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Just Accepted manuscripts are peer-reviewed and accepted for publication. They are posted online prior to technical editing formatting for publication and author proofing.
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, Available online ,
doi: 10.11884/HPLPB202638.250330
Abstract:
Background Purpose Methods Results Conclusions
With the continuous advancement of photoelectric applications such as LiDAR, three-dimensional sensing, and free-space communication towards longer distances, larger fields of view, and higher precision, large-spot, nanosecond-pulse lasers are progressively emerging as a critical type of light source, owing to their advantages in far-field uniform illumination and weak signal detection.
To address the challenges of amplitude distortion and sampling difficulties in beam quality measurements of large-spot, nanosecond-pulse lasers caused by optical path shaping distortions, transient capture limitations, and coherence requirements, this paper proposes a beam quality measurement system tailored for nanosecond pulsed large-aperture lasers.
The system employs a three-dimensional stepping platform combined with a photodetector to reconstruct the spatial intensity distribution of the beam, and incorporates a multi-channel peak-hold circuit to accurately latch pulse peaks, thereby ensuring transient fidelity in amplitude acquisition. To mitigate non-ideal conditions such as partial beam truncation and incomplete boundaries, a circle-fitting method is introduced as a complement to the second-moment calculation of energy, enhancing the robustness of beam size evaluation.
Experiments employing a typical vertical-cavity surface-emitting laser (VCSEL) were conducted through multi-position 3D axial scanning, comparing the consistency of beam size and energy distribution measured by different methods.
The results verify the measurement reliability and applicability of the proposed system under large-spot, nanosecond-pulse conditions, offering an effective means for laser beam quality assessment in related applications.
, Available online ,
doi: 10.11884/HPLPB202638.250384
Abstract:
The rapid advancement of ultra-short and ultra-intense laser technology has established laser-plasma acceleration as a premier approach for generating GeV-level electron beams and high-quality radiation sources. Among these, Betatron radiation—emitted as electrons oscillate transversely in plasma channels—has emerged as a unique source characterized by its femtosecond pulse duration, micron-scale source size, and high peak brightness. It holds significant potential in high-energy-density physics, materials science, and ultrafast imaging. This review systematically outlines the physical principles and reviews the latest research progress of Betatron radiation generated via two core mechanisms: laser wakefield acceleration (LWFA) and direct laser acceleration (DLA). A detailed comparison reveals that while the LWFA scheme excels in producing highly collimated, high-energy photons with superior brilliance, the DLA mechanism within near-critical-density plasmas offers a different trade-off. Although DLA generates a significantly larger number of electrons and a higher photon flux, these are characterized by lower photon energies and a wider angular spread. Consequently, the divergence of the emitted X-rays typically reaches hundreds of milliradians, which limits the overall brilliance. The review concludes that the future of Betatron radiation lies in enhancing repetition rates and achieving active control over radiation parameters. Developing Hybrid schemes and structured targets offer potential to overcome the trade-off between high flux and high brilliance, guiding future experiments at large-scale facilities.
The rapid advancement of ultra-short and ultra-intense laser technology has established laser-plasma acceleration as a premier approach for generating GeV-level electron beams and high-quality radiation sources. Among these, Betatron radiation—emitted as electrons oscillate transversely in plasma channels—has emerged as a unique source characterized by its femtosecond pulse duration, micron-scale source size, and high peak brightness. It holds significant potential in high-energy-density physics, materials science, and ultrafast imaging. This review systematically outlines the physical principles and reviews the latest research progress of Betatron radiation generated via two core mechanisms: laser wakefield acceleration (LWFA) and direct laser acceleration (DLA). A detailed comparison reveals that while the LWFA scheme excels in producing highly collimated, high-energy photons with superior brilliance, the DLA mechanism within near-critical-density plasmas offers a different trade-off. Although DLA generates a significantly larger number of electrons and a higher photon flux, these are characterized by lower photon energies and a wider angular spread. Consequently, the divergence of the emitted X-rays typically reaches hundreds of milliradians, which limits the overall brilliance. The review concludes that the future of Betatron radiation lies in enhancing repetition rates and achieving active control over radiation parameters. Developing Hybrid schemes and structured targets offer potential to overcome the trade-off between high flux and high brilliance, guiding future experiments at large-scale facilities.
, Available online ,
doi: 10.11884/HPLPB202638.250407
Abstract:
High-intensity laser technology, based on chirped pulse amplification, produces extreme optical fields on ultrashort timescales, providing a powerful platform for studying strong-field quantum electrodynamics, laser-plasma interactions, and extreme nuclear environments. This review summarizes the major progress made by the Laser Nuclear Physics Research Team at the Department of Nuclear Physics, China Institute of Atomic Energy, in developing petawatt-class laser systems, theoretical modeling, diagnostic techniques, and applications in nuclear science and industry. The team successfully commissioned a 100 TW ultrafast ultra-intense laser facility in 2023, featuring advanced high-contrast pulse shaping through cross-polarized wave generation and spectral broadening techniques. Additional innovations include thermally optimized eye-safe micro-lasers with improved bonding structures. Theoretical efforts used particle-in-cell simulations to enhance ion acceleration via Coulomb explosion in multilayer targets, achieving high-quality quasi-monoenergetic proton beams under optimized dual-pulse configurations. A novel approach for generating bright circularly polarized γ-rays was proposed, exploiting vacuum dichroism-assisted vacuum birefringence effects. Diagnostic advancements involved refined Nomarski interferometry for precise gas-jet target profiling and fission-source-gated methods for accurate neutron detector calibration. Key applications encompass plasma-based measurements of astrophysical nuclear reaction factors, vortex γ-photon manipulation of nuclear multipole resonances, laser-driven flyer acceleration for high-pressure equation-of-state studies, and enhanced laser-induced breakdown spectroscopy for trace element monitoring in nuclear facilities. These achievements facilitate simulation of stellar nuclear synthesis, advanced radiation sources, materials testing under extreme conditions, and nuclear safety monitoring, laying the foundation for future compact, high-repetition-rate laser systems in energy security and frontier nuclear research.
High-intensity laser technology, based on chirped pulse amplification, produces extreme optical fields on ultrashort timescales, providing a powerful platform for studying strong-field quantum electrodynamics, laser-plasma interactions, and extreme nuclear environments. This review summarizes the major progress made by the Laser Nuclear Physics Research Team at the Department of Nuclear Physics, China Institute of Atomic Energy, in developing petawatt-class laser systems, theoretical modeling, diagnostic techniques, and applications in nuclear science and industry. The team successfully commissioned a 100 TW ultrafast ultra-intense laser facility in 2023, featuring advanced high-contrast pulse shaping through cross-polarized wave generation and spectral broadening techniques. Additional innovations include thermally optimized eye-safe micro-lasers with improved bonding structures. Theoretical efforts used particle-in-cell simulations to enhance ion acceleration via Coulomb explosion in multilayer targets, achieving high-quality quasi-monoenergetic proton beams under optimized dual-pulse configurations. A novel approach for generating bright circularly polarized γ-rays was proposed, exploiting vacuum dichroism-assisted vacuum birefringence effects. Diagnostic advancements involved refined Nomarski interferometry for precise gas-jet target profiling and fission-source-gated methods for accurate neutron detector calibration. Key applications encompass plasma-based measurements of astrophysical nuclear reaction factors, vortex γ-photon manipulation of nuclear multipole resonances, laser-driven flyer acceleration for high-pressure equation-of-state studies, and enhanced laser-induced breakdown spectroscopy for trace element monitoring in nuclear facilities. These achievements facilitate simulation of stellar nuclear synthesis, advanced radiation sources, materials testing under extreme conditions, and nuclear safety monitoring, laying the foundation for future compact, high-repetition-rate laser systems in energy security and frontier nuclear research.
, Available online ,
doi: 10.11884/HPLPB202638.250424
Abstract:
Background Purpose Methods Results Conclusions
Diamond is considered a promising candidate for photoconductive semiconductor switches (PCSSs) due to its exceptional material properties.
However, the development of high-performance diamond PCSSs is primarily impeded by their high on-state resistance and relatively low breakdown voltage. This study aims to improve the performance of the diamond PCSSs.
