Email alert
RSSJust Accepted
Display Method:
, Available online , doi: 10.11884/HPLPB202638.250460
Abstract:
Background Purpose Methods Results Conclusions
Reverse blocking diode thyristors (RBDTs) are attractive solid-state switches for pulsed power systems because of their high blocking capability and high di/dt turn-on potential. In practical DSRD-triggered operation, the rising-edge voltage slew rate (dv/dt) of the trigger pulse is a key waveform parameter that can alter the initial carrier injection and regenerative turn-on process, and therefore affects the switching transient and current build-up.
This work aims to quantify how the output dv/dt of a silicon-based drift step recovery diode (Si DSRD) influences the turn-on characteristics of an RBDT, and to identify the dv/dt range where further increase brings diminishing improvement under a fixed pulsed power circuit configuration.
A numerical analysis model of an Si DSRD-triggered RBDT was established by combining TCAD device simulation with an equivalent external circuit. In the simulations, the trigger pulse parameters other than the rising-edge dv/dt were kept constant to isolate the dv/dt effect, and the RBDT turn-on delay time, current rise time, and peak current were evaluated for multiple dv/dt conditions. An Si DSRD-based trigger circuit was then built for experimental verification. Different dv/dt levels were obtained by adjusting trigger-circuit parameters (including the pulse transformer core and turns as well as the shaping capacitor), and the trigger voltage across the RBDT and the corresponding current waveforms were measured to extract the same turn-on metrics.
Both simulation and experiment show that increasing the Si DSRD output dv/dt shortens the RBDT turn-on delay time and current rise time, while the peak current exhibits a slight increase under the tested circuit parameters. When dv/dt is raised beyond a certain range, the reductions in delay and rise time become progressively smaller and tend to saturate, indicating diminishing sensitivity of the turn-on transient to further dv/dt enhancement. The overall trends obtained from TCAD and measurements are consistent across the investigated dv/dt range.
The voltage rise rate of the Si DSRD trigger waveform is an effective control parameter for tailoring the RBDT turn-on transient, mainly reflected in reduced delay and faster current build-up, with a saturation tendency at higher dv/dt. The reported TCAD–experiment comparison provides a practical basis for selecting dv/dt levels and designing Si DSRD-based trigger conditions for RBDT switching in pulsed power applications.
, Available online , doi: 10.11884/HPLPB202638.250366
Abstract:
Background Purpose Methods Results Conclusions
The compensated pulsed alternator (CPA) is a pulsed power source that integrates rotor inertial energy storage, electromechanical energy conversion and power regulation. It connects the prime mover and the electromagnetic launch load directly as a “unit component”, reducing many intermediate links. It has the advantages of high output voltage, high power density, high frequency of repetition and long service life, and is regarded as the most promising pulsed power source for electromagnetic launch systems.
The air-core CPA (ACCPA) overcomes the limitations of ferromagnetic material saturation on magnetic field strength and rotational speed, significantly improving the motor’s energy storage density and power density. The Halbach permanent magnet array (HPMA) possesses a magnetic shielding, eliminating the need for a rotor core while generating an air-gap magnetic flux density (AGMFD) waveform with good sinusoidal characteristics. Therefore, this paper investigates the application of a double-layer HPMA rotor, which is simple in structure, strong in integrity, and easy to optimize, in the topological structure of ACCPA.
Without considering magnetic saturation, an analytical calculation model for the no-load electromagnetic field in an ACCPA was established using the subdomain model method in polar coordinates. Starting from the basic theory of electromagnetic fields, this method used the vector magnetic potential method to establish Laplace’s equations (for no- curl fields) or Poisson’s equations (for curl fields) for four subdomains respectively. By combining the boundary conditions between adjacent subdomains, the equations were solved jointly to obtain the mathematical expression for the no-load AGMFD of the motor, and the distribution of the no-load AGMFD was analyzed.
This analytical model could directly reflect the relationship between the no-load AGMFD distribution of the motor and its design parameters. The analytical model’s calculation results were highly consistent with the results of finite element analysis, verifying the accuracy of the analytical model. Its calculation results could relatively accurately reflect the static and steady-state performance of the motor.
