Search
Most DownloadedMore >
- A fast analysis method of electromagnetic bandgap structure
- Development of laser technology in Research Center of Laser Fusion
- Attenuation characteristics of electromagnetic wave penetrating walls
- Application of high power microwave vacuum electron devices
- Generation and propagation characteristics of vacuum pulse discharge metal plasma
- Design of 77 GHz vehicle millimeter long- and medium-range radar antenna array
- Development of interface options of hybrid reactor driven with fast Z-pinch neutron source
Most CitedMore >
- Review of Chinese pulsed power science and technology
- Conceptual research on Z-pinch driven fusion-fission hybrid reactor
- Infrared small dim target detection based on local contrast combined with region saliency
- Super-power repetitive Z-pinch driver for fusion-fission reactor
- SG-Ⅲ laser facility has successfully achieved 60 TW/180 kJ ultraviolet laser (351 nm) output
- Repetition rate pulsed power technology and its applications:(ⅵ) Typical applications
- Repetition rate pulsed power technology and its applications:(vii) Major challenges and future trends
Email alert
RSSRecommend ArticlesMore >
Just Accepted manuscripts are peer-reviewed and accepted for publication. They are posted online prior to technical editing formatting for publication and author proofing.
Display Method:
, Available online ,
doi: 10.11884/HPLPB202537.240304
Abstract:
Femtosecond laser precision machining technology has three characteristics: “extremely short duration time to avoid or alleviate thermal effects”, “extremely high peak power density suitable for any solid material”, and “extremely small focal spot size to achieve precise removal or modification of micro areas”, meeting the safety and precision machining needs of various difficult to machine and special materials involved in precision diagnosis/measurement experiments. The application of high stability and high repetition rate femtosecond lasers fills the gap of low repetition rate femtosecond lasers that cannot achieve high-speed scanning, providing an important energy source for efficient and precise processing of various precision samples/specimens required for precision diagnosis/measurement experiments. This article takes the precision diagnosis/measurement experiments of various research institutes of the China Academy of Engineering Physics as the starting point for the safe, efficient and precise processing requirements of precision samples/specimens. Taking typical application scenarios such as laser X-ray precision target materials and structures, explosive material microstructures, superhard material composite refractive lens structures, micro probe fiber precision fixed structures, and terahertz filter core structures as examples, the research progress of high-frequency femtosecond laser precision processing technology in the safe, efficient and precise processing of difficult to process materials and special materials is introduced.
Femtosecond laser precision machining technology has three characteristics: “extremely short duration time to avoid or alleviate thermal effects”, “extremely high peak power density suitable for any solid material”, and “extremely small focal spot size to achieve precise removal or modification of micro areas”, meeting the safety and precision machining needs of various difficult to machine and special materials involved in precision diagnosis/measurement experiments. The application of high stability and high repetition rate femtosecond lasers fills the gap of low repetition rate femtosecond lasers that cannot achieve high-speed scanning, providing an important energy source for efficient and precise processing of various precision samples/specimens required for precision diagnosis/measurement experiments. This article takes the precision diagnosis/measurement experiments of various research institutes of the China Academy of Engineering Physics as the starting point for the safe, efficient and precise processing requirements of precision samples/specimens. Taking typical application scenarios such as laser X-ray precision target materials and structures, explosive material microstructures, superhard material composite refractive lens structures, micro probe fiber precision fixed structures, and terahertz filter core structures as examples, the research progress of high-frequency femtosecond laser precision processing technology in the safe, efficient and precise processing of difficult to process materials and special materials is introduced.
, Available online ,
doi: 10.11884/HPLPB202537.240347
Abstract:
Introduced the overall layout of the Free Electron Laser & High Magnetic Field device under construction at Anhui University, and analyzed in detail the design requirements and difficulties of the water-cooling system for the stable operation of the device, and completed the design and development of the water-cooling system of the whole device according to the requirements, the water-cooling system of the device contains two independent water-cooling unit systems, with the design temperatures of (42±0.1)℃ and (25±0.5)℃, and can be adjusted within a certain range. The device water-cooling control system is developed based on EPICS ( Experimental Physics and Industrial Control System ) framework, the temperature regulation control function is realized by PLC ( Programmable Logic Controller ) program, and the PID (Proportion Integration Differentiation) parameter configuration is realized by PID regulator. The software development of the control system is mainly to realize the setting of the device parameters and the reading back of the status data under the EPICS environment, and to store the historical data into the Archiver Appliances database. The temperature control accuracy of the water-cooling control system during the trial operation reaches (42±0.03)℃ and (25±0.08)℃, which is in line with the design requirements, and the system is stable and reliable during the operation, which can well guarantee the safe and stable operation of the device.
