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, Available online ,
doi: 10.11884/HPLPB202537.240413
Abstract:
In high-energy laser systems, the performance parameters of large-aperture sampling optics determine the accuracy of beam testing and evaluation, as well as the precision of overall system performance control. This paper focuses on the performance testing requirements of sampling optics with high-reflectivity (HR) on the front surface and anti-reflectivity (AR) on the back surface. Utilizing the cavity ring-down (CRD) based reflectivity uniformity testing of large-aperture sampling optics, the reflectivity distribution, optical loss, and high-resolution scanning imaging of defects of sampling optics are obtained by scanning measuring the incident light form both the reflective film surface and the anti-reflective film surface, respectively. Furthermore, by comparing and analyzing the defect distribution maps, the classification of defects in the reflective film, transmissive film, and substrate of the sampling optics can be achieved. Finally, by establishing a dual channel CRD system, the residual reflectance distribution of anti-reflective film and the types of defects in the transmissive film were obtained. The testing and analysis method proposed in this paper provides a systematic and comprehensive characterization tool for the performance evaluation and defect analysis of sampling optics.
In high-energy laser systems, the performance parameters of large-aperture sampling optics determine the accuracy of beam testing and evaluation, as well as the precision of overall system performance control. This paper focuses on the performance testing requirements of sampling optics with high-reflectivity (HR) on the front surface and anti-reflectivity (AR) on the back surface. Utilizing the cavity ring-down (CRD) based reflectivity uniformity testing of large-aperture sampling optics, the reflectivity distribution, optical loss, and high-resolution scanning imaging of defects of sampling optics are obtained by scanning measuring the incident light form both the reflective film surface and the anti-reflective film surface, respectively. Furthermore, by comparing and analyzing the defect distribution maps, the classification of defects in the reflective film, transmissive film, and substrate of the sampling optics can be achieved. Finally, by establishing a dual channel CRD system, the residual reflectance distribution of anti-reflective film and the types of defects in the transmissive film were obtained. The testing and analysis method proposed in this paper provides a systematic and comprehensive characterization tool for the performance evaluation and defect analysis of sampling optics.
, Available online ,
doi: 10.11884/HPLPB202537.240444
Abstract:
This paper reports on a room-temperature Yb:YAG rod laser with high power and high beam quality. The oscillator utilizes a moderately doped Yb:YAG rod crystal (Yb3+ concentration 2.0 at%) and employs quasi-continuous-wave end-pumping. At a repetition rate of 100 Hz, it achieved a 22 W linearly polarized laser output, with a slope efficiency of 53.5% and an optical-to-optical efficiency of 47.4%, while maintaining a beam quality of M2 = 1.22. Using acousto-optic Q-switching, the laser produced a 20.8 W pulse output with an energy of 9.9 mJ and a beam quality of M2 = 1.39, demonstrating the laser's capability for high-repetition-rate Q-switched pulse output.
This paper reports on a room-temperature Yb:YAG rod laser with high power and high beam quality. The oscillator utilizes a moderately doped Yb:YAG rod crystal (Yb3+ concentration 2.0 at%) and employs quasi-continuous-wave end-pumping. At a repetition rate of 100 Hz, it achieved a 22 W linearly polarized laser output, with a slope efficiency of 53.5% and an optical-to-optical efficiency of 47.4%, while maintaining a beam quality of M2 = 1.22. Using acousto-optic Q-switching, the laser produced a 20.8 W pulse output with an energy of 9.9 mJ and a beam quality of M2 = 1.39, demonstrating the laser's capability for high-repetition-rate Q-switched pulse output.
, Available online ,
doi: 10.11884/HPLPB202537.240400
Abstract:
In order to effectively solve the problem of strong electromagnetic pulse power required to drive particle reactions, a new pulse power synchronous amplification technology based on hydrogen plasma loading and wave-particle resonance mechanism is studied on the basis of piezoelectric ceramic stack pulse source. The amplification mechanism is as follows: first, the energy of hydrogen molecule bonding orbitals is lower than that of antibonding orbitals, and internal energy will be released during the ionization process to promote the efficient occurrence of the ionization process driven by pulse power; Second, after the ionization of hydrogen atoms, the electromagnetic field and electrons undergo wave-particle resonance, and the electron energy is synchronously converted into electromagnetic field energy. After the amplification of wave-particle resonance, a stronger electromagnetic pulse is obtained, which can form a spherical electromagnetic field when applied to the spiral electrode, and has an extremely high acceleration gradient, which can accelerate a large number of protons produced after efficient ionization of hydrogen atoms. In this paper, the above theory is effectively proved through experimental tests and simulation analysis, and this research is expected to lay a foundation for a miniaturized and low-cost proton generator driven by strong electromagnetic pulses.
In order to effectively solve the problem of strong electromagnetic pulse power required to drive particle reactions, a new pulse power synchronous amplification technology based on hydrogen plasma loading and wave-particle resonance mechanism is studied on the basis of piezoelectric ceramic stack pulse source. The amplification mechanism is as follows: first, the energy of hydrogen molecule bonding orbitals is lower than that of antibonding orbitals, and internal energy will be released during the ionization process to promote the efficient occurrence of the ionization process driven by pulse power; Second, after the ionization of hydrogen atoms, the electromagnetic field and electrons undergo wave-particle resonance, and the electron energy is synchronously converted into electromagnetic field energy. After the amplification of wave-particle resonance, a stronger electromagnetic pulse is obtained, which can form a spherical electromagnetic field when applied to the spiral electrode, and has an extremely high acceleration gradient, which can accelerate a large number of protons produced after efficient ionization of hydrogen atoms. In this paper, the above theory is effectively proved through experimental tests and simulation analysis, and this research is expected to lay a foundation for a miniaturized and low-cost proton generator driven by strong electromagnetic pulses.
, Available online ,
doi: 10.11884/HPLPB202537.240401
Abstract:
In this paper, the working principle, composition and configuration of a miniaturized high-throughput neutron source system are introduced. This paper systematically introduces the piezoelectric pulse power source technology, nuclear reaction design technology, spherical electromagnetic field generation technology, particle proximity acceleration technology, particle polarization and resonance collision technology required for the development of this neutron source system. A complete neutron source physical system was developed and tested for energy spectrum and flux. The expected physical phenomena were observed in the experiments, and the occurrence of nuclear reactions was proved by online and offline neutron measurement methods, and the test results showed that the neutron radiation flux of the new miniature neutron source with a diameter of 2 cm and a length of 4 cm reached the level of 1010 n/(cm2·s), which belongs to strong neutron radiation source.
In this paper, the working principle, composition and configuration of a miniaturized high-throughput neutron source system are introduced. This paper systematically introduces the piezoelectric pulse power source technology, nuclear reaction design technology, spherical electromagnetic field generation technology, particle proximity acceleration technology, particle polarization and resonance collision technology required for the development of this neutron source system. A complete neutron source physical system was developed and tested for energy spectrum and flux. The expected physical phenomena were observed in the experiments, and the occurrence of nuclear reactions was proved by online and offline neutron measurement methods, and the test results showed that the neutron radiation flux of the new miniature neutron source with a diameter of 2 cm and a length of 4 cm reached the level of 1010 n/(cm2·s), which belongs to strong neutron radiation source.
, Available online ,
doi: 10.11884/HPLPB202537.240131
Abstract:
The Peking University (petawatt) laser proton accelerator develops a laser proton radiotherapy system in response to the needs of proton radiation tumor treatment. The common collection section of its horizontal and vertical beam lines mainly consists of three superconducting solenoids (S1-S3). Large stresses are generated in the solenoids during the cooling down and excitation process, in addition, the superconducting solenoids are operated by fast ramping, and the AC loss in the process will have an important impact on the solenoid excitation speed and stable operation. In this paper, the highest field strength and the most complex structure of 7.8T-120 mm solenoid S1 is taken as the research object, and COMSOL Multiphysics software is used to carry out the stress analysis of superconducting solenoids under multi-field conditions, and at the same time, the simulation of the AC loss due to the rapid change of the current is carried out. Subsequently, corresponding experimental studies were carried out to obtain the variation curves of strain with temperature, correlations betweencurrent, magnetic field and strain correspondingly. According to the experiment data, there is a significant positive correlation between the measured values of magnetic field and strain and the change of current, which verifies the rationality of the superconducting solenoid design. It provides experience and reference for the subsequent design and development of similar superconducting magnets.
The Peking University (petawatt) laser proton accelerator develops a laser proton radiotherapy system in response to the needs of proton radiation tumor treatment. The common collection section of its horizontal and vertical beam lines mainly consists of three superconducting solenoids (S1-S3). Large stresses are generated in the solenoids during the cooling down and excitation process, in addition, the superconducting solenoids are operated by fast ramping, and the AC loss in the process will have an important impact on the solenoid excitation speed and stable operation. In this paper, the highest field strength and the most complex structure of 7.8T-120 mm solenoid S1 is taken as the research object, and COMSOL Multiphysics software is used to carry out the stress analysis of superconducting solenoids under multi-field conditions, and at the same time, the simulation of the AC loss due to the rapid change of the current is carried out. Subsequently, corresponding experimental studies were carried out to obtain the variation curves of strain with temperature, correlations betweencurrent, magnetic field and strain correspondingly. According to the experiment data, there is a significant positive correlation between the measured values of magnetic field and strain and the change of current, which verifies the rationality of the superconducting solenoid design. It provides experience and reference for the subsequent design and development of similar superconducting magnets.
, Available online ,
doi: 10.11884/HPLPB202537.240407
Abstract:
This paper conducts a detailed study on the influence of second-harmonic parasitic effects in non-collinear ultra-broadband degenerate optical parametric amplification (OPA), which is pumped by frequency-doubled Ti:sapphire lasers. We consider both walk-off compensation and non-walk-off compensation scenarios. The study reveals that, under the non-walk-off compensation method, by appropriately increasing the non-collinear angle between the pump and signal beams, the impact of second-harmonic parasitic effects on the signal's output spectrum can be effectively reduced while ensuring broad-spectrum amplification of the signal. The evolution of the signal's output spectrum and output flux is investigated for different pump spectral bandwidths, clarifying the requirements for the pump spectral bandwidth given a specific signal output spectral bandwidth. The research findings provide design guidelines for generating ultra-broadband, high-temporal contrast femtosecond seed based on degenerate OPA.
This paper conducts a detailed study on the influence of second-harmonic parasitic effects in non-collinear ultra-broadband degenerate optical parametric amplification (OPA), which is pumped by frequency-doubled Ti:sapphire lasers. We consider both walk-off compensation and non-walk-off compensation scenarios. The study reveals that, under the non-walk-off compensation method, by appropriately increasing the non-collinear angle between the pump and signal beams, the impact of second-harmonic parasitic effects on the signal's output spectrum can be effectively reduced while ensuring broad-spectrum amplification of the signal. The evolution of the signal's output spectrum and output flux is investigated for different pump spectral bandwidths, clarifying the requirements for the pump spectral bandwidth given a specific signal output spectral bandwidth. The research findings provide design guidelines for generating ultra-broadband, high-temporal contrast femtosecond seed based on degenerate OPA.
, Available online ,
doi: 10.11884/HPLPB202537.240392
Abstract:
The influence of grating height on the diffraction efficiency of SU-8 micron gratings was studied.The diffraction efficiency of gratings with heights of 6-8 μm, 12-16 μm, and 6-30 μm was simulated and analyzed using rigorous coupled wave theory. The simulation results show that when the grating height is 6 μm, the 0th order diffraction efficiency is the lowest and the 1st order diffraction efficiency is the highest; At 12 μm, the 0th order diffraction efficiency is the highest and the 1st order diffraction efficiency is the lowest. When the grating height continuously changes from 6-30 μm, the diffraction efficiency varies periodically. SU-8 thin films with different thicknesses were prepared, and 40 μm periodic gratings with different gate heights were fabricated using picosecond laser etching technology. The measurement results show that when the grating height of the 40 μm period grating is 6.83 μm, the -1st order diffraction efficiency is 28.4%, and the 0th order diffraction efficiency is about 14.7%; When the grating height is 13.45 μm , the 0th order diffraction efficiency is 31.46% and the 1st order diffraction efficiency is 12.35%. The magnitude of the 0th and 1st order diffraction efficiencies varies with the grating height period. Theoretical simulation and experimental exploration will provide important references for the preparation of SU-8 micron gratings and the improvement of first-order diffraction efficiency.
