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Display Method:
, Available online ,
doi: 10.11884/HPLPB202638.250310
Abstract:
Background Purpose Methods Results Conclusions
Fiber lasers have been widely used in numerous fields such as industrial processing and scientific research detection, due to their significant advantages including high efficiency, low cost, and miniaturization. In the R&D (Research and Development) and mass production of fiber lasers, the synchronous testing of core performance indicators such as power, spectrum, time-domain characteristics, and beam quality is a key technical support. It enables comprehensive evaluation of the device’s overall performance, accurate localization of design defects, optimization of production process parameters, and guarantee of consistent product delivery. However, the traditional testing mode requires temporarily building a dedicated test system for each laser under test. It has problems such as long time consumption, cumbersome operation, and low testing efficiency, making it difficult to meet the needs of large-scale production and high-efficiency R&D.
To address the above issues, this paper proposes an integrated synchronous testing system for multi-parameter fiber lasers. The system aims to realize the synchronous acquisition and testing of multiple indicators, including power, spectrum, time-domain characteristics, and beam quality. It further improves the scientificity of the comprehensive performance evaluation of lasers, provides reliable technical support for production practice and scientific research in related fields, and achieves the core goals of improving testing efficiency and simplifying testing processes.
The system achieves the integrated integration of multi-module hardware testing equipment, as well as standardized interfaces and external connections, based on optical principle design and precision mechanical structure design. From the perspective of safe operation, an emergency shutdown device for abnormal working conditions is equipped to ensure the safety of the system and the laser under test during the testing process. The control software adopts LabVIEW multi-threading technology to realize the synchronous acquisition and real-time transmission of various parameters.
The system can adapt to the testing needs of fiber lasers with an output power range of 80 W to 10 kW. During testing, users only need to connect the fiber end cap of the laser under test to the system, and can start multi-parameter synchronous testing through the upper computer software without manual intervention in the optical adjustment link. After the test, the system can automatically complete the analysis and processing of raw data and generate a standardized test report. Verification experiments conducted with a 10 kW fiber laser as the test object show that the system has good operability, reliability, test repeatability, and technical feasibility.
The system significantly improves the efficiency of multi-parameter testing of fiber lasers and greatly reduces the complexity of data processing, providing an efficient and reliable solution for scientific research and industrial laser testing.
, Available online ,
doi: 10.11884/HPLPB202638.250327
Abstract:
Background Purpose Methods Results Conclusions
In voltage multiplication process of a spiral generator based on the principle of vector inversion, its voltage efficiency is constrained by losses such as switching loss, transmission line loss and leakage inductance loss.
To quantitatively investigate the impact of key design parameters––including coil turn number n, dielectric/electrode thickness, average dielectric diameter D, magnetic core permeability, and switch position on leakage loss and overall efficiency.
This study employs a field-circuit collaborative simulation method for modeling and analysis.
The simulation results demonstrate that utilizing a high-permeability magnetic core can significantly enhances voltage efficiency; increasing D/n ratio improves output efficiency; while a higher turn number n boosts output voltage amplitude, it concurrently reduces voltage efficiency; enlarging the average diameter D enhances voltage efficiency but at the cost of increased device volume; reducing dielectric thickness benefits efficiency, though excessively thin layers risk insulation breakdown; and positioning the switch at the middle of the coil, rather than at the end, substantially increases voltage efficiency.
Furthermore, an in-depth analysis of the electromagnetic energy conversion process after switch closure revels that a high-efficiency spiral generator must achieve complete conversion of magnetic energy into electric field energy while ensuring the electric fields in the active and passive layers are oriented in the same direction, while is essential for optimal performance.
, Available online ,
doi: 10.11884/HPLPB202638.250318
Abstract:
Background Purpose Methods Results Conclusions
The C-band photocathode electron gun is a key front-end device of the accelerator for the Southern Light Source Free-Electron Laser, whose resonant frequency stability is crucial for beam quality and long-term operation. During high-power microwave excitation, electromagnetic power loss on the inner surfaces of the resonant cavity produces non-uniform thermal loading, leading to structural deformation and subsequent resonant frequency drift, which cannot be accurately characterized by traditional single-physical-field analyses.