The relationship between the four main parameters of the motor and the amplitude and sinusoidal characteristics of the radial and tangential components of the no-load AGMFD is studied, which can provide technical support for the subsequent optimization of the motor’s no-load air-gap magnetic field and further calculation design.
, Available online , doi: 10.11884/HPLPB202638.250454
Abstract:
Background Purpose Methods Results Conclusions
To address the challenge of achieving central fueling in future fusion reactors, this study carried out fueling experiments on the Compact Torus (CT) injection system based on pulse high-power technology. A CT is a high-density plasma blob with self-organized magnetic confinement, and its characteristics make it an ideal carrier for central fueling in fusion devices.
The CT injection system is a novel fueling device centered on such plasma blobs. Driven by a pulsed high-power power supply, the system generates stable CT plasma within coaxial electrodes, which undergoes secondary acceleration to form a high-density plasma blob capable of long-distance stable propagation.
System discharge tests show that the peak discharge current of CT is 300 kA, the average electron density is \begin{document}$ 1.2\times {10}^{22}{\text{ m}}^{-3} $\end{document}
When applied to the EAST tokamak experiment, the results indicate that after CT injection, the plasma stored energy increases by 18%, the plasma density rises by 22%, and the plasma density rise rate is \begin{document}$ 0.4\times {10}^{20}{\text{ m}}^{-3}{\text{s}}^{-1} $\end{document}
Comparative studies with conventional gas puffing (GP) and supersonic molecular beam injection (SMBI) reveal that CT injection outperforms these techniques in terms of injected particle number, fueling efficiency, and particle confinement time during single-shot injections.
, Available online , doi: 10.11884/HPLPB202638.250398
Abstract:
Background Purpose Methods Results Conclusions
SiC-based light-initiated multi-gate semiconductor switches (LIMS) deliver superior response speeds due to the faster injection of photo-generated carriers compared to conventional electrically injected carriers. They can be used in a variety of applications, including radars, accelerators, and pulse sources.
Regarding the problems such as the long falling edge and slow turn-off speed of LIMS, an anode structure design with turn-off capability is proposed.
The model and its parameters are calibrated based on experimental data, and the simulation is used to study the conduction characteristics of devices with a turn-off anode structure.
The simulation results show that devices with a turn-off anode structure can achieve positive feedback in the pnpn configuration following laser activation, thereby increasing the conduction current. When the laser pulse ends, the recombination of photo-generated carriers and the extraction of carriers from the base region by the turn-off anode structure significantly enhance the turn-off speed of the device.
With a 4 kV anode bias and a peak current of several hundred amperes, the modified LIMS reduces the full-width-at-half-maximum of the current pulse from 0.79 µs to <100 ns and shortens the turn-off time to 0.6 µs. These results indicate suitability for repetitive operation at kilohertz frequencies and above.
, Available online , doi: 10.11884/HPLPB202638.250367
Abstract:
Background Purpose Methods Results Conclusions
High-energy flash X-ray photography has important applications in the hydrodynamic experiments. As an important means of generating multi-pulse X-ray, the technical scheme of multi-pulse linear induction accelerators (LIA) of each countries have their own characteristics.
Based on requirements for the compactness, mobility, and high reliability of multi-pulse LIAs, the project team is exploring various novel multi-pulse power source technologies that can be used for multi-pulse LIAs.
In this paper, a 100 kV four-pulse generation technology is explored, that is, a low-pressure pseudo-spark switch of tens of kV is used to drive the Blumlein line of tri-coaxial cables to generate multi-pulse high voltage, and the multi-pulse high voltage of tens of kV is superimposed by an induction voltage adder to generate a multi-pulse high voltage of 100 kV. The same four sets of pulse high voltage generators are used to output multi-pulse high voltage of 100 kV, which are converged by a coaxial high-voltage diode to obtain four-pulse high voltage output of 100 kV.
Simulation and experimental results show that the scheme could generate four-pulse high voltage of more than 100 kV with adjustable pulse interval.
This compact and movable 100 kV four-pulse high voltage generator is expected to become a new multi-pulse power source for multi-pulse LIAs.
