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Articles in press have been peer-reviewed and accepted, which are not yet assigned to volumes/issues, but are citable by Digital Object Identifier (DOI).
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, Available online , doi: 10.11884/HPLPB202638.250243
Abstract:
Background Purpose Methods Results Conclusions
The traditional Monte-Carlo (MC) method faces an inherent trade-off between geometric modeling accuracy and computational efficiency when addressing real-world irregular terrain modeling.
This paper proposes a fast MC particle transport modeling method based on irregular triangular networks for complex terrains, addressing the technical challenge of achieving adaptive and efficient MC modeling under high-resolution complex terrain scenarios.
The methodology consists of three key phases: First, high-resolution raster-format terrain elevation data are processed through two-dimensional wavelet transformation to precisely identify abrupt terrain variations and extract significant elevation points. Subsequently, the Delaunay triangulation algorithm is employed to construct TIN-structured terrain models from discrete point sets. Finally, the MCNP code’s “arbitrary polyhedron” macrobody definition is leveraged to establish geometric planes, with Boolean operations applied to synthesize intricate geometric entities, thereby realizing rapid automated MC modeling for high-resolution complex terrains.
The results demonstrate that the proposed method accurately reproduces terrain-induced effects on radiation transport, achieving high-fidelity simulations while significantly compressing the number of cells and enhancing computational efficiency.
This methodology represents a novel approach for large-scale radiation field modeling under complex terrain constraints, demonstrating broad applicability to MC particle transport simulations in arbitrary large-scale complex terrain scenarios.
, Available online , doi: 10.11884/HPLPB202638.250234
Abstract:
Background Purpose Methods Results Conclusions
With the development of neutron calculation methods and improved modeling capabilities, the errors introduced by model approximations and discretization methods in nuclear reactor physics calculations have gradually decreased. However, nuclear data, due to the challenges in measurement, have become the key input parameter affecting computational accuracy.
In this study, a nuclear data adjustment module based on sensitivity analysis and the generalized linear least squares algorithm was developed within the self-developed sensitivity and uncertainty analysis platform, SUPES.
First, sensitivity analysis was used to determine the relationship between system responses and input parameter variations. Next, similarity analysis was applied to select experimental setups with high similarity at the neutron physics level. Finally, the generalized linear least squares algorithm was employed to minimize the error between computed and measured values, resulting in nuclear data adjustments.
The adjustment of the ACE format continuous energy database was performed on 22 cases from the critical benchmark HEU-MET-FAST-078. The numerical results show that the root mean square error of the effective multiplication factor (keff) was reduced from 3.10×10−3 to 1.53×10−3.
The comparison and analysis verified the correctness of the developed nuclear data adjustment module.
, Available online , doi: 10.11884/HPLPB202638.250369
Abstract:
Background Purpose Methods Results Conclusions
The self-absorption effect of target materials plays a crucial role in shaping the performance of laser-driven X-ray sources, directly impacting their energy spectrum and angular distribution, which are critical parameters for applications such as high-resolution backlighting and radiographic diagnostics.
This study aims to systematically investigate how key parameters, including the electron source position relative to the wire target end-face, the diameter of the wire target, and the atomic number of the target material, affect the energy spectrum and angular distribution of emitted X rays.
A series of Geant4-based Monte Carlo simulations were performed using a validated wire target model. Key parameters were varied: electron source offset (50–150 μm), wire diameter, and target material (Cu, Mo, W, Au). The simulation model was benchmarked against experimental data obtained from the Xingguang-III laser facility.
The results indicate that varying the electron source position within the studied range has a negligible influence on both the photon energy spectrum and angular distribution. In contrast, increasing the wire diameter leads to enhanced absorption of low-energy photons, resulting in noticeable spectral hardening and a broadening of the angular distribution due to increased multiple scattering. Furthermore, higher-Z target materials (W, Au) significantly enhance the high-energy photon yield but concurrently induce greater angular divergence.
The findings provide quantitative insights into the self-absorption mechanism and its differential impact across parameters. This study offers concrete guidance for optimizing target design: selecting appropriate wire diameter and high-Z materials can tailor the spectral hardness and brightness, while mindful management of angular broadening is necessary for applications requiring high directivity.
