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, Available online , doi: 10.11884/HPLPB202638.250393
Abstract:
Background Purpose Methods Results Conclusions
The retention and diffusion of helium on the surface of the first wall is one of the key problems in the study of magnetic confinement fusion. And laser-induced breakdown spectroscopy is the most promising technique for in-situ diagnosis of the first wall. Compared with the optical spectral range, laser-induced extreme ultraviolet spectra has more advantages in sensitivity, noise suppression and accuracy.
In order to meet the requirement of high precision on-site measurement of helium impurity lines in magnetic confinement fusion, a ultra-high resolution EUV spectroscopy system was developed.
The grazing incidence Czerny-Turner structure is used in the spectrometer, and the luminous flux and spectral resolution are adjusted through an adjustable incidence slit. The ray tracing simulation is carried out with a self-developed optical design software. And the wavelength calibration and performance testing are carried out by microwave plasma light source.
The simulation results show that the spectral resolution is better than 20 000, and the experimental results indicate that the spectrometer achieves a spectral resolution of 0.001 4 nm at He II (30.3786 nm).
The spectrometer can meet the requirement of high-precision measurement of helium extreme ultraviolet spectral lines, and it is expected to provide an important theoretical support for the research on the helium retention and diffusion in the first wall.
, 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/HPLPB202638.250234
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/HPLPB202638.250382
Abstract:
Background Purpose Methods Results Conclusions
Ultrashort and ultraintense laser-driven plasma X-ray sources offer femtosecond pulse durations, intrinsic spatiotemporal synchronization, compactness, and cost-effectiveness, serving as an important complement to traditional large-scale light sources and providing novel experimental tools for ultrafast dynamics research.
Built upon the Synthetic Extreme Condition Facility (SECUF), the first open-access user experimental station in China based on high-power femtosecond lasers was established to deliver various types of ultrafast radiation sources, supporting studies on ultrafast material dynamics and frontier strong-field physics.
The station is equipped with a dual-beam titanium-sapphire laser system (3 TW/100 Hz and PW/1 shot/min) and multiple beamlines with multifunctional target chambers. Through interactions between the laser and solid targets, gas targets, or plasmas, various ultrafast light sources—such as Kα X-rays, Betatron radiation, and inverse Compton scattering—are generated. Platforms for strong-field terahertz pump–X-ray probe (TPXP) experiments and tabletop epithermal neutron resonance spectroscopy have also been developed.
A highly stable ultrafast X-ray diffraction and TPXP platform was successfully established, enabling direct observation of strong-field terahertz-induced phase transition in VO2. The world’s first tabletop high-resolution epithermal neutron resonance spectroscopy device was developed. On the PW beamline, hundred-millijoule-level intense terahertz radiation, efficient inverse Compton scattering, and high-charge electron beams were achieved.
Integrating high-performance lasers, diverse radiation sources, and advanced diagnostic platforms, this experimental station provides a flexible and efficient comprehensive facility for ultrafast science, promising to advance ultrafast dynamics research toward broader accessibility and more cutting-edge directions.
, Available online , doi: 10.11884/HPLPB202638.250177
Abstract:
Background Purpose Method Results Conclusions
The dual-pulse LIBS (DP-LIBS) technology can effectively enhance the spectral intensity of LIBS and has received widespread attention in LIBS analysis.
For the purpose to understand the enhancement mechanism of traditional collinear dual pulse LIBS and long-short collinear dual pulse LIBS spectra, a comparative study was conducted on two DP-LIBS with different laser excitation schemes, i.e. the conventional collinear dual nanosecond pulse excitation scheme, and the long-short collinear dual-pulse excitation scheme which combining a microsecond pulse and a nanosecond pulse.
The enhancement mechanism and variation trend of spectral intensity were investigated by systematically analyzing the laser ablation morphology and LIBS spectra collected under different inter-pulse delay, spectral acquisition delay and laser pulse energy in both DP-LIBS modes.