To clarify the intrinsic mechanism of this phenomenon, a comprehensive electromagnetic–thermal–structural multi-physical field coupling model is developed based on the COMSOL Multiphysics® simulation platform.
First, high-frequency electromagnetic simulations are carried out to obtain the designed resonant frequency of the vacuum cavity at 5.712 GHz and to calculate the surface electromagnetic loss power density. Based on these results, an equivalent boundary heat source model is established, and the external mechanical structure of the electron gun together with the cooling pipeline is modeled. By employing a fluid–solid coupling method, the non-uniform temperature distribution of the cavity under realistic cooling conditions is obtained. Subsequently, the solid mechanics interface is used to compute the thermally induced deformation of the cavity geometry, and the deformed structure is introduced into a secondary high-frequency simulation to evaluate the resulting resonant frequency drift.
The results reveal a clear transmission path from microwave power loading to temperature rise, structural deformation, and frequency shift, quantitatively demonstrating the strong coupling among electromagnetic, thermal, and mechanical fields.
This study realizes a complete multi-physical field coupling analysis of the C-band photocathode electron gun and provides an effective numerical framework for predicting resonant frequency drift, offering important guidance for the thermal–mechanical coupling design and frequency stability optimization of high-precision microwave cavities.
, Available online ,
doi: 10.11884/HPLPB202638.250219
Abstract:
Background Purpose Method Results Conclusions
With the continuous development of nuclear power technology, reactor design has put forward higher requirements for the accuracy, efficiency and multi-functionality of nuclear computing software. The current mainstream Monte Carlo software has deficiencies in the balance between reactor radiation shielding design and nuclear design calibration, which restricts the critical simulation efficiency of the reactor core. Therefore, CNPRI has specifically developed the 3D Monte Carlo software LARCH 1.0 to meet the actual needs of nuclear power engineering design.
To optimize the particle energy search mechanism in Monte Carlo simulation and address the pain point of low efficiency in traditional search methods; Thirdly, based on the optimized search method, the delta-tracking algorithm is further improved to enhance the efficiency of core critical calculation and provide efficient and accurate calculation support for reactor design.
During the development of the LARCH software, the core technological innovation lies in the adoption of a unified energy grid design to replace the traditional binary search and logarithmic search methods. Through the standardization and unification of the energy grid, the number of searches in the particle energy matching process is reduced, and the time consumption of a single search is shortened. Based on the technology of unified energy grid, further develop and optimize the delta-tracking algorithm to achieve the improvement of computing efficiency; By designing a targeted numerical verification scheme, the LARCH 1.0 software and the traditional Monte Carlo software were compared and tested in the reactor problem simulation.
The optimized technical solution has achieved remarkable results. The search method based on the unified energy grid has significantly reduced the time cost of particle energy search compared with the traditional method. Based on this, the optimized delta-tracking algorithm has increased the critical computing efficiency of the Monka software core by approximately 25%.
The unified energy grid method and the optimized delta-tracking algorithm adopted by the LARCH 1.0 3D Monte Carlo software provide an effective technical path for the efficiency improvement of the Monte Carlo software and significantly enhance the critical computing efficiency of the reactor core. The application potential of this software indicates that it can provide more efficient and reliable numerical simulation tools for reactor design. Subsequently, more extensive engineering verification and functional iterations will be further carried out.
, Available online ,
doi: 10.11884/HPLPB202638.250376
Abstract:
Background Purposes Methods Results Conclusions
U-band fiber lasers are of significant value for applications in communications, sensing, and scientific research.
This paper employs a 1.55 μm fiber laser as the pump source and demonstrates U-band 1.65 μm Raman fiber lasers based on commercially available single-mode silica fiber. The effects of the Raman fiber length and the reflectivity of the output coupling fiber Bragg grating (OC-FBG) on the power conversion efficiency of the Raman laser were systematically investigated.