Introduced the overall layout of the Free Electron Laser & High Magnetic Field device under construction at Anhui University, and analyzed in detail the design requirements and difficulties of the water-cooling system for the stable operation of the device, and completed the design and development of the water-cooling system of the whole device according to the requirements, the water-cooling system of the device contains two independent water-cooling unit systems, with the design temperatures of (42±0.1)℃ and (25±0.5)℃, and can be adjusted within a certain range. The device water-cooling control system is developed based on EPICS ( Experimental Physics and Industrial Control System ) framework, the temperature regulation control function is realized by PLC ( Programmable Logic Controller ) program, and the PID (Proportion Integration Differentiation) parameter configuration is realized by PID regulator. The software development of the control system is mainly to realize the setting of the device parameters and the reading back of the status data under the EPICS environment, and to store the historical data into the Archiver Appliances database. The temperature control accuracy of the water-cooling control system during the trial operation reaches (42±0.03)℃ and (25±0.08)℃, which is in line with the design requirements, and the system is stable and reliable during the operation, which can well guarantee the safe and stable operation of the device.
, Available online ,
doi: 10.11884/HPLPB202537.240150
Abstract:
This paper presents a model for aerosol inertial collision removal model under mixed gas jet conditions with high Weber number, based on the hydrodynamic model of jet penetration length and entrained droplet fraction. An analysis code of the aerosol pool scrubbing is constructed by spatial discretization of the injection zone. The experimental cases are adopted to validate the model, which includes two cases of 64% steam fraction, 0.7 m submergence depth, and mass fluxes of 217 kg/(m2·s) and 120 kg/(m2·s), conducted by small scale aerosol pool scrubbing facility, and Reinforced Concerted Action 2 (RCA2) with non-condensable gas-carrying aerosols at 0.5 m submergence depth and mass fluxes of 95 kg/(m2·s). The results show that the predictions of the model considering the jet hydrodynamic characteristics are in good agreement with the experimental values. Parameter analysis shows that as the Weber number of immersed jet increases, both jet penetration length and entrained droplet fraction increase, thereby enhancing the inertial collision between aerosols and droplets.
This paper presents a model for aerosol inertial collision removal model under mixed gas jet conditions with high Weber number, based on the hydrodynamic model of jet penetration length and entrained droplet fraction. An analysis code of the aerosol pool scrubbing is constructed by spatial discretization of the injection zone. The experimental cases are adopted to validate the model, which includes two cases of 64% steam fraction, 0.7 m submergence depth, and mass fluxes of 217 kg/(m2·s) and 120 kg/(m2·s), conducted by small scale aerosol pool scrubbing facility, and Reinforced Concerted Action 2 (RCA2) with non-condensable gas-carrying aerosols at 0.5 m submergence depth and mass fluxes of 95 kg/(m2·s). The results show that the predictions of the model considering the jet hydrodynamic characteristics are in good agreement with the experimental values. Parameter analysis shows that as the Weber number of immersed jet increases, both jet penetration length and entrained droplet fraction increase, thereby enhancing the inertial collision between aerosols and droplets.
, Available online ,
doi: 10.11884/HPLPB202537.240340
Abstract:
The complexity of UAV systems and the diversity of fault modes present significant challenges to their reliability, stability, and safety. To address the issue of incomplete fault data samples in UAV, a fault simulation dataset was constructed using a predefined fault injection method. This dataset is based on four models of faults: bias faults, drift faults, lock faults, and scale faults, allowing for the equivalent simulation of the drone in fault-free states, actuator failures, and sensor failures. Furthermore, the dataset was evaluated using deep learning networks. Simulation results demonstrate that the three deep learning architectures—WDCNN, ResNet, and QCNN—validate the completeness and effectiveness of the construction method and the fault simulation dataset in this paper. In terms of precision, WDCNN achieved over 82%, ResNet exceeded 90%, and QCNN surpassed 92%. The methods proposed in this study provides a complete dataset and evaluation method for data-driven research on UAV fault diagnosis.