Passivated with Si3N4, vertical PCSSs were fabricated using nitrogen-doped single-crystal diamonds with different doping concentrations and thicknesses. The doping concentrations of diamond samples were analyzed. The photoresponse of the PCSSs was characterized under 532 nm laser excitation over a range of DC bias voltages.
The experimental results showed that the nitrogen-doped diamond PCSSs present a large on/off ratio (～1011) along with sub-nanosecond rise and fall times. Among them, the diamond PCSS device with the highest nitrogen doping concentration exhibited the minimum on-state resistance. By reducing material thickness, a peak output power of 128 kW was achieved at a bias voltage of 4 kV (corresponding to the electric field strength of 110 kV/cm), with the PCSS exhibiting an on-state resistance of 28.9 Ω, further improving the device performance.
Through the design of nitrogen doping concentration, reduction of substrate thickness, and application of Si3N4 passivation, this work successfully developed diamond PCSSs with good performance, paving the way for the development of high-performance diamond PCSSs.
, Available online ,
doi: 10.11884/HPLPB202638.250237
Abstract:
Background Purpose Methods Results Conclusions
With the advancement of high-power microwave (HPM) technology, there is a growing demand for HPM antennas with beam scanning capabilities.
This paper focuses on the beam-scanning technology in HPM field and proposes a novel circularly-polarized all-metal beam-scanning lens antenna based on the Risley-prism principle, aiming to address the challenges of wide-angle beam scanning and high power handling capacity (PHC).
By introducing circular slots and metamaterial structures into hexagonal units, a circular polarization orthogonal conversion efficiency(the conversion efficiency of incident left-hand/right-hand circularly polarized (LHCP/RHCP) waves to their orthogonal RHCP/LHCP waves) of over 99% at the central frequency and a continuous phase tuning range of 0° to 360° are achieved. After arraying, the two-layer lens, together with the radial line slot array (RLSA) antenna, constitutes the beam scanning antenna system. Specifically, the first lens converts the circularly polarized hollow beam radiated by the feed antenna into a solid beam while achieving a 25.66° beam deflection synchronously. The second lens further deflects the beam, and two-dimensional beam scanning within a conical angle of ±60° can be realized by independently rotating the two layers of lenses.
A beam scanning lens antenna operating at 14.25 GHz with an axial length of 5.6λ is designed and simulated. During the scanning process, the gain varies within the range of 34.7–37.9 dB, the reflection coefficient remains consistently below −25 dB, and the maximum aperture efficiency exceeds 79%, with the PHC of the beam scanning antenna exceeds 1 GW.
The antenna proposed in this paper exhibits excellent beam scanning performance and high PHC, demonstrating great potential for applications in the HPM field.
, Available online ,
doi: 10.11884/HPLPB202638.250420
Abstract:
Background Purpose Methods Results Conclusions
High-power Yb-doped fiber lasers operating in the 1 μm band have been widely applied in fields such as laser processing, biomedicine, and national defense security. However, with the continuous increase in output power, traditional large-core fibers are susceptible to transverse mode instability (TMI) and stimulated Raman scattering (SRS), among other nonlinear effects. Based on their unique anti-resonant light-guiding mechanism, all-solid anti-resonant silica fibers (AS-ARFs) can realize ultra-large mode area (LMA) propagation while suppressing higher-order modes (HOMs), thus providing an innovative technical approach for balancing high power and high beam quality. Nevertheless, for active Yb-doped AS-ARFs targeting high-power gain applications, the influence mechanism of core refractive index fluctuations on mode characteristics and the fusion-splicing transmission characteristics of “step-index fiber - AS-ARF” structures have not been systematically investigated, which restricts their practical application process.
To address the above problems, this study aims to clarify the critical value of refractive index variation for maintaining the original light-guiding mechanism of AS-ARFs, verify their capabilities of low loss, large mode area and beam quality maintenance, explore the fusion-splicing coupling transmission laws between SIFs and AS-ARFs, quantify the core control parameters of active AS-ARFs, and provide theoretical support for their fabrication process optimization and coupling scheme design.
A six-ring AS-ARF theoretical model was constructed, combined with theoretical derivation and numerical simulation: Comsol Multiphysics was used to analyze the mode characteristics and the influence of refractive index fluctuations, and the Rsoft-BeamPROP module (based on the beam propagation method) was adopted to simulate the light transmission laws in the fusion-splicing coupling scenario.
The critical value of refractive index variation was clarified; the designed AS-ARFs were verified to have the characteristics of low loss, large mode area and excellent beam quality at the target wavelength; the fusion-splicing coupling transmission laws were revealed, and the transmitted energy attenuation was less than 2% when the incident beam diameter matched the core diameter of AS-ARFs.
This study realizes the quantification of core control parameters for active AS-ARFs, laying an important theoretical foundation for the fabrication process optimization of Yb3+-doped AS-ARFs (with a focus on refractive index uniformity control) and the design of practical coupling schemes.
, Available online ,
doi: 10.11884/HPLPB202638.250168
Abstract:
Background Purpose Methods Results Conclusions
Gamma and thermal neutron imaging are important non-destructive testing methods, which are complementary in many aspects. The thermal neutron and Gamma bimodal imaging can combine the advantages of both. Compares with single beam imaging, the bimodal imaging has the ability to identify different substances and the sensitivity to both nuclides and elements simultaneous.
Utilizing the reaction between protons and target material producing neutrons and Gamma together, based on the 18 MeV cyclotron accelerator being developed by the Institute of Atomic Energy, this paper designs a bimodal imaging neutron source by simulation.
Beryllium with a high （p, n） reaction cross-section is selected as the neutron target to generate neutrons. To obtain thermal neutrons with higher flux, polyethylene is used as the neutron moderator and reflector. By the different spatial distributions of thermal neutrons and Gamma, these two types of radiation are separately extracted from different directions. Besides, by designing the neutron and Gamma exits on polyethylene, high neutron flux and Gamma beams are simultaneously obtained.
After simulation optimization, the thermal neutron flux at the thermal neutron outlet can reach 1.78×1010 n/（cm2·s） , and the gamma dose at the gamma outlet can reach 2.23×104 rad/h.
This paper design a neutron source for thermal-neutron-gamma imaging based on the 18 MeV/1 mA cyclotron accelerator. The design efficiently extracts thermal neutron flux and gamma flux from a single target, implementing a single-target-dual-source configuration.
, Available online ,
doi: 10.11884/HPLPB202638.250453
Abstract:
Background Purpose Methods Results Conclusions
Solid-state linear transformer drivers (SSLTDs), featuring modular architecture, solid-state implementation, high reliability, and high repetition-rate capability, have become an important development direction in pulsed-power technology.
This paper proposes and develops a compact SSLTD based on a stacked Blumlein pulse generation module (SBPGM) and experimentally validates its performance.
The SBPGM integrates a hybrid pulse-forming network composed of high-voltage ceramic capacitors and the distributed inductance of PCB traces, a series--parallel IGBT switching array, and inductively isolated gate-driver circuits. The proposed common-ground bipolar-charging SBPGM topology eliminates the need for high-voltage isolation within an individual module and equalizes the driver insulation voltage stress, thereby significantly improving the compactness and reliability of the overall system.
Circuit simulations of a single SBPGM verify the voltage-doubling behavior and the desired high-voltage isolation characteristics, producing a 10.8 kV output under a charging voltage of 5.5 kV. Based on this module, a 30-stage SSLTD prototype is constructed. With a per-stage charging voltage of 5 kV and a 90 Ωwater load, the prototype generates a 279 kV quasi-square pulse with a peak current of 3.1 kA, a pulse width of 77 ns, and a rise time of 22.4 ns at a repetition rate of 50 Hz, corresponding to a peak power of 0.9 GW.
This SSLTD adopts a modular, scalable architecture. The SBPGMs are electrically and mechanically consistent yet independent, enabling straightforward voltage scaling and simplified implementation. Experiments confirm compact size and high power density, demonstrating the potential of high-repetition-rate all-solid-state pulsed-power sources.
, Available online ,
doi: 10.11884/HPLPB202638.250352
Abstract:
Background Purpose Methods Results Conclusions
Electromagnetic pulses generated in high-power laser–solid interactions can cause serious electromagnetic interference and threaten diagnostic systems, making their mechanism study essential.