, Available online , doi: 10.11884/HPLPB202638.250251
Abstract:
Background Purpose Methods Results Conclusions
Fiber lasers have gained extensive adoption across medical, telecommunications, industrial processing, and defense sectors owing to their exceptional beam quality, operational stability, compact architecture, and high reliability. Among them, narrow-linewidth linearly polarized fiber lasers have become a key research focus due to their outstanding spectral purity and coherence, with current efforts concentrated on further scaling their output power and brightness.
In this work, we demonstrate a 5.09 kW narrow-linewidth linearly polarized fiber laser system designed to overcome stimulated Brillouin scattering (SBS) and transverse mode instability (TMI).
A white-noise radio frequency phase modulation scheme is implemented to broaden the seed laser spectrum into a Gaussian profile with an 89 GHz full width at half maximum, enabling effective SBS suppression. A polarization-maintaining ytterbium-doped fiber (PMYDF) with low numerical aperture (about 0.05), large mode area (about 237 μm2), and high birefringence coefficient (4.23×10−4) is employed to simultaneously mitigate SBS and intermodal thermal coupling.
The system achieves 5.09 kW output power while maintaining an 89 GHz spectral linewidth, polarization extinction ratio above 19.6 dB, and beam quality factor of M2 < 1.2. No self-pulsing or temporal instability is observed at maximum power, confirming suppression of both SBS and TMI.
By employing a white-noise radio frequency signal to modulate the phase of a single-frequency laser, the SBS effect in high-power fiber laser systems is effectively suppressed. Concurrently, intermodal thermal coupling and SBS are further mitigated using a fabricated low-numerical-aperture, large-mode-area PMYDF. The demonstrated performance supports the feasibility of high-power, narrow-linewidth polarized fiber lasers for long-term stable operation.
, Available online , doi: 10.11884/HPLPB202638.250376
Abstract:
Background Purpose Methods Results Conclusions
U-band fiber lasers are of significant value for applications in communications, sensing, and scientific research.
This paper employs a 1.55 μm fiber laser as the pump source and demonstrates a U-band 1.65 μm Raman fiber laser based on commercially available single-mode silica fiber. The effects of the Raman fiber length and the reflectivity of the output coupling fiber Bragg grating (OC-FBG) on the power conversion efficiency of the Raman laser were systematically investigated.
The optimal Raman fiber length was determined to be 2.1 km in experiment. Then, with the optimal Raman fiber length, experiments were conducted by varying the reflectivity of the OC-FBG to analyze its influence on the output power and spectral broadening of Stokes light. By combining the measured forward and backward Stokes powers with the collected forward and backward spectra, the optimal OC-FBG reflectivity under the current experimental conditions was determined.
The results indicated that as the Raman laser power increased, the broadening of the Stokes spectral linewidth reduced the effective reflectivity of the fiber Bragg grating, leading to backward power leakage, which became the main factor limiting the forward output power.
By selecting an OC-FBG with a low reflectivity of 15.7% and using a 2.1 km silica fiber as the Raman gain medium, a 1648.8 nm Raman laser output with a power of 10.1 W and a 3 dB bandwidth of 2.5 nm was achieved, corresponding to an optical-to-optical conversion efficiency of 65.2%.
, Available online , doi: 10.11884/HPLPB202638.250371
Abstract:
High harmonic generation (HHG) and attosecond pulses driven by relativistically intense lasers interacting with solid-density plasma mirrors constitute a vital pathway for realizing high-brightness, short-wavelength, ultrafast coherent light sources and exploring extreme strong-field physics. In recent years, benefiting from the rapid development of laser technology, the precise control over light field degrees of freedom, such as amplitude, phase, and polarization, has spurred the emergence of structured light fields. Structured light fields significantly enrich the methods for controlling laser-matter interaction and broaden its scope of applications. This article aims to review the latest progress in controlling relativistic laser-plasma HHG and attosecond pulses using structured light fields. The work specifically discusses methods for characteristic control and the physical mechanisms of HHG driven by novel structured light fields, including polarization structures (e.g., circularly polarized light, vector beams), phase structures (e.g., spatial vortex beams, spatiotemporal vortex beams), and amplitude structures (e.g., Bessel beams, Airy beams), with the goal of providing new perspectives for research on novel light sources based on strong-field laser-plasma interactions.
