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2025,
37: 1-2.
2025,
37: 091001.
doi: 10.11884/HPLPB202537.250287
Abstract:
Background Purpose Methods Results Conclusions
The 1035 nm short-wavelength-band fiber laser serves as a critically important light source with extensive and growing applications across numerous advanced technological fields. Its unique spectral properties make it highly suitable for spectral beam combining (SBC), nonlinear frequency conversion, and high-resolution lidar systems. However, the power scaling of 1035 nm fiber lasers has long been constrained by the amplified spontaneous emission (ASE) effect. This phenomenon has historically impeded significant progress, with the output power from conventional master oscillator power amplifier (MOPA) configurations remaining confined below 2 kW, creating a bottleneck for higher-performance applications.
To realize high-power, high-brightness laser output in the 1035 nm band, we designed and constructed a counter-pumped MOPA fiber laser.
The system’s performance was enhanced through multi-parameter optimization, including optimizing the temporal characteristics of the fiber seed source, the bending and coiling parameter of the gain fiber in the amplifier stage, and refining the backward pump scheme.
Finally, when the seed laser power was 24 W and the total pump power was 2.9 kW, a maximum output power of over 2 kW was reached, and the corresponding optical-to-optical conversion efficiency of the amplifier stage was approximately 69.5%. At the maximum output power, the ASE suppression ratio was measured to be around 32 dB, indicating effective control over noise. Furthermore, the beam quality factors were measured to be \begin{document}$M_x^2 $\end{document} ![]()
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The results represent a significant stride forward in the power scaling of high-brightness 1035 nm fiber lasers. Next research will focus on further elevating the output power and beam quality by implementing seed source with more stable temporal characteristics and optimizing the overall fiber laser structure to mitigate ASE and other nonlinear effects.
2025,
37: 091002.
doi: 10.11884/HPLPB202537.250033
Abstract:
Background Purpose Methods Results Conclusions
Laser-driven betatron radiation is a wide-energy-spectrum X-ray source analogous to synchrotron radiation. Compared to the quasi-monochromatic X-ray spectra of synchrotron radiation or free-electron lasers, the broad energy spectrum of betatron radiation is more favorable for X-ray absorption spectroscopy. Additionally, laser-driven betatron radiation features a small source size, short pulse duration, low divergence, and high brightness, making it comparable to third-generation synchrotron sources.
The photon energy yield of betatron radiation is closely related to the quality of the electron beam, plasma density, and transverse oscillation amplitude. However, current technology faces two major challenges: first, there is a trade-off between electron beam charge and energy, with single-shot charges typically limited to the hundreds-of-pC range; second, the radiation conversion efficiency is significantly influenced by target parameters, necessitating breakthroughs through innovative target structures.
For typical petawatt-class femtosecond laser facility parameters, a capillary-type gas-cell structure target is proposed to generate a near-critical density plasma with a hundred-micrometer scale and a steep density gradient. This gas-cell structure target features low back pressure and minimal gas injection. Due to the confinement by the gas cell walls, a more stable platform-like gas density distribution can be produced within the cell.
Particle-in-cell simulation methods were employed to study the electron acceleration and betatron radiation processes resulting from the interaction of petawatt-class femtosecond lasers with this near-critical density plasma. By adjusting the gas density and laser pulse width, a high-charge and high-energy electron beam can be induced to undergo transverse oscillations within the plasma channel, thereby generating a high-brightness betatron radiation source with a peak photon energy of approximately 8 keV and a brightness of \begin{document}$ 1.75\times {10}^{20}\;\mathrm{p}\mathrm{h}\cdot {\mathrm{s}}^{-1}\cdot {\mathrm{m}\mathrm{m}}^{-2}\cdot {\mathrm{m}\mathrm{r}\mathrm{a}\mathrm{d}}^{-2}\cdot $\end{document} ![]()
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The results indicate that appropriate gas density and laser pulse width are conducive to the stable formation of plasma channels. Within these channels, electrons undergo effective laser wakefield acceleration firstly. These accelerated high-energy electrons interact directly with the tail of the laser. Through betatron resonance and direct laser acceleration, their yield and cutoff energy can be further enhanced. Additionally, the study focuses on the impact of gas density and laser pulse width on the betatron radiation source and elucidates the underlying mechanisms.
2025,
37: 093001.
doi: 10.11884/HPLPB202537.250131
Abstract:
Background Purpose Methods Results Conclusions
With the increasing demand for solid-state, modular, and miniaturized pulsed power systems, wide-band-gap photoconductive semiconductor switches (PCSSs) have attracted significant attention due to their high-power capacity and fast response characteristics.
This study aims to develop a vertical PCSS on high-purity semi-insulating (HPSI) 4H-SiC substrate with an improved package structure to enhance laser energy utilization, while optimizing the pulse-forming circuit to minimize parasitic effects.
We fabricated vertical PCSSs on HPSI 4H-SiC substrates and proposed a novel package structure with a high reflector based on MgF2/TiO2 to improve laser energy utilization. And a slotted pulse-forming line structure is introduced to reduce parasitic inductance.