The complexity of UAV systems and the diversity of fault modes present significant challenges to their reliability, stability, and safety. To address the issue of incomplete fault data samples in UAV, a fault simulation dataset was constructed using a predefined fault injection method. This dataset is based on four models of faults: bias faults, drift faults, lock faults, and scale faults, allowing for the equivalent simulation of the drone in fault-free states, actuator failures, and sensor failures. Furthermore, the dataset was evaluated using deep learning networks. Simulation results demonstrate that the three deep learning architectures—WDCNN, ResNet, and QCNN—validate the completeness and effectiveness of the construction method and the fault simulation dataset in this paper. In terms of precision, WDCNN achieved over 82%, ResNet exceeded 90%, and QCNN surpassed 92%. The methods proposed in this study provides a complete dataset and evaluation method for data-driven research on UAV fault diagnosis.
, Available online ,
doi: 10.11884/HPLPB202537.240310
Abstract:
In order to solve the problem of hard connection in waveguide transmission line, some waveguide components will use flexible waveguide, but the use of flexible waveguide will bring about the increase of transmission line loss. In aiming to investigate its loss and electrical heating under real operating conditions, we built a test platform based on a resonant ring with a 13.4 dB power gain in the traveling wave of the resonant ring, which successfully achieves an equivalent power of 140 kW at the position of the antinode by means of two 2 kW power amplifiers. Based on the results of simulations and experiments, we optimized the design of the rectangular flexible waveguide and improved its structure and materials to better cope with the thermal deformation and stress under high power input. The optimized flexible waveguide's electrical and thermal performance is better than that of similar foreign products.
In order to solve the problem of hard connection in waveguide transmission line, some waveguide components will use flexible waveguide, but the use of flexible waveguide will bring about the increase of transmission line loss. In aiming to investigate its loss and electrical heating under real operating conditions, we built a test platform based on a resonant ring with a 13.4 dB power gain in the traveling wave of the resonant ring, which successfully achieves an equivalent power of 140 kW at the position of the antinode by means of two 2 kW power amplifiers. Based on the results of simulations and experiments, we optimized the design of the rectangular flexible waveguide and improved its structure and materials to better cope with the thermal deformation and stress under high power input. The optimized flexible waveguide's electrical and thermal performance is better than that of similar foreign products.
, Available online ,
doi: 10.11884/HPLPB202537.240353
Abstract:
The design of permanent magnet packaging for a compact S-band 8-cavity all-cavity axial extraction relativistic magnetron (R8 ACAE-RM) with an output mode of TE11 is preliminarily explored. The inner magnetic block is placed at both ends of the anode block in the anode cylinder, and the outer magnetic block is placed outside the RM, which generates a magnetic field of about 0.34 T and a length of 72 mm on the axial uniform zone in the interaction zone, and the weight of the permanent magnet is only 21 kg. Compared with the traditional external magnet system, this design can reduce the weight of the magnet, the magnetic field strength in the interaction zone is more uniform, and the system structure is more compact, which can meet the lightweight and miniaturization requirements of high-power microwave source systems. The device applied π mode as its operating mode, four 90° sector TE11 modes are extracted through all-cavity axial extraction structure, in order to obtain TE11 mode in circular waveguide, a coaxial-plate-inserted mode converter is designed for mode conversion. In particle-in-cell (PIC) simulation, the proposed R8 ACAE-RM can generate a microwave power of 1.06 GW with a pure TE11 mode at the frequency of 2.44 GHz under the conditions of a guiding magnetic generated by the inner and outer magnetic blocks, a diode voltage of 320 kV, and the power conversion efficiency is 47%.
The design of permanent magnet packaging for a compact S-band 8-cavity all-cavity axial extraction relativistic magnetron (R8 ACAE-RM) with an output mode of TE11 is preliminarily explored. The inner magnetic block is placed at both ends of the anode block in the anode cylinder, and the outer magnetic block is placed outside the RM, which generates a magnetic field of about 0.34 T and a length of 72 mm on the axial uniform zone in the interaction zone, and the weight of the permanent magnet is only 21 kg. Compared with the traditional external magnet system, this design can reduce the weight of the magnet, the magnetic field strength in the interaction zone is more uniform, and the system structure is more compact, which can meet the lightweight and miniaturization requirements of high-power microwave source systems. The device applied π mode as its operating mode, four 90° sector TE11 modes are extracted through all-cavity axial extraction structure, in order to obtain TE11 mode in circular waveguide, a coaxial-plate-inserted mode converter is designed for mode conversion. In particle-in-cell (PIC) simulation, the proposed R8 ACAE-RM can generate a microwave power of 1.06 GW with a pure TE11 mode at the frequency of 2.44 GHz under the conditions of a guiding magnetic generated by the inner and outer magnetic blocks, a diode voltage of 320 kV, and the power conversion efficiency is 47%.