This work aims to investigate the characteristics and generation mechanisms of electromagnetic pulses induced by picosecond and nanosecond laser irradiation on solid targets.
Experiments were carried out on the Shenguang II Upgrade laser facility. The temporal waveforms and frequency spectra of the emitted electromagnetic fields were measured under various pulse durations, laser energies, and irradiation geometries.
For picosecond laser irradiation, the electromagnetic pulses mainly originated from the neutralization current flowing through the target mount, and the peak electric field increased nearly linearly with laser energy. In the nanosecond experiments, the electromagnetic pulse intensity was lower, with the electric field oscillation decaying rapidly and a quasi-DC component observed. Using only the upper eight nanosecond beams produced stronger pulses than sixteen-beam irradiation, showing a modulation. In the combined picosecond and nanosecond laser experiment, the electromagnetic pulse peak generated by the picosecond laser was significantly reduced, which is attributed to the large-scale plasma formed by the nanosecond laser.
These findings clarify the generation behavior of electromagnetic pulses and provide references for mitigating electromagnetic interference in high-power laser experiments.
, Available online ,
doi: 10.11884/HPLPB202638.250370
Abstract:
Background Purpose Methods Results Conclusions
Laser self-mixing interferometry (SMI) is a highly sensitive and non-contact technique widely used for micro-displacement measurement. However, traditional displacement reconstruction methods typically involve complex phase unwrapping calculations, which increases computational difficulty and limits the efficiency of signal processing in practical applications.
This study aims to propose a novel micro-displacement reconstruction method for semiconductor laser SMI based on convolutional neural networks (CNN). The objective is to achieve direct and accurate reconstruction of micron-scale displacement while bypassing the tedious phase unwrapping process.
The proposed method involves segmenting the SMI signal and using the window-averaged displacement as the label for training the CNN. The architecture of the network consists of three sets of convolutional layers, pooling layers, and Rectified Linear Unit (ReLU) functions. Specifically, the convolutional layers are utilized to extract local displacement features from the SMI signal, the pooling layers are designed to compress feature information and enhance noise immunity, and the ReLU functions help highlight critical displacement features within the signal.
In theoretical simulations, SMI signals with 10 dB noise were input into the trained CNN, resulting in a displacement reconstruction RMSE of 5.3 × 10−8. In experimental tests, SMI signals containing system noise were processed by the network, yielding a reconstructed displacement RMSE of 2.1 × 10−7. The simulation and experimental results demonstrate consistent performance.
Both theoretical and experimental results indicate that the convolutional neural network can effectively achieve micron-level displacement reconstruction by analyzing the temporal segments of SMI signals. This method provides an efficient alternative for semiconductor laser self-mixing interference systems by eliminating the need for complex phase-based algorithms.
Study on manipulation mechanism of polarized positrons in nonlinear Breit-Wheeler scattering process
, Available online ,
doi: 10.11884/HPLPB202638.250410
Abstract:
Background Purpose Methods Results Conclusions
Polarized positron beams are vital probes in fundamental physics. Generating them via the nonlinear Breit-Wheeler process in laser fields is a promising new approach, but control over the positron polarization requires further understanding.
This study investigates how laser and γ-photon parameters control the final polarization of positrons in this process.
Within strong-field QED, we fully include all particle spins and the laser pulse's finite envelope. Systematic calculations are performed across various laser intensities, γ-photon energies, and polarization configurations.
Key findings are: (1) No positron polarization arises with linearly polarized lasers and γ-photons. (2) When only one is circularly polarized, it dominates the positron polarization, which decreases with higher laser intensity or γ-photon energy. (3) With both circularly polarized, γ-photons dominate high-energy positron polarization, while both sources co-determine low-energy positron polarization, with laser intensity playing a stronger regulatory role.
These results clarify the dominant factors for positron polarization, providing a key theoretical basis for designing optimized laser-driven polarized positron sources.
, Available online ,
doi: 10.11884/HPLPB202638.250395
Abstract:
Background Purpose Methods Results Conclusions
Alumina (Al2O3) ceramics are extensively employed as insulating components in vacuum electronic devices. However, under high voltage, charge accumulation on their surface can easily lead to surface flashover, which severely degrades the insulation performance of the device and affects its operation. Therefore, enhancing the vacuum surface insulation performance of Al2O3 ceramics holds significant academic value and practical implications. Surface coating represents a widely adopted strategy for enhancing the insulation performance of Al2O3 ceramics. Nevertheless, the specific influence of the glass phase within the coating on the insulating properties remains largely unexplored.
The present work is dedicated to exploring how the glass phase in coatings affects the vacuum insulation performance of Al2O3 ceramics.
A Cr2O3-based coating was fabricated on the surface of Al2O3 ceramics, and the effects of the glass phase within the coating on phase structure, surface morphology, secondary electron emission coefficient (SEE), surface resistivity, and the vacuum insulation performance of the coated ceramics were systematically investigated.
The results indicate that Al element from the substrate diffuses into the coating under high-temperature firing. The content of Cr2O3 phase in the coating exhibits a gradual decrease and eventually disappears with the rise of the glass phase content, causing it to fully react with the ceramic substrate to form Al2-xCrxO3 (0＜x＜2)、Mg(Al2-yCry)O4 (0＜y＜2), along with small amounts of ZnAl2O4 and (Na,Ca)Al(Si,Al)3O8. The coating improves the surface grain homogeneity and the density of the ceramic surface, although variations in the glass phase content have a negligible effect on its microstructure. Additionally, the Cr2O3 coating reduces both the SEE coefficient and the surface resistivity of the Al2O3 ceramic. However, as the glass phase content in the coating increases, both the SEE coefficient and surface resistivity of the coated ceramics exhibit a gradual upward trend. The optimal insulation performance is achieved when the glass phase content reaches 20%. At this point, the vacuum surface hold-off strength attains 119.63 kV/cm.
Modulation of the glass phase content in the surface coating enables the tunability of the vacuum surface insulation performance of the Al2O3 ceramics, with the performance improvement stemming from the decreased SEE coefficient and the appropriate surface resistivity.
, Available online ,
doi: 10.11884/HPLPB202638.250444
Abstract:
Background Purpose Methods Results Conclusions
The rapid advancement of high-power pulse technology towards practical application imposes higher demands on the self-breakdown stability of high-voltage gas switches.
This paper proposes a pre-ionization cathode switch concept, which utilizes an auxiliary annular blade edge to regulate initial electrons and an annular hemisphere to conduct the main current. A 300 kV-level pre-ionization annular cathode gas switch was designed.
With a switch gap of 35 mm, the field enhancement factor at the blade edge of the pre-ionization switch was designed to be 6.2, resulting in a ratio of 3.2 compared to the field enhancement factor at the hemisphere. Experimental investigations on the breakdown characteristics under microsecond-level pulses were conducted.
The results indicate that in nitrogen at 0.5 MPa and a repetition rate of 1 Hz, the pre-ionization gas switch achieved an average breakdown voltage of 322.5 kV with a amplitude jitter of 0.44%. Compared to a pure annular hemispherical switch, the pre-ionization switch exhibits a 17.6% reduction in breakdown voltage and an 82% decrease in amplitude jitter.
The experimental study demonstrates that this pre-ionization gas switch offers significant advantages in achieving high voltage and low jitter.
, Available online ,
doi: 10.11884/HPLPB202638.250414
Abstract:
Background Purpose Methods Results Conclusions
The W-band constitutes a critical atmospheric window in the millimeter-wave spectrum, with significant importance for advanced applications such as high-capacity communications, high-resolution imaging, and high-precision sensing. As essential components within core millimeter-wave transmitter and receiver systems, filters fundamentally determine transceiver performance. However, conventional designs frequently face challenges in simultaneously achieving high electrical performance and favorable manufacturability, representing a key obstacle in contemporary W-band filter development.
This work aims to develop a low-loss, low-order, and readily fabricable waveguide quasi-elliptic bandpass filter for the W-band. The goal is to maximize structural simplicity while maintaining high performance, thereby addressing the requirements of next-generation highly-integrated transceiver systems.