Under 10 kV bias voltage with 532 nm laser excitation (500 ps pulse width, 90 μJ energy), the system generated 7.6 kV pulses across 50 Ω load with 620 ps rise time and 2.2 ns pulse width. The peak output power reached 1.1 MW with 7.7 dB photoelectric power gain.
The developed SiC PCSS with high-reflector package demonstrates enhanced laser energy utilization. The slotted pulse-forming line effectively reduces parasitic inductance, enabling high-power, fast-response performance suitable for compact pulsed power systems.
2025,
37: 093002.
doi: 10.11884/HPLPB202537.250097
Abstract:
Background Purpose Methods Results Conclusions
High power microwave (HPM) pulse technology has developed rapidly due to its applications in particle accelerators, radar, communications, directed energy, plasma physics, and other fields. Pulse compression technology provides an effective method for enhancing the peak power of microwave pulses.
In order to study a low-cost, miniaturized, stable, and arrayable SLAC Energy Doubler (SLED) based on vacuum electronic oscillators such as magnetrons, a high power fast bi-phase modulator with megawatt-level capacity and nanosecond response time has been designed.
Insert a conventional PIN diode loaded-line type phase-shifting circuit into the waveguide structure, and the equivalent impedance of the phase-shifting circuit changes by switching the “on” and “off” states of the PIN diodes through the waveguide external bias circuit, then the waveguide transmission microwave phase changes. The high-power characteristics of such PIN diode waveguide phase shifters have been verified by high-power experiments.
In this paper, a 180° phase shift is realized by cascading 8 phase-shifting circuit cells. The frequency-domain and time-domain parameters of the designed bi-phase modulator are tested. The frequency-domain test results show that the insertion loss of the bi-phase modulator is less than 0.7 dB, and the phase shift is 172° at the center frequency of 2.458 GHz. The error of the phase shift is within ±4° compared with that of the design value in simulation. The time-domain test results show that the inversion time of the bi-phase modulator is about 5 ns.
Compared with traditional semiconductor phase shifters, this bi-phase modulator can achieve the same phase-reversal speed while withstanding high power capacities, making it extremely valuable in the HPM field.
2025,
37: 093003.
doi: 10.11884/HPLPB202537.250041
Abstract:
Background Purpose Methods Results Conclusions
The confocal waveguide structure can effectively suppress mode competition due to its characteristic of reducing mode density through diffraction loss, thereby facilitating stable operation of gyro-traveling-wave-tube (gyro-TWT) amplifiers in the terahertz (more than 100 GHz) frequency range.
This study aims to conduct a comprehensive analysis of the diffraction loss rate (DLR) in a 220 GHz confocal waveguide gyro-TWT, employing a combination of theoretical analysis and three-dimensional particle-in-cell (3D-PIC) simulations.
The research integrates field distribution theory with 3D-PIC simulations to investigate the DLR of the confocal waveguide. A non-ideal waveguide model incorporating the mirror width angle was utilized, and simulations were performed to evaluate beam-wave interaction dynamics under varying DLR conditions.
The study reveals that a low DLR induces gyro-backward-wave oscillation (GBWO) in low-order competing modes, while a high DLR significantly reduces beam-wave interaction efficiency, gain, and bandwidth, and lowers tolerance to electron beam velocity spread.
For stable single-mode operation of the HE07 mode in the designed gyro-TWT, the DLR should not be less than 0.38 dB/cm, with the corresponding mirror-surface width angle not exceeding 47°. These findings provide crucial design guidelines for terahertz gyro-TWTs.
2025,
37: 093004.
doi: 10.11884/HPLPB202537.250048
Abstract:
Background Purpose Methods Results Conclusions
In modern radar and communication systems, power amplifiers determine the system's transmission output power and bandwidth, thereby affecting key performance metrics such as operating range and resolution. As operating frequencies continue to rise, the output power of a single power amplifier device is limited and cannot fully meet the current demands of radar and communication systems for broadband and high power. Therefore, it is necessary to design power synthesizer to achieve multi-channel power synthesis.
In order to achieve broadband high-power synthesis output in the microwave bands, this paper presents a novel high-power, broadband four-way rectangular waveguide TE10 mode to circular waveguide TE01 mode conversion power synthesizer.
This mode conversion power synthesizer consists of two parts, namely the structure of four rectangular waveguide TE10 mode synthesis and transformation to cross waveguide TE22 mode, and the structure of cross waveguide TE22 mode transformation to overmoded circular waveguide TE01 mode.
The simulation results show that in the Ku-band of 15.2−18.2 GHz, the synthesis efficiency of TE10-TE01 mode is greater than 99.4%, and it can withstand a maximum pulse power output of 1.6 MW. The back-to-back cold test of the experimental verification sample shows that the lowest synthesis efficiency of the power synthesizer in the frequency band of 15.2−18.2 GHz is 94%.
The simulation results and cold test show that the mode conversion power synthesizer has the characteristics of wide working bandwidth, high synthesis efficiency, and high power capacity, which can effectively solve the problem of high-power synthesis output in microwave and millimeter-wave bands.
