotron CT scans of high-density objects. The primary objective is to achieve high-resolution, high-fidelity image reconstruction that effectively suppresses noise while preserving the fine structural edges essential for accurate defect detection.
A novel iterative algorithm, termed Projection Onto Convex Sets regularized by Bilateral Total Variation (POCS-BTV), is proposed. The algorithm integrates BTV, a regularizer known for its superior edge-preservation properties, into the POCS framework to constrain the solution during iterations. The performance of POCS-BTV was evaluated against the Simultaneous Iterative Reconstruction Technique (SIRT), POCS-TV, and POCS-RTV algorithms. The evaluation involved two stages: a simulation experiment using a Shepp-Logan phantom with added Poisson-Gaussian noise to mimic low-SNR conditions, and a physical experiment using a 70 mm diameter high-strength steel wire rope phantom scanned by a 9 MeV Rhodotron accelerator CT system.
In the simulation experiment, the POCS-BTV algorithm demonstrated superior quantitative performance, achieving a Peak Signal-to-Noise Ratio (PSNR) of 30.76 and a Structural Similarity Index (SSIM) of 0.8405 , which were significantly better than the comparison algorithms. In the real data experiment, visual analysis of the reconstructed images showed that POCS-BTV successfully resolved the fine gaps between individual steel wires. This was in stark contrast to other methods, which suffered from structural aliasing and blurred edges due to noise.
The POCS-BTV algorithm effectively unlocks the high-resolution potential of the Rhodotron accelerator hardware, even in challenging low-SNR scenarios. By achieving an optimal balance between noise suppression and detail preservation, it provides a robust and reliable solution for the precision NDT of critical high-density industrial components, demonstrating significant value for practical engineering applications.
2025, 37: 124005.
doi: 10.11884/HPLPB202537.250186
Abstract:
Background Purpose Methods Results Conclusions
The long counters are widely applied among various types of neutron sources.
In this work, neutron spectra in the long counters are specifically studied, in order to obtain a better understanding of the influences on the detection efficiency due to the size of moderators.
According to the basic structure of long counters, a simple model is built to systematically simulate the spectrum and time distribution of neutrons entering the proportional counter tube from a pulsed fast neutron source.
The calculated results show that the evolution of the neutron spectrum is rapid at first, and becomes slower later. After 31 μs, the neutron spectrum almost no longer changes. The time distribution is different for neutrons of different energy. The lower the energy, the wider the distribution. For the energy of thermal neutrons, the time lasts more than 1 m s. Utilizing the time distribution of different energy, the change of counts of the long counter over time is calculated.
Basically, the flux and spectra of neutrons which enter the long counters do not change with the variation of the moderator radius when it exceeds 20 cm. This result can provide a reference for the optimal design of the long counter.
2025, 37: 124006.
doi: 10.11884/HPLPB202537.250175
Abstract:
Background Purpose Methods Results Conclusions
The very-high-frequency (VHF) photocathode electron gun operates in continuous-wave mode and serves as a critical electron source for generating high-repetition-rate, high-quality electron beams. It is widely used in advanced scientific facilities such as X-ray free-electron lasers and ultrafast electron diffraction systems. However, during operation, resonant frequency shifts caused by variations in feed power and cooling water temperature can destabilize the radio-frequency (RF) field inside the cavity.
This study aims to achieve stable amplitude and phase control of the RF field in a VHF electron gun under high-power continuous-wave operation by accurately tracking and tuning the resonant frequency of the cavity in real time.
Based on an LCR oscillator circuit model, the phase difference between the cavity-sampled microwave and the incident wave was analyzed to determine the cavity's resonant frequency. A three-step tuning strategy—comprising frequency scanning, frequency tracking, and active tuning—was implemented and applied to a VHF electron gun at Tsinghua University.
Using the proposed tuning method, the electron gun maintained resonance during high-power operation, with a resonant frequency deviation controlled at an RMS value of 94.2 Hz under full power. The amplitude stability at the microwave sampling port reached an RMS value of 0.0046 %, and the phase-locking accuracy achieved an RMS value of 0.0023 °. These results enabled long-term, stable full-power operation of the electron gun.