, 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/HPLPB202638.250446
Abstract:
Background Purpose Methods Results Conclusions
Vacuum breakdown under intense electromagnetic fields in Relativistic Backward Wave Oscillator (RBWO) critically compromise the reliability of high power microwave sources. To meet increasingly demanding power capacity requirments, it is essential to further enhance the performances of resistance to vacuum breakdown. The processes of lectron emission and electron beam bombardment are closely associated with the physical interactions at the material surface. Furthermore, studies have indicated that refining the grain size of titanium suifaces may significantly increase their ability to withstand intense electromagnetic field-induced vacuum breakdown.
Given that surface self-nanocrystallization is a highly effective approach for improving the mechanical properties of metallic materials, particularly through grain fefinement at the nanometer scale, this article proposes a novel strategy utilizing surface self-nanocrystallization technology to suppress vacuum breakdown in RBWO under intense electromagnetic fields. Experimental validation was conducted to evaluate the effectiveness of this method in inhibiting vacuum breakdown under such extreme conditions.
This paper employs commercially pure titanium (TA2) as the research object, utilizing ultrasonic peening (USP) and microshot peening (MSP) as two distinct nanoparticle surface processing techniques. The nanostructural effects were characterized through scanning electron microscopy coupled with X-ray diffraction analysis. Subsequently, field emission testing apparatus and an X-band RBWO were employed to conduct comparatice experiments on field electron emission characteristics and vacuum breakdown performance high power microwave generation, respectively.
USP produces a gradient nanocrystalline layer extending 2-3 μm beneath the surface, with grain size refined to approximately 40 nm. MSP generates a more extensive gradient nanocrystalline layer reaching 30 μm in depth, with surface grains refined to about 48 nm. After undergoing MSP and USP treatment, TA2 exhibits a sequential reduction in the field emission current under the identical electric field, the tail erosion in the output microwave waveforms vanishes, and damage in the high-field region of the slow wave structure is mitigated.
The results demonstrate that both MSP and USP treatments successfully refine the surface grain size of TA2 to the nanoscale range of several tens of nanometers, forming a gradient nanostructured layer. Such surface self-nanocrystallization effectively suppresses field-induced electron emission and vacuum breakdown under intense electromagnetic fields. Notably, the USP treatment exhibits particularly pronounced inhibitory effects. This methodology provides technical support for further enhancing the power capacity of high power microwave generators based on RBWO.
, Available online , doi: 10.11884/HPLPB202638.250312
Abstract:
Background Purpose Methods Results Conclusions
Owing to their simple configuration, stable operating behavior, and high electronic efficiency, magnetrons have been extensively employed in high-power microwave applications. Nevertheless, the output capability of a single microwave source is inherently constrained, making it difficult to satisfy the increasing demands of high-power applications. Magnetron array configurations offer an effective approach for enhancing the peak power of microwave systems.
To address the demand for frequency controllability and output consistency in large-scale magnetron arrays, this work integrates the advantages of injection locking and mutual coupling locking and proposes an injection-locking-based amplitude consistency control scheme for coupled magnetron arrays.
Five magnetrons are interconnected through directional couplers and coaxial lines to form a cascaded mutually coupled structure, in which an external signal is injected solely into the central magnetron to pull and control the operating frequency of the entire array via coupling paths. High-power experimental measurements were performed to systematically collect and analyze the output signals under five operating conditions, including free-running operation, mutual coupling only, and external injection at frequencies of 2.466 GHz, 2.465 GHz, and 2.464 GHz.
The experimental results indicate that introducing an external injection signal under the mutually phase-locked condition modifies the overall frequency characteristics of the cascaded magnetron array, thereby affecting the amplitude distribution of the array output signals. Moreover, effective regulation of the output amplitude of the magnetron array can be realized by tuning the frequency and power of the injected signal. The dispersion of output amplitudes under different conditions is quantitatively characterized using the sample variance of the power spectral density peak of the output signal, and the results show that, at an injection power of 100 W, the variance decreases from 1.868 to 0.446, indicating a significant improvement in amplitude consistency.
This approach offers strong scalability and practical applicability and is well suited for coherent power combining and phase-scanning applications in large-scale magnetron array systems.