The proposed filter employs a novel H-plane offset magnetic coupling configuration, which simplifies the input–output coupling mechanism. Guided by quasi-elliptic filtering theory, transmission zeros are generated on both sides of the passband through the excitation of TE201/TE102 and TE301/TE102 hybrid modes in two respective resonant cavities, resulting in enhanced out-of-band suppression. The filter is implemented in a split-block architecture and fabricated via high-precision computer numerical control (CNC) milling.
Measured results demonstrate an operational passband from 91.5 GHz to 98 GHz, corresponding to a 3 dB fractional bandwidth of 7%, with an in-band insertion loss as low as 0.4 dB and a return loss greater than 15 dB. Except for a slight deviation observed at the upper band edge, the experimental data show strong agreement with simulation, confirming the design’s manufacturability, integration compatibility, and high-frequency performance.
A compact, low-loss W-band quasi-elliptic filter has been successfully realized using only two hybrid-mode cavities. The presented design exhibits notable advantages in terms of fabrication ease, integration suitability, and electrical performance, providing a viable solution for advanced millimeter-wave system applications.
, Available online ,
doi: 10.11884/HPLPB202638.250419
Abstract:
Background Purpose Methods Results Conclusions
Yb(TMHD)3 (ytterbium tris (2,2,6,6-tetramethyl-3,5-heptanedionate)) is the irreplaceable vapor-phase dopant for fabricating high-gain Yb-doped silica laser fibers, and its exact Yb content dictates final fiber performance. The conventional oxalate gravimetric method requires 6 h per sample, incompatible with the real-time feedback demanded by modern preform manufacture.
In order to enhance the production efficiency,
we report a “nitric acid-hydrogen peroxide open-vessel digestion/EDTA complexometric titration” protocol. After 3 min oxidative decomposition of the organic matrix, the solution is buffered with hexamethylenetetramine (pH=5-6) and titrated with standard EDTA using xylenol orange (XO) as indicator.
The stoichiometric Yb3+ : EDTA ratio is 1∶1; the sharp colour change from rose-red to bright yellow with a relative standard deviation (RSD, n=11) of ≤ 0.5%. Mean recoveries for spiked Yb(TMHD)3 ranged 98.2%-100.2%. Results for ten commercial lots deviated <0.3% from the gravimetric reference, while the total analysis time was reduced from 6 h to 15 min.
The procedure is accurate, precise, inexpensive and field-robust, enabling on-site monitoring of Yb loading and immediate optimisation of preform deposition parameters.
, Available online ,
doi: 10.11884/HPLPB202638.250314
Abstract:
Background Purpose Methods Results Conclusions
High-power fiber lasers have become core devices in key fields such as industrial precision processing, advanced national defense equipment, frontier scientific research, and high-end medical equipment. However, the traditional R&D mode of high-power fiber lasers relies heavily on physical experiments, which are costly and time-consuming. Simulation technology, as an effective auxiliary tool, can significantly reduce experimental costs, shorten the development cycle, and accurately optimize key performance parameters, thus playing an irreplaceable role in promoting the practical application and technological innovation of high-power fiber lasers.
This study aims to systematically sort out and summarize the research progress of typical high-power fiber laser simulation software, clarify the current research status of this field, and provide practical references for the R&D and application of related simulation software in the industry.
This paper focuses on investigating mainstream high-power fiber laser simulation software at home and abroad, conducts in-depth analysis and comparison of their core functional characteristics, technical advantages, and applicable scenarios, and combs the research ideas and technical routes of high-power fiber laser modeling and simulation.
The study summarizes the main research features of high-power fiber laser modeling and simulation, discusses the key technical points in the effective verification and reliable application of simulation software, and clearly sorts out the latest research progress of typical simulation software.
This paper prospects the future development directions of high-power fiber laser simulation software, including the integration of multi-physics field simulation, high-precision model construction, artificial intelligence-enabled fiber laser design, as well as standardized interfaces and an open-source ecosystem. This study provides valuable theoretical and practical references for the R&D and upgrading of simulation software in related industries.
, Available online ,
doi: 10.11884/HPLPB202638.250079
Abstract:
Background Purpose Methods Results Conclusions
In recent years, magnetized laser-plasma research has gained significant importance in multiple frontier fields such as magneto-inertial confinement fusion, magnetic reconnection, collisionless shocks, and magnetohydrodynamic instabilities. Pulsed magnetic field devices have become the mainstream experimental approach, as they can generate magnetic field parameters that meet experimental requirements in terms of strength, spatial scale, and duration. Such devices have been integrated into multiple large-scale laser facilities worldwide, and our research group has also successfully developed several pulsed magnetic field systems adaptable to laser setups of different scales. However, existing devices still face two major challenges: first, strong electromagnetic interference affects data acquisition and equipment safety; second, advances in physical experiments demand higher magnetic field strengths.
This study presents a novel coaxial-structure pulsed magnetic field device, designed to optimize the circuit configuration for suppressing electromagnetic interference (EMI) and enhancing magnetic field strength, thereby providing a more reliable high-field environment for magnetized laser-plasma experiments.
The experiment employs an all-coaxial architecture to enhance electromagnetic compatibility. Multiple soft coaxial cables are connected in parallel to link a 5 μF high-voltage coaxial capacitor with a rigid coaxial transmission line inside the vacuum target chamber, thereby minimizing system inductance.
At 40 kV charging voltage, a discharge current with 105 kA peak intensity, a rise time of 1.2 μs, and a flat top width of 1.4 μs is produced, which generates a intense magnetic field of 22 T in the center of a three-turn magnetic field coil with 12 mm diameter. Compared with our previous pulsed intense magnetic field device, the present device can generate larger current and stronger magnetic field, while the free-space EM noise and potential jitter (voltage fluctuation) of the vacuum chamber are significantly reduced.
Experimental results demonstrate that the key performance of this device has reached the mainstream advanced level of international counterparts, such as relevant systems from the U.S. LLNL, France's LULI, and Germany’s HZDR. This device combines high magnetic field strength, microsecond-level flat-top stability, and low electromagnetic interference, providing precisely controllable strong magnetic field experimental conditions—previously difficult to achieve—for frontier research areas such as magneto-inertial confinement fusion, laboratory astrophysics, magnetohydrodynamic instabilities, and pulsed laser deposition coating.
, Available online ,
doi: 10.11884/HPLPB202638.250390
Abstract:
This review summarizes the evolution and present capabilities of the “XingGuang” ultrashort and ultra-intense laser platform at the National Key Laboratory of Plasma Physics (CAEP), which integrates the XingGuang-III (XG-III) multi-pulse facility and the all-OPCPA SILEX-II multi-petawatt system. Targeting inertial confinement fusion (ICF), high-energy-density physics (HEDP), and matter under extreme conditions, the platform enables both extreme-state creation and time-resolved pump–probe measurements. We outline the system architecture, key enabling technologies, and experimental capabilities. XG-III adopts a common-seed, split-and-amplify design that delivers femtosecond/picosecond/nanosecond beams with sub-picosecond timing jitter (<1.32 ps); typical operating points reach～20 J/26.8 fs,～370 J/(0.48–10 ps) and～575 J/1 ns, with on-target focal spots below 10 μm (fs) and 20 μm (ps). SILEX-II employs a full optical parametric chirped-pulse amplification (OPCPA) chain to achieve～5 PW peak power after compression to～18.6 fs while retaining >90 J, combining >10^10 temporal contrast (tens of ps before the main pulse) with near-diffraction-limited focusing (～3.3×4.0 μm FWHM) enabled by adaptive optics and achromatic compensation, reaching intensities above 1020 W/cm2. In addition, we present representative multi-beam, coordinated experiments enabled by the platform, including three-dimensional proton imaging of temperature-gradient-driven Weibel magnetic fields and energy-loss measurements of intense ion beams in warm dense plasmas, highlighting its strong potential for frontier research.
