Email alert
RSSJust Accepted
Display Method:
, Available online , doi: 10.11884/HPLPB202537.250139
Abstract:
As a strategic material for lightweight design, aluminum alloys occupy an important position in the fields of marine equipment, aerospace, and transportation due to their low specific gravity, corrosion resistance, and good low-temperature properties. It is worth noting that surface wettability, as a key interface parameter for the functionalization of aluminum alloys, directly affects their engineering service performance. In recent years, surface wettability control technology based on laser texturing has broken through the limitations of traditional chemical modification and provided new ideas for the functionalization of aluminum alloy surfaces. This article systematically explains the basic theoretical system of wettability, including the Young model, the Wenzel model, and the Cassie-Baxter model, and analyzes the differences in the application of ultrashort pulse lasers and long pulse laser systems in the construction of biomimetic functionalization of aluminum alloy surfaces. Among them, ultrashort pulse lasers (femtosecond/picosecond) can achieve submicron-level precision texturing due to their extremely short pulse width and ultra-high peak power, while long pulse lasers have advantages in large-area processing efficiency. Research has shown that these functionalized surfaces exhibit significant advantages in areas such as surface self-cleaning, low-temperature anti-icing, Cl− corrosion resistance, efficient boiling heat transfer, bonding, and microfluidics. However, their practical application is still limited by key technical bottlenecks such as wetting stability degradation and insufficient environmental tolerance.
As a strategic material for lightweight design, aluminum alloys occupy an important position in the fields of marine equipment, aerospace, and transportation due to their low specific gravity, corrosion resistance, and good low-temperature properties. It is worth noting that surface wettability, as a key interface parameter for the functionalization of aluminum alloys, directly affects their engineering service performance. In recent years, surface wettability control technology based on laser texturing has broken through the limitations of traditional chemical modification and provided new ideas for the functionalization of aluminum alloy surfaces. This article systematically explains the basic theoretical system of wettability, including the Young model, the Wenzel model, and the Cassie-Baxter model, and analyzes the differences in the application of ultrashort pulse lasers and long pulse laser systems in the construction of biomimetic functionalization of aluminum alloy surfaces. Among them, ultrashort pulse lasers (femtosecond/picosecond) can achieve submicron-level precision texturing due to their extremely short pulse width and ultra-high peak power, while long pulse lasers have advantages in large-area processing efficiency. Research has shown that these functionalized surfaces exhibit significant advantages in areas such as surface self-cleaning, low-temperature anti-icing, Cl− corrosion resistance, efficient boiling heat transfer, bonding, and microfluidics. However, their practical application is still limited by key technical bottlenecks such as wetting stability degradation and insufficient environmental tolerance.
, Available online , doi: 10.11884/HPLPB202537.250194
Abstract:
Background Purpose Methods Results Conclusions
The Low Energy High Intensity High Charge State Heavy Ion Accelerator Facility (LEAF) is a national scientific instrument developed by the Institute of Modern Physics, Chinese Academy of Sciences, to provide high-current, high-charge-state, full-spectrum low-energy heavy ion beams for interdisciplinary studies.
To meet research needs in nuclear astrophysics, atomic and molecular physics, and nuclear materials, LEAF offers tunable energies from 0.3 to 0.7 MeV/u and supports continuous-wave acceleration for ions with A/q = 2-7.
This paper presents an overview of the construction progress, key design parameters, and operational performance of the facility, summarizing recent achievements and outlining future development goals.
The paper introduces the system architecture—comprising the 45 GHz superconducting ECR ion source FECR, RFQ, IH-DTL, and terminal beamlines—and describes beam commissioning and diagnostic approaches.
LEAF has successfully achieved stable acceleration of multi-species, high-charge-state heavy ion beams with intensities up to 1 emA. It has delivered more than 13,000 hours of beam time, realized efficient operation of“cocktail”multi-ion beams, and established a high-current, low-energy-spread 12C2+ beamline for precise reaction measurements in the Gamow window.