2025,
37: 093005.
doi: 10.11884/HPLPB202537.250069
Abstract:
Background Purpose Methods Results Conclusions
Terahertz waves are widely utilized in radar, communications, and electronic warfare due to their unique properties, making terahertz radiation sources a critical research focus. As one of the primary terahertz sources, the backward wave oscillator (BWO) is a vacuum electronic device based on the interaction between the electron beam and the slow-wave structure (SWS). As the core component, the SWS significantly influences BWO performance. Recent studies have proposed various terahertz SWS designs, however, high losses in the terahertz band and low interaction impedance of existing SWSs remain key limiting factors for terahertz vacuum electronic devices.
This study aims to address these challenges by proposing a trapezoidal double ridge waveguide (TRWG) SWS, with the goal of enhancing interaction impedance to improve BWO output power.
The electric field distributions of the TRWG, sinusoidal double-ridge waveguide (SRWG), and flat-roofed SRWG were compared. Both on-axis and average interaction impedance were evaluated at the identical normalized phase velocities. The TRWG geometry was optimized through simulation, and input/output structures were designed. Performance comparisons were conducted using particle-in-cell (PIC) simulations.
Simulation results indicate that in the frequency range of 320 to 360 GHz, the average interaction impedance of the TRWG is 78.33%−86.97% higher than that of the SRWG and at least 46.65% higher than that of the flat-roofed SRWG. Under the same operating conditions and within the same frequency range, the output power of the TRWG BWO in the 340 GHz band reaches 5.55−8.03 W, representing an increase of 26.97% to 73.44% compared to the SRWG BWO and an enhancement of 33.65%−52.47% over the flat-roofed SRWG BWO. After optimizing the tube length for all three BWOs, the TRWG BWO is at least 16.5% shorter than the other two structures.
The TRWG SWS exhibits superior interaction impedance and output power compared to the other designs, offering a promising solution for high-performance terahertz BWOs.
2025,
37: 093006.
doi: 10.11884/HPLPB202537.250159
Abstract:
Background Purpose Methods Results Conclusions
Relativistic magnetrons (RMs) are promising high-power microwave (HPM) sources due to their high efficiency, low operating magnetic field, and compact configuration. Miniaturization and lightweight design are critical for expanding their applications. However, the structural dimensions of traditional microwave sources, particularly those operating in low-frequency bands, are constrained by the correlation between wavelength and radial size. As a result, the radial size of their slow-wave structures often needs to be of the same magnitude as the working wavelength, which seriously limits their miniaturization and compact design.
To address this issue, a C-band RM with all-cavity extraction based on metamaterials (MTMs) is proposed in this paper. This design aims to overcome the traditional design limitations, enabling an effective reduction in the device's radial size and weight.
Particle-in-cell (PIC) simulations are conducted using CST Studio Suite to verify the performance of the MTM-based RM. For comparison, a traditional RM with identical key operating parameters such as voltage, magnetic field, internal anode radius, and frequency is simulated to validate the impact of MTMs on reducing the anode outer radius. In addition, preliminary designs of the permanent magnets for both structures are carried out using magnetic field simulation software.
Simulation results show that under an input voltage of 675 kV and a magnetic field of 0.29 T, the designed MTM-based RM generates a TEM-mode output with a power of 1.42 GW at a frequency of 4.3 GHz, corresponding to an efficiency of 52.6%. Compared with that of the traditional RM, when the operating performance metrics are nearly the same, the external anode radius is reduced by 5.5 mm, representing a 12% reduction in size, and the weight of the permanent magnet is reduced by 22.8%.
These results demonstrate that the integration of MTMs effectively reduces the radial size of the C-band RM and the weight of the corresponding permanent magnet, which highlights the significant potential of MTMs in miniaturizing low-frequency HPM sources and provides a viable pathway for the development of lightweight, compact, and practical HPM systems.
2025,
37: 094001.
doi: 10.11884/HPLPB202537.250106
Abstract:
Background Purpose Methods Results Conclusions
In the hard X-ray free electron laser (Shanghai high repetition rate XFEL and extreme light facility, SHINE), the normal-conducting L-band buncher plays a critical role in the compression of electron bunches, significantly improving beam quality and meeting the stringent injection requirements of low emittance and low energy spread.
Due to its 2-cell structure, a dedicated digital low-level RF control system was developed.
This system, based on an architecture comprising FPGA and RF front-end boards, and adopts I/Q demodulation techniques. It incorporates amplitude and phase feedback, frequency tuning, and multi-motor coordination for field flatness control.
During 10 kW continuous-wave (CW) operation, the amplitude stability (peak-to-peak) improved from ±0.17% in open-loop mode to within ±0.03% under closed-loop mode, while the phase stability (peak-to-peak) was controlled within ±0.05°, and field flatness was maintained within ±2%, fully meeting design specifications. Additionally, a radio-frequency (RF) power calibration method based on ADC acquisition of LLRF was proposed.
Experimental results showed calibration error was within ±2% when compared with a power meter, demonstrating reliability of this method as an alternative solution for RF power calibration.