This review summarizes the evolution and present capabilities of the “XingGuang” ultrashort and ultra-intense laser platform at the National Key Laboratory of Plasma Physics (CAEP), which integrates the XingGuang-III (XG-III) multi-pulse facility and the all-OPCPA SILEX-II multi-petawatt system. Targeting inertial confinement fusion (ICF), high-energy-density physics (HEDP), and matter under extreme conditions, the platform enables both extreme-state creation and time-resolved pump–probe measurements. We outline the system architecture, key enabling technologies, and experimental capabilities. XG-III adopts a common-seed, split-and-amplify design that delivers femtosecond/picosecond/nanosecond beams with sub-picosecond timing jitter (<1.32 ps); typical operating points reach～20 J/26.8 fs,～370 J/(0.48–10 ps) and～575 J/1 ns, with on-target focal spots below 10 μm (fs) and 20 μm (ps). SILEX-II employs a full optical parametric chirped-pulse amplification (OPCPA) chain to achieve～5 PW peak power after compression to～18.6 fs while retaining >90 J, combining >10^10 temporal contrast (tens of ps before the main pulse) with near-diffraction-limited focusing (～3.3×4.0 μm FWHM) enabled by adaptive optics and achromatic compensation, reaching intensities above 1020 W/cm2. In addition, we present representative multi-beam, coordinated experiments enabled by the platform, including three-dimensional proton imaging of temperature-gradient-driven Weibel magnetic fields and energy-loss measurements of intense ion beams in warm dense plasmas, highlighting its strong potential for frontier research.
, Available online ,
doi: 10.11884/HPLPB202638.250403
Abstract:
This paper focuses on the element doping technology of low-density polymer foams for inertial confinement fusion (ICF) experiments and summarizes their research status and development trends. As key target materials for ICF, low-density polymer foams can optimize radiation transport, suppress hydrodynamic instability, and achieve diagnostic functions by introducing doping elements such as chlorine, argon, and germanium. The paper systematically analyzes the principles, advantages, disadvantages, and application bottlenecks of two major types of technologies: physical doping (particle dispersion, physical vapor deposition) and chemical doping (copolymerization, monomer functionalization, polymer substitution), with an emphasis on core issues such as uniformity control and doping precision. Finally, it looks forward to cutting-edge directions including composite doping, two-photon polymerization, and ion implantation, providing technical references for the high-performance and precise preparation of ICF target materials and facilitating the development of high-repetition-rate ICF experiments.
This paper focuses on the element doping technology of low-density polymer foams for inertial confinement fusion (ICF) experiments and summarizes their research status and development trends. As key target materials for ICF, low-density polymer foams can optimize radiation transport, suppress hydrodynamic instability, and achieve diagnostic functions by introducing doping elements such as chlorine, argon, and germanium. The paper systematically analyzes the principles, advantages, disadvantages, and application bottlenecks of two major types of technologies: physical doping (particle dispersion, physical vapor deposition) and chemical doping (copolymerization, monomer functionalization, polymer substitution), with an emphasis on core issues such as uniformity control and doping precision. Finally, it looks forward to cutting-edge directions including composite doping, two-photon polymerization, and ion implantation, providing technical references for the high-performance and precise preparation of ICF target materials and facilitating the development of high-repetition-rate ICF experiments.
, Available online ,
doi: 10.11884/HPLPB202638.250282
Abstract:
Background Purpose Methods Results Conclusion
The China Institute of Atomic Energy has designed of a 9.5 MeV ultra-compact cyclotron to support the independent of Positron Emission Tomography (PET) cyclotrons. A high-performance control system is critical for the equipment, as the stability of the acceleration field directly impacts beam quality.
In order to ensure the stable acceleration of the accelerator beam, this study aims to develop a Low-Level Radio Frequency (LLRF) control algorithm based on a fully digital hardware platform.
To enhance control precision and increase the feedback rate, a high-speed Digital Down-Conversion(DDC) demodulation system was designed. Addressing the issue where the IQ sequence after digital down-conversion may be distributed in arbitrary quadrants, an innovative quadrant preprocessing module was developed to extend applicability across the Cartesian plane. A position-type Proportion-Integral-Derivative (PID) tuning loop was implemented for automatic frequency compensation, integrating adaptive protection, timed detection, and one-click startup. Furthermore,a robust cross-clock-domain data path is constructed to ensure accurate and stable amplitude regulation.
Closed-loop tests verified the reliability of the demodulation system. During the joint commissioning with the accelerator, a stable internal target beam current of 100 μA was successfully extracted. The system achieved a cavity voltage amplitude stability of 0.047% (RMSE) and maintained a detuning angle of 0.46°(RMSE).
The experimental results demonstrate that the proposed LLRF system fully meets the control requirements of the accelerator. The design ensures high stability and precision, providing reliable technical support for the operation of the 9.5 MeV ultra-compact cyclotron.
, Available online ,
doi: 10.11884/HPLPB202638.250430
Abstract:
Background Purpose Methods Results Conclusions
High-power femtosecond fiber lasers have extensive applications in advanced manufacturing, laser particle acceleration, high-order harmonic generation and so on. Coherent beam combining (CBC) of femtosecond fiber lasers serves as an effective technical approach to overcome the power limitations of single fibers and achieve high-power femtosecond laser output.
This work aims to develop a high-power femtosecond fiber laser CBC system to achieve kilowatt-level average power output with high stability.
The presented femtosecond fiber laser CBC system is based on a three-channel all-fiber chirped pulse amplifier. Phase adjustment and stable coherent combining of three laser amplifiers are achieved using fiber stretchers in combination with the stochastic parallel gradient descent (SPGD) algorithm.
At a total output power of 1219.1 W, the system delivers a combined power of 1072 W, corresponding to a combining efficiency of 87%. The combined beam exhibits near-diffraction-limited beam quality (M2=1.23), and the compressed pulse width is 899 fs. Furthermore, the influence of beam quality degradation on the combining efficiency is theoretically analyzed. The results show that the combining efficiency would decrease as the beam quality degradation rate increased, and the combining efficiency is more sensitive to the degradation of multi-channel beam quality.
The demonstrated all-fiber coherent beam combining system exhibits excellent stability and high-power output. Further power scaling can be realized by increasing the number of combining channels, thereby providing crucial technical support for the advanced applications of high flux ultrafast and ultra-intense lasers.
, Available online ,
doi: 10.11884/HPLPB202638.250291
Abstract:
Background Purpose Methods Results Conclusions
Boron Neutron Capture Therapy (BNCT) is an innovative binary targeted cancer treatment technology with high relative biological effect and cell-scale precision, but its clinical application is limited by the long computation time of traditional Monte Carlo methods for dose calculation and insufficient dosimetric research on head tumors.
This study aims to address these challenges by optimizing the Monte Carlo algorithm and developing pre-processing/post-processing modules, verifying the accuracy of the computational system, and analyzing the dosimetric characteristics of BNCT for head tumors.
Based on NECP-MCX, three acceleration strategies voxel geometry fast tracking, transport-counting integration, MPI parallel optimization were adopted to improve computational efficiency. Pre-processing (DICOM image parsing, material-boron concentration mapping, 3D voxel modeling) and post-processing (dose-depth curve, Dose-Volume Histogram (DVH), dose distribution cloud map) modules were developed. Both NECP-MCX and MCNP were used to calculate the dose distribution of a head tumor case (RADCURE-700) for comparison.
The single-dose calculation time was reduced from 2 hours to 9.4 minutes. The dose curves, DVH, and cloud maps from the two programs showed good consistency with relative deviations below 5% within 10 cm depth. BNCT achieved a tumor target volume D90 of 60 Gy in 63 minutes, with healthy tissue dose below 12.5 Gy.
The optimized NECP-MCX system realizes efficient and accurate dose calculation for BNCT. The consistent results validate its reliability, and the dosimetric analysis demonstrates BNCT’s potential for head tumor treatment, providing methodological support for clinical treatment planning.
, Available online ,
doi: 10.11884/HPLPB202638.250245
Abstract:
Background Purpose Methods Results Conclusions
Neutron multiplicity measurement technology, as a core method in the field of non-destructive testing, plays a critical role in determining the mass of fissionable material (235U). However, it suffers from technical bottlenecks such as prolonged measurement cycles and measurement deviations under non-ideal conditions.
This paper aims to explore feasible pathways for integrating neutron multiplicity measurement methods with neural network technology. The goal is to provide new research perspectives for advancing neutron multiplicity measurement technology toward greater efficiency and intelligence.