The influence of grating height on the diffraction efficiency of SU-8 micron gratings was studied.The diffraction efficiency of gratings with heights of 6-8 μm, 12-16 μm, and 6-30 μm was simulated and analyzed using rigorous coupled wave theory. The simulation results show that when the grating height is 6 μm, the 0th order diffraction efficiency is the lowest and the 1st order diffraction efficiency is the highest; At 12 μm, the 0th order diffraction efficiency is the highest and the 1st order diffraction efficiency is the lowest. When the grating height continuously changes from 6-30 μm, the diffraction efficiency varies periodically. SU-8 thin films with different thicknesses were prepared, and 40 μm periodic gratings with different gate heights were fabricated using picosecond laser etching technology. The measurement results show that when the grating height of the 40 μm period grating is 6.83 μm, the -1st order diffraction efficiency is 28.4%, and the 0th order diffraction efficiency is about 14.7%; When the grating height is 13.45 μm , the 0th order diffraction efficiency is 31.46% and the 1st order diffraction efficiency is 12.35%. The magnitude of the 0th and 1st order diffraction efficiencies varies with the grating height period. Theoretical simulation and experimental exploration will provide important references for the preparation of SU-8 micron gratings and the improvement of first-order diffraction efficiency.
, Available online ,
doi: 10.11884/HPLPB202537.240257
Abstract:
To facilitate online replacement and maintenance of solid-state power sources in particle accelerators, a cavity power combiner with online decoupling capability is required. While cavity combiners offer high power capacity, adjustable input coupling has not been achievable online. Therefore, we designed a 650 MHz eight-in-one cavity power combiner with a rotatable decoupling system. By integrating non-contact open-circuit slits at the RF input port and separating the coupling loop from the cavity, we enabled online rotation adjustment of the magnetic coupling loop. This adjustment allows real-time tuning of input coupling according to the operational status of solid-state power sources, facilitating hot-swapping and efficiency optimization. Simulation results demonstrate high synthesis efficiency and minimal power loss, with excellent amplitude consistency between input and output ports (deviations within 0.25 dB). The ability to adjust coupling online enhances RF isolation at input ports, enabling seamless hot-swappable replacement of power amplifier modules and significantly improving maintainability and flexibility.
To facilitate online replacement and maintenance of solid-state power sources in particle accelerators, a cavity power combiner with online decoupling capability is required. While cavity combiners offer high power capacity, adjustable input coupling has not been achievable online. Therefore, we designed a 650 MHz eight-in-one cavity power combiner with a rotatable decoupling system. By integrating non-contact open-circuit slits at the RF input port and separating the coupling loop from the cavity, we enabled online rotation adjustment of the magnetic coupling loop. This adjustment allows real-time tuning of input coupling according to the operational status of solid-state power sources, facilitating hot-swapping and efficiency optimization. Simulation results demonstrate high synthesis efficiency and minimal power loss, with excellent amplitude consistency between input and output ports (deviations within 0.25 dB). The ability to adjust coupling online enhances RF isolation at input ports, enabling seamless hot-swappable replacement of power amplifier modules and significantly improving maintainability and flexibility.
, Available online ,
doi: 10.11884/HPLPB202537.240386
Abstract:
During the integration of High Power Microwave (HPM) systems, the docking condition of the microwave source and the transmission-emission subsystem affects the HPM system performance directly. Poor docking conditions may cause radio frequency breakdown at the connection surface, which will result in the reduction of the entire system’s output power. Therefore, diagnosing the docking state of the system is of great engineering significance. For this reason, a non-contact high-power microwave transmission technology is investigated in this paper, and an injection power measurement method is proposed for a Ku-band GW-level HPM system using a conical horn as the feed source. Based on simulation designs, key subassembly of the technology was developed. In addition, the small signal test and power handling capacity assessment of the subassembly were carried out. The experimental outcomes demonstrated that the reflection coefficient was consistently below −26 dB, the coupling coefficient was (−0.31±0.07) dB within the frequency band of (15±0.15) GHz, and the power handling capacity exceeded 900 MW. The experimental and simulation results show that not only the proposed measurement technology has the characteristics of stable coupling coefficient and low test errors, but also can effectively measure the microwave power injected by HPM source through the feed-horn and diagnose the docking state of the HPM system.
During the integration of High Power Microwave (HPM) systems, the docking condition of the microwave source and the transmission-emission subsystem affects the HPM system performance directly. Poor docking conditions may cause radio frequency breakdown at the connection surface, which will result in the reduction of the entire system’s output power. Therefore, diagnosing the docking state of the system is of great engineering significance. For this reason, a non-contact high-power microwave transmission technology is investigated in this paper, and an injection power measurement method is proposed for a Ku-band GW-level HPM system using a conical horn as the feed source. Based on simulation designs, key subassembly of the technology was developed. In addition, the small signal test and power handling capacity assessment of the subassembly were carried out. The experimental outcomes demonstrated that the reflection coefficient was consistently below −26 dB, the coupling coefficient was (−0.31±0.07) dB within the frequency band of (15±0.15) GHz, and the power handling capacity exceeded 900 MW. The experimental and simulation results show that not only the proposed measurement technology has the characteristics of stable coupling coefficient and low test errors, but also can effectively measure the microwave power injected by HPM source through the feed-horn and diagnose the docking state of the HPM system.
, Available online ,
doi: 10.11884/HPLPB202537.240360
Abstract:
A simple and effective improved A* algorithm is proposed to solve the problem of robot path planning in the integrated installation of large-scale laser devices. Compared with the traditional A* algorithm, the algorithm has been improved in three steps. Firstly, the walking direction is limited, which avoids the phenomenon of crossing obstacles occurred in the traditional A* algorithm; Secondly, the heuristic function is optimized as a weighted Manhattan distance function, which accelerates the expansion of nodes to X direction or Y direction, and reduces the surge of traversal nodes caused by limiting the walking direction. Thirdly, the turning penalty term is introduced to reduce the turning times in the path planning process, and improve the search efficiency and quality. The performance of the three-step improved A* algorithm is verified in different size raster maps, and compared with the traditional A* algorithm. Experimental results show that in simple maps, the number of nodes traversed by the three-step improved A* algorithm is slightly higher than that of the traditional A* algorithm, and the number of turns is equivalent to that of the traditional A* algorithm, but the obstacle avoidance performance is obviously better than that of the traditional A* algorithm, which is more conducive to the safe walking of robots. In complex maps, considering the priority relationship of traversal nodes, turn times and path length, the parameters of the three-step improved A* algorithm can be adjusted to obtain the optimal path planning result.
A simple and effective improved A* algorithm is proposed to solve the problem of robot path planning in the integrated installation of large-scale laser devices. Compared with the traditional A* algorithm, the algorithm has been improved in three steps. Firstly, the walking direction is limited, which avoids the phenomenon of crossing obstacles occurred in the traditional A* algorithm; Secondly, the heuristic function is optimized as a weighted Manhattan distance function, which accelerates the expansion of nodes to X direction or Y direction, and reduces the surge of traversal nodes caused by limiting the walking direction. Thirdly, the turning penalty term is introduced to reduce the turning times in the path planning process, and improve the search efficiency and quality. The performance of the three-step improved A* algorithm is verified in different size raster maps, and compared with the traditional A* algorithm. Experimental results show that in simple maps, the number of nodes traversed by the three-step improved A* algorithm is slightly higher than that of the traditional A* algorithm, and the number of turns is equivalent to that of the traditional A* algorithm, but the obstacle avoidance performance is obviously better than that of the traditional A* algorithm, which is more conducive to the safe walking of robots. In complex maps, considering the priority relationship of traversal nodes, turn times and path length, the parameters of the three-step improved A* algorithm can be adjusted to obtain the optimal path planning result.
, Available online ,
doi: 10.11884/HPLPB202537.240186
Abstract:
When the photoconductive switch operates continuously under the working conditions of long pulse width and high repetition frequency, due to the existence of a certain conduction resistance, the thermal deposition phenomenon inside the switch is relatively serious, which is likely to cause thermal damage and thermal breakdown of the photoconductive switch, seriously affecting the service life of the photoconductive switch. Therefore, it is necessary to effectively dissipate heat from the high-power photoconductive switch. The conventional cooling circulation system uses the method of pumping out by a circulation pump to cool the object. There are problems such as too high or too low pressure of the cooling medium during the circulation process, resulting in uneven cooling of the object, which is extremely likely to cause damage to the object. In addition, the impeller of the circulation pump will generate bubbles during the circulation process, reducing the insulation strength of the photoconductive switch and leading to flashover breakdown along the surface. To address this issue, this paper has developed a cooling system that eliminates bubbles based on the negative pressure suction mechanism and achieves precise temperature control through a dual-loop system. This system has achieved good heat dissipation for the photoconductive switch. Under the conditions of a working voltage of 11 kV, an output current of 560 A, a pulse width of 55 ns, and a repetition frequency of 1 kHz, the service life of the photoconductive switch has reached 106 times, significantly increasing the service life of the photoconductive switch.
When the photoconductive switch operates continuously under the working conditions of long pulse width and high repetition frequency, due to the existence of a certain conduction resistance, the thermal deposition phenomenon inside the switch is relatively serious, which is likely to cause thermal damage and thermal breakdown of the photoconductive switch, seriously affecting the service life of the photoconductive switch. Therefore, it is necessary to effectively dissipate heat from the high-power photoconductive switch. The conventional cooling circulation system uses the method of pumping out by a circulation pump to cool the object. There are problems such as too high or too low pressure of the cooling medium during the circulation process, resulting in uneven cooling of the object, which is extremely likely to cause damage to the object. In addition, the impeller of the circulation pump will generate bubbles during the circulation process, reducing the insulation strength of the photoconductive switch and leading to flashover breakdown along the surface. To address this issue, this paper has developed a cooling system that eliminates bubbles based on the negative pressure suction mechanism and achieves precise temperature control through a dual-loop system. This system has achieved good heat dissipation for the photoconductive switch. Under the conditions of a working voltage of 11 kV, an output current of 560 A, a pulse width of 55 ns, and a repetition frequency of 1 kHz, the service life of the photoconductive switch has reached 106 times, significantly increasing the service life of the photoconductive switch.
, Available online ,
doi: 10.11884/HPLPB202537.240299
Abstract:
For a facility used multi-group magnetic cores, it's operation stability will be affected by the different working points of multi-group magnetic cores reset in parallel. A direct current reset system of the multi-pulse induction cells is developed instead of the original parallel pulsed reset system of a multi-pulse high power Linear Induction Accelerator (LIA) at burst mode. Resetting multi-group magnetic cores one by one is realized by separate relay switch for every induction cell and constant current sources with periodical output with the direct current reset system, the inconsistency in working points caused by parallel pulsed reset is effectively resolved. During engineering implementation, the system operates with two sets of constant current sources and eight switch control boxes to reset 94 groups of induction cell magnetic cores, significantly reducing system complexity and maintenance costs. Practical validation demonstrates that the improved accelerator exhibits enhanced multi-pulse stability, with beam centroid position jitter reduced from 1.3 mm to less than 1 mm. This paper describes the physics design of the direct current reset unit, and introduces the layout of the whole reset system which include the main units. The improvement effect is also presented in this paper.
For a facility used multi-group magnetic cores, it's operation stability will be affected by the different working points of multi-group magnetic cores reset in parallel. A direct current reset system of the multi-pulse induction cells is developed instead of the original parallel pulsed reset system of a multi-pulse high power Linear Induction Accelerator (LIA) at burst mode. Resetting multi-group magnetic cores one by one is realized by separate relay switch for every induction cell and constant current sources with periodical output with the direct current reset system, the inconsistency in working points caused by parallel pulsed reset is effectively resolved. During engineering implementation, the system operates with two sets of constant current sources and eight switch control boxes to reset 94 groups of induction cell magnetic cores, significantly reducing system complexity and maintenance costs. Practical validation demonstrates that the improved accelerator exhibits enhanced multi-pulse stability, with beam centroid position jitter reduced from 1.3 mm to less than 1 mm. This paper describes the physics design of the direct current reset unit, and introduces the layout of the whole reset system which include the main units. The improvement effect is also presented in this paper.
, Available online ,
doi: 10.11884/HPLPB202537.240411
Abstract:
To address the wideband and beam scanning requirements of high-power microwave (HPM) systems, this paper proposes an X-band varactor-based high-power wideband beam-scanning reflectarray antenna. The antenna employs a linearly polarized horn feed and a sandwich-structured embedded patch element, where the nested dual-resonance structure integrated with varactors simultaneously extends the phase tuning range (360°) and operational bandwidth. By eliminating abrupt structural discontinuities and adopting a sandwich dielectric configuration, the design effectively suppresses triple-junction formation, achieving a power capacity of 5 MW in 1 atm SF6 environment. Varactor capacitance adjustment enables a 12% relative tuning bandwidth within 8.55-9.65 GHz. Simulations of an 11×11 rectangular grid reflectarray demonstrate: a maximum gain of 25.12 dBi with 54.39% aperture efficiency for a 242-mm aperture, and full-band 0°～20° beam scanning capability. Compared with existing technologies, this design exhibits superior tuning bandwidth (12%) and power capacity (5 MW), providing an effective solution for wideband beam control in HPM systems.