, Available online ,
doi: 10.11884/HPLPB202537.240183
Abstract:
Neutral beam injection heating is an effective heating method in magnetic confinement fusion experiments. If the ion source ignites during experimental operation, the extraction of the ion beam is terminated, reducing the efficiency and power of the neutral beam ion source beam extraction. In order to prolong the extraction of the ion source beam in case of abnormal situations, research on high-voltage power fast recovery technology is carried out, which means that the beam is re extracted by running the high-voltage power supply again. A fast recovery control system was developed based on PXI Express technology, using the PXIe-8861 processor and PXIe-7820R programmable logic gate array hardware board for fast recovery technology. The control system adopts a heartbeat packet mechanism for board and communication status monitoring, with two parameter configuration methods for client and upper computer, meeting the functions of online/offline data viewing and analysis. Through the configuration of the upper computer mode, the control system supports voltage and quantity control, meeting multiple working modes such as modulation, fast recovery, and single operation. Test results on a megawatt-class strong ion source show that the control system interface is user-friendly, the logical structure is designed clearly, and it can meet various control modes. Furthermore, the system can restart the high-voltage power supply to improve the extraction power of the ion source beam during the experiment.
Neutral beam injection heating is an effective heating method in magnetic confinement fusion experiments. If the ion source ignites during experimental operation, the extraction of the ion beam is terminated, reducing the efficiency and power of the neutral beam ion source beam extraction. In order to prolong the extraction of the ion source beam in case of abnormal situations, research on high-voltage power fast recovery technology is carried out, which means that the beam is re extracted by running the high-voltage power supply again. A fast recovery control system was developed based on PXI Express technology, using the PXIe-8861 processor and PXIe-7820R programmable logic gate array hardware board for fast recovery technology. The control system adopts a heartbeat packet mechanism for board and communication status monitoring, with two parameter configuration methods for client and upper computer, meeting the functions of online/offline data viewing and analysis. Through the configuration of the upper computer mode, the control system supports voltage and quantity control, meeting multiple working modes such as modulation, fast recovery, and single operation. Test results on a megawatt-class strong ion source show that the control system interface is user-friendly, the logical structure is designed clearly, and it can meet various control modes. Furthermore, the system can restart the high-voltage power supply to improve the extraction power of the ion source beam during the experiment.
, Available online ,
doi: 10.11884/HPLPB202537.240373
Abstract:
An ionic liquid ion source has demonstrated the capability of generating diverse heavy molecular ions, and its applications have been investigated in the field of ion thrusters. This study aims to determine the quality parameters of ionic liquid ion beams and establish methods for their control. Firstly, the beam acceleration process in an ionic liquid ion source was simulated using particle methods, and the effects of the beam current, acceleration voltage, and emitter-extraction gap on the beam emittance and Twiss parameters were investigated. The results indicate that the normalized emittance decreases with a reduction in the beam current and emitter-extraction gap, as well as with an increase in the acceleration voltage. The kinetic energy broadens during the acceleration process. The acceleration efficiency is not obviously affected by the beam current or acceleration voltage. However, it increases with the expansion of the emitter-extraction gap. Secondly, the control of a centimeter-scale beam was simulated by utilizing the beam parameters derived from the simulation of the acceleration process. The results demonstrate that the divergence, velocity distribution, and specific impulse can be controlled by a set of three-electrode electrostatic lenses without imposing additional demands on the power source on the ionic liquid electric thruster.