Leveraging Geant4 and MATLAB software, an Active Well Coincidence Counter (AWCC) simulation model is constructed to achieve high-precision simulation of the entire active neutron multiplicity measurement process. Building upon this, three neural networks—Backpropagation Neural Network (BPNN), Convolutional Neural Network (CNN), and Long Short-Term Memory network (LSTM)—are developed using the PyTorch framework to analyze and investigate neutron multiplicity distribution data.
Compared with traditional calculation methods based on the active neutron multiplicity equation, neural network models represented by CNN and LSTM demonstrate significant advantages in measurement accuracy and efficiency. Specifically, in terms of relative error metrics, neural network models can reduce errors to lower levels; in the time dimension of measurement, they substantially shorten data processing cycles, effectively overcoming the timeliness constraints inherent to traditional approaches.
This achievement fully validates the theoretical feasibility and technical superiority of the neural network-based neutron multiplicity measurement approach, providing a novel solution for advancing neutron multiplicity detection toward greater efficiency and intelligence. Subsequent work will enhance the adaptability and noise resistance of neural network models for complex data by increasing simulation scenario complexity and introducing diversified factors such as noise interference and geometric variations. Meanwhile, building upon simulation studies, physical experimental validation will be conducted using AWCC instrumentation to drive the transition of neural network-based neutron multiplicity measurement technology from simulation to engineering application.
, Available online ,
doi: 10.11884/HPLPB202638.250297
Abstract:
Background Purpose Methods Results Conclusions
With the rapid development of low-earth orbit (LEO) satellite communications, there is a pressing need for circularly polarized phased arrays that offer wide-angle scanning capability while maintaining a low profile, which remains a significant challenge in current designs.
This study aims to design a low-profile, wide-beam circularly polarized antenna element and its corresponding wide-angle scanning array to address the limitations of narrow scan angles and high profiles in existing solutions.
A double-layer antenna element was designed, utilizing corner perturbation and cross-slots to achieve left-hand circular polarization, while beamwidth was broadened via an upper parasitic structure and metallic posts based on pattern superposition. A 4×4 array was constructed by rotating these elements, with annular open slots integrated into the ground plane to suppress mutual coupling.
The proposed antenna element exhibits a 3-dB axial ratio beamwidth greater than 175°, a gain beamwidth of 120°, and a profile of only 0.07λ0. Simulations of the 4×4 array demonstrate a scan coverage of ±60°, with axial ratio consistently below 2 dB and a stable gain fluctuation of 3.38 dB throughout the scanning range.
The designed antenna and array effectively achieve wide-angle circularly polarized scanning with low profile and stable performance, offering a promising solution for LEO satellite communication terminals and other integrated systems requiring wide spatial coverage.
, Available online ,
doi: 10.11884/HPLPB202638.250347
Abstract:
Background Purpose Methods Results Conclusions
Gigahertz-repetition-rate femtosecond fiber lasers have attracted increasing attention for applications requiring high temporal resolution and high average power, while most existing GHz fiber amplification systems are limited to fixed repetition rates.
This work aims to realize repetition-rate-tunable amplification of gigahertz femtosecond pulses within a single fiber-based platform by employing a passively harmonic mode-locked fiber laser as the seed source.
The seed laser provides stable pulse operation with repetition rates tunable from 1 to 3 GHz. A two-stage fiber amplification scheme combined with dispersion management is implemented to maintain stable amplification over the entire tuning range. In the pre-amplification stage, controllable chirp is introduced to achieve near-linear temporal broadening, which effectively suppresses excessive nonlinear effects during power scaling. Pulse compression is subsequently implemented at the output using single-mode fiber.
Experimental results show that stable pulse trains with regular temporal distribution are preserved throughout the tuning range. The maximum average output power reaches 2.1 W at a repetition rate of 3.1 GHz, while the shortest pulse duration of 195 fs is obtained at 2.0 GHz. After amplification, the side-mode suppression ratio remains higher than 33 dB.
These results indicate the feasibility of gigahertz repetition-rate-tunable amplification of femtosecond fiber lasers on a single all-fiber platform.
, Available online ,
doi: 10.11884/HPLPB202638.250387
Abstract:
Ultrafast intense laser pulse possesses the characteristic of ultrafast time domain and high peak power. With the rapid development of laser technology, its pulse repetition rate has been gradually increased as well. This kind of repetitive high-power femtosecond laser provides the human beings the unprecedented extreme physical conditions in ultrafast time and ultrahigh intensity field, providing new opportunities, means and directions for driving frontier basic science and cross-application research, such as the generation of novel ultrafast particle beam and intense pulse radiation source. In this paper, we will mainly introduce the newly-built experimental platform by the ultrafast light physics team of Shanghai Normal University based on the repetitive high-power femtosecond laser system. The recent research progress on the generation of gas high-order harmonics, intense terahertz radiation sources, high-brightness ultrafast electron beam and the relevant practical applications are all included, as well with the resume of the main progress and future prospect in these frontier physics.
Ultrafast intense laser pulse possesses the characteristic of ultrafast time domain and high peak power. With the rapid development of laser technology, its pulse repetition rate has been gradually increased as well. This kind of repetitive high-power femtosecond laser provides the human beings the unprecedented extreme physical conditions in ultrafast time and ultrahigh intensity field, providing new opportunities, means and directions for driving frontier basic science and cross-application research, such as the generation of novel ultrafast particle beam and intense pulse radiation source. In this paper, we will mainly introduce the newly-built experimental platform by the ultrafast light physics team of Shanghai Normal University based on the repetitive high-power femtosecond laser system. The recent research progress on the generation of gas high-order harmonics, intense terahertz radiation sources, high-brightness ultrafast electron beam and the relevant practical applications are all included, as well with the resume of the main progress and future prospect in these frontier physics.
, Available online ,
doi: 10.11884/HPLPB202638.250298
Abstract:
Background Purpose Methods Results Conclusions
The reaction kinetics in lasers often involves a lots of excited state species. The mutual effects and numerical stiffness arising from the excited state species pose significant challenges in numerical simulations of lasers. The development of artificial intelligence has made Neural Networks (NNs) a promising approach to address the computational intensity and instability in Excited State Reaction Kinetics (ESRK).
However, the complexity of ESRK poses challenges for NN training. These reactions involve numerous species and mutual effects, resulting in a high-dimensional variable space. This demands that the NN possess the capability to establish complex mapping relationships. Moreover, the significant change in state before and after the reaction leads to a broad variable space coverage, which amplifies the demand for NN's accuracy.
To address the aforementioned challenges, this study introduces the successful sequence-to-sequence learning from large language learning into ESRK to enhance prediction accuracy in complex, high-dimensional regression. Additionally, a statistical regularization method is proposed to improve the diversity of the outputs. NNs with different architectures were trained using randomly sampled data, and their capabilities were compared and analyzed.
The proposed method is validated using a vibrational reaction mechanism for hydrogen fluoride, which involves 16 species and 137 reactions. The results demonstrate that the sequential model achieves lower training loss and relative error during training. Furthermore, experiments with different hyperparameters reveal that variation in the random seed can significantly impact model performance.
In this work, the introduction of the sequential model successfully reduced the parameter count of the conventional wide model without compromising accuracy. However, due to the intrinsic complexity of ESRK, there remains considerable room for improvement in NN-based regression tasks for this domain.
, 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/HPLPB202638.250337
Abstract:
Background Purpose Methods Results Conclusions
As an important branch of electromagnetic launch, multi-stage synchronous induction coil gun has become one of the hotspots of launch research because of its non-contact, linear propulsion and high efficiency. Among them, the armature outlet velocity is an important index, which is affected by many factors such as the structural parameters, material parameters and coil circuit parameters. However, the existing research lacks theoretical analysis on various factors.
The purpose of this paper is to analyze theoretical approaches for improving the armature outlet velocity, and to explore the factors affecting it.
Based on the equivalent circuit model, this paper derives the analytical formula of armature induced eddy current., and investigates these factors affecting the outlet velocity via finite element simulation.
Theoretical analysis shows that reducing the total inductance of the coil-armature equivalent circuit can increase the armature outlet velocity. Simulation results show that under the same initial electric energy, reducing the number of turns of coils, reducing the cross-sectional shape factor of rectangular wire, increasing the thickness and length of armature, and reducing the line inductance can improve the armature outlet velocity. Considering various factors, the simulated outlet velocity of 32 kg armature driven by 5-stage coil can reach 202.1 m/s, and the launch efficiency is 33.3%. The influence of various factors on the armature is in line with the theoretical analysis results.