To address the wideband and beam scanning requirements of high-power microwave (HPM) systems, this paper proposes an X-band varactor-based high-power wideband beam-scanning reflectarray antenna. The antenna employs a linearly polarized horn feed and a sandwich-structured embedded patch element, where the nested dual-resonance structure integrated with varactors simultaneously extends the phase tuning range (360°) and operational bandwidth. By eliminating abrupt structural discontinuities and adopting a sandwich dielectric configuration, the design effectively suppresses triple-junction formation, achieving a power capacity of 5 MW in 1 atm SF6 environment. Varactor capacitance adjustment enables a 12% relative tuning bandwidth within 8.55-9.65 GHz. Simulations of an 11×11 rectangular grid reflectarray demonstrate: a maximum gain of 25.12 dBi with 54.39% aperture efficiency for a 242-mm aperture, and full-band 0°～20° beam scanning capability. Compared with existing technologies, this design exhibits superior tuning bandwidth (12%) and power capacity (5 MW), providing an effective solution for wideband beam control in HPM systems.
, Available online ,
doi: 10.11884/HPLPB202537.250001
Abstract:
Terahertz waves, spanning the millimeter and submillimeter wavelength ranges between the microwave and far-infrared regions (approximately 3 mm to 30 μm), represent a critical spectral range in astrophysical and cosmological research. Of the photons detectable since the beginning of the universe, approximately 98% fall within the terahertz and far-infrared bands. A significant proportion of these photons originate from the cosmic microwave background radiation, while others arise from excited molecules that exhibit bright spectral emissions in the terahertz range. As a result, terahertz-based astronomical observation techniques are becoming increasingly essential for investigating the universe’s fundamental properties. Through the observation of interstellar atoms, molecules, and dust, terahertz astronomy provides valuable insights into the internal conditions of the interstellar medium and offers a unique observational window into the formation and evolution of stars, planets, galaxies, and the universe itself. In recent years, many large astronomical telescopes have begun incorporating terahertz detectors based on microwave kinetic inductance detector (MKID), positioning MKID as a pivotal technology in the field of terahertz astronomical detection. This paper outlines the fundamental principles of MKID, reviews recent advancements in their application to terahertz detection, and discusses future developments in this promising area of research.
Terahertz waves, spanning the millimeter and submillimeter wavelength ranges between the microwave and far-infrared regions (approximately 3 mm to 30 μm), represent a critical spectral range in astrophysical and cosmological research. Of the photons detectable since the beginning of the universe, approximately 98% fall within the terahertz and far-infrared bands. A significant proportion of these photons originate from the cosmic microwave background radiation, while others arise from excited molecules that exhibit bright spectral emissions in the terahertz range. As a result, terahertz-based astronomical observation techniques are becoming increasingly essential for investigating the universe’s fundamental properties. Through the observation of interstellar atoms, molecules, and dust, terahertz astronomy provides valuable insights into the internal conditions of the interstellar medium and offers a unique observational window into the formation and evolution of stars, planets, galaxies, and the universe itself. In recent years, many large astronomical telescopes have begun incorporating terahertz detectors based on microwave kinetic inductance detector (MKID), positioning MKID as a pivotal technology in the field of terahertz astronomical detection. This paper outlines the fundamental principles of MKID, reviews recent advancements in their application to terahertz detection, and discusses future developments in this promising area of research.
, Available online ,
doi: 10.11884/HPLPB202537.240346
Abstract:
Aiming at the problems of low extraction accuracy and weak anti-interference ability of line structure light centroids in turbid water bodies, this study proposes an improved internal advancement algorithm, which aims to enhance the accuracy and robustness of the extraction of line structure light centroids in complex environments. Firstly, the median filter is used to preprocess the image to suppress the noise, and combined with the eight-neighborhood method to quickly locate the starting point of the light stripe; subsequently, the grayscale neighborhood attribute method is introduced to dynamically estimate the pixel width of the current line of the line structured light, and based on the range of the maximum interclass variance method is applied to adaptively determine the binarized threshold value, which effectively reduces the background interference; finally, the grayscale gravity method is used to calculate the initial centroid in the constrained range of pixel widths and use this as the basis to advance upward and downward to search for the center point of the line structured light. Comparison tests are conducted in various turbid water environments and different structured light patterns. The results show that compared with the original internal advancement algorithm, the root mean square error of this paper's method is reduced by 13.33%, and the running speed of the algorithm is increased by 69.07% compared with Steger's algorithm, which realizes the balance between accuracy and speed.
Aiming at the problems of low extraction accuracy and weak anti-interference ability of line structure light centroids in turbid water bodies, this study proposes an improved internal advancement algorithm, which aims to enhance the accuracy and robustness of the extraction of line structure light centroids in complex environments. Firstly, the median filter is used to preprocess the image to suppress the noise, and combined with the eight-neighborhood method to quickly locate the starting point of the light stripe; subsequently, the grayscale neighborhood attribute method is introduced to dynamically estimate the pixel width of the current line of the line structured light, and based on the range of the maximum interclass variance method is applied to adaptively determine the binarized threshold value, which effectively reduces the background interference; finally, the grayscale gravity method is used to calculate the initial centroid in the constrained range of pixel widths and use this as the basis to advance upward and downward to search for the center point of the line structured light. Comparison tests are conducted in various turbid water environments and different structured light patterns. The results show that compared with the original internal advancement algorithm, the root mean square error of this paper's method is reduced by 13.33%, and the running speed of the algorithm is increased by 69.07% compared with Steger's algorithm, which realizes the balance between accuracy and speed.
, Available online ,
doi: 10.11884/HPLPB202537.240229
Abstract:
To optimize the performance of the pulsed xenon lamp sterilization device, the influence of spectral range and specifications of lamps on the sterilization effect is studied based on a self-developed high-energy microsecond pulse power supply and xenon lamps with different specifications. The results show that in the UV-visible spectrum of a xenon lamp with an arc length of 50 mm and a pressure of 50 kPa, the UV accounts for 38.5% and the UVC accounts for 17.6%. Increasing the arc length and decreasing the pressure can both increase the spectral intensity, and the latter can also increase the ratio of UV. The xenon lamp with an arc length of 100 mm and a pressure of 50 kPa can basically inactivate all Escherichia coli in 3 seconds with a discharge energy of 20 J. The sterilization rate is positively correlated with arc length and discharge energy of the lamp, negatively correlated with pressure. The all bands of xenon lamp radiation have sterilization effects, with UV accounting for 87.7% and the wavelength band less than 280 nm accounting for 64.6%. The AFM images show that pulsed xenon lamp changed the morphology and mechanical properties of Escherichia coli, hence the bacteria shrank, their surface roughness, elasticity, and adhesion increased.
To optimize the performance of the pulsed xenon lamp sterilization device, the influence of spectral range and specifications of lamps on the sterilization effect is studied based on a self-developed high-energy microsecond pulse power supply and xenon lamps with different specifications. The results show that in the UV-visible spectrum of a xenon lamp with an arc length of 50 mm and a pressure of 50 kPa, the UV accounts for 38.5% and the UVC accounts for 17.6%. Increasing the arc length and decreasing the pressure can both increase the spectral intensity, and the latter can also increase the ratio of UV. The xenon lamp with an arc length of 100 mm and a pressure of 50 kPa can basically inactivate all Escherichia coli in 3 seconds with a discharge energy of 20 J. The sterilization rate is positively correlated with arc length and discharge energy of the lamp, negatively correlated with pressure. The all bands of xenon lamp radiation have sterilization effects, with UV accounting for 87.7% and the wavelength band less than 280 nm accounting for 64.6%. The AFM images show that pulsed xenon lamp changed the morphology and mechanical properties of Escherichia coli, hence the bacteria shrank, their surface roughness, elasticity, and adhesion increased.
, Available online ,
doi: 10.11884/HPLPB202537.240271
Abstract:
The ionization profile monitor (IPM) can provide critical beam distribution information required for real-time debugging and stable operation of high-current proton accelerators. The IPM system of the China Spallation Neutron Source (CSNS) Linac adopts a compact structural design. It collects data in ion mode and performs one-dimensional transverse beam distribution measurement through an optical imaging system. However, the honeycomb mesh structure at the electrode plate apertures blocks some ions or electrons from entering the microchannel plate, causing imaging shadows and introducing beam distribution distortion. Offline numerical algorithms must be used for correction. In this paper, partial differential equation (PDE) restoration and machine learning algorithms are used to correct the imaging shadows and beam distribution distortion caused by the honeycomb mesh of the IPM in the CSNS linac. The unsupervised machine learning method DIP (Deep Image Prior) was employed, and the corrected beam size deviates from the theoretical expectation by less than 10%, while maintaining a good signal-to-noise ratio.
The ionization profile monitor (IPM) can provide critical beam distribution information required for real-time debugging and stable operation of high-current proton accelerators. The IPM system of the China Spallation Neutron Source (CSNS) Linac adopts a compact structural design. It collects data in ion mode and performs one-dimensional transverse beam distribution measurement through an optical imaging system. However, the honeycomb mesh structure at the electrode plate apertures blocks some ions or electrons from entering the microchannel plate, causing imaging shadows and introducing beam distribution distortion. Offline numerical algorithms must be used for correction. In this paper, partial differential equation (PDE) restoration and machine learning algorithms are used to correct the imaging shadows and beam distribution distortion caused by the honeycomb mesh of the IPM in the CSNS linac. The unsupervised machine learning method DIP (Deep Image Prior) was employed, and the corrected beam size deviates from the theoretical expectation by less than 10%, while maintaining a good signal-to-noise ratio.
, Available online ,
doi: 10.11884/HPLPB202537.240408
Abstract:
In a surface nuclear leakage scenario, radiation neutrons undergo multiple scatterings with atomic nuclei in the material, rapidly reducing their energy to the thermal neutron range (a few eV). The activation of thermal neutrons significantly impacts the nuclear reaction process. In solid and liquid materials, nuclei typically exist in bound states, differing from free nuclei in gaseous form regarding their interaction with matter. To accurately assess nuclear radiation effects, this study investigates the impact of bound-nucleus effects on thermal neutron activation. Using the Monte Carlo method for particle transport simulation, an air-ground interface model was developed based on surface nuclear radiation scenarios. The study modeled neutron beam interactions with soil, seawater, and concrete, focusing on thermal neutron activation reactions. By incorporating bound-nucleus effects through adjusted reaction cross-sections, the study calculated and compared changes in secondary gamma flux before and after considering these effects. The results show that accounting for bound-nucleus effects enhances thermal neutron activation in solid and liquid media, thereby increasing surface secondary gamma field intensity. Due to factors such as elemental composition and particle shielding, the maximum increases in secondary gamma flux were 18%, 8%, and 11% for the three media, with varying patterns of flux increase over detection distances.
In a surface nuclear leakage scenario, radiation neutrons undergo multiple scatterings with atomic nuclei in the material, rapidly reducing their energy to the thermal neutron range (a few eV). The activation of thermal neutrons significantly impacts the nuclear reaction process. In solid and liquid materials, nuclei typically exist in bound states, differing from free nuclei in gaseous form regarding their interaction with matter. To accurately assess nuclear radiation effects, this study investigates the impact of bound-nucleus effects on thermal neutron activation. Using the Monte Carlo method for particle transport simulation, an air-ground interface model was developed based on surface nuclear radiation scenarios. The study modeled neutron beam interactions with soil, seawater, and concrete, focusing on thermal neutron activation reactions. By incorporating bound-nucleus effects through adjusted reaction cross-sections, the study calculated and compared changes in secondary gamma flux before and after considering these effects. The results show that accounting for bound-nucleus effects enhances thermal neutron activation in solid and liquid media, thereby increasing surface secondary gamma field intensity. Due to factors such as elemental composition and particle shielding, the maximum increases in secondary gamma flux were 18%, 8%, and 11% for the three media, with varying patterns of flux increase over detection distances.
, Available online ,
doi: 10.11884/HPLPB202537.240280
Abstract:
To improve the vacuum surface flashover of insulators, in this paper, a kind of composite surface structure consisting of micro grooves and molecule self-assembly membrane was proposed and prepared on the surface of alumina vacuum insulators by laser carving, water cleaning and molecule self-assembly. Meanwhile, insulators with only micro grooves or pure molecule membrane were also prepared. Secondary electron emission yield test shows that both the micro groove construction and molecule self-assembly can decrease the secondary electron emission yield of the alumina insulator. Their combination the composite surface structure can further decrease the secondary electron emission yield. Correspondingly, surface flashover voltage test indicated that surface micro groove construction and molecule self-assembly could both improve the surface flashover voltages and their combination could further improve the flashover voltages. The results demonstrate that molecule membrane and the micro grooves in the composite structure can form dual suppression to the development of the vacuum flashover.