The developed three-step active tuning method effectively ensures high amplitude and phase stability for the VHF photocathode electron gun under continuous-wave operation, providing a reliable tuning solution for high-repetition-rate accelerator-based light sources and scientific instruments.
2025, 37: 125001.
doi: 10.11884/HPLPB202537.250210
Abstract:
Background Purpose Methods Results Conclusions
In recent years, the development of wound-type mica paper capacitors has significantly enhanced their operating voltage and energy density, and they remain highly reliable, showing potential for improving the overall energy storage density of PFN (pulse forming line)-Marx generators.
The lifetime of the capacitor is a crucial factor in ensuring system reliability. The lifetime of the mica paper capacitor reaches up to 100,000 times, meeting the requirements of highly compact pulse power drivers. However, the lifetime characteristics of this capacitor remain unclear, and its optimal operating conditions have not been well-defined.
In this paper, an investigation into the lifetime characteristics of mica paper capacitors under microsecond pulses is presented. First, the structure of the capacitor is analyzed in detail. Subsequently, numerical simulations of the electrical and thermal fields are carried out to further study its characteristics. To accurately test the mica paper capacitors, a lifetime test platform that can operate stably over an extended period was constructed.
Through the utilization of this platform, the electrical degradation parameters and the failure mechanisms of the mica paper capacitors are obtained and analyzed. Based on the test data, the lifetime empirical model of mica capacitors under given operating conditions is modified.
The results of the experiments and calculations of the lifetime empirical model indicate that the model aligns well with the experimental results. This work contributes to the lifetime prediction of mica capacitors and provides the design reference for system devices using mica capacitor under microsecond pulses.
2025, 37: 129001.
doi: 10.11884/HPLPB202537.250071
Abstract:
Background Purpose Methods Results Conclusions
The Vlasov equation is a cornerstone in plasma physics, governing the evolution of distribution functions in high-temperature, collisionless plasmas. Conventional numerical methods, including Eulerian and Lagrangian approaches, often encounter severe computational challenges due to the rapid increase in cost with fine grid resolutions and the curse of dimensionality. These limitations restrict their effectiveness in large-scale kinetic plasma simulations needed in fusion research and space plasma studies.
This work aims to develop an efficient and scalable computational framework for solving the Vlasov equation that mitigates the drawbacks of traditional methods. The study particularly addresses the need for maintaining accuracy and physical consistency while significantly reducing computational costs in high-dimensional simulations. An approach based on the physics-informed Fourier neural operator (PFNO) is introduced.
The method integrates the high-dimensional function mapping ability of the fourier neural operator with the physical constraints of the Vlasov equation. A physics-informed loss function is constructed to enforce mass, momentum, and energy conservation laws. The framework was evaluated through benchmark tests against finite element and spectral solvers, and its parallel performance was assessed on large-scale computing platforms.
The PFNO approach demonstrates accuracy comparable to conventional solvers while achieving computational efficiency improvements of one to two orders of magnitude. The method shows strong generalization under sparse-data conditions, exhibits grid independence, and scales effectively in parallel computing environments, enabling efficient treatment of high-dimensional plasma dynamics. The study presents a novel paradigm for solving high-dimensional Vlasov equations by combining deep learning operators with physical principles.
The PFNO framework enhances efficiency without sacrificing physical accuracy, making it a promising tool for applications in inertial confinement fusion, astrophysical plasma modeling, and space plasma simulations. Future research directions include extension to multi-species and relativistic plasma systems.
2025, 37: 129002.
doi: 10.11884/HPLPB202537.250197
Abstract:
Background Purpose Methods Results Conclusions
The ion source system for DC high-voltage accelerators operates at megavolt-level high-potential platforms, where wired communication media such as optical fibers face the risk of dielectric breakdown in compact applications due to voltage withstand constraints.
To address this, a prototype of an ion source control and acquisition system based on wireless optical communication (WOC) is designed.
