Email alert
RSSJust Accepted
Display Method:
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/HPLPB202638.250419
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/HPLPB202638.250390
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/HPLPB202638.250430
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/HPLPB202638.250270
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, 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 3.83N 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 mbar·L−1.
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/HPLPB202638.250387
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/HPLPB202638.250310
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/HPLPB202638.250382
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/HPLPB202638.250395
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/HPLPB202638.250079
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/HPLPB202638.250337
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.
, 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/HPLPB202638.250297
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/HPLPB202638.250403
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/HPLPB202638.250291
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/HPLPB202638.250219
Abstract:
Background Purpose Method Results Conclusions
With the continuous development of nuclear power technology, reactor design has put forward higher requirements for the accuracy, efficiency and multi-functionality of nuclear computing software. The current mainstream Monte Carlo software has deficiencies in the balance between reactor radiation shielding design and nuclear design calibration, which restricts the critical simulation efficiency of the reactor core. Therefore, CNPRI has specifically developed the 3D Monte Carlo software LARCH 1.0 to meet the actual needs of nuclear power engineering design.
To optimize the particle energy search mechanism in Monte Carlo simulation and address the pain point of low efficiency in traditional search methods; Thirdly, based on the optimized search method, the delta-tracking algorithm is further improved to enhance the efficiency of core critical calculation and provide efficient and accurate calculation support for reactor design.
During the development of the LARCH software, the core technological innovation lies in the adoption of a unified energy grid design to replace the traditional binary search and logarithmic search methods. Through the standardization and unification of the energy grid, the number of searches in the particle energy matching process is reduced, and the time consumption of a single search is shortened. Based on the technology of unified energy grid, further develop and optimize the delta-tracking algorithm to achieve the improvement of computing efficiency; By designing a targeted numerical verification scheme, the LARCH 1.0 software and the traditional Monte Carlo software were compared and tested in the reactor problem simulation.
The optimized technical solution has achieved remarkable results. The search method based on the unified energy grid has significantly reduced the time cost of particle energy search compared with the traditional method. Based on this, the optimized delta-tracking algorithm has increased the critical computing efficiency of the Monka software core by approximately 25%.
The unified energy grid method and the optimized delta-tracking algorithm adopted by the LARCH 1.0 3D Monte Carlo software provide an effective technical path for the efficiency improvement of the Monte Carlo software and significantly enhance the critical computing efficiency of the reactor core. The application potential of this software indicates that it can provide more efficient and reliable numerical simulation tools for reactor design. Subsequently, more extensive engineering verification and functional iterations will be further carried out.
, Available online , doi: 10.11884/HPLPB202638.250245
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/HPLPB202638.250298
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/HPLPB202638.250347
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.
