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, Available online , doi: 10.11884/HPLPB202638.250342
Abstract:
Background Purpose Methods Results Conclusions
In all-solid-state Marx pulse generators, the isolated gate driver plays a critical role in ensuring reliable high-voltage and high-speed switching. Conventional isolation driving schemes based on magnetic-core transformers often suffer from large volume, high cost, and poor integration, which limit further miniaturization and system-level integration.
To address these issues, this study proposes a synchronous isolated gate driving scheme based on a PCB-embedded coreless transformer, aiming to reduce driver size and cost while improving integration and manufacturability for all-solid-state Marx pulse generator applications.
The proposed coreless transformer was first modeled, and its key electromagnetic parameters were extracted using Q3D electromagnetic simulation and validated through experimental measurements. Based on theoretical analysis and LTspice simulations of the driving circuit, the operating principles and driving sequence characteristics were investigated and compared with those of conventional magnetic-core transformer-based drivers. Finally, a prototype driving system was developed and experimentally evaluated.
Simulation and experimental results show that the proposed PCB coreless transformer-based driving scheme exhibits a wide dynamic driving range, excellent electrical isolation performance, and good compatibility with standard PCB manufacturing processes. The experimental waveforms are consistent with theoretical analysis and simulation results, confirming the correctness of the proposed design and modeling approach.
The proposed synchronous isolated driving scheme based on a PCB coreless transformer provides an effective solution to the challenges of volume, cost, and integration in conventional isolation drivers for all-solid-state Marx pulse generators. The results demonstrate its feasibility and strong potential for practical engineering applications in compact and highly integrated pulsed power systems.
, 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/HPLPB202638.250395
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/HPLPB202638.250301
Abstract:
Background Purpose Methods Results Conclusions
Simultaneous and accurate detection of multiple physical and biochemical parameters, such as refractive index (RI) and temperature, is critically important in complex sensing environments including biological analysis and cancer cell detection. Photonic crystal fiber sensors based on surface plasmon resonance (PCF-SPR) have attracted considerable attention due to their high sensitivity and compact structure. However, achieving ultra-wide RI detection ranges, effective temperature compensation, and low cross-sensitivity within a single fiber platform remains a significant challenge, particularly when higher-order mode excitation and polarization selectivity are required.
The purpose of this study is to propose and numerically investigate a dual-channel PCF-SPR sensor capable of simultaneous RI and temperature sensing over an ultra-wide range, while achieving polarization-resolved mode excitation and reduced cross-interference between sensing channels.
An anchor-shaped asymmetric photonic crystal fiber with orthogonally polished semi-circular surfaces is designed. Gold (Au) and polydimethylsiloxane (PDMS) thin films are selectively deposited on different polished surfaces to construct two independent SPR sensing channels. Polarization-resolved excitation of high-order modes is realized by structural asymmetry and selective coating. A full-vector finite-element method based on COMSOL Multiphysics is employed to analyze mode distributions, loss spectra, and resonance wavelength shifts. Key structural parameters, including air-hole geometry and metal-dielectric layer thicknesses, are systematically optimized to enhance plasmonic coupling strength and mode confinement.
Simulation results indicate that the x-polarized channel coated with Au and PDMS exhibits dual sensitivity to RI and temperature, whereas the y-polarized channel coated only with Au responds exclusively to RI variations of another analyte. The proposed sensor achieves an ultra-wide RI detection range from 1.21 to 1.44, with a maximum RI sensitivity of 14 500 nm/RIU. The temperature sensing range spans from −100 ℃ to 100 ℃, and a peak temperature sensitivity of 4 nm/℃ is obtained. Clear polarization-dependent resonance characteristics and effective channel decoupling are demonstrated.