To improve the vacuum surface flashover of insulators, in this paper, a kind of composite surface structure consisting of micro grooves and molecule self-assembly membrane was proposed and prepared on the surface of alumina vacuum insulators by laser carving, water cleaning and molecule self-assembly. Meanwhile, insulators with only micro grooves or pure molecule membrane were also prepared. Secondary electron emission yield test shows that both the micro groove construction and molecule self-assembly can decrease the secondary electron emission yield of the alumina insulator. Their combination the composite surface structure can further decrease the secondary electron emission yield. Correspondingly, surface flashover voltage test indicated that surface micro groove construction and molecule self-assembly could both improve the surface flashover voltages and their combination could further improve the flashover voltages. The results demonstrate that molecule membrane and the micro grooves in the composite structure can form dual suppression to the development of the vacuum flashover.
, Available online ,
doi: 10.11884/HPLPB202537.240349
Abstract:
In order to improve the performance of waveform digital readout systems based on Analog to Digital Converter (ADC) technology, this paper proposes a multi-channel mismatch error estimation calibration method. Used two domestically produced high-speed ADCs to form a Time-interleaved A/D Conversion (TIADC) system, and the estimation of channel mismatch error (Gain, Time-skew and Offset) can be obtained by integrating particle swarm optimization (PSO) algorithm and gradient descent (GD) method. Meanwhile, using filter equations and Kaiser window truncation to obtain compensation calibration filter coefficient values. This compensation method can be directly implemented on the TIADC hardware platform using Field-Programmable Gate Array(FPGA) as the central processing unit. Moreover this algorithm can achieve online reconstruction of sampling system data. The experimental results show that the algorithm can effectively compensate for channel mismatch errors, and using the behavior level simulation of Vivado development software, the spurious free dynamic range (SFDR) is increased from 32.1 dBFS to 53.1 dBFS, Improve the SFDR to 60.8 dBFS during hardware platform testing. Also this signal reconstruction method is easy to implement in hardware systems and is not limited by the number of channels. has high engineering applicability. This method has high engineering applicability and is simple and easy to implement.
In order to improve the performance of waveform digital readout systems based on Analog to Digital Converter (ADC) technology, this paper proposes a multi-channel mismatch error estimation calibration method. Used two domestically produced high-speed ADCs to form a Time-interleaved A/D Conversion (TIADC) system, and the estimation of channel mismatch error (Gain, Time-skew and Offset) can be obtained by integrating particle swarm optimization (PSO) algorithm and gradient descent (GD) method. Meanwhile, using filter equations and Kaiser window truncation to obtain compensation calibration filter coefficient values. This compensation method can be directly implemented on the TIADC hardware platform using Field-Programmable Gate Array(FPGA) as the central processing unit. Moreover this algorithm can achieve online reconstruction of sampling system data. The experimental results show that the algorithm can effectively compensate for channel mismatch errors, and using the behavior level simulation of Vivado development software, the spurious free dynamic range (SFDR) is increased from 32.1 dBFS to 53.1 dBFS, Improve the SFDR to 60.8 dBFS during hardware platform testing. Also this signal reconstruction method is easy to implement in hardware systems and is not limited by the number of channels. has high engineering applicability. This method has high engineering applicability and is simple and easy to implement.
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).
Display Method:
, Available online ,
doi: 10.11884/HPLPB202537.240433
Abstract:
The output characteristics of a narrow line width optical parametric oscillator with KTP as the nonlinear crystal pumped by a 532 nm wavelength all-solid-state quasi-continuous-wave Nd:YAG laser are studied. A quartz etalon is inserted into the resonant cavity to compress the output laser line width. Through theoretical analysis, the transmission spectra line width of the etalon for the idler wave within the pulsed optical parametric oscillator’s resonant cavity is estimated. Based on the calculation results, the parameters of the etalon for experimental use are designed. By inserting another KTP crystal into the optical parametric oscillator resonant cavity to perform intracavity frequency doubling on the idler, a tunable yellow laser output with a wavelength tuning range of 574.5-577.2 nm and a pm-level line width is achieved. At a repetition rate of 10 kHz and an average pump power of 30 W, the peak wavelength of the frequency doubled yellow light is 575.81 nm, with a corresponding average output power of 155 mW and a pulse width of about 35 ns. The line width at the peak wavelength is only 0.8 pm, and the beam quality factor in the x and y directions is measured respectively as 1.286 and 1.807.
The output characteristics of a narrow line width optical parametric oscillator with KTP as the nonlinear crystal pumped by a 532 nm wavelength all-solid-state quasi-continuous-wave Nd:YAG laser are studied. A quartz etalon is inserted into the resonant cavity to compress the output laser line width. Through theoretical analysis, the transmission spectra line width of the etalon for the idler wave within the pulsed optical parametric oscillator’s resonant cavity is estimated. Based on the calculation results, the parameters of the etalon for experimental use are designed. By inserting another KTP crystal into the optical parametric oscillator resonant cavity to perform intracavity frequency doubling on the idler, a tunable yellow laser output with a wavelength tuning range of 574.5-577.2 nm and a pm-level line width is achieved. At a repetition rate of 10 kHz and an average pump power of 30 W, the peak wavelength of the frequency doubled yellow light is 575.81 nm, with a corresponding average output power of 155 mW and a pulse width of about 35 ns. The line width at the peak wavelength is only 0.8 pm, and the beam quality factor in the x and y directions is measured respectively as 1.286 and 1.807.
, Available online ,
doi: 10.11884/HPLPB202537.250011
Abstract:
The geoelectric fields induced by late-time high altitude electromagnetic pulse (HEMP E3) and geomagnetic storms lead to low frequency geomagnetically induced currents in the transmission grids, and the resulting half-cycle saturation of a large number of transformers could potentially threaten the power system voltage stability. However, in the existing study on HEMP E3 effect evaluation, it is typically assuming a uniform or 1D layered earth structure, without adequately considering the influence of lateral variations in earth conductivity on the induced geoelectric fields. Thus, it is difficult to rigorously assess the electromagnetic security of power systems under complex geological conditions such as coasts. This paper establishes a 3D computational model for HEMP E3 geoelectric fields based on finite element method, then studies the influence of complex earth conductivity structure on the spatiotemporal distribution of HEMP E3 geoelectric fields, and finally evaluates the power system voltage stability via electromagnetic transient simulation method. The results uncover substantial changes in the amplitude and duration of HEMP E3 geoelectric fields near the conductivity interface, which may lead to significant deviation in the voltage stability results of the power system. The method developed in this paper provides an important basis for the HEMP effect evaluation and protection of infrastructure located in complex geological areas.
The geoelectric fields induced by late-time high altitude electromagnetic pulse (HEMP E3) and geomagnetic storms lead to low frequency geomagnetically induced currents in the transmission grids, and the resulting half-cycle saturation of a large number of transformers could potentially threaten the power system voltage stability. However, in the existing study on HEMP E3 effect evaluation, it is typically assuming a uniform or 1D layered earth structure, without adequately considering the influence of lateral variations in earth conductivity on the induced geoelectric fields. Thus, it is difficult to rigorously assess the electromagnetic security of power systems under complex geological conditions such as coasts. This paper establishes a 3D computational model for HEMP E3 geoelectric fields based on finite element method, then studies the influence of complex earth conductivity structure on the spatiotemporal distribution of HEMP E3 geoelectric fields, and finally evaluates the power system voltage stability via electromagnetic transient simulation method. The results uncover substantial changes in the amplitude and duration of HEMP E3 geoelectric fields near the conductivity interface, which may lead to significant deviation in the voltage stability results of the power system. The method developed in this paper provides an important basis for the HEMP effect evaluation and protection of infrastructure located in complex geological areas.
, Available online ,
doi: 10.11884/HPLPB202537.240426
Abstract:
This study focuses on the performance of vertical photoconductive semiconductor switch (PCSS) based on Fe: β-Ga2O3 under high voltage. The results show that deep levels in Fe: β-Ga2O3 can provide carriers of non-intrinsic excitation. The device did not exhibit breakdown tendencies when subjected to a 20 kV input voltage with single-shot laser triggering. After more than5000 trigger cycles at 15 kV by a 10 Hz laser, the switch eventually failed. Nevertheless, pulse performance remained stable throughout the effective data collection period, preliminarily demonstrating the potential of Ga2O3 PCSS for applications in extreme conditions such as high power and high frequency. Failure analysis indicates that a wide bandgap is not the sole determinant of high breakdown voltage. In addition to employing precise doping techniques to introduce specific defects and modify material properties, further improvements in existing material growth methods and device packaging structures can also contribute to enhancing the output and lifetime of PCSS.
This study focuses on the performance of vertical photoconductive semiconductor switch (PCSS) based on Fe: β-Ga2O3 under high voltage. The results show that deep levels in Fe: β-Ga2O3 can provide carriers of non-intrinsic excitation. The device did not exhibit breakdown tendencies when subjected to a 20 kV input voltage with single-shot laser triggering. After more than
, Available online ,
doi: 10.11884/HPLPB202537.250028
Abstract:
The signal compensation method based on Wiener filtering has been demonstrated to have excellent compensation performance towards the signal distortion induced by the long-distance transmission in coaxial cable. However, how the parameters of this compensation method affect the compensation performance has not yet been investigated and analyzed, which may in turn bring some obstacles in the practical utilization of this modified method. Herein, we carried out a systematic study on the effect of the parameters on the signal compensation performance of this modified method. The results show that: for the signal-to-noise ratio (SNR), When the SNR is less than 25 dB, the compensation performance is continuously improved as the SNR increases. Once the SNR attains～25 dB, the relative error (δ) in between the compensated signal and input signal nearly keeps unchanged. For the sampling frequency interval Δf in S21 parameter measurement, the compensation performance keeps unchanged when Δf is small, and the compensation performance slowly deteriorates as Δf exceeds a certain value. As for the power estimation method, it is proved that among the traditional power estimation methods, the Burg method can obtain better compensation performance. This study can provide a beneficial reference for the application of the signal compensation method based on Wiener filtering.
The signal compensation method based on Wiener filtering has been demonstrated to have excellent compensation performance towards the signal distortion induced by the long-distance transmission in coaxial cable. However, how the parameters of this compensation method affect the compensation performance has not yet been investigated and analyzed, which may in turn bring some obstacles in the practical utilization of this modified method. Herein, we carried out a systematic study on the effect of the parameters on the signal compensation performance of this modified method. The results show that: for the signal-to-noise ratio (SNR), When the SNR is less than 25 dB, the compensation performance is continuously improved as the SNR increases. Once the SNR attains～25 dB, the relative error (δ) in between the compensated signal and input signal nearly keeps unchanged. For the sampling frequency interval Δf in S21 parameter measurement, the compensation performance keeps unchanged when Δf is small, and the compensation performance slowly deteriorates as Δf exceeds a certain value. As for the power estimation method, it is proved that among the traditional power estimation methods, the Burg method can obtain better compensation performance. This study can provide a beneficial reference for the application of the signal compensation method based on Wiener filtering.
, Available online ,
doi: 10.11884/HPLPB202537.240412
Abstract:
With the continuous development of photoconductive microwave technology towards high-frequency, high-power, long-life, and high-efficiency directions, lateral photoconductive devices have the potential to achieve high photoelectric gain and high main frequency response due to intrinsic light triggering and low parasitic capacitance. We investigated the photocurrent response of intrinsic light back-illuminated lateral silicon carbide (SiC) photoconductive switches. Based on semiconductor numerical simulation, the output photocurrent of the device under intrinsic light triggering with different substrate thicknesses and different light powers was compared for front and back illumination. The internal current and electric field distribution of the device were analyzed and compared. Finally, experimental tests were conducted on the front and back triggering of a 50 μm lateral SiC photoconductive switch. The experimental results show that under a 40 kW peak light power, the on-resistance of the back-triggered device is reduced by 40% compared to the front-triggered device, confirming the high photoelectric conversion efficiency of the back-illuminated device, and the internal electric field and current of the back-triggered device are more uniform, which is more conducive to improving the device’s high-power capacity. The results provide simulation and experimental references for the intrinsic triggering of planar photoconductive switches.