The optimal Raman fiber length was determined to be 2.1 km in experiment. Then, with the optimal Raman fiber length, experiments conducted by varying the reflectivity of the OC-FBG to analyze its influence on the output power and spectral broadening of Stokes light. By combining the measured forward and backward Stokes powers with the collected forward and backward spectra, the optimal OC-FBG reflectivity parameter under the current experimental conditions was determined.
The results indicated that as the Raman laser power increased, the broadening of the Stokes spectral linewidth reduced the effective reflectivity of the fiber Bragg grating, leading to backward power leakage, which became the main factor limiting the forward output power.
By selecting an OC-FBG with a low reflectivity of 15.7% and using a 2.1 km silica fiber as the Raman gain medium, a 1648.8 nm Raman laser output with a power of 10.1 W and a 3 dB bandwidth of 2.5 nm was achieved, corresponding to an optical-to-optical conversion efficiency of 65.2%.
, Available online ,
doi: 10.11884/HPLPB202638.250328
Abstract:
Background Purpose Methods Results Conclusions
The PFN (pulsed forming network)-Marx generator shows robust capabilities for enhancing the output efficiency and miniaturization level of pulsed power system, and offers the most significant potential for compact and lightweight design.
This study aims to develop a compact PFN-Marx generator, which is capable of generating high-power pulses with flat-top duration, while keeps low output jitter.
A tailored pulsed forming module (PFM) was developed by employing a non-uniform PFN whose sections were reduced to 2, aiming for enhanced compact characteristics. The influence of key circuit parameters on its output waveform was investigated. A PFN-Marx generator was designed and assembled by employing the PFMs and low-jitter plane-triggering-electrode gas switches et al.
The effects of key circuit parameters in the pulse shaping was quantitatively analyzed, and waveform tailoring of the PFM is achieved. The PFM could output a high-voltage pulse with pulse width and flat-top duration (90%-90%) of about 150 ns and 80 ns, respectively. Once assembled into the Marx generator, it could deliver a 190 kV, 3.4 GW high pulsed power to a 10.6 Ω resistive load, while keeps a flat-top duration of about 80 ns. When operating at a repetition rate of 50 Hz, it exhibits highly consistent output waveforms, with an output jitter as low as 2.4 ns.
A compact PFN-Marx generator was developed by employing a 2-sections tailored PFM that is capable of generating high-power pulses with flat-top duration. It is helpful for the development of compact Marx generator with requested waveform and low output jitter.
, Available online ,
doi: 10.11884/HPLPB202638.250369
Abstract:
Background Purpose Methods Results Conclusions
The self-absorption effect of target materials plays a crucial role in shaping the performance of laser-driven X-ray sources, directly impacting their energy spectrum and angular distribution, which are critical parameters for applications such as high-resolution backlighting and radiographic diagnostics.
This study aims to systematically investigate how key parameters, including the electron source position relative to the wire target end-face, the diameter of the wire target, and the atomic number of the target material, affect the energy spectrum and angular distribution of emitted X-rays.
A series of Geant4-based Monte Carlo simulations were performed using a validated wire target model. Key parameters were varied: electron source offset (50–150 μm), wire diameter, and target material (Cu, Mo, W, Au). The simulation model was benchmarked against experimental data obtained from the Xingguang-III laser facility.
Results indicate that varying the electron source position within the studied range has a negligible influence on both the photon energy spectrum and angular distribution. In contrast, increasing the wire diameter leads to enhanced absorption of low-energy photons, resulting in noticeable spectral hardening and a broadening of the angular distribution due to increased multiple scattering. Furthermore, higher-Z target materials (W, Au) significantly enhance the high-energy photon yield but concurrently induce greater angular divergence.
The findings provide quantitative insights into the self-absorption mechanism and its differential impact across parameters. This study offers concrete guidance for optimizing target design: selecting appropriate wire diameter and high-Z materials can tailor the spectral hardness and brightness, while mindful management of angular broadening is necessary for applications requiring high directivity.