These results verify LEAF’s excellent beam quality and operational reliability. Planned upgrades—including an extended energy tuning range and triple-ion beam capability—will further enhance its role as a frontier platform for experimental studies in nuclear astrophysics and radiation effects in advanced materials.
, Available online , doi: 10.11884/HPLPB202537.250263
Abstract:
Background Purpose Methods Results Conclusions
High-resolution industrial computed tomography (CT) is crucial for the non-destructive testing (NDT) of critical components, particularly in the aerospace industry where high-density materials are common. The Rhodotron accelerator, with its micro-focus capability, offers a hardware advantage for achieving high spatial resolution over traditional linear accelerators. However, its potential is severely hampered when inspecting large, high-density workpieces. The strong X-ray attenuation leads to projection data with a very low signal-to-noise ratio (SNR), causing conventional reconstruction algorithms to either produce noisy images or oversmooth critical details, thereby limiting the system's effective resolution.
This study aims to develop and validate a reconstruction algorithm capable of overcoming the low-SNR challenge inherent in Rhodotron CT scans of high-density objects. The primary objective is to achieve high-resolution, high-fidelity image reconstruction that effectively suppresses noise while preserving the fine structural edges essential for accurate defect detection.
A novel iterative algorithm, termed Projections Onto Convex Sets regularized by Bilateral Total Variation (POCS-BTV), is proposed. The algorithm integrates BTV, a regularizer known for its superior edge-preservation properties, into the POCS framework to constrain the solution during iterations. The performance of POCS-BTV was evaluated against the Simultaneous Iterative Reconstruction Technique (SIRT), POCS-TV, and POCS-RTV algorithms. The evaluation involved two stages: a simulation experiment using a Shepp-Logan phantom with added Poisson-Gaussian noise to mimic low-SNR conditions, and a physical experiment using a 70 mm diameter high-strength steel wire rope phantom scanned by a 9 MeV Rhodotron accelerator CT system.
In the simulation experiment, the POCS-BTV algorithm demonstrated superior quantitative performance, achieving a Peak Signal-to-Noise Ratio (PSNR) of 30.76 and a Structural Similarity Index (SSIM) of 0.8405 , which were significantly better than the comparison algorithms. In the real data experiment, visual analysis of the reconstructed images showed that POCS-BTV successfully resolved the fine gaps between individual steel wires. This was in stark contrast to other methods, which suffered from structural aliasing and blurred edges due to noise.
The POCS-BTV algorithm effectively unlocks the high-resolution potential of the Rhodotron accelerator hardware, even in challenging low-SNR scenarios. By achieving an optimal balance between noise suppression and detail preservation, it provides a robust and reliable solution for the precision NDT of critical high-density industrial components, demonstrating significant value for practical engineering applications.
, Available online , doi: 10.11884/HPLPB202537.250175
Abstract:
Background Purpose Methods Results Conclusions
The very-high-frequency (VHF) photocathode electron gun operates in continuous-wave mode and serves as a critical electron source for generating high-repetition-rate, high-quality electron beams. It is widely used in advanced scientific facilities such as X-ray free-electron lasers and ultrafast electron diffraction systems. However, during operation, resonant frequency shifts caused by variations in feed power and cooling water temperature can destabilize the radio-frequency (RF) field inside the cavity.
This study aims to achieve stable amplitude and phase control of the RF field in a VHF electron gun under high-power continuous-wave operation by accurately tracking and tuning the resonant frequency of the cavity in real time.
Based on an LCR oscillator circuit model, the phase difference between the cavity-sampled microwave and the incident wave was analyzed to determine the cavity's resonant frequency. A three-step tuning strategy—comprising frequency scanning, frequency tracking, and active tuning—was implemented and applied to a VHF electron gun at Tsinghua University.
Using the proposed tuning method, the electron gun maintained resonance during high-power operation, with a resonant frequency deviation controlled at an RMS value of 94.2 Hz under full power. The amplitude stability at the microwave sampling port reached an RMS value of 0.0046 %, and the phase-locking accuracy achieved an RMS value of 0.0023 °. These results enabled long-term, stable full-power operation of the electron gun.