With the continuous development of photoconductive microwave technology towards high-frequency, high-power, long-life, and high-efficiency directions, lateral photoconductive devices have the potential to achieve high photoelectric gain and high main frequency response due to intrinsic light triggering and low parasitic capacitance. We investigated the photocurrent response of intrinsic light back-illuminated lateral silicon carbide (SiC) photoconductive switches. Based on semiconductor numerical simulation, the output photocurrent of the device under intrinsic light triggering with different substrate thicknesses and different light powers was compared for front and back illumination. The internal current and electric field distribution of the device were analyzed and compared. Finally, experimental tests were conducted on the front and back triggering of a 50 μm lateral SiC photoconductive switch. The experimental results show that under a 40 kW peak light power, the on-resistance of the back-triggered device is reduced by 40% compared to the front-triggered device, confirming the high photoelectric conversion efficiency of the back-illuminated device, and the internal electric field and current of the back-triggered device are more uniform, which is more conducive to improving the device’s high-power capacity. The results provide simulation and experimental references for the intrinsic triggering of planar photoconductive switches.
, Available online ,
doi: 10.11884/HPLPB202537.240383
Abstract:
The insulating property of water medium affects the operation status of pulse power device, and air bubbles in water are the main factor causing breakdown of water medium. In order to remove air bubbles and dissolved gases in the water medium, the causes of air bubbles in the water medium are analyzed, and for the removal of body-phase air bubbles and surface adsorption air bubbles in the water medium, the methods of removing air bubbles by using vortex separators and reverse osmosis membranes are compared, and experimental research is carried out to study the performance of their air bubble removal. The results show that the vortex separator's low cyclonic strength leads to low separation efficiency, and the reverse osmosis membrane degassing makes the surface adsorbed bubbles re-dissolve by reducing the solubility of the gas in the water, and the separation efficiency is high, which can remove the gas bubbles and dissolved gases in the water, and it is of great significance for the stable operation of the pulsed power device.
The insulating property of water medium affects the operation status of pulse power device, and air bubbles in water are the main factor causing breakdown of water medium. In order to remove air bubbles and dissolved gases in the water medium, the causes of air bubbles in the water medium are analyzed, and for the removal of body-phase air bubbles and surface adsorption air bubbles in the water medium, the methods of removing air bubbles by using vortex separators and reverse osmosis membranes are compared, and experimental research is carried out to study the performance of their air bubble removal. The results show that the vortex separator's low cyclonic strength leads to low separation efficiency, and the reverse osmosis membrane degassing makes the surface adsorbed bubbles re-dissolve by reducing the solubility of the gas in the water, and the separation efficiency is high, which can remove the gas bubbles and dissolved gases in the water, and it is of great significance for the stable operation of the pulsed power device.
, Available online ,
doi: 10.11884/HPLPB202537.240240
Abstract:
In response to the timing requirements for the commissioning and offline operation of many pre-research equipments at the China Spallation Neutron Source Phase II (CSNS-II), a synchronous timing system has been designed and developed independently based on “high-precision timing generator + low-jitter fiber optical transmission link”, which provides accurate triggers for the pre-research equipments in accordance with the physical design requirements. The hardware mainly consists of with cost-effective master boards and terminal boards, which realize strict synchronization and low-jitter transmission. Meanwhile, the master board has the ability to expand the number of output channels by using multimode optical fiber to realize the cascade connection of the hardware boards through high-speed serial transmission links; the upper software adopts adopts the method of "Serial Server + PC soft IOC" to realise the data interaction mechanism between the master board and Experimental Physics and Industrial Control System (EPICS), which can accurately configure the frequency, delay, pulse width and other parameters remotely. The synchronous timing system has been successfully used in the commissioning and operation of key pre-research equipments such as the radio frequency ion source of the CSNS-II, which has been operated stably and reliably for a long period of time. In addition, compared with commercial products, the synchronous timing system has the advantages of flexible design, strong anti-interference capability, and high versatility, which can provide a practical technical reference for the design and realisation of synchronous timing system for particle accelerator equipment at home and abroad.
In response to the timing requirements for the commissioning and offline operation of many pre-research equipments at the China Spallation Neutron Source Phase II (CSNS-II), a synchronous timing system has been designed and developed independently based on “high-precision timing generator + low-jitter fiber optical transmission link”, which provides accurate triggers for the pre-research equipments in accordance with the physical design requirements. The hardware mainly consists of with cost-effective master boards and terminal boards, which realize strict synchronization and low-jitter transmission. Meanwhile, the master board has the ability to expand the number of output channels by using multimode optical fiber to realize the cascade connection of the hardware boards through high-speed serial transmission links; the upper software adopts adopts the method of "Serial Server + PC soft IOC" to realise the data interaction mechanism between the master board and Experimental Physics and Industrial Control System (EPICS), which can accurately configure the frequency, delay, pulse width and other parameters remotely. The synchronous timing system has been successfully used in the commissioning and operation of key pre-research equipments such as the radio frequency ion source of the CSNS-II, which has been operated stably and reliably for a long period of time. In addition, compared with commercial products, the synchronous timing system has the advantages of flexible design, strong anti-interference capability, and high versatility, which can provide a practical technical reference for the design and realisation of synchronous timing system for particle accelerator equipment at home and abroad.
, Available online ,
doi: 10.11884/HPLPB202537.250004
Abstract:
Laser wireless energy transmission technology has the advantages of high power, long transmission distance, non-contact operation, and simultaneous energy and information transmission, and is expected to become a revolutionary energy transmission method, showing great application potential in consumer electronics, drones, aerospace and other fields. In this paper, the core module of laser wireless energy transmission technology and its development status in the fields of ground, aerospace and underwater at home and abroad are analyzed, and the technical challenges are summarized. Finally, the future development trend of laser wireless energy transmission system is discussed.
Laser wireless energy transmission technology has the advantages of high power, long transmission distance, non-contact operation, and simultaneous energy and information transmission, and is expected to become a revolutionary energy transmission method, showing great application potential in consumer electronics, drones, aerospace and other fields. In this paper, the core module of laser wireless energy transmission technology and its development status in the fields of ground, aerospace and underwater at home and abroad are analyzed, and the technical challenges are summarized. Finally, the future development trend of laser wireless energy transmission system is discussed.
, Available online ,
doi: 10.11884/HPLPB202436.240163
Abstract:
The quantitative study of combat effectiveness index is crucial for the informatization construction of the armed forces. To solve the problems of limits of quantitative research, low method accuracy, and weak robustness in the study of combat effectiveness index, and to break through the limitations of dominating complex rules, multivariate mathematical models, and strong coupling of influencing factors in the combat effectiveness index function, inspired by the mathematical analysis methods of rules in fuzzy logic theory, we proposed a local approximation based method for fitting combat effectiveness index function. Combining the powerful self-learning and self-deduction capabilities of neural networks, we constructed a corresponding quantitative calculation model based on radial basis function (RBF). Simulation comparative experiments show that the proposed method has an error rate of about 2% and 6% lower than the current best performing method using global approximation, and exhibits stronger robustness. Our method has strong practicality, can be migrated to other military fields, and has good engineering application prospects.
The quantitative study of combat effectiveness index is crucial for the informatization construction of the armed forces. To solve the problems of limits of quantitative research, low method accuracy, and weak robustness in the study of combat effectiveness index, and to break through the limitations of dominating complex rules, multivariate mathematical models, and strong coupling of influencing factors in the combat effectiveness index function, inspired by the mathematical analysis methods of rules in fuzzy logic theory, we proposed a local approximation based method for fitting combat effectiveness index function. Combining the powerful self-learning and self-deduction capabilities of neural networks, we constructed a corresponding quantitative calculation model based on radial basis function (RBF). Simulation comparative experiments show that the proposed method has an error rate of about 2% and 6% lower than the current best performing method using global approximation, and exhibits stronger robustness. Our method has strong practicality, can be migrated to other military fields, and has good engineering application prospects.
Column
- Cover and Contents
- High Power Laser Physics and Technology
- Inertial Confinement Fusion Physics and Technology
- High Power Microwave Technology
- Particle Beams and Accelerator Technology
- Pulsed Power Technology
- Nuclear Science and Engineering
- Advanced Interdisciplinary Science
- Special Column of 4th Symposium on Frontier of HPLPB
- Research News
Display Method:
2025, 37: 051001.
doi: 10.11884/HPLPB202537.240370
Abstract:
Compared with single-band object detection technology, multispectral object detection technology greatly improves the accuracy of object detection and the robustness in dealing with complex environments by capturing the reflection or radiation information of objects in multiple spectral bands of different wavelengths. Therefore, it has extensive applications in fields such as remote sensing, agricultural detection, environmental protection, industrial production, and national defense security. However, the field of multispectral object detection still faces severe challenges at present: the lack of diverse high-quality datasets and efficient object detection algorithms seriously restricts further development and application of this technology. In view of this, this paper comprehensively explains the production method of multispectral object detection datasets and the important progress of multispectral object detection algorithms. First, the article systematically analyzes the construction process of multispectral datasets, including data acquisition, preprocessing, and data annotation, aiming to provide technical support for the subsequent construction of high-quality multispectral object detection datasets. Second, this paper comprehensively analyzes the historical context of the development of object detection algorithms. These algorithms cover object detection algorithms based on traditional feature extraction technologies, deep learning methods, and their improved versions. In addition, this paper summarizes the key improvements made by algorithm developers in terms of feature fusion, model architecture, and sub-networks to improve the performance of multispectral object detection based on deep learning-based object detection algorithms. Finally, this paper discusses future development direction of multispectral object detection technology, hoping to indicate potential research hotspots and application fields for researchers, and promote the wider application of multispectral object detection technology in actual scenarios and enhance its social value.
Compared with single-band object detection technology, multispectral object detection technology greatly improves the accuracy of object detection and the robustness in dealing with complex environments by capturing the reflection or radiation information of objects in multiple spectral bands of different wavelengths. Therefore, it has extensive applications in fields such as remote sensing, agricultural detection, environmental protection, industrial production, and national defense security. However, the field of multispectral object detection still faces severe challenges at present: the lack of diverse high-quality datasets and efficient object detection algorithms seriously restricts further development and application of this technology. In view of this, this paper comprehensively explains the production method of multispectral object detection datasets and the important progress of multispectral object detection algorithms. First, the article systematically analyzes the construction process of multispectral datasets, including data acquisition, preprocessing, and data annotation, aiming to provide technical support for the subsequent construction of high-quality multispectral object detection datasets. Second, this paper comprehensively analyzes the historical context of the development of object detection algorithms. These algorithms cover object detection algorithms based on traditional feature extraction technologies, deep learning methods, and their improved versions. In addition, this paper summarizes the key improvements made by algorithm developers in terms of feature fusion, model architecture, and sub-networks to improve the performance of multispectral object detection based on deep learning-based object detection algorithms. Finally, this paper discusses future development direction of multispectral object detection technology, hoping to indicate potential research hotspots and application fields for researchers, and promote the wider application of multispectral object detection technology in actual scenarios and enhance its social value.
2025, 37: 051002.
doi: 10.11884/HPLPB202537.240314
Abstract:
Thermal diffusion coefficient is an important parameter of optical components in high-energy and high-power laser systems, and it is related to the laser damage resistance of components. However, the measurement error of the existing thermal diffusion coefficient measurement methods is large under the condition of multi-dimensional thermal conduction. As thermal diffusion length is the basis of thermal diffusion coefficient measurement, our study used the finite element method to simulate the two-dimensional heat conduction under continuous heating of heat source, and summarized the relationship between thermal diffusion length, thermal diffusion coefficient and heating time. On this basis, it proposed a model and method for measuring two-dimensional thermal diffusion length under continuous heating of heat source. Firstly, finite element analysis was used to establish a model to simulate the relationship between thermal diffusion length and thermal diffusion coefficient in one-dimensional heat conduction, and the two models were compared with numerical analytical expressions. The feasibility of using continuous heat source and thermal diffusion length to solve the thermal diffusion coefficient was verified. The effects of heat loss, sample thickness and heat source loading time on the results were discussed. Finally, the practical measurement scheme and measures to improve the measurement accuracy were put forward. This study provides a way to measure the thermal diffusion length of materials or components conveniently and accurately, and is of great significance for fabrication of high power and high energy laser system components.