, Available online ,
doi: 10.11884/HPLPB202638.250234
Abstract:
Background Purpose Methods Results Conclusions
With the development of neutron calculation methods and improved modeling capabilities, the errors introduced by model approximations and discretization methods in nuclear reactor physics calculations have gradually decreased. However, nuclear data, due to the challenges in measurement, have become the key input parameter affecting computational accuracy.
In this study, a nuclear data adjustment module based on sensitivity analysis and the generalized linear least squares algorithm was developed within the self-developed sensitivity and uncertainty analysis platform, SUPES.
First, sensitivity analysis was used to determine the relationship between system responses and input parameter variations. Next, similarity analysis was applied to select experimental setups with high similarity at the neutron physics level. Finally, the generalized linear least squares algorithm was employed to minimize the error between computed and measured values, resulting in nuclear data adjustments.
The adjustment of the ACE format continuous energy database was performed on 22 cases from the critical benchmark HEU-MET-FAST-078. The numerical results show that the root mean square error of effective multiplication factor (keff) reduced from 3.10×10−3 to 1.53×10−3.
The comparison and analysis verified the correctness of the developed nuclear data adjustment module.
, Available online ,
doi: 10.11884/HPLPB202638.250371
Abstract:
High harmonic generation (HHG) and attosecond pulses driven by relativistically intense lasers interacting with solid-density plasma mirrors constitute a vital pathway for realizing high-brightness, short-wavelength, ultrafast coherent light sources and exploring extreme strong-field physics. In recent years, benefiting from the rapid development of laser technology, the precise control over light field degrees of freedom, such as amplitude, phase, and polarization, has spurred the emergence of structured light fields. Structured light fields significantly enrich the methods for controlling laser-matter interaction and broaden the scope of applications. This article aims to review the latest progress in controlling relativistic laser-plasma HHG and attosecond pulses using structured light fields. The work specifically discusses the characteristic control and physical mechanisms of HHG driven by novel structured light fields, including polarization structures (e.g., circularly polarized light, vector beams), phase structures (e.g., spatial vortex beams, spatiotemporal vortex beams), and amplitude structures (e.g., Bessel beams, Airy beams), with the goal of providing new perspectives for research on novel light sources based on strong-field laser-plasma interactions.
High harmonic generation (HHG) and attosecond pulses driven by relativistically intense lasers interacting with solid-density plasma mirrors constitute a vital pathway for realizing high-brightness, short-wavelength, ultrafast coherent light sources and exploring extreme strong-field physics. In recent years, benefiting from the rapid development of laser technology, the precise control over light field degrees of freedom, such as amplitude, phase, and polarization, has spurred the emergence of structured light fields. Structured light fields significantly enrich the methods for controlling laser-matter interaction and broaden the scope of applications. This article aims to review the latest progress in controlling relativistic laser-plasma HHG and attosecond pulses using structured light fields. The work specifically discusses the characteristic control and physical mechanisms of HHG driven by novel structured light fields, including polarization structures (e.g., circularly polarized light, vector beams), phase structures (e.g., spatial vortex beams, spatiotemporal vortex beams), and amplitude structures (e.g., Bessel beams, Airy beams), with the goal of providing new perspectives for research on novel light sources based on strong-field laser-plasma interactions.
, Available online ,
doi: 10.11884/HPLPB202638.250101
Abstract:
Background Purpose Methods Results Conclusions
The intense electron beam-plasma system serves as an important platform for investigating beam-plasma interactions. Research in this field focuses on the design of electron beam window and the transport characteristics of electron beam in plasma.
The study aims to design and evaluate the electron beam window with excellent comprehensive performance, and to investigate the physical mechanisms underlying the focusing and transmission of intense annular electron beams in plasma.
Finite element analysis and Monte Carlo simulations were employed to compare and evaluate the mechanical, thermal, and transmission properties of candidate window materials. Theoretical analysis and particle-in-cell (PIC) simulations were used to study the self-focusing transmission behavior of intense annular electron beams in plasma.