The results show that, in conventional collinear DP-LIBS, the spectral intensity increases rapidly within a short delay time of 0–2 μs, but remains relatively high in the longer delay range of 2–14 μs. And the optimal inter-pulse delay is around 4 μs in conventional collinear DP-LIBS. In contrast, the optimal inter-pulse delay for the long-short collinear DP-LIBS is approximately 25 μs, which is determined by the peak power timing of the long-pulse laser.
In the conventional DP-LIBS configuration, spectral enhancement is more sensitive to the energy variations of the second pulse than that of the first pulse. In the long-short pulse scheme, increasing the energy of the long-pulse laser facilitates sample heating and surface modification, thereby enhancing spectral intensity. However, excessive long-pulse laser energy might cause sample melting and material ejection, which in turn diminishes the ablation efficiency of the subsequent short-pulse laser and reduces the overall spectral intensity. Further analysis of the ablation morphology reveals that the conventional collinear DP-LIBS tends to produce deeper ablation craters, whereas the long-short collinear DP-LIBS is more likely to generate larger ablation craters.
, 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/HPLPB202638.250376
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/HPLPB202638.250369
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/HPLPB202638.250371
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/HPLPB202638.250412
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/HPLPB202638.250351
Abstract:
Background Purpose Methods Results Conclusions
Water-dielectric self-breakdown switches are critical components in pulsed power devices such as the 10 MA facility. The plate-sphere electrode structure is specifically designed to achieve simultaneous multi-channel discharge, which is essential for minimizing switch inductance and reducing timing jitter.
This study investigates the factors affecting multi-channel formation in a water-dielectric, three-electrode plate-sphere self-breakdown switch operating at 3 MV, with the aim of validating the theoretical formation criterion.
Theoretical analysis was conducted based on the specific parameters of the switch structure, focusing on key temporal characteristics influencing discharge behavior. Experimental validation was performed at the nominal breakdown voltage of 3 MV, utilizing diagnostic techniques to observe the development of discharge arcs across all electrode pairs.
The calculated characteristic value for multi-channel formation was determined to be 8.6 ns, exceeding twice the measured switch jitter time of 3 ns, thereby satisfying the theoretical criterion. Observations confirmed that discharge arcs initiated nearly synchronously at the three sphere electrodes and propagated toward the plate electrodes, with complete multi-channel formation achieved within approximately 30 ns.
The study validates the criterion for multi-channel discharge in the plate-sphere switch structure. The design effectively enables simultaneous formation of multiple discharge channels within tens of nanoseconds, meeting essential requirements for high-performance pulsed power devices and contributing to improved operational stability.
, 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/HPLPB202638.250328
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/HPLPB202638.250250
Abstract:
Backgrounds Purpose Methods Results Conclusions
In complex electromagnetic environments, due to the multipath propagation of signals and the impact of co-channel interference, direction-finding systems will receive coherent signals. The mutual coupling between antenna elements or the inconsistency of gains will cause the superimposed noise of each channel to become spatial colored noise. Due to the low signal-to-noise ratio (SNR) of signals or short transmission time, it is difficult to obtain sufficient high-quality signal samples. When using array direction finding systems for DOA estimation, it is difficult to achieve DOA estimation under conditions of small samples, overlapping colored noise, and coherent incident signals.
This study aims how to solve the array direction-finding problems caused by radiation source coherence, aliased colored noise and small samples, which has become a research hotspot and difficulty in array signal processing area.
From the requirement of DOA estimation of narrowband signals, A DOA estimation method is proposed for small samples, overlapping colored noise, and coherent incident signals by using covariance matrix shrinkage estimation to improve the covariance estimation effect under small sample conditions, then using the covariance difference method to process the shrunk covariance matrix to suppress colored noise and signal coherence, and finally applying the MUSIC algorithm for DOA estimation.
Simulation experiments verify the effectiveness of the proposed method, providing an effective solution for solving DOA estimation problems in complex environments.
The proposed method offers an effective approach to array direction-finding under complex environments.
, 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/HPLPB202638.250101
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.