Thermal diffusion coefficient is an important parameter of optical components in high-energy and high-power laser systems, and it is related to the laser damage resistance of components. However, the measurement error of the existing thermal diffusion coefficient measurement methods is large under the condition of multi-dimensional thermal conduction. As thermal diffusion length is the basis of thermal diffusion coefficient measurement, our study used the finite element method to simulate the two-dimensional heat conduction under continuous heating of heat source, and summarized the relationship between thermal diffusion length, thermal diffusion coefficient and heating time. On this basis, it proposed a model and method for measuring two-dimensional thermal diffusion length under continuous heating of heat source. Firstly, finite element analysis was used to establish a model to simulate the relationship between thermal diffusion length and thermal diffusion coefficient in one-dimensional heat conduction, and the two models were compared with numerical analytical expressions. The feasibility of using continuous heat source and thermal diffusion length to solve the thermal diffusion coefficient was verified. The effects of heat loss, sample thickness and heat source loading time on the results were discussed. Finally, the practical measurement scheme and measures to improve the measurement accuracy were put forward. This study provides a way to measure the thermal diffusion length of materials or components conveniently and accurately, and is of great significance for fabrication of high power and high energy laser system components.
2025, 37: 051003.
doi: 10.11884/HPLPB202537.240362
Abstract:
The electron irradiation effect of a 4H-SiC npn bipolar transistor UV detector is investigated in this paper. When the phototransistor is biased at 5 V, before irradiation, its dark current is about 58 nA, and its responsivity to 365 nm UV light is about 31A/W. After the device is irradiated by a 10 MeV e-beam, the order of magnitude of the dark current decreases to 10−11 A, and the responsivity decreases to about 1/8 of the original one. After irradiation, the responsivity of the device is significantly affected by the bias voltage: it decreases as the bias voltage decreases, and when the phototransistor is biased at 3 V, the responsivity decreases to 2.25 A/W. E-beam irradiation also affects the switching response of the UV detector, which results in a longer total time of response. In this paper, the circuit model of phototransistor operation is established, and the decrease of light generation current, the decrease of transistor gain and the increase of series resistance caused by electron beam irradiation are the main reasons for the degradation of photodetector’s UV response performance.
The electron irradiation effect of a 4H-SiC npn bipolar transistor UV detector is investigated in this paper. When the phototransistor is biased at 5 V, before irradiation, its dark current is about 58 nA, and its responsivity to 365 nm UV light is about 31A/W. After the device is irradiated by a 10 MeV e-beam, the order of magnitude of the dark current decreases to 10−11 A, and the responsivity decreases to about 1/8 of the original one. After irradiation, the responsivity of the device is significantly affected by the bias voltage: it decreases as the bias voltage decreases, and when the phototransistor is biased at 3 V, the responsivity decreases to 2.25 A/W. E-beam irradiation also affects the switching response of the UV detector, which results in a longer total time of response. In this paper, the circuit model of phototransistor operation is established, and the decrease of light generation current, the decrease of transistor gain and the increase of series resistance caused by electron beam irradiation are the main reasons for the degradation of photodetector’s UV response performance.
2025, 37: 052001.
doi: 10.11884/HPLPB202537.240312
Abstract:
With the increasing demand for diagnostics of high-energy-density (HED) materials, X-ray interferometric imaging technology has gained significant attention and application in this field. This paper primarily reviews the latest domestic and international advancements in X-ray interferometric imaging techniques and systems, focusing on the principles and capabilities of X-ray grating imaging based on Talbot and Talbot-Lau interferometry. Talbot and Talbot-Lau interferometry utilize gratings with periodic structures to perform high-precision measurements of X-ray phase, absorption, and scattering properties, enabling non-destructive inspection and imaging of internal structures of samples. This work summarizes the application of these techniques in diagnostic experiments for HED materials, introduces the Talbot Interferometric Analysis (TIA) code, and demonstrates an initial simulation by integrating the TIA program with the Flash hydrodynamics code. The simulation successfully retrieved three types of information: absorption, phase, and dark-field from the Flash model. Finally, the paper concludes with a summary and outlook on the application of X-ray Talbot-Lau interferometric diagnostic technology in HED plasma experiments.
With the increasing demand for diagnostics of high-energy-density (HED) materials, X-ray interferometric imaging technology has gained significant attention and application in this field. This paper primarily reviews the latest domestic and international advancements in X-ray interferometric imaging techniques and systems, focusing on the principles and capabilities of X-ray grating imaging based on Talbot and Talbot-Lau interferometry. Talbot and Talbot-Lau interferometry utilize gratings with periodic structures to perform high-precision measurements of X-ray phase, absorption, and scattering properties, enabling non-destructive inspection and imaging of internal structures of samples. This work summarizes the application of these techniques in diagnostic experiments for HED materials, introduces the Talbot Interferometric Analysis (TIA) code, and demonstrates an initial simulation by integrating the TIA program with the Flash hydrodynamics code. The simulation successfully retrieved three types of information: absorption, phase, and dark-field from the Flash model. Finally, the paper concludes with a summary and outlook on the application of X-ray Talbot-Lau interferometric diagnostic technology in HED plasma experiments.
2025, 37: 052002.
doi: 10.11884/HPLPB202537.240335
Abstract:
This paper discusses early experiments on indirect laser-driven implosion of double-metal-shell targets conducted with a hundred-kilojoule-class laser facility. The design of the double-metal-shell target is derived from the volume ignition scheme, which decouples the radiation ablation and implosion compression processes, thereby improving the robustness of the implosion. However, due to the high difficulty in manufacturing the double-metal-shell target, the neutron yield in the initial experiments was much lower than expected from simulations. To address this issue, two key improvements are proposed: first, optimizing the joint design of the outer shell to reduce the impact of hydrodynamic instability, thus to improve the collision efficiency of the inner and outer shells and the implosion efficiency of the inner core; second, enhancing the coupling efficiency of the hohlraum-target to improve the effective transfer of laser energy. With these improvements, the compression performance and implosion efficiency of the target were significantly enhanced, resulting in a substantial increase in neutron yield, from\begin{document}$ 5.0\times {10}^{7} $\end{document} ![]()
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This paper discusses early experiments on indirect laser-driven implosion of double-metal-shell targets conducted with a hundred-kilojoule-class laser facility. The design of the double-metal-shell target is derived from the volume ignition scheme, which decouples the radiation ablation and implosion compression processes, thereby improving the robustness of the implosion. However, due to the high difficulty in manufacturing the double-metal-shell target, the neutron yield in the initial experiments was much lower than expected from simulations. To address this issue, two key improvements are proposed: first, optimizing the joint design of the outer shell to reduce the impact of hydrodynamic instability, thus to improve the collision efficiency of the inner and outer shells and the implosion efficiency of the inner core; second, enhancing the coupling efficiency of the hohlraum-target to improve the effective transfer of laser energy. With these improvements, the compression performance and implosion efficiency of the target were significantly enhanced, resulting in a substantial increase in neutron yield, from
2025, 37: 052003.
doi: 10.11884/HPLPB202537.240327
Abstract:
To understand the effect of laser focal spot size on the extreme ultraviolet conversion efficiency and the physical mechanism that produces the effect, we developed a two-dimensional transient expansion model of laser ablation of planar target to produce coronal plasma by means of theoretical analysis. It is found that under condition with light intensity of 7.45×1010 W/cm2, full width at half maxima of 5 ns, wavelength of1064 nm, as the laser focal spot radius increases from 60 μm to 300 μm, the corresponding extreme ultraviolet conversion efficiency increases from 1% to 5.5%, while the corresponding extreme ultraviolet conversion efficiency stays at 5.5% after the focal spot radius is larger than 300 μm. This is due to the fact that the plasma in the coronal region generated by laser ablation of planar targets expands from the initial one-dimensional expansion to the subsequent two-dimensional expansion, which determines the saturation size of the plasma region emitting extreme ultraviolet light and ultimately determines the conversion efficiency of the extreme ultraviolet light. Our theoretical analysis on trend of conversion efficiency with focal spot radius can explain the physical phenomena observed in the laser ablation of a tin target experiment.
To understand the effect of laser focal spot size on the extreme ultraviolet conversion efficiency and the physical mechanism that produces the effect, we developed a two-dimensional transient expansion model of laser ablation of planar target to produce coronal plasma by means of theoretical analysis. It is found that under condition with light intensity of 7.45×1010 W/cm2, full width at half maxima of 5 ns, wavelength of
2025, 37: 053001.
doi: 10.11884/HPLPB202537.240391
Abstract:
In the field of high-power microwave radiation, mode converter and horn antenna are commonly used technologies to achieve rotational axisymmetric mode-directed radiation, but the separate design of mode converter and horn antenna often results in a large axial and aperture size of the antenna. To meet the demand for miniaturization of antennas in actual application scenarios, a stepped double semicircular waveguides radiation antenna with mode control and radiation integration is proposed. The antenna is fed with a circular waveguide TM01 mode and divided into two 180° phase difference semicircular waveguides by a plate. Then, two asymmetric stepped semicircular waveguide radiation elements are connected to achieve microwave radiation. The power divider uses a gradually tapered circular waveguide for matching, and a large inner conductor is used to improve power capacity. The dual semicircular waveguide radiation elements use the mode matching method combined with the Particle Swarm Optimization algorithm for phase adjustment and mode control. By integrating mode control and radiation in a multi-region design, a more uniform co-phase electric field distribution is achieved at the radiation aperture, achieving directed radiation, thereby shortening the antenna length and reducing the aperture size. An antenna model with a center frequency of 2.85 GHz is optimized, with dimensions of 1.18λ×1.18λ×2.42λ. Simulation results show that the return loss of the antenna is greater than 15 dB in the 2.75−2.96 GHz band, the realized gain is greater than 15.5 dBi in the 2.71−3 GHz band, the realized gain at the center frequency is 16.14 dBi and the vacuum power capacity is 906 MW. Compared with the traditional mode converter and horn antenna technology route, the proposed antenna has the characteristics of high power capacity and miniaturization.
In the field of high-power microwave radiation, mode converter and horn antenna are commonly used technologies to achieve rotational axisymmetric mode-directed radiation, but the separate design of mode converter and horn antenna often results in a large axial and aperture size of the antenna. To meet the demand for miniaturization of antennas in actual application scenarios, a stepped double semicircular waveguides radiation antenna with mode control and radiation integration is proposed. The antenna is fed with a circular waveguide TM01 mode and divided into two 180° phase difference semicircular waveguides by a plate. Then, two asymmetric stepped semicircular waveguide radiation elements are connected to achieve microwave radiation. The power divider uses a gradually tapered circular waveguide for matching, and a large inner conductor is used to improve power capacity. The dual semicircular waveguide radiation elements use the mode matching method combined with the Particle Swarm Optimization algorithm for phase adjustment and mode control. By integrating mode control and radiation in a multi-region design, a more uniform co-phase electric field distribution is achieved at the radiation aperture, achieving directed radiation, thereby shortening the antenna length and reducing the aperture size. An antenna model with a center frequency of 2.85 GHz is optimized, with dimensions of 1.18λ×1.18λ×2.42λ. Simulation results show that the return loss of the antenna is greater than 15 dB in the 2.75−2.96 GHz band, the realized gain is greater than 15.5 dBi in the 2.71−3 GHz band, the realized gain at the center frequency is 16.14 dBi and the vacuum power capacity is 906 MW. Compared with the traditional mode converter and horn antenna technology route, the proposed antenna has the characteristics of high power capacity and miniaturization.
2025, 37: 053002.
doi: 10.11884/HPLPB202537.240323
Abstract:
To explore the root cause of the reboot and shutdown phenomenon of electronic equipment in a strong electromagnetic field environment, this study considered a certain type of DC-regulated power supply as a test object and observed the susceptibility phenomena exhibited by the power supply under strong continuous wave electromagnetic radiation. In this experiment, the relative variation in voltage was selected as the effect parameter, and the variation feature of the effect parameter with the interference field strength was described. The irradiation test was carried out in the GTEM cell with an interference signal frequency range of 80–1000 MHz and a maximum field strength of 300 V/m. The test results indicate that the output voltage variation of the test power supply can be divided into two stages. When the interference field strength was low, the variation types of voltage included monotone rise, monotone fall, or first rise and then fall. At this stage, the voltage variation did not exceed 20%, and the load equipment could still operate normally. When the interference field strength was high, the voltage variation showed a sudden change. It could be divided into three types of interference phenomena such as shutting down after stopping interference (80–120 MHz, 320–350 MHz), shutting down when jamming (220–270 MHz, 360–420 MHz), rebooting (570–590 MHz, 700–720 MHz, 860–880 MHz), which posed actual threat to the load electrical equipment. There was no obvious correspondence between the susceptibility phenomena of the two stages.