The developed three-step active tuning method effectively ensures high amplitude and phase stability for the VHF photocathode electron gun under continuous-wave operation, providing a reliable tuning solution for high-repetition-rate accelerator-based light sources and scientific instruments.
, Available online , doi: 10.11884/HPLPB202537.250023
Abstract:
Background Purpose Method Result Conclusions
Shenzhen Superconducting Soft X-Ray Free Electron Laser (S3FEL) is newly proposed by Institute of Advanced Science Facilities, Shenzhen (IASF). The linear accelerator based on TESLA-type superconducting RF cavity is used to obtain high-repetition-frequency and high-gradient field. The cryomodule is the most challenging core part in S3FEL device and ultra-high vacuum differential system is located at the module beam pipe outlet, which is used to realize the transition from cryomodule to ambient temperature section. The vacuum interlock protection is required on differential system to protect the superconducting RF cavity in cryomodule from emergency.
This study aims to analyze the transient process of quick protection.
Traditional fast closing valve protection process is only calculated according to gas molecular rate, and the finite element method and the Monte Carlo method are used in this paper.
The transient pressure distribution results of sensor-fast closing valve section show that setting the sensor 8-10 m away from the fast closing valve can provide sufficient buffer reaction time.
The differential system analyses show that the pressure here reaches 1E-5 Pa within 2 s when the gate valve is completely closed, corresponding to leakage sizes of 0.5 mm, which still maintains a high-vacuum environment and meets working requirement of ion pumps. This work provides important theory basis for the S3FEL.
, Available online , doi: 10.11884/HPLPB202537.250038
Abstract:
Background Purpose Methods Results Conclusions
To enhance the performance of the next-generation X-ray free electron laser (XFEL), a photocathode RF gun capable of providing the required high-quality electron beam with a small emittance has been a significant research objective. In comparison to the conventional L-band or S-band RF gun, the C-band RF gun features a higher acceleration gradient above 150 MV/m and the ability to generate a small-emittance beam. Low-emittance electron beams are critical for enhancing XFEL coherence and brightness, driving demand for advanced RF gun designs. For a bunch charge of 100 pC, a normalized emittance of less than 0.2 mm.mrad has been expected at the gun exit.
This paper presents the design of an emittance measurement device, which can accurately measure such a small emittance at the C-band RF gun exit to ensure beam quality for XFEL applications.
To achieve the desired accuracy, the primary parameters —slit width, slit thickness, and beamlet-drift length—have been systematically optimized through numerical simulations using Astra and Python based on the single-slit-scan method. Dynamic errors, including motor displacement and imaging resolution, were quantified to ensure measurement reliability.
The evaluations indicate that the measurement error of 95% emittance is less than 5%, employing a slit width of 5 μm, a slit thickness of 1 mm, and a beamlet-drift length of 0.11 m under dynamic conditions.
This optimized emittance measurement device supports precise beam quality characterization for XFELs, offering potential for further advancements in electron beam diagnostics.
Study on the influence of electromagnetic parameters in large-orbit gyrotron electron gun in Ka-band
, Available online , doi: 10.11884/HPLPB202537.250185
Abstract:
Background Purpose Methods Results Conclusions
Gyrotron traveling-wave tubes (gyro-TWTs), based on the electron cyclotron maser mechanism, are extensively utilized in critical military domains such as high-resolution millimeter-wave imaging radar, communications, and electronic countermeasures. Experimental observations indicate that when the cathode magnetic field exceeds a specific range, occur the electron beam bombardment of the tube wall.
In order to reduce damage risks to the electron gun during experiments, provide guidance for identifying optimal operating points in experimental testing of Ka-band second-harmonic large-orbit gyrotron traveling wave tube (gyro-TWT).
This paper introduces the formation theory of large-orbit electron guns and analyzes the motion of electron beams in non-ideal CUSP magnetic fields. Using CST Particle Studio and E-gun software modeled and simulated the electron gun. The effects of magnetic fields, operating voltage, and beam current on the quality and trajectories of large-orbit electron beams were investigated.