For the analog control and acquisition requirements of high-voltage power supplies, RF power sources, and mass flow controllers in the 2.5 MV DC high-voltage accelerator’s inductively coupled plasma (ICP) ion source system, differential-input analog-to-digital conversion (ADC) is adopted to sample raw control and acquisition signals. After digital processing, signals are transmitted via WOC. The optical signals are converted via photoelectric conversion, then reconstructed into original analog signals through digital-to-analog conversion (DAC) and amplification circuits. In this design, a ZYNQ-based digital processing platform coordinates the acquisition, transmission, and reconstruction processes, which enables ADC/DAC data interaction and stable Ethernet optical communication, ensuring the overall integrity of the wireless optical control system.
An offline test platform verified that the designed WOC system can stably control the relevant equipment in the DC high-voltage accelerator ion source system. The transmission accuracy remained within the 1.5% deviation requirement, and the link operated reliably over long durations.
Experimental results indicate that the WOC system meets the technical requirements of the BNCT project and is feasible for application in the 2.5 MV DC high-voltage accelerator ion source system.
2025, 37: 121001.
doi: 10.11884/HPLPB202537.250139
Abstract:
As a strategic material for lightweight design, aluminum alloys occupy an important position in the fields of marine equipment, aerospace, and transportation due to their low specific gravity, corrosion resistance, and good low-temperature properties. It is worth noting that surface wettability, as a key interface parameter for the functionalization of aluminum alloys, directly affects their engineering service performance. In recent years, surface wettability control technology based on laser texturing has broken through the limitations of traditional chemical modification and provided new ideas for the functionalization of aluminum alloy surfaces. This article systematically explains the basic theoretical system of wettability, including the Young model, the Wenzel model, and the Cassie-Baxter model, and analyzes the differences in the application of ultrashort pulse lasers and long pulse laser systems in the construction of biomimetic functionalization of aluminum alloy surfaces. Among them, ultrashort pulse lasers (femtosecond/picosecond) can achieve submicron-level precision texturing due to their extremely short pulse width and ultra-high peak power, while long pulse lasers have advantages in large-area processing efficiency. Research has shown that these functionalized surfaces exhibit significant advantages in areas such as surface self-cleaning, low-temperature anti-icing, Cl− corrosion resistance, efficient boiling heat transfer, bonding, and microfluidics. However, their practical application is still limited by key technical bottlenecks such as wetting stability degradation and insufficient environmental tolerance.
As a strategic material for lightweight design, aluminum alloys occupy an important position in the fields of marine equipment, aerospace, and transportation due to their low specific gravity, corrosion resistance, and good low-temperature properties. It is worth noting that surface wettability, as a key interface parameter for the functionalization of aluminum alloys, directly affects their engineering service performance. In recent years, surface wettability control technology based on laser texturing has broken through the limitations of traditional chemical modification and provided new ideas for the functionalization of aluminum alloy surfaces. This article systematically explains the basic theoretical system of wettability, including the Young model, the Wenzel model, and the Cassie-Baxter model, and analyzes the differences in the application of ultrashort pulse lasers and long pulse laser systems in the construction of biomimetic functionalization of aluminum alloy surfaces. Among them, ultrashort pulse lasers (femtosecond/picosecond) can achieve submicron-level precision texturing due to their extremely short pulse width and ultra-high peak power, while long pulse lasers have advantages in large-area processing efficiency. Research has shown that these functionalized surfaces exhibit significant advantages in areas such as surface self-cleaning, low-temperature anti-icing, Cl− corrosion resistance, efficient boiling heat transfer, bonding, and microfluidics. However, their practical application is still limited by key technical bottlenecks such as wetting stability degradation and insufficient environmental tolerance.
2025, 37: 123006.
doi: 10.11884/HPLPB202537.250183
Abstract:
Background Purpose Methods Results Conclusions
Gyrotron traveling-wave tubes (gyro-TWTs) hold significant potential for applications in millimeter-wave radar, communications, electronic countermeasures, and deep-space exploration.
This paper investigates the high-frequency interaction circuit of a gyro-TWT operating in the Q-band under third-harmonic conditions. With an operational magnetic field of approximately 0.6 T, achievable using conventional solenoid magnets, this design overcomes the limitations associated with superconducting magnets. Furthermore, the adoption of a large-orbit electron beam for interaction addresses the low efficiency inherent in small-orbit electron beams under high-harmonic operation. The interaction structure employs a five-fold helical corrugated waveguide, which not only enhances interaction bandwidth but also effectively suppresses mode competition.