, Available online , doi: 10.11884/HPLPB202638.250473
Abstract:
Background Purpose Methods Results Conclusions
Advanced sheet electron beam vacuum electron devices, particularly Ka-band traveling-wave tubes, are required to meet increasingly stringent broadband operational demands. However, energy leakage and impedance mismatch at millimeter-wave output interconnections remain major challenges that limit transmission efficiency and bandwidth performance.
To address these challenges, this work aims to design and validate a broadband, high-efficiency output circuit for a Ka-band sheet beam TWT. A novel non-contact double-layer choke-mode output circuit with an air-gap configuration is proposed to suppress leakage and enable broadband operation.
The design is based on the fundamental theory of conventional rectangular waveguides. The output circuit structure is carefully optimized, and matching stepped waveguides are introduced to improve impedance matching and reduce reflections. A comprehensive electromagnetic simulation model is developed and analyzed using High-Frequency Structure Simulator (HFSS). Furthermore, cold-test measurements are conducted on a fabricated prototype to experimentally verify the design.
HFSS simulation results show that the choke grooves effectively suppress parasitic leakage while enabling broadband transmission. The proposed output circuit achieves an absolute bandwidth of 11.9 GHz with a return loss better than −20 dB. The simulated transmission efficiency reaches 93.3%, corresponding to a relative bandwidth of 36.9%, which satisfies broadband operation requirements. Experimental cold-test results are in good agreement with the simulations, confirming the validity of the design.
Both simulation and experimental results demonstrate that the proposed choke-mode output circuit exhibits wide operating bandwidth, high transmission efficiency, low reflection, and effective voltage depression capability. The structure also shows strong anti-interference performance and operational reliability, making it well suited for high-power, broadband millimeter-wave sheet beam TWT applications.
, Available online , doi: 10.11884/HPLPB202638.250450
Abstract:
Background Purpose Methods Results Conclusions
Unmanned aerial vehicles (UAVs) pose significant military threats and civil security risks, and microwave technology has become a core counter-UAV means due to its low cost, area-effect engagement, and all-weather capability. Research on UAV microwave effects is the foundation for counter-UAV equipment development and protection design.
This paper aims to systematically review the research progress of UAV microwave effects, clarify existing challenges, and provide directional references for future studies.
By combing through domestic and foreign relevant research, this review summarizes the characteristics of different microwave effects, analyzes key influencing factors, and sorts out current research limitations and development trends.
Front-door effects involve coupling through intentional electromagnetic channels (e.g., data links) with low-noise amplifiers as sensitive components, and thresholds are related to frequency matching; back-door effects rely on unintentional channels (e.g., cables, housing gaps) with cables as the main path, but relevant research is insufficient; system-level effects show hierarchical failure, affected by UAV models, microwave parameters, and attitudes. Current research faces “black box” coupling mechanisms, fragmented methods, and inadequate connection with protection design.
Future research should focus on multi-path collaborative coupling modeling, complex scenario assessment, and countermeasure-protection collaborative technologies. This review provides a systematic reference for the field, supporting counter-UAV equipment development and safe UAV application.
, 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/HPLPB202638.250358
Abstract:
Background Purpose Methods Results Conclusions
In the 2024 series of Beirut explosions in Lebanon, terrorists hid trace high-explosive materials in electronic products to carry out attacks, exposing the shortcomings of the current detection system. Existing trace detection technologies cannot penetrate the casings of electronic products, while in bulk detection technologies, CT has limitations in imaging plate-like components such as mobile phones, and conventional X-ray security inspectors lack sufficient resolution. Neither of these can meet the detection needs. Computed Lamography (CL) technology is suitable for detecting plate-like components but lacks specialized research on trace explosives.
This study aims to explore the adaptation path of dual-energy CL technology to trace explosive detection and provide a technical solution for the accurate identification of hidden explosives in electronic products.
A simulation model of a mobile phone containing trace TNT and an R-value measurement model were built using Geant4 to obtain dual-energy X-ray projection data. In MATLAB, the POCS-TVM algorithm was used for image reconstruction, and the ratio of attenuation coefficients (R-value) was calculated to determine the effective atomic number of substances for explosive identification.