The proposed dual-channel anchor-shaped PCF-SPR sensor combines ultra-wide RI detection, temperature sensing capability, and polarization-resolved selectivity within a compact fiber structure. Its high sensitivity, flexible channel configuration, and strong resistance to cross-interference make it a promising platform for real-time multi-parameter sensing in complex biological and chemical applications, such as cancer cell detection and biochemical analysis.
, Available online , doi: 10.11884/HPLPB202638.250303
Abstract:
Background Purpose Methods Results Conclusions
Pinhole cameras based on the principle of pinhole imaging are widely used in high-energy-density physics experiments to monitor laser-target interaction regions. However, traditional pinhole cameras often suffer from signal acquisition failures due to the lack of online aiming capability, especially for small targets such as wire targets in facilities like the Xingguang-Ⅲ laser system.
This study aims to develop an X-ray online-aiming pinhole camera for the Xingguang-Ⅲ laser facility, addressing the challenge of precise target alignment under vacuum conditions and enhancing the reliability of signal acquisition.
An integrated design combining a visible-light CCD and an X-ray CCD was implemented. A revolver-type pinhole adjustment device was developed to switch between aiming apertures and imaging pinholes with a concentricity error below 3.5 µm. High-precision two-dimensional pointing adjustments (pitch and tilt) were achieved using a motorized stage, with a targeting accuracy of 15 µm. The visible-light CCD enabled real-time target imaging, while different aperture sizes on a precision adjustment disk facilitated coarse-to-fine aiming.
The camera was tested on the Xingguang-Ⅲ laser facility using a Cu planar target irradiated by a picosecond laser. Clear X-ray spot images were obtained, with a peak intensity of 52,040 and a background noise of approximately 2,500. The full width at half maximum of the spot was 43 µm horizontally and 38 µm vertically, confirming successful online aiming and imaging performance.
The developed X-ray online-aiming pinhole camera fulfills the operational requirements of the Xingguang-Ⅲ laser facility. It enables real-time, high-precision target alignment under vacuum, significantly improving the success rate of signal acquisition in high-energy-density physics experiments.
, Available online , doi: 10.11884/HPLPB202638.250468
Abstract:
Ultra-short and ultra-intense mid-infrared laser pulses hold unique application value in fields such as strong-field physics, ultrafast chemistry, environmental monitoring, and biomedical applications. Particularly in strong-field physics research, ultra-short and ultra-intense mid-infrared pulses provide a new wavelength scale distinct from the conventional near-infrared range, enabling the exploration of novel physics in the interaction between ultra-intense lasers and matter. However, due to the damage thresholds of traditional laser crystals and nonlinear crystals, the generation of high-energy, single-cycle mid-infrared light sources has long remained a significant challenge in ultrafast laser technology. In recent years, utilizing plasma as a nonlinear optical medium, the generation of ultra-short and ultra-intense mid-infrared pulses through photon deceleration process based on laser wakes has emerged as a new research direction in laser-plasma physics. This paper systematically reviews the fundamental principles, numerical simulations, experimental progress, and future application prospects surrounding this physical mechanism of plasma photon deceleration.
Ultra-short and ultra-intense mid-infrared laser pulses hold unique application value in fields such as strong-field physics, ultrafast chemistry, environmental monitoring, and biomedical applications. Particularly in strong-field physics research, ultra-short and ultra-intense mid-infrared pulses provide a new wavelength scale distinct from the conventional near-infrared range, enabling the exploration of novel physics in the interaction between ultra-intense lasers and matter. However, due to the damage thresholds of traditional laser crystals and nonlinear crystals, the generation of high-energy, single-cycle mid-infrared light sources has long remained a significant challenge in ultrafast laser technology. In recent years, utilizing plasma as a nonlinear optical medium, the generation of ultra-short and ultra-intense mid-infrared pulses through photon deceleration process based on laser wakes has emerged as a new research direction in laser-plasma physics. This paper systematically reviews the fundamental principles, numerical simulations, experimental progress, and future application prospects surrounding this physical mechanism of plasma photon deceleration.