2025,
37: 094002.
doi: 10.11884/HPLPB202537.250024
Abstract:
Background Purpose Methods Results Conclusions
High-repetition-rate electron accelerators face beam instabilities induced by wake fields from beam-vacuum chamber interactions. Geometric discontinuities at ubiquitous con flat (CF) knife-edge flange connections are a dominant source of beam-induced impedance in all-metal vacuum chambers.
To mitigate this impedance, this paper presents the design of an RF-shielded flange-gasket connection structure that achieves a smooth post-tightening transition at the interface, thereby minimizing impedance.
Electromagnetic simulation: 3D simulations (CST) analyzed impedance effects of radial step heights and axial gaps at the transition, establishing allowable parameter ranges. Deformation simulation: ANSYS simulations modeled the shielded flange-copper gasket assembly to preliminarily determine inner diameter specifications for various gasket models. Vacuum sealing tests: Verified ultra-high vacuum integrity under applied tightening torque. Transition geometry testing: Measured the achieved radial step and axial gap post-tightening to define optimal copper gasket dimensions and tightening torque. Comparative simulation: CST simulations compared power loss and impedance for smooth chambers, standard flange-gasket transitions, and the proposed shielded transition.
Electromagnetic simulations were used to define critical tolerance ranges for radial step and axial gap. Deformation simulations were utilized to provide initial gasket inner diameter specifications. Vacuum tests confirmed effective sealing at a tightening torque ≥6 N·m. Transition testing established the optimal tightening torque and key copper gasket dimensions ensuring minimal geometric discontinuity. Comparative simulations demonstrated that the RF-shielded flange-gasket transition significantly reduces power loss and impedance compared to a standard CF transition, achieving performance close to that of a smooth vacuum chamber.
The designed RF-shielded flange-gasket connection structure effectively minimizes geometric discontinuity at the joint. Through combined electromagnetic, mechanical, and vacuum testing, critical parameters, including radial step, axial gap, gasket dimensions, and tightening torque, were optimized.. Electromagnetic verification confirms this design provides effective impedance shielding, offering a solution to mitigate wake-field-induced instabilities at flange connections in high-energy accelerators.
2025,
37: 094003.
doi: 10.11884/HPLPB202537.250022
Abstract:
Background Purpose Methods Results Conclusions
Free electron lasers (FEL) have emerged as significant advanced light sources owing to their unique advantages, including high power, excellent coherence, and wavelength tunability. Given that the peak and average brightness of an FEL depend on the quality of the electron beam generated by its injector, the optimization of the beam injector constitutes a key technical challenge in FEL development. The hefei infrared free electron laser facility is a state-of-the-art, oscillator-type user facility that provides continuously tunable mid-to-far-infrared radiation.
The injector structure of hefei infrared free electron laser is optimized to obtain electron beams with lower emittance, shorter beam length, smaller energy spread and higher peak current intensity, so as to improve the performance of driven infrared free electron laser light source.
The optimization research is carried out by combining beam dynamics simulation with numerical simulation. Based on the previous optimization of the electron gun’s grid structure, the improved design is carried out. A new 12th sub-harmonic buncher is added to the front stage of the existing 6th sub-harmonic buncher, and then the beam is bunched and accelerated using the appropriate traveling-wave buncher. Key parameters including the beam injection phase and the phase velocity variation in the traveling-wave buncher’s tapered section are systematically scanned to achieve 100% bunch capture efficiency and accelerate the electron beam to near-light-speed energy during the bunching stage.
Finally, the beam energy was increased to 64 MeV, and the root mean square length of the whole bunch reached 8.5 ps. The high-energy scattered electrons were filtered out, and the electron beams scattered by ±1% bunch energy were counted. The optimized beam core achieved a root-mean-square longitudinal bunch length of 3.1 ps with an energy spread below 0.23 MeV, while the normalized transverse emittance was reduced to 9.8 mm·mrad. At the same time, the peak current intensity reaches 270 A, which was 2.7 times that of the original optimization results.
The simulation shows that the longitudinal length, energy dispersion and emittance of the core region of the bunch are significantly reduced after optimization, and the peak current intensity is greatly improved. Compared with the original structure, this scheme has significant advantages in the key performance of free electron laser, which has important engineering value for light source upgrading. The optimization method can be extended to the design of other light source injectors.
2025,
37: 094004.
doi: 10.11884/HPLPB202537.250055
Abstract:
Background Purpose Methods Results Conclusions
With the increasing requirement of beam stability in particle accelerators, the accuracy of engineering control network is required to be higher.
This study aims to elaborate on the specific observation scheme for large-scale tunnel control network, and introduce the control network layout, measurement mode and data processing procedures.
In this paper, taking the booster of high energy photon source (HEPS) with a circumference of 454 m as an example, aiming at the disadvantages of narrow space in the tunnel, the control network layout scheme and measurement method based on laser tracker precision measurement are proposed. At the same time, in the face of the problem of data validity detection of multiple stations and close points in the measurement process, the quality control method of adjacent single station fitting and multi-station fitting is proposed, and the point fitting error root mean square (RMS) is better than 0.1 mm.