The TC4 titanium alloy window with a thickness of only 0.04 mm was found sufficient to withstand a pressure differential of 10 kPa. It achieved an energy transmission efficiency exceeding 90% while maintaining controllable temperature variations. The physical mechanism of self-focusing transmission of intense annular electron beams in plasma under conditions of 500 kV and 20 kA was revealed, clarifying the relationship between the focusing transmission period of the electron beam and the plasma density. Furthermore, an equivalent relationship between plasma density and magnetic field was established based on the correspondence between the plasma oscillation period and the electron beam cyclotron period.
The research demonstrates that TC4 titanium alloy is a suitable material for electron beam window, offering high transmission efficiency and structural stability. It also elucidates the self-focusing transmission mechanism of intense annular electron beams in plasma and establishes a periodic equivalent relationship between plasma and magnetic fields for electron beam transport.
, Available online ,
doi: 10.11884/HPLPB202638.250261
Abstract:
Background Purpose Methods Results Conclusions
Traditional Mie theory, assuming spherical particles, is inadequate for characterizing the scattering of atmospheric non-spherical ice crystals. Existing studies are largely limited to single frequency (e.g., 94 GHz), lacking systematic quantification of key dual-polarization parameters across the millimeter/submillimeter wave spectrum, which constrains the accuracy of polarimetric radar for meteorological target detection and classification.
This study aims to systematically investigate the dual-polarization scattering properties of six typical non-spherical ice crystals—hexagonal columns, plates, hollow columns, bullet rosettes, aggregates, and supercooled water droplets—across 35, 94, 140, and 220 GHz bands. It quantifies the responses of differential reflectivity (ZDR) and linear depolarization ratio (LDR) to particle shape and orientation, providing crucial theoretical support for wideband polarimetric radar meteorology.
Scattering models were developed using the Discrete Dipole Approximation (DDA) and Finite-Difference Time-Domain (FDTD) methods, cross-validated with commercial software (XFDTD, HFSS). Backscattering cross-sections, ZDR, and LDR were computed for different ice crystals across the frequency bands, analyzing the influence of particle size, geometry, and frequency.
1）The reliability of DDA was systematically validated across the 35–220 GHz range. Calculation errors for backscattering cross-sections were ≤1.5 dB for all particles except highly random aggregates. 2) Radar reflectivity factor showed a coupled wavelength dependence: small particles (equivalent radius <100 μm) were wavelength-insensitive (<1 dB difference), while large particles (>100 μm) exhibited significant shape-dependent resonance. The equivalent radius corresponding to resonance extrema increased with wavelength. 3) Characteristic ranges of ZDR and LDR for the six ice crystal types were quantified. Hexagonal plates showed the widest ZDR range (9 dB to –9 dB), while axisymmetric particles exhibited stable LDR values (–40 dB to –50 dB).
This wideband, multi-particle study addresses prior limitations in frequency coverage and parameter quantification. It demonstrates that the shape-sensitive ZDR and LDR parameters can reduce dependence on particle size distribution and significantly improve ice crystal identification accuracy, providing a key theoretical basis for millimeter/submillimeter wave polarimetric radar applications in cloud microphysics and meteorological target classification.
, Available online ,
doi: 10.11884/HPLPB202638.250412
Abstract:
The emergence and rapid advancement of ultrafast and ultraintense lasers have created unprecedented extreme physical conditions and novel experimental methods, significantly deepening and expanding our understanding of the laws governing the objective world. These developments have greatly promoted innovation in basic and frontier interdisciplinary fields as well as strategic high technology areas. Particle acceleration using the interaction of ultrafast and ultraintense lasers with plasmas is regarded as a next-generation technology for accelerators and radiation sources. It offers the potential to shrink the footprint of conventional accelerator facilities by two orders of magnitude. This dramatic reduction in size greatly expands the applicability of accelerator and radiation source technologies in industry, national defense, medicine, and scientific research, enabling transformative possibilities such as precision nondestructive testing of critical components, ultralow dose and high precision tumor diagnostics, novel low damage radiotherapy methods, and tabletop ultrafast light sources. The ultrafast and ultraintense laser platform at Zhengzhou University introduced in this paper is precisely such a next-generation facility dedicated to advanced laser accelerator research and applications. In addition, this article provides a systematic review of the significant progress achieved by Zhengzhou University in recent years in strong-field physics and advanced accelerator science.