High harmonic generation (HHG) and attosecond pulses driven by relativistically intense lasers interacting with solid-density plasma mirrors constitute a vital pathway for realizing high-brightness, short-wavelength, ultrafast coherent light sources and exploring extreme strong-field physics. In recent years, benefiting from the rapid development of laser technology, the precise control over light field degrees of freedom, such as amplitude, phase, and polarization, has spurred the emergence of structured light fields. Structured light fields significantly enrich the methods for controlling laser-matter interaction and broaden its scope of applications. This article aims to review the latest progress in controlling relativistic laser-plasma HHG and attosecond pulses using structured light fields. The work specifically discusses methods for characteristic control and the physical mechanisms of HHG driven by novel structured light fields, including polarization structures (e.g., circularly polarized light, vector beams), phase structures (e.g., spatial vortex beams, spatiotemporal vortex beams), and amplitude structures (e.g., Bessel beams, Airy beams), with the goal of providing new perspectives for research on novel light sources based on strong-field laser-plasma interactions.
, Available online , doi: 10.11884/HPLPB202638.250412
Abstract:
The emergence and rapid advancement of ultrafast and ultraintense lasers have created unprecedented extreme physical conditions and novel experimental methods, significantly deepening and expanding our understanding of the laws governing the objective world. These developments have greatly promoted innovation in basic and frontier interdisciplinary fields as well as strategic high technology areas. Particle acceleration using the interaction of ultrafast and ultraintense lasers with plasmas is regarded as a next-generation technology for accelerators and radiation sources. It offers the potential to shrink the footprint of conventional accelerator facilities by two orders of magnitude. This dramatic reduction in size greatly expands the applicability of accelerator and radiation source technologies in industry, national defense, medicine, and scientific research, enabling transformative possibilities such as precision nondestructive testing of critical components, ultralow dose and high precision tumor diagnostics, novel low damage radiotherapy methods, and tabletop ultrafast light sources. The ultrafast and ultraintense laser platform at Zhengzhou University introduced in this paper is precisely such a next-generation facility dedicated to advanced laser accelerator research and applications. In addition, this article provides a systematic review of the significant progress achieved by Zhengzhou University in recent years in strong-field physics and advanced accelerator science.
The emergence and rapid advancement of ultrafast and ultraintense lasers have created unprecedented extreme physical conditions and novel experimental methods, significantly deepening and expanding our understanding of the laws governing the objective world. These developments have greatly promoted innovation in basic and frontier interdisciplinary fields as well as strategic high technology areas. Particle acceleration using the interaction of ultrafast and ultraintense lasers with plasmas is regarded as a next-generation technology for accelerators and radiation sources. It offers the potential to shrink the footprint of conventional accelerator facilities by two orders of magnitude. This dramatic reduction in size greatly expands the applicability of accelerator and radiation source technologies in industry, national defense, medicine, and scientific research, enabling transformative possibilities such as precision nondestructive testing of critical components, ultralow dose and high precision tumor diagnostics, novel low damage radiotherapy methods, and tabletop ultrafast light sources. The ultrafast and ultraintense laser platform at Zhengzhou University introduced in this paper is precisely such a next-generation facility dedicated to advanced laser accelerator research and applications. In addition, this article provides a systematic review of the significant progress achieved by Zhengzhou University in recent years in strong-field physics and advanced accelerator science.
, Available online , doi: 10.11884/HPLPB202638.250351
Abstract:
Background Purpose Methods Results Conclusions
Water-dielectric self-breakdown switches are critical components in pulsed power devices such as the 10 MA facility. The plate-sphere electrode structure is specifically designed to achieve simultaneous multi-channel discharge, which is essential for minimizing switch inductance and reducing timing jitter.
This study investigates the factors affecting multi-channel formation in a water-dielectric, three-electrode plate-sphere self-breakdown switch operating at 3 MV, with the aim of validating the theoretical formation criterion.
