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, 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/HPLPB202537.240407
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/HPLPB202537.240346
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/HPLPB202537.240433
Abstract:
The output characteristics of a narrow line width optical parametric oscillator with KTP as the nonlinear crystal which 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 at 575.81 nm, with a corresponding average output power of 155 mW and a pulse width of 35 ns. The line width at the peak wavelength is only 0.8 pm. Beam quality factor in the x and y direction 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 which 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 at 575.81 nm, with a corresponding average output power of 155 mW and a pulse width of 35 ns. The line width at the peak wavelength is only 0.8 pm. Beam quality factor in the x and y direction is measured respectively as 1.286 and 1.807.
, 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/HPLPB202537.240360
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/HPLPB202537.250001
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/HPLPB202537.240229
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/HPLPB202537.240131
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/HPLPB202537.240257
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/HPLPB202537.240299
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/HPLPB202537.240271
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/HPLPB202537.240386
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/HPLPB202537.240411
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/HPLPB202537.240186
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/HPLPB202537.240280
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/HPLPB202537.240408
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/HPLPB202537.240349
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.