Finally, the absolute point error RMS of radial, tangential and elevation coordinate components of the control network reaches 0.2 mm, which meets the installation accuracy requirements of the equipment. At the same time, in order to monitor the stability of the booster after the initial construction, two phases of the booster control network were observed over a one-year period. The measurement results show that the deformation of the booster tunnel is about 10 mm within this period. The specific manifestation is that the tunnel foundation expands outward in the three areas of southeast, northwest and southwest.
Overall, the point accuracy of the three directions of the control network is different. The correctness and reliability of the results of the control network can be ensured through multiple control network measurements and data processing and analysis, which provides a reference for other synchrotron radiation light sources.
2025,
37: 094005.
doi: 10.11884/HPLPB202537.250172
Abstract:
Background Purpose Methods Results Conclusions
As the working power of Hall thrusters increases, the overall temperature of the thrusters will rise accordingly. A significant increase in temperature can lead to a decline in work performance and structural failure of the thruster. Therefore, a reasonable thermal design can significantly enhance the performance stability and reliability of Hall thrusters.
The purpose of this paper is to provide engineering guidance for the reasonable thermal design of a 12.5 kW Hall thruster without a cooling plate. In addition, a thermal model of the thruster is established and verified for the continuous optimization of the thruster’s structure.
The heat loss distribution of the 12.5 kW Hall thruster is calculated by theoretical analysis, then FEM (finite element method) is used to bulid the thermal build of a 12.5 kW Hall thruster, and six different thermal design methods are proposed in this paper. In addition, the effectiveness of different thermal design methods is analyzed by finite element simulation combined with a thermal balance experiment.
The results show that the average temperature rise of each thruster part reaches 50~150 ℃ after the cooling plate is removed. Therefore, considering the main heat transfer paths of the thruster, six thermal design methods are proposed and simulated, respectively. The results indicate that Method 4 and Method 6, namely, intercept the radiation heat exchange between the hollow cathode and the inner coil, and increasing the emission coefficient of outer magnetic screen and the outer coil sleeve. Meanwhile, based on Method 1, that is, blocking the heat conduction between the inner coil and the magnetic base, then a 5-mm-thick heat insulation pad is added between the inner coil and the magnetic base. The test results show that the comparison errors between simulations and the measurements of each component are less than 10%, and the comparison error between the magnetic base and the thruster base is the largest, which is caused by the top-down axial heat conduction in the test.
Axial heat conduction and radial heat radiation are the main heat transfer methods of the Hall thruster. According to the research results, the combination of Method 4 and 6 is the most effective way for thermal design optimization. Subsequently, the process will be verified to achieve the purpose of significantly reducing the temperature of the thruster.
2025,
37: 095001.
doi: 10.11884/HPLPB202537.250017
Abstract:
Background Purpose Methods Results Conclusions
Magnetically driven flyer plate technology can be used for the study of high-pressure equation of state and material properties. Generally, when the same force pushes objects of different masses, the lighter object always gains greater velocity. However, in a magnetically driven symmetrical flyer plate launch experiment, the same current drove two flyer plate couple of thicknesses 0.37 mm and 0.48 mm. The final measurement velocity of the 0.37 mm flyer plate couple was 18 km/s, and the final measurement velocity of 0.48 mm flyer plate couple was 19 km/s; that is, the measured velocity of the thick flyer plate couple was even greater.
This paper studies the physical mechanism of this anomalous phenomenon in the magnetically driven symmetrical flyer plate launch experiment.
A two-dimensional magnetically driven simulation code (MDSC2), in which the boundary magnetic field is affected by ablation, was used to simulate and analyze this experiment.
The numerical simulation shows that, the MDSC2 code with the boundary magnetic field affected by ablation can correctly simulate the dynamic process of 0.37 mm and 0.48 mm flyer plate couple, and the simulated velocities of 0.37 mm and 0.48 mm flyer plate couple are consistent with the measured velocities. The reason the final recorded velocity of the thicker flyer plate couple is larger than that of thinner one is that the time to complete melting for the thicker flyer plate is longer than that of thinner one in the magnetically driven symmetrical flyer plate experiment.
This work advances the physical understanding of magnetically driven flyer plate launch process, and further confirms the correctness of the boundary magnetic field formula with the ablation effect.
2025,
37: 095002.
doi: 10.11884/HPLPB202537.250043
Abstract:
Background Purpose Methods Results Conclusions
With the development of active phased array radar systems, the demand for transmit-receive (TR) power supplies has increased significantly. Modern TR modules require power supplies with wide input voltage ranges, high-frequency operation, and high efficiency. dual-active bridge (DAB) converters are widely recognized for their ability to achieve these characteristics, offering diverse control strategies and broad application potential. However, key system parameters such as inductance and switching frequency in DAB converters significantly impact power transmission capabilities and the on-state current of power MOSFETs, posing challenges for optimal design.
This study aims to address these challenges by proposing a parameter optimization design method for DAB converters based on extended phase-shift (EPS) modulation. The goal is to ensure reliable operation under overload conditions while meeting critical design constraints, including maximum power transfer, MOSFET current derating, and output voltage ripple reduction.