To explore the root cause of the reboot and shutdown phenomenon of electronic equipment in a strong electromagnetic field environment, this study considered a certain type of DC-regulated power supply as a test object and observed the susceptibility phenomena exhibited by the power supply under strong continuous wave electromagnetic radiation. In this experiment, the relative variation in voltage was selected as the effect parameter, and the variation feature of the effect parameter with the interference field strength was described. The irradiation test was carried out in the GTEM cell with an interference signal frequency range of 80–
2025, 37: 054001.
doi: 10.11884/HPLPB202537.240365
Abstract:
The electron beam test platform, as a pre-research project for Shenzhen Superconducting Soft X-ray Free Electron Laser (S3FEL), will be used to overcome several major key technology challenges in high repetition frequency free electron laser. In this paper, the structural design of the injector dump beam window for the Electron Beam Test Platform of S3FEL is carried out, and a brazing water-cooled copper window is designed based on the electron beam parameters. The thermal structural calculation of the beam window is carried out using finite element analysis method, and the temperature, stress and deformation under different cooling channels and cooling water flow rates are analyzed. Considering the cooling effect, economic efficiency and flow vibration factors, the M-type cooling channel with the flow rate of 1 m/s is finally selected for the beam window. In addition, the vacuum distribution at the beam window is calculated, and all the results meet the design requirements, verifying the rationality of the design and ensuring the stable and reliable operation of the facility.
The electron beam test platform, as a pre-research project for Shenzhen Superconducting Soft X-ray Free Electron Laser (S3FEL), will be used to overcome several major key technology challenges in high repetition frequency free electron laser. In this paper, the structural design of the injector dump beam window for the Electron Beam Test Platform of S3FEL is carried out, and a brazing water-cooled copper window is designed based on the electron beam parameters. The thermal structural calculation of the beam window is carried out using finite element analysis method, and the temperature, stress and deformation under different cooling channels and cooling water flow rates are analyzed. Considering the cooling effect, economic efficiency and flow vibration factors, the M-type cooling channel with the flow rate of 1 m/s is finally selected for the beam window. In addition, the vacuum distribution at the beam window is calculated, and all the results meet the design requirements, verifying the rationality of the design and ensuring the stable and reliable operation of the facility.
2025, 37: 054002.
doi: 10.11884/HPLPB202537.240235
Abstract:
The BCD technology integrates Bipolar, Complementary Metal Oxide Semiconductor (CMOS), and Double Diffused MOSFET (DMOS) within a single chip, widely utilized in electronic components and system production. Gate drivers fabricated by BCD technology can reduce transmission delays, lower power consumption, and enhance drive capabilities. However, the radiation effects in space environments may lead to performance degradation and potentially jeopardize the safety of spacecraft. This paper focuses on gate drivers based on BCD technology, employing an enclosed layout structure for total ionizing dose (TID) radiation hardening. Through TID irradiation tests, the electrical parameter variations between hardened and unhardened devices are compared. Results indicate that TID radiation causes degradation in the output voltage and current characteristics of the device, manifesting as a decrease in switching voltage and an increase in output current, while having a negligible impact on the output resistance. Comparing test outcomes from both types of drivers, it is evident that the ring-gate hardening method effectively mitigates edge leakage induced by TID radiation to a certain extent. Nevertheless, functional failure occurs in the devices at 500 krad(Si).
The BCD technology integrates Bipolar, Complementary Metal Oxide Semiconductor (CMOS), and Double Diffused MOSFET (DMOS) within a single chip, widely utilized in electronic components and system production. Gate drivers fabricated by BCD technology can reduce transmission delays, lower power consumption, and enhance drive capabilities. However, the radiation effects in space environments may lead to performance degradation and potentially jeopardize the safety of spacecraft. This paper focuses on gate drivers based on BCD technology, employing an enclosed layout structure for total ionizing dose (TID) radiation hardening. Through TID irradiation tests, the electrical parameter variations between hardened and unhardened devices are compared. Results indicate that TID radiation causes degradation in the output voltage and current characteristics of the device, manifesting as a decrease in switching voltage and an increase in output current, while having a negligible impact on the output resistance. Comparing test outcomes from both types of drivers, it is evident that the ring-gate hardening method effectively mitigates edge leakage induced by TID radiation to a certain extent. Nevertheless, functional failure occurs in the devices at 500 krad(Si).
2025, 37: 055001.
doi: 10.11884/HPLPB202537.240350
Abstract:
Electric blasting based on electromagnetic energy equipment has great application prospects in foundation pit engineering. This article proposes the synergistic rock breaking technology based on pulse power supply and electric explosion load arrays, which achieves controllable electric blasting of large volume hard rock through the superposition of multiple shock waves. The article analyzes the mechanism of overvoltage in the process of electric explosion and the mechanism of overvoltage conduction in the multi-array collaborative process, and proposes the overvoltage suppression method. It compares the rock breaking effects of single pulse power supply and multi-array and the specific energy consumption of the dual load array is 38% of a single load for rock breaking, which indicates the electric explosion load array can effectively achieve controllable electric blasting of large volume hard rocks.
Electric blasting based on electromagnetic energy equipment has great application prospects in foundation pit engineering. This article proposes the synergistic rock breaking technology based on pulse power supply and electric explosion load arrays, which achieves controllable electric blasting of large volume hard rock through the superposition of multiple shock waves. The article analyzes the mechanism of overvoltage in the process of electric explosion and the mechanism of overvoltage conduction in the multi-array collaborative process, and proposes the overvoltage suppression method. It compares the rock breaking effects of single pulse power supply and multi-array and the specific energy consumption of the dual load array is 38% of a single load for rock breaking, which indicates the electric explosion load array can effectively achieve controllable electric blasting of large volume hard rocks.
2025, 37: 055002.
doi: 10.11884/HPLPB202537.240356
Abstract:
The solid-state high-voltage pulse switch with high index, compact structure and good stability is of great significance to the progress of pulse power technology. This paper proposes a high-voltage nanosecond switching technology route based on Photoconductive Semiconductor Switches (PCSS) and thyristor surge suppressor (TSS) arrays, and a new type of high voltage switching module (PCSS triggering thyristor surge suppressors module, PTTSSM) is developed by using PCSS, which is convenient for realizing the high-voltage isolation, as the triggering unit of TSS arrays. The 20 kV PTTSSM has a peak output current of 23.7 A, a pulse width of 122.1 ns, a rise time and a fall time of 55.9 ns and 128.3 ns, respectively, and a size of 60 mm×60 mm×40 mm. The 100 kV PTTSSM has an adjustable peak output voltage of 60−100 kV, a maximum peak output current of 356 A, a pulse width of 1.308 µs, rise time and fall time of 160.4 ns and 2.454 µs, respectively, and its size is 150 mm×100 mm×50 mm. All of them can work stably for a long time. Pulse power supply based on a new solid-state switching module successfully generates a large number of stable low-temperature plasmas in organic wastewater treatment experiments, verifying the feasibility and effectiveness of the switching module-driven plasma generation.
The solid-state high-voltage pulse switch with high index, compact structure and good stability is of great significance to the progress of pulse power technology. This paper proposes a high-voltage nanosecond switching technology route based on Photoconductive Semiconductor Switches (PCSS) and thyristor surge suppressor (TSS) arrays, and a new type of high voltage switching module (PCSS triggering thyristor surge suppressors module, PTTSSM) is developed by using PCSS, which is convenient for realizing the high-voltage isolation, as the triggering unit of TSS arrays. The 20 kV PTTSSM has a peak output current of 23.7 A, a pulse width of 122.1 ns, a rise time and a fall time of 55.9 ns and 128.3 ns, respectively, and a size of 60 mm×60 mm×40 mm. The 100 kV PTTSSM has an adjustable peak output voltage of 60−100 kV, a maximum peak output current of 356 A, a pulse width of 1.308 µs, rise time and fall time of 160.4 ns and 2.454 µs, respectively, and its size is 150 mm×100 mm×50 mm. All of them can work stably for a long time. Pulse power supply based on a new solid-state switching module successfully generates a large number of stable low-temperature plasmas in organic wastewater treatment experiments, verifying the feasibility and effectiveness of the switching module-driven plasma generation.
2025, 37: 055003.
doi: 10.11884/HPLPB202537.240358
Abstract:
Constructing a photoconductive semiconductor switch (PCSS)-metal coil structure, we discovered a new phenomenon of electromagnetic oscillation in vanadium-compensation semi-insulating (VCSI) PCSS. Here the PCSS responds to laser pulse and high-voltage signal while the metal coil generates an oscillating voltage pulse envelope signal. The generation of this oscillating signal is not related to the input bias voltage of the PCSS, the pulse circuit components, or the electrode structure of the PCSS, rather it is related to the output characteristic of the PCSS. This physical phenomenon can be explained using the current surge model in photoconducting antenna. Preparing ohmic contact electrode on the silicon carbide material forms the PCSS, which generates a large number of photogenerated carriers when ultra-fast laser pulses irradiate the surface of the material and Simultaneously applies a bias voltage signal between the electrode. At this time inside the PCSS the electric field causes the transient current, radiating electromagnetic wave to the metal coil to generate oscillating signal.
2025, 37: 056001.
doi: 10.11884/HPLPB202537.240326
Abstract:
Flash radiography enables the diagnosis of rapid physical processes, yet the instantaneous nature of image acquisition results in a severely limited number of projections. This study investigates uncertainty quantification methods for computed tomography (CT) image reconstruction under the typical scenario of a single projection view. Current approaches for single-view CT uncertainty quantification often adopt oversimplified physical models, assuming linearized optical path equations with Gaussian noise. To address this limitation, we derive a more realistic nonlinear reconstruction framework based on the Lambert-Beer’s law, constructing an exponential attenuation model for transmittance with an integrated Gaussian noise term. This formulation yields a nonlinear posterior probability density function, which is subsequently sampled using the Randomize-Then-Optimize (RTO) algorithm combined with Gibbs sampling. The reconstructed image and its associated uncertainty are obtained through statistical analysis of the sampled data. Numerical simulations validate the proposed method, with comparative results against conventional linearized models demonstrating its superior potential for accurate uncertainty estimation in image reconstruction.
Flash radiography enables the diagnosis of rapid physical processes, yet the instantaneous nature of image acquisition results in a severely limited number of projections. This study investigates uncertainty quantification methods for computed tomography (CT) image reconstruction under the typical scenario of a single projection view. Current approaches for single-view CT uncertainty quantification often adopt oversimplified physical models, assuming linearized optical path equations with Gaussian noise. To address this limitation, we derive a more realistic nonlinear reconstruction framework based on the Lambert-Beer’s law, constructing an exponential attenuation model for transmittance with an integrated Gaussian noise term. This formulation yields a nonlinear posterior probability density function, which is subsequently sampled using the Randomize-Then-Optimize (RTO) algorithm combined with Gibbs sampling. The reconstructed image and its associated uncertainty are obtained through statistical analysis of the sampled data. Numerical simulations validate the proposed method, with comparative results against conventional linearized models demonstrating its superior potential for accurate uncertainty estimation in image reconstruction.
2025, 37: 056002.
doi: 10.11884/HPLPB202537.240241
Abstract:
In this study, double-sided Al film was prepared on the surface of polyethylene terephthalate (PET) by controlling different Al target currents with magnetron sputtering technology. The micro-morphology of the Al film was observed using scanning electron microscope (SEM) and atomic force microscope (AFM). Phase analysis of the Al film was carried out using X-ray diffraction (XRD). The adhesion between the Al film and PET was detected by the cross-cut method. The light-blocking property of the Al film was measured by an ultraviolet-visible spectrophotometer. The transmittance of α and β particles in the Al film was detected using a handheld nuclear radiation detector. The results show that the surface of the Al film is smooth and flat with a metallic luster, and the Al grains are uniform and dense. The Al film has no defects such as pores and cracks. As the Al target current increases, the Al grain size, the thickness of the Al film, and the deposition rate all increase, and the roughness of the Al film first decreases and then increases. The light-blocking property of the Al film first improves and then decreases, and the average transmittance of both α and β particles gradually decreases. When the Al target current is 2.0 A, the roughness of the Al film is the minimum, which is 2.49 nm. The light transmittance is the lowest, around 0.025%. The average transmittance of α and β particles is the highest, being 581.7 CPS and 547.2 CPS respectively.
In this study, double-sided Al film was prepared on the surface of polyethylene terephthalate (PET) by controlling different Al target currents with magnetron sputtering technology. The micro-morphology of the Al film was observed using scanning electron microscope (SEM) and atomic force microscope (AFM). Phase analysis of the Al film was carried out using X-ray diffraction (XRD). The adhesion between the Al film and PET was detected by the cross-cut method. The light-blocking property of the Al film was measured by an ultraviolet-visible spectrophotometer. The transmittance of α and β particles in the Al film was detected using a handheld nuclear radiation detector. The results show that the surface of the Al film is smooth and flat with a metallic luster, and the Al grains are uniform and dense. The Al film has no defects such as pores and cracks. As the Al target current increases, the Al grain size, the thickness of the Al film, and the deposition rate all increase, and the roughness of the Al film first decreases and then increases. The light-blocking property of the Al film first improves and then decreases, and the average transmittance of both α and β particles gradually decreases. When the Al target current is 2.0 A, the roughness of the Al film is the minimum, which is 2.49 nm. The light transmittance is the lowest, around 0.025%. The average transmittance of α and β particles is the highest, being 581.7 CPS and 547.2 CPS respectively.