The emergence and rapid advancement of ultrafast and ultraintense lasers have created unprecedented extreme physical conditions and novel experimental methods, significantly deepening and expanding our understanding of the laws governing the objective world. These developments have greatly promoted innovation in basic and frontier interdisciplinary fields as well as strategic high technology areas. Particle acceleration using the interaction of ultrafast and ultraintense lasers with plasmas is regarded as a next-generation technology for accelerators and radiation sources. It offers the potential to shrink the footprint of conventional accelerator facilities by two orders of magnitude. This dramatic reduction in size greatly expands the applicability of accelerator and radiation source technologies in industry, national defense, medicine, and scientific research, enabling transformative possibilities such as precision nondestructive testing of critical components, ultralow dose and high precision tumor diagnostics, novel low damage radiotherapy methods, and tabletop ultrafast light sources. The ultrafast and ultraintense laser platform at Zhengzhou University introduced in this paper is precisely such a next-generation facility dedicated to advanced laser accelerator research and applications. In addition, this article provides a systematic review of the significant progress achieved by Zhengzhou University in recent years in strong-field physics and advanced accelerator science.
, 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.
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/HPLPB202638.250184
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 this 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 this structure, the mathematical model of the switch gap adjustment system is established. Thirdly, to address 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 using Matlab simulation software.
Simulation results of the whole regulation process show 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 200 s, 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/HPLPB202638.250123
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/HPLPB202638.250129
Abstract:
Background Purpose Method Results Conclusion
The gyrotron is a relativistic nonlinear device capable of generating high-power electromagnetic radiation in the millimeter-wave and terahertz frequency ranges. In most operating magnetically confined thermonuclear fusion reactors (for electron cyclotron heating and current drive, ECH&CD), high-power gyrotrons serve as the core microwave source devices for their electron cyclotron wave heating and current drive systems. For high-power gyrotrons, the high-frequency cavity must operate in a high-order whispering gallery mode to meet the power capacity requirements. However, high-order mode operation conversely introduces severe mode competition. Electron beam performance is a major factor affecting the mode competition, further limiting their efficient and stable operation, particularly in long-pulse or continuous-wave regimes. Therefore, it is essential to investigate the impact of megawatt-level gyrotron electron beam performance on beam-wave interaction.
The study focuses on a self-developed megawatt-level 170 GHz gyrotron operating at TE25,10 mode, analyzing the structural parameter variations of the high-frequency cavity, the start-oscillation current, and the mode competition in single/dual-anode electron beam modulation.
This paper comprehensively considers electron beam performance (velocity spread, beam thickness, space charge effects, oscillation startup process, single/dual-anode configuration) and establishes a sophisticated time-domain, multi-mode, multi-frequency self-consistent nonlinear beam-wave interaction model.
Under operating conditions of 80 kV beam voltage, 40 A beam current, 6.72 T magnetic field, and a velocity ratio of 1.3, the output power reaches 1.35 MW with an interaction efficiency of 42.2%.
Numerical simulations demonstrate that the dual-anode modulation method significantly suppresses mode competition. The successful demonstration of this device establishes a foundation for further studies on higher power and higher-frequency gyrotron.
, 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/HPLPB202638.250363
Abstract:
Background Purpose Methods Results Conclusions
In recent years, emerging application fields such as FLASH radiotherapy and flash radiography have created an urgent demand for high-repetition-rate linear induction accelerators (LIA) capable of operating at kHz-level frequencies. Whether the magnetic cores of induction accelerator cavities can effectively reset between repetitive pulses has become one of the critical factors determining the feasibility of high-repetition-rate LIA.
This paper focuses on the reset methods for magnetic cores in high-repetition-rate pulsed induction accelerator cavities.