, Available online , doi: 10.11884/HPLPB202638.260005
Abstract:
The rapid development of ultra-short and ultra-intense laser technology has greatly advanced frontier research in physics under extreme strong-field conditions. This includes compact accelerators, high-brightness radiation sources, nonlinear strong-field quantum electrodynamics, as well as the production and detection of axion dark matter based on intense lasers. Over the past decade, Shanghai Jiao Tong University has carried out systematic theoretical, simulation and experimental research in this field, and has successively built a relativistic plasma research platform based on a single-beam hundred terawatt-level laser and an extreme relativistic plasma research platform based on a dual-beam hundred terawatt-level laser with high-precision spatiotemporal synchronization. In this paper, we present the layout, key parameters and characteristics of the newly commissioned dual-beam “Chongming” Laser-plasma Experimental Facility (CLEF), and highlights both completed and ongoing scientific activities, including the studies on laser-solid high-order harmonic generation, laser-plasma wakefield acceleration, nonlinear Compton scattering, and the production and detection of axion dark matter driven by intense lasers. The completion and operation of this facility will provide an essential supporting platform for experimental research in the field of extreme relativistic plasma physics.
The rapid development of ultra-short and ultra-intense laser technology has greatly advanced frontier research in physics under extreme strong-field conditions. This includes compact accelerators, high-brightness radiation sources, nonlinear strong-field quantum electrodynamics, as well as the production and detection of axion dark matter based on intense lasers. Over the past decade, Shanghai Jiao Tong University has carried out systematic theoretical, simulation and experimental research in this field, and has successively built a relativistic plasma research platform based on a single-beam hundred terawatt-level laser and an extreme relativistic plasma research platform based on a dual-beam hundred terawatt-level laser with high-precision spatiotemporal synchronization. In this paper, we present the layout, key parameters and characteristics of the newly commissioned dual-beam “Chongming” Laser-plasma Experimental Facility (CLEF), and highlights both completed and ongoing scientific activities, including the studies on laser-solid high-order harmonic generation, laser-plasma wakefield acceleration, nonlinear Compton scattering, and the production and detection of axion dark matter driven by intense lasers. The completion and operation of this facility will provide an essential supporting platform for experimental research in the field of extreme relativistic plasma physics.
, 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/HPLPB202638.250420
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/HPLPB202638.250352
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/HPLPB202638.250419
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/HPLPB202638.250387
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/HPLPB202638.250382
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/HPLPB202638.250378
Abstract:
Background Purpose Methods Results Conclusions
High-fidelity neutronics simulation of nuclear reactor cores, particularly those with complex geometries such as the AP1000, remains computationally challenging. Efficient deterministic methods that can achieve Monte Carlo-level accuracy are highly desirable for design and analysis.
This study aims to develop, apply, and validate the FLASH code, which implements an advanced Fission Response Function (FRF) algorithm, for performing efficient and accurate full-core, pin-wise neutronics calculations of the AP1000 reactor core.
The FRF database was generated through reference-state simulations using the Serpent Monte Carlo code. To enhance accuracy in complex geometries, the methodology incorporated a local inter-assembly environmental correction factor to address fuel assembly heterogeneity and a predictor-corrector scheme to precisely simulate reflector environmental effects. The performance of the FLASH code was validated against reference Monte Carlo solutions under Hot Zero Power (HZP) conditions.
The validation results demonstrated high accuracy. Deviations in the effective multiplication factor (keff) were within +220 pcm for all 2D axial slices and +209 pcm for the full 3D core calculation. The root-mean-square error (RMSE) was below 1.1% for the 2D pin power distribution, while the 3D pin power RMSE was 1.05% and the 3D assembly power RMSE was 0.67%. In terms of efficiency, the FLASH code completed the pin-wise full-core 3D calculation for the AP1000 in 106 seconds using 64 CPU cores.