As the absolute value of the cathode magnetic field increases, both the velocity ratio and the Larmor radius increase, while the velocity spread decreases. With an increase in voltage, the velocity ratio decreases, and the Larmor radius drops to a minimum at a certain point before rising again. Variations in current have limited impact on the Larmor radius and the transverse-to-longitudinal velocity ratio; however, the electron-wave interaction efficiency reaches its maximum at the optimal operating current.
The study demonstrates that excessively low operating voltage leads to high transverse-to-longitudinal velocity ratios (α) and electron back-bombardment phenomena, which detrimentally affect the cathode. Therefore, within this voltage range (20–40 kV), the power supply voltage should be increased promptly. Conversely, excessively high reverse magnetic fields at the cathode result in oversized electron cyclotron radius, causing beam-wall bombardment and gun damage. To prevent electron beam bombardment of the tube wall, the cathode magnetic field should not exceed -85 Gs.
, Available online , doi: 10.11884/HPLPB202537.250285
Abstract:
Background Purpose Methods Results Conclusions
With the rapid development of microsatellite platforms such as CubeSats, microwave plasma thrusters have become ideal for orbit maintenance and attitude control due to their high specific impulse, no electrode ablation, compact structure, and flexible working fluid. However, the thrust of such thrusters (at the 1000W power level) is usually in the millinewton range, and its accurate measurement is crucial for performance verification. Existing thrust measurement schemes require at least 50 cm of space, conflicting with the extreme spatial constraint of 18 cm×16 cm in the current laboratory vacuum chamber; traditional indirect measurement also needs 2-3 parameters, increasing experimental complexity.
This study aims to address the spatial limitation of the vacuum chamber, develop miniaturized thrust measurement schemes, establish a complete testing system including direct mechanical measurement and indirect parameter estimation, and verify the effectiveness and feasibility of these methods for ground testing of thrusters.
Four thrust measurement methods were developed: 1) Modified NH-2 electronic push-pull force gauge (2 N range, 0.001 N resolution) with a 5.5 cm metal target and 3D-printed bracket; 2) Pendulum thrust meter using an eddy current displacement sensor (2 mV/μm sensitivity) to measure small displacements, with force analysis under small angles (<10°); 3) Thrust calculation based on resonant cavity gas temperature (measured by WRe26 thermocouple, 0-1800 ℃ range) using adiabatic process and ideal gas equations; 4) Thrust calculation based on resonant cavity pressure (measured by a precision pressure gauge) via derived formulas. Experiments used a 1500 W 2.45 GHz magnetron microwave source with helium as the working fluid, conducted under cold gas (microwave off) and discharge (microwave on) conditions.
In cold gas experiments, thrust increased almost linearly with helium flow; push-pull force gauge and pendulum data were highly consistent, while temperature- and pressure-based calculated values were higher. In discharge experiments, thrust still increased with flow (slower at high flow), specific impulse remained stable (slight drop at high flow), and temperature- and pressure-based values showed better consistency. All four methods performed well within the 0-600 mN thrust range, with indirect methods consistent with direct measurements.
The four methods effectively solve the spatial constraint issue. Direct measurements (push-pull force gauge, pendulum) are effective, and indirect calculations (temperature, pressure) are feasible. The modular design is particularly suitable for CubeSats, providing reliable, low-cost, and easy-to-implement solutions for micro thruster performance verification and optimization, with promising application prospects.
Study of field distribution characteristics of large split EMP simulator with distributed terminator
, Available online , doi: 10.11884/HPLPB202537.250080
Abstract:
Background Purpose Methods Results Conclusions
There is currently little research on the choice of the effective work-space of large split vertically polarized electromagnetic pulse (EMP) simulator with distributed terminator.
In order to get the distribution characteristics of the peak-value of electric field’s vertical component (called “field peak-value”) inside large simulators,
two typical planes were chosen as testing-planes found on an example of selecting the effective working-space of this type of simulator firstly, then the influences of the maximum width, the maximum height, and the maximum width of the upper plate’s void on (normalized) field peak-value distribution characteristics on the two testing-planes, are studied and analyzed based on parallel finite-difference time-domain (FDTD) method.