CL technology overcame the imaging limitations of CT for plate-like components. The R-value-based algorithm showed that the effective atomic number of TNT was 7.1388 , which fell within the range of 7.1-7.4 for explosives. Additionally, the correlation coefficient of the fitted curve for low-high energy projection data reached 0.999.
This study verifies the feasibility of dual-energy CL for trace explosive detection, provides a new technical path for identifying hidden explosives in electronic products, and is of great significance for enhancing nuclear security and anti-terrorism security inspection capabilities.
, Available online , doi: 10.11884/HPLPB202638.250242
Abstract:
Background Purpose Methods Results Conclusions
Precise γ-ray spectrum analysis is essential for nuclide identification and activity quantification, but faces significant challenges when using low-resolution detectors such as CLYC scintillators in complex radiation fields. The limited energy resolution of these detectors often leads to overlapping peaks and obscured characteristic spectral features, which complicates accurate spectrum interpretation.
This study aims to overcome the inherent energy resolution limitations of CLYC detectors by developing a spectrum deconvolution method that can recover clear spectral information and separate overlapping peaks in complex γ-ray spectra.
A detector energy response matrix was constructed by combining Monte Carlo simulations to calculate γ-ray energy response functions with an interpolation method. Response functions were derived across the 0～3 MeV energy range at intervals of 0.05 MeV to ensure high precision. Spectrum deconvolution was then performed using the Maximum Likelihood Expectation Maximization (MLEM) algorithm, which was then applied to analyze the original complex spectrum.
The method was validated by unfolding the spectra of a 226Ra source, a mixed 60Co - 137Cs source, and the complex spectrum of 152Eu. The unfolded spectrum exhibited well-resolved characteristic peaks, effective separation of severely overlapping spectral regions, and stable quantitative results for characteristic peak areas.
The proposed approach significantly enhances the precision of γ-ray spectrum analysis with CLYC detectors. It successfully reveals the energy and intensity information of incident γ-rays, mitigates the detector’s resolution limitations, and provides a reliable method for analyzing spectrum in complex radiation environment.
, Available online , doi: 10.11884/HPLPB202638.250281
Abstract:
Background Purpose Method Results Conclusions
When using the Monte Carlo method for radiation shielding simulations, the efficiency is low. Employing specific variance reduction techniques is one of the methods to accelerate radiation shielding simulations, while another more universal approach is to use large-scale parallel technology to enhance the simulation speed from the hardware aspect. At present, due to the enormous demand for computing power triggered by the development of artificial intelligence technology, major supercomputing platforms have steadily improved their support for large-scale GPU parallel architectures. To adapt to the current and future GPU parallel architectures of supercomputing platforms, it is necessary to develop Monte Carlo transport algorithms suitable for GPU platforms.
This paper aims to accelerate fixed-source calculation of the NECP-MCX Monte Carlo particle transport code by utilizing GPU parallel, thereby enhancing the efficiency of radiation shielding transport simulations.
This paper analyzes the characteristics of the GPU event-based parallel algorithm under the fixed-source mode. The GPU event-based parallel algorithm has been preliminarily implemented within the NECP-MCX code and was tested and analyzed using a simple fixed-source problem.
The results show that the maximum number of simultaneous simulated events is positively correlated with the simulation speed. Sorting particle information can accelerate the simulation by 28%, and the GPU parallel implementation is 25 times faster than the single-core CPU implementation.
The initial implementation shows significant potential for acceleration; however, further research is essential to fully exploit its capabilities and optimize performance.
, 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/HPLPB202638.250429
Abstract:
Background Purpose Methods Results Conclusions
Tandem pumping scheme is commonly employed for high power fiber laser systems, where the 1 018 nm fiber laser serves as the most prevalent pump source. However, the output power of monolithic 1 018 nm fiber lasers is limited to one-kilowatt level due to the amplified spontaneous emission (ASE) effect. This limitation necessitates the use of a large number of these pump sources in tandem-pumped fiber laser systems, resulting in bulky and complex configurations.
This paper presents a modeling and optimization framework for scaling the power of 1 018 nm fiber lasers.
The framework, built upon the beam propagation method and broad-spectrum rate equations, targets the optimization of critical parameters to strategically balance laser efficiency against signal-to-ASE ratio.