The developed FLASH code, based on the FRF algorithm with integrated correction schemes, successfully bridges the gap between efficiency and high fidelity. It provides a rapid and accurate computational tool for AP1000 core analysis, confirming the practicality and effectiveness of the proposed methodology for detailed reactor physics calculations.
, 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/HPLPB202638.250291
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/HPLPB202638.250380
Abstract:
Inverse Compton Scattering (ICS) is a fundamental physical process involving energy exchange between photons and electrons. ICS light sources, generated by collision between relativistic electron beams and intense laser pulses, offer high-brightness, energy-tunable, and short-pulsed X-rays or gamma-rays, which are supporting diverse scientific research and applications world wide today. This paper aims to review the current technological status and future development prospects of ICS light sources, which are categorized into three evolutionary phases. The first phase, Incoherent Inverse Compton Scattering (InICS), is the mature foundational technology for most existing ICS light sources and has been widely applied in various fields. The second phase, Coherent Inverse Compton Scattering (CoICS), enhances radiation brightness and beam quality through coherent interactions between electron and photon beams, with key technical approaches including periodic photon structures and periodic electron structures. The third phase, Stimulated Inverse Compton Scattering (StICS), achieves nonlinear enhancement of scattering intensity via stimulated emission amplification, analogous to free-electron lasers (FEL), and holds promise for ultra-high brightness radiation. In this paper, a systematic analysis of the principles, key steps, and technical challenges of each phase will be provided. Furthermore, numerical simulations demonstrate that periodic electron structures induced by optical fields can achieve significant coherent enhancement, producing high-quality beams with smaller energy spread and angular divergence. It is envisioned that with advancements in high-intensity short-pulse laser technology, Flying Focus, and high-current short-pulse electron acceleration, CoICS and StICS are expected to develop rapidly, providing superior brightness and beam quality in the ultraviolet to soft X-ray bands, and opening new avenues for related scientific research and industrial applications.
Inverse Compton Scattering (ICS) is a fundamental physical process involving energy exchange between photons and electrons. ICS light sources, generated by collision between relativistic electron beams and intense laser pulses, offer high-brightness, energy-tunable, and short-pulsed X-rays or gamma-rays, which are supporting diverse scientific research and applications world wide today. This paper aims to review the current technological status and future development prospects of ICS light sources, which are categorized into three evolutionary phases. The first phase, Incoherent Inverse Compton Scattering (InICS), is the mature foundational technology for most existing ICS light sources and has been widely applied in various fields. The second phase, Coherent Inverse Compton Scattering (CoICS), enhances radiation brightness and beam quality through coherent interactions between electron and photon beams, with key technical approaches including periodic photon structures and periodic electron structures. The third phase, Stimulated Inverse Compton Scattering (StICS), achieves nonlinear enhancement of scattering intensity via stimulated emission amplification, analogous to free-electron lasers (FEL), and holds promise for ultra-high brightness radiation. In this paper, a systematic analysis of the principles, key steps, and technical challenges of each phase will be provided. Furthermore, numerical simulations demonstrate that periodic electron structures induced by optical fields can achieve significant coherent enhancement, producing high-quality beams with smaller energy spread and angular divergence. It is envisioned that with advancements in high-intensity short-pulse laser technology, Flying Focus, and high-current short-pulse electron acceleration, CoICS and StICS are expected to develop rapidly, providing superior brightness and beam quality in the ultraviolet to soft X-ray bands, and opening new avenues for related scientific research and industrial applications.