The impedance perturbation method and coupled-wave equations are used.
The transmission coupling characteristics of the five-fold Q-band helical waveguide have been derived.
The mode coupling mechanisms have been analyzed, and the dispersion equation has been formulated, yielding the dispersion curve of the waveguide. Analysis of the dispersion properties reveals the existence of three eigenmodes. Mode 1 is largely decoupled from Modes 2 and 3. Mode 1 has been selected as the operational mode, as it exhibits broad tangential interaction with the electron beam mode within the 42–47 GHz frequency range. This feature significantly extends the interaction bandwidth while simultaneously suppressing mode competition.
2025, 37: 124007.
doi: 10.11884/HPLPB202537.250124
Abstract:
Background Purpose Methods Results Conclusions
The china spallation neutron source (CSNS) is a high-current proton accelerator, which relies on its beam loss monitor (BLM) system for critical roles in equipment machine protection and residual activation dose control; in CSNS Phase I, the BLM system adopted NI’s PXIe-6358 acquisition card combined with self-developed front-end analog electronics, while the rapid cycling synchrotron (RCS) of CSNS-II requires an upgraded and fully localized BLM system to meet enhanced operational demands.
This study aims to develop a novel ZYNQ-based BLM electronics system to replace the existing NI data acquisition system in CSNS-II RCS, realizing comprehensive functions including beam loss signal acquisition, gain control, Machine Protection Signal (MPS) output, and EPICS PV publishing.
The system comprises custom-developed components: a 19-inch 3U chassis with a dedicated backplane bus, 3 kV low-ripple high-voltage power modules, front-end analog boards, and digital acquisition boards based on the ZYNQ7020 system-on-chip (SOC) integrated with AD7060 and LTC2668, along with developed Linux drivers (including an AXI-DMA-based ADC driver and an AXI-GPIO-based gain control driver) and EPICS IOC software; it was subjected to laboratory functional tests using 25 Hz, 50 μs–1 ms pulse signals to simulate ion chamber outputs and on-beam tests at the RCS local station.
Laboratory tests validated key functions such as external trigger waveform acquisition, gain control, MPS threshold output, and background subtraction, while on-beam tests at the RCS local station clearly captured beam loss signals and extraction interference signals, with the system achieving 100% localization and meeting all engineering specifications.
In conclusion, the ZYNQ-based BLM system has completed the development of core components and demonstrated full functionality, enabling it to effectively replace the existing NI acquisition system and making it well-suited for beam loss measurement in CSNS-II.
2025, 37: 125002.
doi: 10.11884/HPLPB202537.250122
Abstract:
Background Purpose Methods Results Conclusions
Pulse drive sources are critical components of high-power microwave systems. Existing drive sources based on Tesla+PFL or LTD technology offer good waveform quality but are limited by their large size and weight. PFN-Marx technology sequentially stacks voltages during pulse discharge, which requires relatively low insulation and makes it an ideal technical approach for drive source miniaturization. However, current PFN-Marx-based drive sources struggle to balance compact structural design with output waveform quality.
This study aims to design a compact high-power pulse drive source based on PFN-Marx technology to meet the requirements of a specific high-power microwave system.
To achieve this goal, a 7-stage unipolar pulse charging PFN-Marx generator is employed, with a high-power constant-current charging power supply powered by lithium batteries used to charge the primary capacitor of the Tesla transformer. The PFN modules are designed with identical charging loop inductors to ensure synchronized pulse charging waveforms, and their modular structure allows for flexible scalability. Additionally, the air-core Tesla transformer (with a coupling coefficient greater than 0.8) is integrated with the PFN-Marx within a high-voltage chamber filled with SF6 gas to ensure insulation.