An ionic liquid ion source has demonstrated the capability of generating diverse heavy molecular ions, and its applications have been investigated in the field of ion thrusters. This study aims to determine the quality parameters of ionic liquid ion beams and establish methods for their control. Firstly, the beam acceleration process in an ionic liquid ion source was simulated using particle methods, and the effects of the beam current, acceleration voltage, and emitter-extraction gap on the beam emittance and Twiss parameters were investigated. The results indicate that the normalized emittance decreases with a reduction in the beam current and emitter-extraction gap, as well as with an increase in the acceleration voltage. The kinetic energy broadens during the acceleration process. The acceleration efficiency is not obviously affected by the beam current or acceleration voltage. However, it increases with the expansion of the emitter-extraction gap. Secondly, the control of a centimeter-scale beam was simulated by utilizing the beam parameters derived from the simulation of the acceleration process. The results demonstrate that the divergence, velocity distribution, and specific impulse can be controlled by a set of three-electrode electrostatic lenses without imposing additional demands on the power source on the ionic liquid electric thruster.
, Available online ,
doi: 10.11884/HPLPB202537.240288
Abstract:
In this paper, four typical high purity graphite and their titanium carbide coating modified materials were tested as anodes in high current electron beam diodes. The results showed that the currents of four graphite were obviously different under electron beam bombardment with voltage 860 kV, current 11 kA and pulse width 40 ns. The current curve of graphite 4 # was normal even when electron beam acted 167 times, while the other graphite current curves showed different degree of tail erosion. The ablative experiments of titanium carbide coating on graphite further verified the difference of the graphite, indicating that the thermal conductivity of graphite has an important effect on its ablative resistance. The higher the thermal conductivity of graphite, the lower the degree of recrystallization of titanium carbide, the better the corrosion resistance of graphite. Therefore, graphite 4# has an excellent resistance to electron beam bombardment and should be promising for application as collector materials in relativistic traveling wave tubes.
In this paper, four typical high purity graphite and their titanium carbide coating modified materials were tested as anodes in high current electron beam diodes. The results showed that the currents of four graphite were obviously different under electron beam bombardment with voltage 860 kV, current 11 kA and pulse width 40 ns. The current curve of graphite 4 # was normal even when electron beam acted 167 times, while the other graphite current curves showed different degree of tail erosion. The ablative experiments of titanium carbide coating on graphite further verified the difference of the graphite, indicating that the thermal conductivity of graphite has an important effect on its ablative resistance. The higher the thermal conductivity of graphite, the lower the degree of recrystallization of titanium carbide, the better the corrosion resistance of graphite. Therefore, graphite 4# has an excellent resistance to electron beam bombardment and should be promising for application as collector materials in relativistic traveling wave tubes.
, Available online ,
doi: 10.11884/HPLPB202537.240266
Abstract:
During the operation of vacuum system in high-Flux laser device, molecular contamination generated by the pump lubricating oil in the vacuum environment may diffuse and deposit on the surface of optical system components, induce damage under high-Flux laser irradiation, and reduce the device's load capacity. Research has been conducted on the cleanliness control of vacuum systems, and a series of technical measures have been taken, We have developed a vacuum system cleanliness control method that includes optimizing the vacuum pump group, increasing low-temperature cold trap adsorption, and adding online heating regeneration technology for the cold trap.The experimental research results show that after 120 h of continuous operation, the average surface deposition of non-volatile residues in the vacuum system reaches a clean level of 2.86 × 10−9 g/cm2 after 24 h; The transmittance at 350 nm and the damage density curve below 12.3 J/cm2 flux of the fused quartz optical test piece assessment group and control group are basically consistent, proving the effectiveness of this method.
During the operation of vacuum system in high-Flux laser device, molecular contamination generated by the pump lubricating oil in the vacuum environment may diffuse and deposit on the surface of optical system components, induce damage under high-Flux laser irradiation, and reduce the device's load capacity. Research has been conducted on the cleanliness control of vacuum systems, and a series of technical measures have been taken, We have developed a vacuum system cleanliness control method that includes optimizing the vacuum pump group, increasing low-temperature cold trap adsorption, and adding online heating regeneration technology for the cold trap.The experimental research results show that after 120 h of continuous operation, the average surface deposition of non-volatile residues in the vacuum system reaches a clean level of 2.86 × 10−9 g/cm2 after 24 h; The transmittance at 350 nm and the damage density curve below 12.3 J/cm2 flux of the fused quartz optical test piece assessment group and control group are basically consistent, proving the effectiveness of this method.