The power transfer characteristics and inductor current expressions of the EPS-modulated DAB converter were derived theoretically. A reliability-oriented operating region (ROA) was defined by integrating constraints such as maximum power transfer under overload, MOSFET on-state current derating, and minimum output voltage ripple frequency. The optimization process involved systematic parameter planning to determine optimal inductance values and switching frequencies.
MATLAB simulations of a dual-output DAB converter demonstrated that the proposed method effectively reduced output voltage ripple, minimized MOSFET on-state current, and achieved the desired power output. The simulation results aligned with theoretical predictions, validating the accuracy of the derived equations and the feasibility of the optimization approach.
The EPS-based parameter optimization method provides a systematic framework for designing DAB converters tailored to TR power supply requirements. By addressing key design constraints and leveraging ROA analysis, this approach enhances power transmission efficiency and device reliability. The results highlight the potential of EPS-modulated DAB converters in advanced TR modules, offering a practical solution for high-performance phased array radar systems.
2025,
37: 096001.
doi: 10.11884/HPLPB202537.250009
Abstract:
Background Purpose Methods Results Conclusions
Shutdown dose rate (SDR) analysis plays a critical role in ensuring radiation safety during reactor maintenance, transportation, and decommissioning. Traditional methods such as the direct one-step (D1S) method and the rigorous two-step (R2S) method face limitations in accuracy and implementation, especially for compact and complex geometries like vehicle-mounted micro-nuclear power systems.
This study aims to develop and validate a cell-in-mesh-based R2S method for SDR calculations, with enhanced sampling efficiency and spatial resolution. The goal is to enable accurate prediction of post-shutdown radiation fields for both benchmarking and practical reactor applications.
An improved R2S methodology was implemented by integrating nested cell-in-mesh geometry with a Monte Carlo (MC) transport framework. Photon source sampling was optimized using bounding box division and local mesh-based distribution sampling. The method was validated using the ITER shutdown dose rate benchmark and applied to the Megapower microreactor model, which employs HALEU fuel, heat pipe cooling, and composite shielding.
The developed method produced SDR distributions with statistical deviations below 2% and matched international benchmark results within 4% deviation. In the Megapower case, the highest dose rate (16.3 mSv/h) at a radial location 30 cm occurred near the heat pipe outlet, primarily due to activated structural materials and neutron streaming along the heat pipe path.
The cell-in-mesh-based R2S method improves the accuracy and resolution of SDR calculations without significantly increasing computational costs. It is suitable for advanced shielding analysis of compact nuclear systems and provides a reliable tool for guiding safety design, maintenance planning, and decommissioning strategies.
2025,
37: 096002.
doi: 10.11884/HPLPB202537.250012
Abstract:
Background Purpose Methods Results Conclusions
When the primary system of nuclear reactors experiences overpressure, the overpressure discharge system can be utilized to release high-temperature and high-pressure fluid through the safety valve and downstream pipelines to achieve pressure reduction.
However, the rapid opening of the safety valve can lead to a violent fluid release, which may impose severe transient load impacts on the pipelines and the pool.
Analyzing the typical characteristics and influencing factors of the emission phenomenon can provide references for system operation and design. A systematic analysis model including the pressure vessel, pipelines, and water pool was established. The model was finely divided, with the length of the pipeline control body not exceeding 0.3 m, and the water pool was composed of multiple control bodies. The load was solved using the momentum balance method, and calculation results were compared with the EPRI/CE international test data. The established analysis model can quickly obtain the thermal response and load response during the discharge process.
The results show that during the overpressure discharge process, there is a water seal at the valve inlet and, the opening time reduction will cause the peak load on the pipelines and the water pool to increase.
A decrease in the nozzle immersion depth or an increase in the water pool cross-sectional area will result in a reduction in the peak load at the water pool.
2025,
37: 096003.
doi: 10.11884/HPLPB202537.250061
Abstract:
Background Purpose Methods Results Conclusions
Tritium production pathways are well-established for large pressurized water reactors (PWRs). Integrated small reactors (ISRs), however, operate without soluble boron reactivity control and use no chemical additives (e.g., lithium hydroxide) for pH adjustment, necessitating dedicated analysis of their tritium sources.
This study aims to identify tritium production pathways in ISRs, establish a computational model for quantifying tritium source terms, and propose design optimizations to minimize tritium generation.
A theoretical model was established by solving differential equations for tritium production and removal based on identified neutron activation reaction mechanisms. Key parameters included neutron flux and nuclear cross-sections derived from Monte Carlo simulations of the ISR core. Validation was performed against normalized operational tritium release data from boiling water reactors (BWRs) with analogous B4C control rods and Sb-Be neutron sources, considering thermal power and load factors.
The annual tritium production in ISR primary coolant is 1.81 TBq. The primary contributors are neutron-activated products from Sb-Be and B4C material, accounting for 46% and 51% of the total production, respectively. Analysis of tritium discharge data from operational BWRs validates the conservatism of the theoretical results.