The results show that the drive source outputs a single pulse energy of 45.6 J, and can output a quasi-square wave pulse at a 75 Ω load, with an amplitude of −189.2 kV, a pulse width of 93.2 ns, a rise time of 8.4 ns, and a peak power of 477 MW. The lithium-ion battery charging and control power supply has dimensions of 482 mm×443 mm×177 mm and weighs 12.6 kg; the integrated Tesla transformer and PFN-Marx generator have dimensions of ϕ370 mm×848 mm and weigh 28.7 kg. At a repetition rate of 5 Hz, the average output voltage is −183.4 kV, with a voltage dispersion of 4.1%.
Therefore, this compact PFN-Marx-based pulse drive source achieves both miniaturization and high-quality waveform output, laying the foundation for the development of higher-power and higher-performance compact pulse drive sources.
2025, 37: 126001.
doi: 10.11884/HPLPB202537.250157
Abstract:
Background Purpose Methods Results Conclusions
The assessment of gamma radiation dose released by strong explosions is an important direction in the research of nuclear emergency protection systems. Traditional research has mostly focused on dose assessment of prompt gamma radiation (with a duration of less that 1 μs）, while delayed gamma radiation (on the second timescale) is often overlooked due to time delay.
This article focuses on the study of the delayed gamma dose released by fission products after a strong explosion within 0.2–0.5 s, as well as the secondary gamma dose generated by neutron leakage, with the aim of systematically evaluating their radiation hazards in the near to medium range.
Based on Monte Carlo (MC) method, a three-dimensional full-scale model coupling strong explosive source term atmospheric transport surface activation was constructed, and a dynamic dose assessment framework based on MC multi-step calculation was proposed. By modifying the importance card method, the variance of the simulation results at medium to close distances was effectively reduced, and a detailed comparison was made between the changing trends of delayed gamma and prompt gamma doses over time and distance.
The simulation results show that within a time window of 0.2– 0.5 s: at a distance of 500 m from the explosion source, the total dose of delayed gamma radiation reaches 0.829 Gy, which is 1.88 times that of the instantaneous gamma radiation dose (0.441 Gy); At a distance of 1000 m from the explosion source, the delayed gamma dose generated by fission products alone is 0.0318 Gy, which is 7.6 times that of the instantaneous gamma dose (0.0042 Gy), indicating that the hazard of delayed gamma is significantly higher than that of instantaneous gamma at longer distances. The secondary gamma dose generated by neutron leakage decays from 0.634 Gy at 500 m to 0.0485 Gy at 1000 m.
The dynamic dose assessment framework proposed in this article effectively reveals the significant contribution of delayed gamma radiation in the early radiation field after a strong explosion, especially at a distance where its hazard far exceeds that of instantaneous gamma radiation. This study provides key data support for optimizing nuclear emergency protection strategies.
Modeling and calculation of radiation effects of high-energy rays on PCB inside a shielded enclosure
2025, 37: 126002.
doi: 10.11884/HPLPB202537.250098
Abstract:
Background Purpose Methods Results Conclusions
X/γ-ray irradiation of an electronic system shielding box will penetrate the box body, generate photoelectrons or Compton electrons on the surface layers or inside the system, and excite electromagnetic pulses. These particles or electromagnetic fields will interfere with or even damage the sensitive electronic components of the electronic system inside the box, affecting the regular operation of the electronic system.
To rapidly assess the particle and electromagnetic environment inside electronic systems under radiation exposure and enable timely protective measures that mitigate radiation-induced damage and ensure reliable operation.
We present a theoretical analysis of irradiation responses arising from two coupling mechanisms: electromagnetic pulses excited by primary particles within the cavity of a shielded enclosure and their field-to-circuit coupling to a printed circuit board (PCB), and direct multi-layer penetration coupling of ionizing radiation. Equivalent-circuit models were constructed to represent these coupling paths, and transient current responses were calculated analytically.
The transient current responses of the shielded enclosure under high-energy radiation, computed using the equivalent-circuit approach, reproduce the trends observed in published experimental measurements and exhibit approximate numerical agreement.
The results validate the proposed theoretical modeling approach, showing that analytical equivalent-circuit analysis can provide rapid, simulation-free estimates of radiation effects on electronic systems. The method can be extended to scenarios that more closely match practical applications.