, Available online , doi: 10.11884/HPLPB202638.250346
Abstract:
In indirect-drive laser inertial confinement fusion (ICF), the precise calculation of X-ray drive intensity at the capsule is crucial for accurately predicting the implosion performance of deuterium-tritium fuel capsules. Achieving this requires detailed radiation-hydrodynamic simulations that accurately capture processes such as laser-to-X-ray conversion and X-ray absorption losses at the hohlraum walls. However, since the inception of the National Ignition Campaign at the National Ignition Facility (NIF), radiation-hydrodynamic simulations have consistently overestimated the experimentally measured X-ray drive flux intensity at the capsule, reflecting the widespread presence of hohlraum energy deficits. Although extensive experimental studies have been conducted at NIF along with continuous optimization of its radiation-hydrodynamic simulation models, the challenging issue of hohlraum energy deficit remains unresolved, constituting one of the critical barriers to achieving high-gain inertial confinement fusion. This paper systematically reviews the critical research developments regarding hohlraum energy deficit at NIF and introduces the methods adopted by NIF and China for characterizing the X-ray radiation flux intensity at the capsule.
In indirect-drive laser inertial confinement fusion (ICF), the precise calculation of X-ray drive intensity at the capsule is crucial for accurately predicting the implosion performance of deuterium-tritium fuel capsules. Achieving this requires detailed radiation-hydrodynamic simulations that accurately capture processes such as laser-to-X-ray conversion and X-ray absorption losses at the hohlraum walls. However, since the inception of the National Ignition Campaign at the National Ignition Facility (NIF), radiation-hydrodynamic simulations have consistently overestimated the experimentally measured X-ray drive flux intensity at the capsule, reflecting the widespread presence of hohlraum energy deficits. Although extensive experimental studies have been conducted at NIF along with continuous optimization of its radiation-hydrodynamic simulation models, the challenging issue of hohlraum energy deficit remains unresolved, constituting one of the critical barriers to achieving high-gain inertial confinement fusion. This paper systematically reviews the critical research developments regarding hohlraum energy deficit at NIF and introduces the methods adopted by NIF and China for characterizing the X-ray radiation flux intensity at the capsule.
, 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/HPLPB202638.250386
Abstract:
This paper briefly reviews the series of work carried out by the research team from the Laser Fusion Research Center, China Academy of Engineering Physics, based on the Xingguang-III and Shenguang-II Upgrade laser facilities, in the field of laser-driven neutron source generation and applications. In terms of generation mechanisms, it highlights explorations of several technical approaches, including enhancing photo-nuclear neutron production efficiency through novel target design, increasing neutron yield based on the target normal sheath acceleration mechanism, and obtaining high-quality neutron sources via collisionless electrostatic shock acceleration. On the application front, preliminary experimental studies have been conducted in areas such as fast neutron radiography, material radiation effects, and nuclear material detection, demonstrating the potential application value of such neutron sources as short-pulse, high-flux sources. With continuous advancements in laser technology and ongoing optimization of generation mechanisms, this new type of neutron source is expected to play an increasingly important role in basic scientific research, nuclear energy technology development, and industrial applications, providing new research tools and technical support for the development of related disciplines.
This paper briefly reviews the series of work carried out by the research team from the Laser Fusion Research Center, China Academy of Engineering Physics, based on the Xingguang-III and Shenguang-II Upgrade laser facilities, in the field of laser-driven neutron source generation and applications. In terms of generation mechanisms, it highlights explorations of several technical approaches, including enhancing photo-nuclear neutron production efficiency through novel target design, increasing neutron yield based on the target normal sheath acceleration mechanism, and obtaining high-quality neutron sources via collisionless electrostatic shock acceleration. On the application front, preliminary experimental studies have been conducted in areas such as fast neutron radiography, material radiation effects, and nuclear material detection, demonstrating the potential application value of such neutron sources as short-pulse, high-flux sources. With continuous advancements in laser technology and ongoing optimization of generation mechanisms, this new type of neutron source is expected to play an increasingly important role in basic scientific research, nuclear energy technology development, and industrial applications, providing new research tools and technical support for the development of related disciplines.
, 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/HPLPB202638.250330
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/HPLPB202638.250245
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/HPLPB202638.250424
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/HPLPB202638.250414
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/HPLPB202638.250347
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.