The research content of this paper provides some theoretical support for the design of multi-stage synchronous induction coil gun scheme.
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/HPLPB202638.250310
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/HPLPB202638.250289
Abstract:
Oscillating-amplifying integrated fiber lasers (OAIFLs) have emerged as a promising technology in high-power laser applications by combining the structural simplicity and superior anti-reflection capability of oscillators with the high efficiency of amplifiers. This review systematically summarizes recent progress from both theoretical and experimental perspectives. Theoretically, the focus is on advances in modeling mode instability and nonlinear effects, aiming to provide optimization guidelines for achieving high-power output. Experimentally, OAIFLs have successfully realized kilowatt-level narrow-linewidth and 10-kW-class broadband laser output in conventional wavelength bands. Beyond these bands, research primarily targets1050 nm and 1018 nm fiber lasers. Furthermore, innovative dual-end output designs address core high-power challenges through distributed power extraction, significantly enhancing system power scalability. These advancements will accelerate broader applications in industrial processing, biomedical fields, and national defense. Analysis of current trends highlights key evolutionary pathways: benefiting from the integrated structure’s unique advantages in nonlinear management and amplified spontaneous emission (ASE) suppression, operational wavelengths are expanding from the conventional 1050 –1080 nm range toward shorter specialty bands; driven by demands in coherent beam combining and high-precision spectroscopy for high-brightness sources, output spectra are shifting from broadband to narrow-linewidth emission; gain media are evolving from conventional homogeneous fibers to specially designed geometric structures to simultaneously mitigate nonlinear effects and transverse mode instability (TMI) under high-power conditions; to meet needs in precision machining, spectroscopic sensing, and scientific research for lasers with high peak power and tailored temporal profiles, operational modes are diversifying from continuous-wave to varied pulsed regimes; and output configurations are advancing from simple single-end to sophisticated dual-end designs, effectively addressing key challenges in high-power laser delivery. Nevertheless, persistent limitations include insufficient universality of theoretical models and a lack of systematic experimental validation. Future research should emphasize two complementary dimensions. Theoretically, efforts must deepen model construction and mechanistic analysis—including refining temporal modeling, investigating TMI origins and nonlinear coupling mechanisms, and elucidating the physics of pump-timing-independent operation. Experimentally, the focus should be on continuously optimizing output performance—enhancing power and efficiency, improving spectral characteristics and beam quality, and advancing toward pulsed and supercontinuum generation capabilities.
Oscillating-amplifying integrated fiber lasers (OAIFLs) have emerged as a promising technology in high-power laser applications by combining the structural simplicity and superior anti-reflection capability of oscillators with the high efficiency of amplifiers. This review systematically summarizes recent progress from both theoretical and experimental perspectives. Theoretically, the focus is on advances in modeling mode instability and nonlinear effects, aiming to provide optimization guidelines for achieving high-power output. Experimentally, OAIFLs have successfully realized kilowatt-level narrow-linewidth and 10-kW-class broadband laser output in conventional wavelength bands. Beyond these bands, research primarily targets
, Available online ,
doi: 10.11884/HPLPB202638.250284
Abstract:
Machine learning (ML) has emerged as a transformative approach for advancing fiber laser technology, offering powerful solutions to overcome the limitations of traditional design, optimization, and control methods. This review systematically examines the integration of ML across the entire fiber laser ecosystem. It begins by categorizing fundamental ML paradigms, with a discussion of their respective applicability. The subsequent sections detail recent research progress in key areas including intelligent device design, which encompasses ML-assisted optimization of doped fibers, photonic crystal fibers, anti-resonant fibers, polarization-maintaining fibers, fiber gratings, and mode-selective couplers; laser simulation and prediction, focusing on models for power, temporal dynamics, and spectral evolution; intelligent control of laser output, covering adaptive mode-locking, coherent beam combining, and spatiotemporal pulse shaping; and laser characterization, highlighting ML-enhanced techniques for temporal pulse measurement, mode decomposition, and beam quality evaluation. The review further addresses prevailing challenges such as data dependency, model generalizability, interpretability, and computational efficiency, while outlining future directions toward developing more robust, efficient, and physically interpretable ML-driven fiber laser systems.
Machine learning (ML) has emerged as a transformative approach for advancing fiber laser technology, offering powerful solutions to overcome the limitations of traditional design, optimization, and control methods. This review systematically examines the integration of ML across the entire fiber laser ecosystem. It begins by categorizing fundamental ML paradigms, with a discussion of their respective applicability. The subsequent sections detail recent research progress in key areas including intelligent device design, which encompasses ML-assisted optimization of doped fibers, photonic crystal fibers, anti-resonant fibers, polarization-maintaining fibers, fiber gratings, and mode-selective couplers; laser simulation and prediction, focusing on models for power, temporal dynamics, and spectral evolution; intelligent control of laser output, covering adaptive mode-locking, coherent beam combining, and spatiotemporal pulse shaping; and laser characterization, highlighting ML-enhanced techniques for temporal pulse measurement, mode decomposition, and beam quality evaluation. The review further addresses prevailing challenges such as data dependency, model generalizability, interpretability, and computational efficiency, while outlining future directions toward developing more robust, efficient, and physically interpretable ML-driven fiber laser systems.
, Available online ,
doi: 10.11884/HPLPB202638.250376
Abstract:
Background Purpose 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 a U-band 1.65 μm Raman fiber laser 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 were 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 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/HPLPB202638.250251
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/HPLPB202638.250270
Abstract:
Background Purpose Methods Results Conclusions
Although quartz exhibits excellent light transmittance, the significant difference in thermal expansion coefficients between quartz and metal sealing materials has long been a critical technical bottleneck, leading to interface stress concentration and vacuum sealing failures in low-leakage quartz windows.
This study addresses the urgent demand for ultra-high vacuum precision optical systems by conducting systematic research on sealing technologies for high-performance quartz vacuum windows.
To overcome this challenge, this paper innovatively proposes using magnetron sputtering technology to sequentially deposit a Ti/Mo/Cu/Ag multilayer film system on the quartz welding surface, thereby creating a gradient functional metallization layer with thermal stress buffering capability that achieves effective surface metallization.
Scanning electron microscopy observations revealed continuous, dense, and structurally uniform film layers. Nanoindentation experiments further demonstrated a bonding strength of approximately 3.83 N between the metallized layer and quartz substrate, indicating robust adhesion. Experimental results show that vacuum window components fabricated using this metallization scheme achieve leakage rates below 10−12 Pa·L/s.
This achievement has broad applications in synchrotron radiation, quantum measurement, and space exploration, providing crucial technical support for the development of high-performance vacuum devices.
, 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/HPLPB202638.250219
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.
This study aims to optimize the particle energy search mechanism in Monte Carlo simulation and address the pain point of low efficiency in traditional search methods; thereby 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 unified energy grid technology, we further developed and optimized 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 reactor problem simulations.
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 Monte-Carlo 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 calculation 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. More extensive engineering verification and functional iterations will be further carried out subsequently.
, 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 the effective multiplication factor (keff) was 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/HPLPB202638.250393
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. 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 spectroscopy has more advantages in sensitivity, noise suppression and accuracy.
To meet the requirement for 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 was used in the spectrometer, and the luminous flux and spectral resolution were adjusted through an adjustable incidence slit. The ray tracing simulation was carried out using a self-developed optical design software. And the wavelength calibration and performance testing were 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 for 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/HPLPB202638.250369
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.
The 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/HPLPB202638.250351
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 the 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 enhance 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 reveals 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, which is essential for optimal performance.
, 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/HPLPB202638.250328
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 that is capable of generating high-power pulses with flat-top duration, while maintaining low output jitter.
A tailored pulsed forming module (PFM) was developed by employing a non-uniform PFN sections reduced to 2, aiming for enhanced compactness. 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 on the pulse shaping was quantitatively analyzed, and waveform tailoring of the PFM was achieved. The PFM could output a high-voltage pulse with a 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 maintaining 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 the required waveform and low output jitter.