, Available online ,
doi: 10.11884/HPLPB202537.240273
Abstract:
Shenzhen medium-energy high-repetition-rate X-ray free electron laser (S3FEL) requires 1MHz high-repetition-rate and high-stability Kicker. Transmission line structure Kicker is an effective way to achieve high repetition rate. However, the insufficient waveform stability of the transmission line structure Kicker limits the application of this type of Kicker in large particle accelerators. In order to solve the above problems, this paper studies the input waveform and circuit structure parameters of the transmission line structure Kicker. The main factors affecting the stability of Kicker’s working waveform are analyzed by using mathematical tools such as Fourier analysis, and the relationship between the harmonic order of Kicker ideal waveform and the cut-off frequency of Kicker transmission line structure is revealed. On this basis, this paper proposes a method to reduce the deviation between the actual waveform and the ideal waveform of Kicker. This method can obtain the ideal working waveform of Kicker within a certain range by adjusting the input waveform parameters or the cut-off frequency of Kicker. To verify the above relationship, this paper uses circuit simulation software to simulate different waveforms and different circuit parameters of Kicker. The simulation results verify that the above relationship revealed and confirm the effectiveness of the method mentioned.
Shenzhen medium-energy high-repetition-rate X-ray free electron laser (S3FEL) requires 1MHz high-repetition-rate and high-stability Kicker. Transmission line structure Kicker is an effective way to achieve high repetition rate. However, the insufficient waveform stability of the transmission line structure Kicker limits the application of this type of Kicker in large particle accelerators. In order to solve the above problems, this paper studies the input waveform and circuit structure parameters of the transmission line structure Kicker. The main factors affecting the stability of Kicker’s working waveform are analyzed by using mathematical tools such as Fourier analysis, and the relationship between the harmonic order of Kicker ideal waveform and the cut-off frequency of Kicker transmission line structure is revealed. On this basis, this paper proposes a method to reduce the deviation between the actual waveform and the ideal waveform of Kicker. This method can obtain the ideal working waveform of Kicker within a certain range by adjusting the input waveform parameters or the cut-off frequency of Kicker. To verify the above relationship, this paper uses circuit simulation software to simulate different waveforms and different circuit parameters of Kicker. The simulation results verify that the above relationship revealed and confirm the effectiveness of the method mentioned.
, Available online ,
doi: 10.11884/HPLPB202537.240192
Abstract:
In order to study the characteristics and evolution of the gas-liquid two-phase flow pattern in the rod bundle channel of pressurized water reactor, based on the double-layer wire mesh sensor, the air-water two-phase flow pattern experiment of the 3×3 rod bundle channels was carried out at room temperature and pressure. The flow patterns include bubble flow, cap flow and slug flow. The experimental results show that, the critical bubble diameter range for the reversal of lateral lift direction under normal temperature and pressure is 4 to 5.8 mm. In addition, for bubbly flow, the time-averaged void fraction exhibits a “wall peak” distribution at lower superficial gas velocities and a “center peak” distribution at higher superficial gas velocities. For the cap flow, the cross distribution of cap shaped bubbles within adjacent subchannels triggers large-scale mixing of the liquid phase between adjacent subchannels, and the time-averaged void fraction exhibits a “central peak” distribution. For slug flow, large-sized bubbles develop along the axis and cross subchannel gaps to aggregate into slug shaped bubbles, with a more pronounced distribution of the central peak of void fraction. In addition, the experimental data were used to evaluate drift-flux models, the Bestion’s drift-flux model overestimates the drift velocity, resulting in underestimated void fraction predictions. The Ozaki’s drift-flux model provides more accurate predictions of void fraction, with an average relative error of 9.8%.
In order to study the characteristics and evolution of the gas-liquid two-phase flow pattern in the rod bundle channel of pressurized water reactor, based on the double-layer wire mesh sensor, the air-water two-phase flow pattern experiment of the 3×3 rod bundle channels was carried out at room temperature and pressure. The flow patterns include bubble flow, cap flow and slug flow. The experimental results show that, the critical bubble diameter range for the reversal of lateral lift direction under normal temperature and pressure is 4 to 5.8 mm. In addition, for bubbly flow, the time-averaged void fraction exhibits a “wall peak” distribution at lower superficial gas velocities and a “center peak” distribution at higher superficial gas velocities. For the cap flow, the cross distribution of cap shaped bubbles within adjacent subchannels triggers large-scale mixing of the liquid phase between adjacent subchannels, and the time-averaged void fraction exhibits a “central peak” distribution. For slug flow, large-sized bubbles develop along the axis and cross subchannel gaps to aggregate into slug shaped bubbles, with a more pronounced distribution of the central peak of void fraction. In addition, the experimental data were used to evaluate drift-flux models, the Bestion’s drift-flux model overestimates the drift velocity, resulting in underestimated void fraction predictions. The Ozaki’s drift-flux model provides more accurate predictions of void fraction, with an average relative error of 9.8%.