The results show that, field peak-values increase on the two testing-planes, as the simulator’s maximum width is wider, maximum height is lower, and maximum width of the upper plate’s void is smaller. The field peak-value uniform along the simulator’s width direction becomes better as the simulator’s maximum width increases; The field peak-value uniform along the simulator’s height direction becomes better, but becomes slightly wrong along the simulator’s width direction, as the simulator’s maximum height increases; The field peak-value uniform along the simulator’s width direction becomes better, but becomes wrong along the simulator’s height direction, as the maximum width of the upper plate’s void increases.
When selecting an effective workspace in practical experiments, it is necessary to select the appropriate size-parameters of the simulator according to the field peak-values required by the effect experiment and the actual size of the effector, combined with the engineering practice.
, Available online , doi: 10.11884/HPLPB202537.250148
Abstract:
Background Purpose Methods Results Conclusions
Backward stimulated Raman scattering (SRS) and backward stimulated Brillouin scattering (SBS) are two major laser-plasma instabilities that influence the laser-target energy coupling efficiency in inertial confinement fusion (ICF). Hot electrons excited by SRS can preheat the fuel. Their nonlinear competition determines the effectiveness of laser-plasma coupling and thus the performance of laser-driven fusion. In realistic laser fusion conditions, the electron distribution often deviates from Maxwellian due to strong laser heating, leading to nonthermal effects such as the Langdon effect. Additionally, ion-ion collisions in multispecies plasmas like CH can alter the damping and dispersion of ion acoustic waves.
This study aims to investigate the impact of the Langdon effect and ion-ion collisions on the competition between SRS and SBS in CH plasma, particularly focusing on their respective reflectivities under varying plasma conditions.
Five-wave coupling equations describing the nonlinear interactions among the pump laser, scattered light, Langmuir wave, and ion acoustic wave were numerically solved. A super-Gaussian electron distribution function was employed to incorporate the Langdon effect, while ion-ion collision effects were included through modifications to the ion susceptibility. The dispersion relations and damping characteristics of both electron plasma waves (EPWs) and ion acoustic waves (IAWs) were analyzed in detail.
The results reveal that the Langdon effect notably reduces Landau damping of EPWs and modifies the dispersion relation of SRS, enhancing its growth rate. Simultaneously, ion-ion collisions increase IAW damping and shift the SBS dispersion curve, weakening its instability. These combined effects lead to a dominance of SRS over SBS at lower electron densities, altering the overall backscattering reflectivity spectrum in laser fusion plasma.
Both the Langdon effect and ion-ion collisions play crucial roles in reshaping the nonlinear dynamics of SRS and SBS. Their influence must be considered in predictive models of laser-plasma interactions. These findings provide insight into optimizing plasma parameters for improved control of backscatter instabilities in inertial confinement fusion experiments.
, Available online , doi: 10.11884/HPLPB202537.250210
Abstract:
Background Purpose Methods Results Conclusions
In recent years, the development of wound-type mica paper capacitors has significantly enhanced their operating voltage and energy density, and they remain highly reliable, showing potential for improving the overall energy storage density of PFN (pulse forming line)-Marx generators.
The lifetime of the capacitor is a crucial factor in ensuring system reliability. The lifetime of the mica paper capacitor reaches up to 100,000 times, meeting the requirements of highly compact pulse power drivers. However, the lifetime characteristics of this capacitor remain unclear, and its optimal operating conditions have not been well-defined.
In this paper, an investigation into the lifetime characteristics of mica paper capacitors under microsecond pulses is presented. First, the structure of the capacitor is analyzed in detail. Subsequently, numerical simulations of the electrical and thermal fields are carried out to further study its characteristics. To accurately test the mica paper capacitors, a lifetime test platform that can operate stably over an extended period was constructed.
Through the utilization of this platform, the electrical degradation parameters and the failure mechanisms of the mica paper capacitors are obtained and analyzed. Based on the test data, the lifetime empirical model of mica capacitors under given operating conditions is modified.
The results of the experiments and calculations of the lifetime empirical model indicate that the model aligns well with the experimental results. This work contributes to the lifetime prediction of mica capacitor and provides design reference for system devices using mica capacitor under microsecond pulses.