Optimizing secondary neutron sources (canceling Sb-Be or using double-encapsulated cladding) and replacing B4C control rods with non-tritium-producing absorbers (e.g., Ag-In-Cd or hafnium) could reduce ISR tritium production significantly. These measures are technically feasible based on PWRs operational experience and are recommended for ISR design enhancements. Future work will refine release fractions of control rods using plant-specific operational data.
2025,
37: 096004.
doi: 10.11884/HPLPB202537.240438
Abstract:
Background Purpose Methods Results Conclusions
In high-temperature pebble bed cores, radiative heat transfer plays a crucial role, where the view factor is a key parameter in determining radiative exchange between particles. Traditional methods for calculating view factors rely on complex integration, which varies with geometric configurations and is computationally intensive.
This study aims to accurately calculate view factors in randomly packed pebble beds. It proposes a ray tracing model based on thermal radiation mechanisms to simplify the calculation of view factors between particles in complex packing structures.
Firstly, the particle surface is discretized to generate uniformly distributed ray origin points. Secondly, ray directions are determined based on the characteristics of thermal emission. Thirdly, rays defined in local coordinates are transformed into global space and traced for intersections with target particles. Finally, the view factor is computed as the ratio of rays that collide with target particles to the total number of emitted rays.
The results show that inter-particle radiation is mainly concentrated at the center line and decays towards the periphery, showing a clear cosine distribution. The radiation range of a single particle is mainly concentrated within twice the particle diameter, at which point the view factor exceeds 0.98 and the number of particles is less than 100. Within three times the diameter, the cumulative view factor exceeds 0.99.
The proposed quasi-Monte Carlo ray tracing model provides an accurate and efficient method for computing view factors in dense particle systems. It effectively captures the anisotropic nature of radiative transfer in randomly packed beds and offers a practical tool for analysing thermal radiation in high-temperature pebble beds.
2025,
37: 096005.
doi: 10.11884/HPLPB202537.250051
Abstract:
Background Purpose Methods Results Conclusions
Single-phase AC-input low-ripple DC regulated power supplies are critical for sensitive applications. However, conventional designs often suffer from complex power circuit configurations, increasing cost and size while potentially compromising reliability. Achieving simultaneously low output voltage ripple, high steady-state accuracy, and wide output voltage adjustability remains a significant challenge in power electronics.
This study aims to overcome the limitations of existing topologies by proposing a novel single-phase AC-input low-ripple adjustable DC regulated power supply circuit. Furthermore, it develops a dedicated advanced control strategy to meet stringent performance requirements for low-ripple and high-stability.
The fundamental principles of the proposed topology were analyzed, and its mathematical model was established to characterize voltage transmission. A composite control scheme integrating reference output voltage amplitude self-compensation using improved iterative learning control (ILC), and a dual-loop proportional complex integral (PCI) control structure, was designed for precise low-ripple regulation and stability. The effectiveness was validated via simulation and experimental testing on a prototype.
Validation confirmed successful operation. Comparative analysis demonstrated the topology’s advantages: a simpler and more compact structure, widely adjustable output voltage, significantly reduced ripple, and improved steady-state accuracy. The control strategy effectively ensured stability and met performance targets.
The combined novel topology and advanced control provide a viable solution for high-quality single-phase AC-input adjustable DC supplies.
2025,
37: 099001.
doi: 10.11884/HPLPB202537.250090
Abstract:
Background Purpose Methods Results Conclusions
The structure of cantilever has existed in solid surface antenna for high power microwave system. It is difficult to maintain the low acceleration for feed source structure of solid surface antenna during external vibration excitation. The traditional dynamic vibration absorber has a good control effect on the structure of cantilever. However, the application of traditional dynamic vibration absorber is limited to a narrow range of frequency.
This study aims to solve the problems of large acceleration and narrow range of frequency in traditional vibration absorber of solid surface antenna. A kind of active vibration control method combined with optimal passive absorber is proposed in this paper.
Firstly, the best installed position of dynamic absorber is obtained by analyzing and simulating the model of solid surface antenna. Secondly, the optimal parameters are calculated according to the mathematical model of simplified passive dynamic absorber system. Thirdly, the sliding mode control parameters were obtained by considering the external excitation using an active absorber method. Finally, the stability of sliding mode control method was demonstrated.
This control method combined sliding mode control with an active control absorber, which can reduce the vibration response of antenna effectively. This paper simulated the two-degree-of-freedom vibration system with active control absorber, which gave time-domain vibration response of antenna. The top point displacement of antenna under the predetermined excitation was reduced more than 95% by comparing the condition of no control strategy.
This vibration control method can effectively reduce acceleration for feed source structure, enabling it to maintain a more stable state. Furthermore, this controller can be extended to control the acceleration of various cantilever structures in pulse power equipment.
2025,
37: 094006.
doi: 10.11884/HPLPB202537.250108
Abstract:
Background Purpose Methods Results Conclusions
Aluminum, as a critical constituent material for missile casings, undergoes ablation phase transformation under X-ray irradiation, resulting in structural damage to the surface layer of the missile casing.
The aim of this research is to deeply explore the interaction between X rays and aluminum materials, observe the key physical phenomena during the process, and understand the mechanism of the thermal effect of X-ray irradiation on aluminum foil.