Guided by the framework, a bidirectional pumping scheme was employed alongside an optimized fiber coil diameter, which effectively suppressed both ASE and the transverse mode instability. This approach enabled a monolithic output power of 1.94 kW at 1 018 nm, with an optical-to-optical efficiency of 76.38%, a signal-to-ASE ratio of 33.22 dB, and a beam quality factor M2 of 1.91.
By achieving a monolithic 2-kW 1 018 nm laser, this work enhances the compactness and integration of high-power fiber lasers with tandem pumping scheme, thus enabling future breakthroughs in the power and brightness scaling of tandem-pumped fiber lasers.
, Available online , doi: 10.11884/HPLPB202638.250347
Abstract:
Background Purpose Methods Results Conclusions
Gigahertz-repetition-rate femtosecond fiber lasers have attracted increasing attention for applications requiring high temporal resolution and high average power, while most existing GHz fiber amplification systems are limited to fixed repetition rates.
This work aims to realize repetition-rate-tunable amplification of gigahertz femtosecond pulses within a single fiber-based platform by employing a passively harmonic mode-locked fiber laser as the seed source.
The seed laser provides stable pulse operation with repetition rates tunable from 1 to 3 GHz. A two-stage fiber amplification scheme combined with dispersion management is implemented to maintain stable amplification over the entire tuning range. In the pre-amplification stage, controllable chirp is introduced to achieve near-linear temporal broadening, which effectively suppresses excessive nonlinear effects during power scaling. Pulse compression is subsequently implemented at the output using single-mode fiber.
Experimental results show that stable pulse trains with regular temporal distribution are preserved throughout the tuning range. The maximum average output power reaches 2.1 W at a repetition rate of 3.1 GHz, while the shortest pulse duration of 195 fs is obtained at 2.0 GHz. After amplification, the side-mode suppression ratio remains higher than 33 dB.
These results indicate the feasibility of gigahertz repetition-rate-tunable amplification of femtosecond fiber lasers on a single all-fiber platform.
, Available online , doi: 10.11884/HPLPB202638.250420
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/HPLPB202638.250419
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/HPLPB202638.250430
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/HPLPB202638.250392
Abstract:
Background Purpose Methods Results Conclusions
Typically, radiation detectors require an additional coupled scintillator layer to convert incident radiation rays into optical signals, which are then received by the detector. Compared to other types of glass, lead fluoride (PbF2) glass has a high refractive index, and when electrons pass through a lead fluoride crystal, they generate Cherenkov light. As a result, lead fluoride itself can function as a scintillator.
Using a lead fluoride crystal as the optical window of a detector enables it to both generate and detect light. This optimizes the optical transmission and detection performance, shortens the conversion time from the reaction medium to photons, improves the detector’s efficiency, and provides an experimental foundation for future applications in ultrafast detection.
After cleaning components such as the cathode input window, ceramic parts, and anode of the photomultiplier tube, a transition indium sealing film layer is deposited on the cathode input window. The ceramic and metal components are then sealed and assembled into a tube shell using a hydrogen furnace. Indium sealing solder is melted into the tube shell’s indium sealing groove, and the tube shell is laser-welded to the anode. The processed tube shell, microchannel plate (MCP), and anode are assembled according to the designed structure. After assembly, the tube shell components and cathode window are mounted on a transfer-type cathode activation and exhaust station. Cathode activation and MCP electron scrubbing processes are then performed. Upon completion of these steps, the tube shell and cathode window are sealed together using indium sealing, resulting in the fabrication of an MCP-type photomultiplier tube bare tube.
Two PbF2-window MCP-PMTs were successfully prepared, and their electrical performance, including quantum efficiency and operating voltage, can be measured.
By integrating lead fluoride crystals, fast-time-response microchannel plates, and a fast-time coaxial conical anode, this study has successfully addressed key technical challenges in the preparation of lead fluoride crystals as the optical window for photomultiplier tubes. Post-fabrication performance tests indicate that core parameters such as quantum efficiency, gain, and rise time are generally comparable to those of conventional fast-time-response MCP-PMTs.
, 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/HPLPB202638.250330
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.