2025, 37: 059001.
doi: 10.11884/HPLPB202537.240398
Abstract:
Radionuclides have been widely used in the fields of nuclear medicine, nuclear security and non-destructive testing, and their accurate identification is the basis of qualitative detection of radionuclides. In the portable nuclide recognition instrument, the traditional energy spectrum analysis method has the shortcomings of high delay and low recognition rate. This paper proposes a lightweight neural network model for nuclide recognition based on kernel pulse peak sequence and its FPGA hardware acceleration method. A lightweight and efficient neural network model is constructed by introducing depth-separable convolution and reciprocal residual modules, and using global average pooling to replace the traditional fully connected layer. For the network training data set, NaI (Tl) detector model was constructed through Monte Carlo toolkit Geant4 to obtain the analog energy spectrum, and then a simulator generated nuclear pulse signal sequences according to the energy spectrum, and 16 kinds of nuclear pulse signal data were constructed. Finally, the trained model is deployed to PYNQ-Z2 heterogeneous chip through optimization methods such as quantization, fusion and parallel computing to achieve acceleration. Experimental results show that the recognition accuracy of the proposed model can reach 98.3%, which is 13.2% higher than that of the traditional convolutional neural network model, and the number of parameters is only 2 128. After FPGA optimization and acceleration, the single recognition time is 0.273 ms, and the power consumption is 1.94 W.
Radionuclides have been widely used in the fields of nuclear medicine, nuclear security and non-destructive testing, and their accurate identification is the basis of qualitative detection of radionuclides. In the portable nuclide recognition instrument, the traditional energy spectrum analysis method has the shortcomings of high delay and low recognition rate. This paper proposes a lightweight neural network model for nuclide recognition based on kernel pulse peak sequence and its FPGA hardware acceleration method. A lightweight and efficient neural network model is constructed by introducing depth-separable convolution and reciprocal residual modules, and using global average pooling to replace the traditional fully connected layer. For the network training data set, NaI (Tl) detector model was constructed through Monte Carlo toolkit Geant4 to obtain the analog energy spectrum, and then a simulator generated nuclear pulse signal sequences according to the energy spectrum, and 16 kinds of nuclear pulse signal data were constructed. Finally, the trained model is deployed to PYNQ-Z2 heterogeneous chip through optimization methods such as quantization, fusion and parallel computing to achieve acceleration. Experimental results show that the recognition accuracy of the proposed model can reach 98.3%, which is 13.2% higher than that of the traditional convolutional neural network model, and the number of parameters is only 2 128. After FPGA optimization and acceleration, the single recognition time is 0.273 ms, and the power consumption is 1.94 W.
2025, 37: 059002.
doi: 10.11884/HPLPB202537.240351
Abstract:
Adding the vortex factors to the Gaussian, Lorenz, and Voigt airglow (aurora) light spectrum profiles of the for the upper atmospheric wind measurement, the vortex expressions of the three profiles of airglow (aurora) light sources are derived theoretically. The three profiles of airglow (aurora) with vortex light are simulated, and it is found that the extinction of the three profiles of light sources varies with the topological charge number l. The Gaussian vortex light rotates around the axis and the phase changes by 2πl, and the central extinction part and phase increase with the increase of l. The main extinction direction of Lorenz vortex is the transverse axis distribution direction. With the increase of l, the light intensity decreases, and the center extinction is carried out in discontinuous mode, which has a spiral spatial phase structure. Voigt vortex light profile is symmetrical on both the transverse and longitudinal sides, and the top is V-shaped extinction along the -z direction. The expressions are derived between the interference intensity of the three profile of vortex light, optical path difference and topological charge number, and the 3D diagram of the interference fringe of the three profiles of vortex light is simulated, and it is found that the spatial spectral intensity produces different fork structures under different topological charge number: with the change of vortex phase, the original spatial distribution changes, and the whole extends and extrudes from the maximum light intensity to both sides, and the influence of vortex phase extrude and dislocation is greater under fractional topological load. The experimental results show that there are fringes outside the bright ring of the Gaussian vortex light with the same topological charge number l, and the total topological phase will increase 2π and the beam waist radius will increase with each increase of topological charge number l by 1.
Adding the vortex factors to the Gaussian, Lorenz, and Voigt airglow (aurora) light spectrum profiles of the for the upper atmospheric wind measurement, the vortex expressions of the three profiles of airglow (aurora) light sources are derived theoretically. The three profiles of airglow (aurora) with vortex light are simulated, and it is found that the extinction of the three profiles of light sources varies with the topological charge number l. The Gaussian vortex light rotates around the axis and the phase changes by 2πl, and the central extinction part and phase increase with the increase of l. The main extinction direction of Lorenz vortex is the transverse axis distribution direction. With the increase of l, the light intensity decreases, and the center extinction is carried out in discontinuous mode, which has a spiral spatial phase structure. Voigt vortex light profile is symmetrical on both the transverse and longitudinal sides, and the top is V-shaped extinction along the -z direction. The expressions are derived between the interference intensity of the three profile of vortex light, optical path difference and topological charge number, and the 3D diagram of the interference fringe of the three profiles of vortex light is simulated, and it is found that the spatial spectral intensity produces different fork structures under different topological charge number: with the change of vortex phase, the original spatial distribution changes, and the whole extends and extrudes from the maximum light intensity to both sides, and the influence of vortex phase extrude and dislocation is greater under fractional topological load. The experimental results show that there are fringes outside the bright ring of the Gaussian vortex light with the same topological charge number l, and the total topological phase will increase 2π and the beam waist radius will increase with each increase of topological charge number l by 1.
2025, 37: 052004.
doi: 10.11884/HPLPB202537.240269
Abstract:
To study the hydrodynamic instability in laser fusion implosion, X-ray diagnostic technology with large field of view and high resolution is needed. Fresnel zone plate (FZP) is a kind of circular aperiodic grating structure, which can realize high spatial resolution imaging of X-ray. In this paper, the simulation research of high-resolution X-ray diagnosis technology based on diffraction imaging is carried out, showing the application prospects of FZP for hydrodynamic instability research. Based on the diffraction theory, the theoretical model of FZP is established, and the structural parameters of FZP with working energy point of 8.04 keV are designed according to the diagnostic experimental environment. Based on the optical simulation model, the color difference of FZP imaging is simulated, and the relationship between spatial resolution and spectral bandwidth is given. The simulation results show that the bandwidth of light source is less than 0.2 keV, and the resolution of FZP is better than 3 μm. The simulation of grid backlight imaging shows that FZP can achieve good resolution (less than 3 μm) within 0.8 mm field of view.
To study the hydrodynamic instability in laser fusion implosion, X-ray diagnostic technology with large field of view and high resolution is needed. Fresnel zone plate (FZP) is a kind of circular aperiodic grating structure, which can realize high spatial resolution imaging of X-ray. In this paper, the simulation research of high-resolution X-ray diagnosis technology based on diffraction imaging is carried out, showing the application prospects of FZP for hydrodynamic instability research. Based on the diffraction theory, the theoretical model of FZP is established, and the structural parameters of FZP with working energy point of 8.04 keV are designed according to the diagnostic experimental environment. Based on the optical simulation model, the color difference of FZP imaging is simulated, and the relationship between spatial resolution and spectral bandwidth is given. The simulation results show that the bandwidth of light source is less than 0.2 keV, and the resolution of FZP is better than 3 μm. The simulation of grid backlight imaging shows that FZP can achieve good resolution (less than 3 μm) within 0.8 mm field of view.
2025, 37: 054003.
doi: 10.11884/HPLPB202537.240083
Abstract:
Industrial linear accelerators are gradually moving towards high average beam power in small, compact shapes. The beam break-up effect due to the transverse wakefield is the main limitation to its performance improvement. The hybrid dielectric-iris-loaded structure is a new miniaturization accelerating structure with high average beam power. The main problem is difficulty in assembly and tuning. Through the study of dielectric based accelerating structures, a miniaturization accelerator with high average beam power was designed and optimized. During the research process, the influence of dielectric structural parameters on the accelerating structure size, accelerating gradient, and beam power was analyzed. The optimized accelerating structure size was reduced by about one-third compared to conventional iris-loaded accelerating structure. It can achieve the same acceleration gradient. The insertion of a simple dielectric tube into the dielectric structure made assembly and tuning easier. The optimized accelerator operats at S-band with the frequency of2856 MHz and voltage of 2.5 MeV. During the research process, beam dynamics is calculated through numerical calculation methods and PARMELA. Our research provides an important groundwork for further development of irradiation linear accelerators.
Industrial linear accelerators are gradually moving towards high average beam power in small, compact shapes. The beam break-up effect due to the transverse wakefield is the main limitation to its performance improvement. The hybrid dielectric-iris-loaded structure is a new miniaturization accelerating structure with high average beam power. The main problem is difficulty in assembly and tuning. Through the study of dielectric based accelerating structures, a miniaturization accelerator with high average beam power was designed and optimized. During the research process, the influence of dielectric structural parameters on the accelerating structure size, accelerating gradient, and beam power was analyzed. The optimized accelerating structure size was reduced by about one-third compared to conventional iris-loaded accelerating structure. It can achieve the same acceleration gradient. The insertion of a simple dielectric tube into the dielectric structure made assembly and tuning easier. The optimized accelerator operats at S-band with the frequency of
2025, 37: 054004.
doi: 10.11884/HPLPB202537.240179
Abstract:
This study focuses on the critical challenge of the integrated storage ring injection system in a compact X-ray light source. Utilizing the 3D electromagnetic field simulation software CST and the beam dynamics simulation software ELEGANT, we conducted multi-parameter optimization design for the key component of the injection system—the perturbator. The phase space evolution behavior of the electron beam during half-integer resonance injection processes was systematically investigated, leading to optimized structural parameters of injection components. For the compact storage ring, the optimized injection scheme demonstrates that the perturbator achieves optimal performance when positioned within an angular range of 150°–210° relative to the injection point, with the electron beam injection offset by 30 mm from the equilibrium orbit. After the perturbator stops working, the injected electron oscillation amplitude is minimized to 3.4 mm. Furthermore, the feasibility of implementing a multi-turn multi-pass injection scheme in the compact storage ring was analyzed. Numerical results indicate that maximum injection efficiency can be obtained when the kicker operates at a frequency of 3 MHz. These findings provide critical insights for enhancing beam stability and operational efficiency in compact synchrotron radiation facilities.
This study focuses on the critical challenge of the integrated storage ring injection system in a compact X-ray light source. Utilizing the 3D electromagnetic field simulation software CST and the beam dynamics simulation software ELEGANT, we conducted multi-parameter optimization design for the key component of the injection system—the perturbator. The phase space evolution behavior of the electron beam during half-integer resonance injection processes was systematically investigated, leading to optimized structural parameters of injection components. For the compact storage ring, the optimized injection scheme demonstrates that the perturbator achieves optimal performance when positioned within an angular range of 150°–210° relative to the injection point, with the electron beam injection offset by 30 mm from the equilibrium orbit. After the perturbator stops working, the injected electron oscillation amplitude is minimized to 3.4 mm. Furthermore, the feasibility of implementing a multi-turn multi-pass injection scheme in the compact storage ring was analyzed. Numerical results indicate that maximum injection efficiency can be obtained when the kicker operates at a frequency of 3 MHz. These findings provide critical insights for enhancing beam stability and operational efficiency in compact synchrotron radiation facilities.
2025, 37: 059901.
doi: 10.11884/HPLPB202537.250091
Abstract:
2262 1664
We have developed a femtosecond laser plane-by-plane direct writing method based on beam shaping, enabling single-step fabrication of the large-area fiber Bragg grating (FBG) planes. Using this innovative approach, we successfully fabricated high-reflectivity (HR) and low-reflectivity (LR) FBG pairs in 20/400-m double-clad fibers and implemented them in an all-fiber oscillator. Under a pump power of
W, the oscillator achieved near-single-mode laser output of
W with an optical–optical conversion efficiency of 73.47%, a beam quality factor M2 of 1.46, and a 3-dB spectral bandwidth of 3 nm without stimulated Raman scattering peaks. The results indicate that femtosecond laser direct writing technology offers both fabrication flexibility and thermal management advantages for high-power grating fabrication, and establishes a key technological pathway for enhancing the performance of all-fiber laser systems.