Through multi-scale modeling and simulation, while considering the temperature changes of both the electronic system and the lattice system, the TTM-MD model was selected to conduct thermal effect simulation of X-ray interaction with the material. The temperature of the surface electrons of the material was used to characterize the energy of the incident X rays, in order to simulate the rapid temperature rise process of electrons when X-rays act on the surface of aluminum foil. In-depth research was conducted on the energy deposition of X rays on the aluminum foil and the heat conduction process within the material.
By analyzing the specific influence of X-ray energy on the thermal effect of aluminum foil, the evolution laws of physical parameters such as electron and lattice temperatures, and material density over time were obtained. At the same time, the influence laws of X-ray irradiation on the thermal effect of aluminum foil were also explored: During the X-ray irradiation of the aluminum foil, the energy of the X rays is absorbed by the aluminum foil material and converted into thermal energy. This heating effect leads to a decrease in the surface density of the aluminum foil and its gradual deposition towards the deeper layers. At the same time, the temperature increase caused by the irradiation also results in a dynamic response of the internal pressure of the aluminum foil, which first increases sharply and then gradually stabilizes. The changes in these physical parameters are not only closely related to the irradiation conditions but are also influenced by the inherent properties of the aluminum foil material.
Through multi-scale modeling and simulation studies, this paper analyzed the specific influence of X-ray energy on the thermal effects of aluminum foil, and obtained the evolution laws of physical parameters such as electron and lattice temperatures, and material density over time. The multi-scale simulation method successfully captured the characteristics of these changes, providing a perspective for understanding the thermal effects of aluminum foil under X-ray irradiation.
Effects of electromagnetic pulse and single event effect on electrical characteristics of SOI MOSFET
2025,
37: 096006.
doi: 10.11884/HPLPB202537.250047
Abstract:
Background Purpose Methods Results Conclusions
In space environments, electronic systems are vulnerable to various adverse effects, including electromagnetic pulses (EMP) and particle radiation, which can significantly degrade device performance and reliability. Silicon-on-insulator (SOI) MOSFETs are widely used in aerospace applications due to their excellent electrical characteristics, but their response to the combined radiation effects needs further investigation.
This study aims to analyze the effects of electromagnetic pulses and heavy-ion induced single-particle events on the electrical characteristics of short-channel SOI MOSFETs. It also explores the synergistic impact of when both effects occur simultaneously, providing insights for improving the device robustness in harsh space conditions.
A two-dimensional TCAD-based numerical model of short-channel SOI MOSFETs was developed, incorporating impact ionization, carrier generation and recombination, heat transfer, and thermodynamic effects. Electromagnetic pulses were modeled as transient voltage pulses with varying amplitudes, while heavy-ion effects were simulated through charge deposition profiles characterized by linear energy transfer (LET) parameters. The influence of gate voltage, channel length, and LET on device behavior was systematically studied.
Simulation results indicate that EMP-induced voltage transients can cause avalanche breakdown in the drain PN junction, with the breakdown voltage decreasing as gate bias increases or channel length shortens. The internal electric field, current density, and device temperature intensify during breakdown. Heavy-ion irradiation generates electron-hole pairs, causing transient increases in drain current, which lowers the avalanche breakdown threshold when combined with EMP. Higher LET values further exacerbate device degradation by increasing ionization effects and reducing breakdown voltages. The combined effects produce more severe electrical deterioration compared to single effects.
The research demonstrates that both EMP and heavy-ion irradiation can markedly weaken the electrical stability of short-channel SOI MOSFETs. These findings underscore the importance of designing radiation-hardened devices for space applications. The study provides a theoretical basis for future investigations into the synergistic effects of radiation phenomena on power semiconductor devices.
2025,
37: 099002.
doi: 10.11884/HPLPB202537.250133
Abstract:
Background Purpose Methods Results Conclusions
Optical scattering characteristics are crucial features of space targets and play a vital role in target recognition and detection systems. Traditional methods are limited in simulating optical scattering properties -which only provide optical cross-section (OCS), scattering characteristics, or synthetic target images.
To address the above limitations and meet requirements of rendering spatial target, this paper conducts a comprehensive study on the computational modeling of optical scattering characteristics for space targets.
A systematic workflow is proposed, along with formulas for calculating target OCS, target irradiance, sky background luminance, target magnitude, signal-to-noise ratio (SNR), and detection probability. By integrating solar radiation properties, observer-site positioning, and celestial-terrestrial background sphere radiation characteristics, a graphics processing unit (GPU) accelerated framework combined with shading languages is implemented to compute time-dependent optical scattering properties, including target OCS, detector-received target/background optical power, target magnitude, SNR, detection probability, and synthetic brightness imagery.
Experimental validation using spherical and cylindrical objects confirms the accuracy of the OCS calculations. Simulations under varying observer locations, reflective properties, and detection windows demonstrate the rationality of the computed optical scattering characteristics.
This study provides a complete set of formulas, parameters, and results, offering significant value for research on space target optical scattering modeling and image-based recognition.