Through high-voltage experiments and circuit simulations, various rapid reset methods for both amorphous and nanocrystalline magnetic cores were investigated and comparatively analyzed. Based on this work, experimental tests were conducted on the interpulse reset effectiveness of accelerator cavity cores using self-developed high-repetition-rate pulsed induction accelerator modules.
Research results indicate that nanocrystalline magnetic cores are more suitable for high-repetition-rate induction accelerator cavities. Different reset methods can achieve magnetic core reset at varying repetition frequencies.
Utilizing the inductor-isolated DC reset method, the existing device configuration can meet the reset requirements for nanocrystalline magnetic cores at a 10 kHz repetition rate. By leveraging the self-recovery capability of low-remanence nanocrystalline magnetic cores, automatic reset of accelerator cavity cores can be achieved at 100 kHz repetition rates.
, 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, establishing relationships between slot dimensions and RCS, and developing 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/HPLPB202638.250018
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, where 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 a 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/HPLPB202638.250182
Abstract:
Background Purpose Methods Results Conclusions
With the development of high-power microwave technology, the demand for high-power microwave system has moved towards miniaturization and compactness. Realizing high-efficiency and high-power operation under low magnetic field is an important trend for miniaturization and compactness.
In order to improve the power and efficiency of high-power microwave source under low guiding magnetic field (< 0.4 T), a high-efficiency coaxial dual-mode relativistic Cherenkov oscillator (RCO) under a low guiding magnetic field is proposed.
Traditional over-mode RCO is mostly limited to single mode operation, which greatly restricts the further improvement of efficiency. The proposed RCO adopts the dual-mode working mechanism, works in both coaxial quasi-TEM mode and TM01 mode. The dual-mode working mechanism allows the electron beam to interact with multiple modes, thereby improving power capacity and efficiency simultaneously. 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 a conversion efficiency of 34%.
Both simulation and experimental results show that the proposed RCO can work stably with high efficiency and high power under the low magnetic field, and the 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/HPLPB202638.250362
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/HPLPB202638.250112
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 linacs.
, 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/HPLPB202638.250251
Abstract:
Background Purpose Methods Results Conclusions
Fiber lasers have gained extensive adoption across medical, telecommunications, industrial processing, and defense sectors owing to their exceptional beam quality, operational stability, compact architecture, and high reliability. Among them, narrow-linewidth linearly polarized fiber lasers have become a key research focus due to their outstanding spectral purity and coherence, with current efforts concentrated on further scaling their output power and brightness.
In this work, we demonstrate a 5.09 kW narrow-linewidth linearly polarized fiber laser system designed to overcome stimulated Brillouin scattering (SBS) and transverse mode instability (TMI).
A white-noise radio frequency phase modulation scheme is implemented to broaden the seed laser spectrum into a Gaussian profile with an 89 GHz full width at half maximum, enabling effective SBS suppression. A polarization-maintaining ytterbium-doped fiber (PMYDF) with low numerical aperture (about 0.05), large mode area (about 237 μm2), and high birefringence coefficient (4.23×10−4) is employed to simultaneously mitigate SBS and intermodal thermal coupling.
The system achieves 5.09 kW output power while maintaining an 89 GHz spectral linewidth, polarization extinction ratio above 19.6 dB, and beam quality factor of M2 < 1.2. No self-pulsing or temporal instability is observed at maximum power, confirming suppression of both SBS and TMI.
By employing a white-noise radio frequency signal to modulate the phase of a single-frequency laser, the SBS effect in high-power fiber laser systems is effectively suppressed. Concurrently, intermodal thermal coupling and SBS are further mitigated using a fabricated low-numerical-aperture, large-mode-area PMYDF. The demonstrated performance supports the feasibility of high-power, narrow-linewidth polarized fiber lasers for long-term stable operation.
, 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.
The 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/HPLPB202638.250155
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/HPLPB202638.250181
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 Bayesian 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/HPLPB202638.250257
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 aims to investigate 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, we construct 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.
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.