Theoretical analysis was conducted based on the specific parameters of the switch structure, focusing on key temporal characteristics influencing discharge behavior. Experimental validation was performed at the nominal breakdown voltage of 3 MV, utilizing diagnostic techniques to observe the development of discharge arcs across all electrode pairs.
The calculated characteristic value for multi-channel formation was determined to be 8.6 ns, exceeding twice the measured switch jitter time of 3 ns, thereby satisfying the theoretical criterion. Observations confirmed that discharge arcs initiated nearly synchronously at the three sphere electrodes and propagated toward the plate electrodes, with complete multi-channel formation achieved within approximately 30 ns.
The study validates the criterion for multi-channel discharge in the plate-sphere switch structure. The design effectively enables simultaneous formation of multiple discharge channels within tens of nanoseconds, meeting essential requirements for high-performance pulsed power devices and contributing to improved operational stability.
, Available online , doi: 10.11884/HPLPB202638.250327
Abstract:
Background Purpose Methods Results Conclusions
In the voltage multiplication process of a spiral generator based on the principle of vector inversion, its voltage efficiency is constrained by losses such as switching loss, transmission line loss and leakage inductance loss.
To quantitatively investigate the impact of key design parameters––including coil turn number n, dielectric/electrode thickness, average dielectric diameter D, magnetic core permeability, and switch position on leakage loss and overall efficiency.
This study employs a field-circuit collaborative simulation method for modeling and analysis.
The simulation results demonstrate that utilizing a high-permeability magnetic core can significantly enhance voltage efficiency; increasing D/n ratio improves output efficiency; while a higher turn number n boosts output voltage amplitude, it concurrently reduces voltage efficiency; enlarging the average diameter D enhances voltage efficiency but at the cost of increased device volume; reducing dielectric thickness benefits efficiency, though excessively thin layers risk insulation breakdown; and positioning the switch at the middle of the coil, rather than at the end, substantially increases voltage efficiency.
Furthermore, an in-depth analysis of the electromagnetic energy conversion process after switch closure reveals that a high-efficiency spiral generator must achieve complete conversion of magnetic energy into electric field energy while ensuring the electric fields in the active and passive layers are oriented in the same direction, which is essential for optimal performance.
, Available online , doi: 10.11884/HPLPB202638.250363
Abstract:
Background Purpose Methods Results Conclusions
In recent years, emerging application fields such as FLASH radiotherapy and flash radiography have created an urgent demand for high-repetition-rate linear induction accelerators (LIA) capable of operating at kHz-level frequencies. Whether the magnetic cores of induction accelerator cavities can effectively reset between repetitive pulses has become one of the critical factors determining the feasibility of high-repetition-rate LIA.
This paper focuses on the reset methods for magnetic cores in high-repetition-rate pulsed induction accelerator cavities.
Through high-voltage experiments and circuit simulations, various rapid reset methods for both amorphous and nanocrystalline magnetic cores were investigated and comparatively analyzed. Based on this work, experimental tests were conducted on the interpulse reset effectiveness of accelerator cavity cores using self-developed high-repetition-rate pulsed induction accelerator modules.
Research results indicate that nanocrystalline magnetic cores are more suitable for high-repetition-rate induction accelerator cavities. Different reset methods can achieve magnetic core reset at varying repetition frequencies.
Utilizing the inductor-isolated DC reset method, the existing device configuration can meet the reset requirements for nanocrystalline magnetic cores at a 10 kHz repetition rate. By leveraging the self-recovery capability of low-remanence nanocrystalline magnetic cores, automatic reset of accelerator cavity cores can be achieved at 100 kHz repetition rates.
, Available online , doi: 10.11884/HPLPB202638.250328
Abstract:
Background Purpose Methods Results Conclusions
The PFN (pulsed forming network)-Marx generator shows robust capabilities for enhancing the output efficiency and miniaturization level of pulsed power system, and offers the most significant potential for compact and lightweight design.
This study aims to develop a compact PFN-Marx generator that is capable of generating high-power pulses with flat-top duration, while maintaining low output jitter.