, Available online , doi: 10.11884/HPLPB202537.250019
Abstract:
Background Purpose Methods Results Conclusions
Fiber laser coherent beam combining technology enables high-power laser output through precise phase control of multiple laser channels. However, factors such as phase control accuracy, optical intensity stability, communication link reliability, and environmental interference can degrade system performance.
This study aims to address the challenge of anomaly detection in phase control for large-scale fiber laser coherent combining by proposing a novel deep learning-based detection method.
First, ten-channel fiber laser coherent combining data were collected, system control processes and beam combining principles were analyzed, and potential anomalies were categorized to generate a simulated dataset. Subsequently, an EMA-Transformer network model incorporating a lightweight Efficient Multi-head Attention (EMA) mechanism was designed. Comparative experiments were conducted to evaluate the model's performance. Finally, an eight-beam fiber laser coherent combining experimental setup was established, and the algorithm was deployed using TensorRT for real-time testing.
The proposed algorithm demonstrated significant improvements, achieving approximately 50% higher accuracy on the validation set and a 2.20% enhancement on the test set compared to ResNet50. In practical testing, the algorithm achieved an inference time of 2.153 ms, meeting real-time requirements for phase control anomaly detection.
The EMA-Transformer model effectively addresses anomaly detection in fiber laser coherent combining systems, offering superior accuracy and real-time performance. This method provides a promising solution for enhancing the stability and reliability of high-power laser systems.
, Available online , doi: 10.11884/HPLPB202537.250157
Abstract:
Background Purpose Methods Results Conclusions
The assessment of gamma radiation dose released by strong explosions is an important direction in the research of nuclear emergency protection systems. Traditional research has mostly focused on dose assessment of prompt gamma radiation (duration<1 μs）, while delayed gamma radiation (on the second timescale) is often overlooked due to time delay.
This article focuses on the study of the delayed gamma dose released by fission products after a strong explosion within 0.2-0.5 seconds, as well as the secondary gamma dose generated by neutron leakage, with the aim of systematically evaluating their radiation hazards in the near to medium range.
Based on monte carlo (MC) method, a three-dimensional full-scale model coupling strong explosive source term atmospheric transport surface activation was constructed, and a dynamic dose assessment framework based on MC multi-step calculation was proposed. By modifying the importance card method, the variance of the simulation results at medium to close distances was effectively reduced, and a detailed comparison was made between the changing trends of delayed gamma and prompt gamma doses over time and distance.
The simulation results show that within a time window of 0.2-0.5 seconds: at a distance of 500 meters from the explosion source, the total dose of delayed gamma radiation reaches 0.829 Gy, which is 1.88 times the instantaneous gamma radiation dose (0.441 Gy); At a distance of 1000 meters from the explosion source, the delayed gamma dose generated by fission products alone is 0.0318 Gy, which is 7.6 times the instantaneous gamma dose (0.0042 Gy), indicating that the hazard of delayed gamma is significantly higher than that of instantaneous gamma at longer distances. The secondary gamma dose generated by neutron leakage decays from 0.634 Gy at 500 meters to 0.0485 Gy at 1000 meters.
The dynamic dose assessment framework proposed in this article effectively reveals the significant contribution of delayed gamma radiation in the early radiation field after a strong explosion, especially at a distance where its hazard far exceeds that of instantaneous gamma radiation. This study provides key data support for optimizing nuclear emergency protection strategies.
, Available online , doi: 10.11884/HPLPB202537.250183
Abstract:
Gyrotron traveling wave tube (gyro-TWT) hold significant applications in millimeter-wave radar, communications, electronic warfare, and deep-space exploration. For electron beams operating in the large-orbit regime, interaction occurs exclusively with modes satisfying\begin{document}$ s=m $\end{document} ![]()
![]()
Gyrotron traveling wave tube (gyro-TWT) hold significant applications in millimeter-wave radar, communications, electronic warfare, and deep-space exploration. For electron beams operating in the large-orbit regime, interaction occurs exclusively with modes satisfying