, 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/HPLPB202638.250371
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 its 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 methods for characteristic control and the 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 its 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 methods for characteristic control and the 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 an 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 the 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/HPLPB202638.250412
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.
Display Method:
2026, 38: 021001.
doi: 10.11884/HPLPB202638.250470
Abstract:
Micro- and nano-structured targets represent a pivotal technological pathway for controlling laser-target interactions and advancing intense radiation sources. This review provides a comprehensive overview of the development and future prospects of intense laser-driven radiation sources based on structured targets. First, it outlines their key role in regulating laser-target coupling, energy absorption, and radiation generation. It then summarizes recent advances in experimental and theoretical research, followed by a discussion of frontier physical and technical progress with petawatt-class laser systems. Finally, the future research trends and technological development requirements for the radiation sources based on laser-irradiated structured targets are prospected.
Micro- and nano-structured targets represent a pivotal technological pathway for controlling laser-target interactions and advancing intense radiation sources. This review provides a comprehensive overview of the development and future prospects of intense laser-driven radiation sources based on structured targets. First, it outlines their key role in regulating laser-target coupling, energy absorption, and radiation generation. It then summarizes recent advances in experimental and theoretical research, followed by a discussion of frontier physical and technical progress with petawatt-class laser systems. Finally, the future research trends and technological development requirements for the radiation sources based on laser-irradiated structured targets are prospected.
2026, 38: 021002.
doi: 10.11884/HPLPB202638.250290
Abstract:
Background Purpose Methods Results Conclusions
As an advanced composite material widely used in the aerospace field, carbon fiber reinforced polymer (CFRP) is subjected to extreme service environments characterized by high heat flux and high mechanical loads. Its thermal ablation and high-temperature failure processes are significantly influenced by environmental conditions. Although numerical and experimental studies on the ablation behavior of CFRP have been extensively conducted, systematic experimental research and experimental-simulation comparisons for the ablation behavior of plain-woven CFRP in a vacuum environment remain lacking.
This study aims to conduct laser ablation experiments on plain-woven CFRP in a vacuum environment and to establish corresponding theoretical and numerical models of thermal ablation. The work seeks to reveal the internal heat transfer characteristics and the evolution mechanism of ablation damage, thereby providing theoretical and data support for the design and application of composite materials under vacuum or rarefied gas environments.
Experimentally, a laser was used as the heat source to design and perform thermal ablation tests on plain-woven CFRP under vacuum. An experimental system based on infrared and thermocouple temperature measurements was employed to record the transient temperature field on the irradiated surface and the temperature of the back surface. In terms of simulation, based on a fiber-yarn/matrix dual-phase micro-modeling strategy and combined with a finite element thermal analysis module and user-defined subroutines, a theoretical and numerical model for the thermal ablation of woven composites was developed.
Experimental results show that no open flame combustion occurred in the composite under vacuum. The epoxy resin matrix underwent significant thermal decomposition and mass loss, while the morphology and structure of the carbon fibers remained intact. The established numerical model reasonably accurately simulated the ablation temperature field and ablation morphology, achieving the simulation of the dynamic ablation process including resin decomposition and fiber exposure.
The vacuum environment significantly alters the laser ablation characteristics and final morphology of plain-woven CFRP. Due to the higher energy deposition rate of the laser in the material, a more pronounced heat accumulation effect is induced. The numerical simulation results agree well with the experimental data, verifying the reliability of the model. This study provides an effective analytical tool and theoretical basis for the thermal safety assessment and functional design of woven CFRP in extreme service environments.
2026, 38: 021003.
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.
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 combines 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 delays, spectral acquisition delays 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 to those 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.
2026, 38: 023001.
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.
2026, 38: 023002.
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.
2026, 38: 023003.
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.
2026, 38: 023004.
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.
2026, 38: 023005.
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 the 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.
2026, 38: 024001.
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.
2026, 38: 024002.
doi: 10.11884/HPLPB202638.250164
Abstract:
Background Purpose Methods Results Conclusions
Cancer is a major global health issue. With the development of accelerator physics, boron neutron capture therapy based on accelerator neutron sources has received widespread attention. In the accelerator system, the low energy beam transport is responsible for connecting the ion source and accelerator, as well as processing the beam. For the problem of beam deflection, the chopper is required, so a high-performance chopper is crucial for the entire system.
This study aims to improve the electric field uniformity of the chopper by using circular arc plates instead of parallel plates, and to simulate the chopper design through Python program coupling using CST Studio Suite and TraceWin software.
The beam deflection formula of the chopper was theoretically derived, and the electrostatic and beam dynamics design was completed using CST Studio Suite and TraceWin software. The advantages and feasibility of the circular arc plate were verified through coupling simulation of the two software.
Theoretical calculations and simulations show that the electric field distribution of circular arc plates is more uniform, and the beam deflection function is efficiently completed, confirming the feasibility of the design scheme.
By coupling CST Studio Suite with TraceWin software for simulation, a more realistic simulation of beam dynamics can be achieved, which addresses the issue that TraceWin software is incapable of setting the electric field strength of circular arc plates. The coupled simulation method of CST Studio Suite and TraceWin has been developed, which has certain value for research on chopper design.
2026, 38: 024003.
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.
2026, 38: 025001.
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.
2026, 38: 025002.
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.
2026, 38: 025003.
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.
2026, 38: 026001.
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.
2026, 38: 026002.
doi: 10.11884/HPLPB202638.250239
Abstract:
Background Purpose Methods Results Conclusions
Portable alpha-associated deuterium-tritium (DT) neutron generators have extensive application potential in fields such as nuclear physics experiments, homeland security, and nuclear safeguards and assay.
This study aims to evaluate the correlated neutron distribution characteristics of a domestically developed compact portable alpha-associated DT neutron generator, providing critical technical support for its design validation, manufacturing quality control, and engineering applications.
A specialized measurement system was established, comprising of a liquid scintillator detector, a high precision displacement mechanics, and a coincidence measurement digitizer. This system was used to quantify the spatial extent of the correlated neutron emission region and the corresponding solid angle coefficients.
Experimental measurements on two neutron generators revealed a measurable difference in their correlated neutron distribution areas, with an approximate 15% variation in the effective correlation region.
This study provides essential technical support for both the design validation and quality control testing in the manufacturing of this type of compact portable neutron generator. It also offers valuable reference data for engineering applications by end-users.
2026, 38: 029001.
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 often receive coherent signals. The mutual coupling between antenna elements or gains inconsistency 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 accurate DOA estimation under conditions of small samples, overlapping colored noise, and coherent incident signals.
This study aims to address 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 challenge in the array signal processing field.
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 in complex environments.
2026, 38: 021004.
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.
2026, 38: 022001.
doi: 10.11884/HPLPB202638.250325
Abstract:
Background Purpose Methods Results Conclusions
The dual-axis VISAR diagnostic technology can simultaneously diagnose the shock wave velocity history in different regions of the target and perform in-situ characterization of the temporal asymmetry during the implosion shock wave loading process. It is an important diagnostic technology in inertial confinement fusion (ICF) experimental research.
The integrated implosion experiments of the Shenguang Ten-Thousand-Joule Facility typically use target pellets with an inner diameter of approximately 850 micrometers (μm), and smaller target sizes pose greater challenges to the establishment of the dual-axis VISAR diagnostic technology. Focusing on the small-sized target used in small laser facilities, this paper conducts research on the dual-axis VISAR diagnostic technology.
We established an imaging simulation model. Based on this model, a detailed analysis of three typical influencing factors is conducted, which provides guidance for target design.
Relying on the cavity target structure of small-sized target, the shock wave velocity histories in the equatorial and polar regions are obtained through diagnostics. The comparison of shock wave loading symmetry under different driving conditions is completed.
Based on this study, the technical challenges of dual-axis VISAR diagnostics have been addressed through simulation and optimization design. The experiments validated in-situ characterization techniques for shock-wave loading symmetry, establishing a diagnostic foundation for subsequent optimization of cavity structures and drive waveforms.
2026, 38: 023006.
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.
2026, 38: 024004.
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. Combined with the external mechanical structure and cooling pipline model of the electron gun, the non-uniform temperature distribution of the cavity under realistic cooling conditions is obtained by employing a fluid–solid coupling method. 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.
2026, 38: 024005.
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.