A tailored pulsed forming module (PFM) was developed by employing a non-uniform PFN sections reduced to 2, aiming for enhanced compactness. The influence of key circuit parameters on its output waveform was investigated. A PFN-Marx generator was designed and assembled by employing the PFMs and low-jitter plane-triggering-electrode gas switches et al.
The effects of key circuit parameters on the pulse shaping was quantitatively analyzed, and waveform tailoring of the PFM was achieved. The PFM could output a high-voltage pulse with a pulse width and flat-top duration (90%−90%) of about 150 ns and 80 ns, respectively. Once assembled into the Marx generator, it could deliver a 190 kV, 3.4 GW high pulsed power to a 10.6 Ω resistive load, while maintaining a flat-top duration of about 80 ns. When operating at a repetition rate of 50 Hz, it exhibits highly consistent output waveforms, with an output jitter as low as 2.4 ns.
A compact PFN-Marx generator was developed by employing a 2-sections tailored PFM that is capable of generating high-power pulses with flat-top duration. It is helpful for the development of compact Marx generator with the required waveform and low output jitter.
, Available online , doi: 10.11884/HPLPB202638.250362
Abstract:
Background Purpose Methods Results Conclusions
The rapid development of high-power microwave application technology presents significant challenges for the reliability and installability of pulsed power drivers.
The design methodology of a compact, lightweight Tesla-type pulsed power driver based on high-energy-density liquid dielectric Midel 7131 and a dual-width pulse-forming line (PFL) is introduced.
There was a key breakthrough in the miniaturization of the integrated Tesla transformer and PFL assembly. Through optimization of the electrical length of the short pulse transmission line and its impedance matching characteristics, longstanding challenges associated with conventional single-cylinder PFLs and extended transmission lines using transformer oil dielectrics have been effectively resolved. A high-elevation, high-vacuum oil impregnation technique was developed for the Tesla transformer, successfully mitigating partial discharge in oil-paper insulation systems and thereby enhancing the power rating and operational reliability of the PFL.
The developed pulsed power driver delivers a peak output power of 20 GW, a pulse duration of 50 ns, a pulse flat-top fluctuation of less than 2%, and a maximum repetition rate of 50 Hz. The system has demonstrated stable operation over continuous one-minute durations, accumulating approximately 200 000 pulses with consistent performance. The driver’s overall dimensions are 4.0 m (L)×1.5 m (W)×1.5 m (H), with a total mass of approximately 5 metric tons.
Compared to the conventional 20 GW Tesla-type pulsed power generator, this driver has achieved significant improvements in power density and miniaturization.
, Available online , doi: 10.11884/HPLPB202638.250101
Abstract:
Background Purpose Methods Results Conclusions
The intense electron beam-plasma system serves as an important platform for investigating beam-plasma interactions. Research in this field focuses on the design of electron beam window and the transport characteristics of electron beam in plasma.
The study aims to design and evaluate an electron beam window with excellent comprehensive performance, and to investigate the physical mechanisms underlying the focusing and transmission of intense annular electron beams in plasma.
Finite element analysis and Monte Carlo simulations were employed to compare and evaluate the mechanical, thermal, and transmission properties of candidate window materials. Theoretical analysis and particle-in-cell (PIC) simulations were used to study the self-focusing transmission behavior of intense annular electron beams in plasma.
The TC4 titanium alloy window with a thickness of only 0.04 mm was found sufficient to withstand a pressure differential of 10 kPa. It achieved an energy transmission efficiency exceeding 90% while maintaining controllable temperature variations. The physical mechanism of self-focusing transmission of intense annular electron beams in plasma under conditions of 500 kV and 20 kA was revealed, clarifying the relationship between the focusing transmission period of the electron beam and the plasma density. Furthermore, an equivalent relationship between plasma density and magnetic field was established based on the correspondence between the plasma oscillation period and the electron beam cyclotron period.
The research demonstrates that TC4 titanium alloy is a suitable material for the electron beam window, offering high transmission efficiency and structural stability. It also elucidates the self-focusing transmission mechanism of intense annular electron beams in plasma and establishes a periodic equivalent relationship between plasma and magnetic fields for electron beam transport.