, Available online ,
doi: 10.11884/HPLPB202537.240289
Abstract:
Negative hydrogen stripping injection is the only feasible scheme for accumulating beam in high current proton synchrotrons. Currently, the China Spallation Neutron Source (CSNS) employs negative hydrogen stripping injection by using a stripping foil. The intense temperature rising of the foil caused by energy deposition from the negative hydrogen beam passing through the foil is a critical issue which affecting the foil's lifetime and the stable operation of the accelerator. Additionally, the residual high power electron beam generated during the stripping process may have severe consequences, including electron ionization within the foil causing further temperature increase, thermal damage to the vacuum box from electron impacts, e-p instability from electrons captured by the proton beam in the vacuum tube, and significant electron cloud effects from secondary electrons. This paper focuses on two main topics: first, comprehensive simulations of the foil's temperature rise have been conducted using finite element analysis software, taking into account various parameters, including the average number of particle crossings. Simulation results under various software conditions are compared to obtain the temperature field distribution on the stripping foil and predict surface temperature increases for future higher beam power. Secondly, the electron distribution following the stripping process is analyzed based on theoretical calculations and Geant4 simulations. The 3D computational model is refined by considering the electromagnetic field and beam conditions in the CSNS injection area, and a scheme for capturing stripping electrons is proposed by determining the optimal position for the electron collection device.
Negative hydrogen stripping injection is the only feasible scheme for accumulating beam in high current proton synchrotrons. Currently, the China Spallation Neutron Source (CSNS) employs negative hydrogen stripping injection by using a stripping foil. The intense temperature rising of the foil caused by energy deposition from the negative hydrogen beam passing through the foil is a critical issue which affecting the foil's lifetime and the stable operation of the accelerator. Additionally, the residual high power electron beam generated during the stripping process may have severe consequences, including electron ionization within the foil causing further temperature increase, thermal damage to the vacuum box from electron impacts, e-p instability from electrons captured by the proton beam in the vacuum tube, and significant electron cloud effects from secondary electrons. This paper focuses on two main topics: first, comprehensive simulations of the foil's temperature rise have been conducted using finite element analysis software, taking into account various parameters, including the average number of particle crossings. Simulation results under various software conditions are compared to obtain the temperature field distribution on the stripping foil and predict surface temperature increases for future higher beam power. Secondly, the electron distribution following the stripping process is analyzed based on theoretical calculations and Geant4 simulations. The 3D computational model is refined by considering the electromagnetic field and beam conditions in the CSNS injection area, and a scheme for capturing stripping electrons is proposed by determining the optimal position for the electron collection device.
, Available online ,
doi: 10.11884/HPLPB202537.240274
Abstract:
This paper investigates the application of waveguide slot array antennas in high-power microwave technology and proposes a novel design method, with particular emphasis on the slot coupling, sidelobe levels, and matching between the antenna and the feed. The new method leverages modern computing technology to rapidly compute the slot conductance function considering slot coupling effects, thereby enabling efficient design of waveguide slot array antennas. This approach avoids complex calculations or external structures, ensuring system compactness and demonstrating higher effectiveness in designing waveguide slot planar arrays. Simulation results indicate that antennas designed using the new method exhibit excellent matching performance. At the center frequency f = 2.458 GHz, the reflection coefficient for each port of antenna designed using the new method ranges from −37.2 dB to −27.7 dB. In comparison, antennas designed using the Stevenson formula for the same target parameters have reflection coefficients ranging from −11 dB to −8.7 dB, with the reflection coefficients of antennas designed with the new method being reduced by at least 19 dB. Moreover, the antennas designed with this new method achieve a low sidelobe level of −30.2 dB and a high power capacity of 332.6 MW.
This paper investigates the application of waveguide slot array antennas in high-power microwave technology and proposes a novel design method, with particular emphasis on the slot coupling, sidelobe levels, and matching between the antenna and the feed. The new method leverages modern computing technology to rapidly compute the slot conductance function considering slot coupling effects, thereby enabling efficient design of waveguide slot array antennas. This approach avoids complex calculations or external structures, ensuring system compactness and demonstrating higher effectiveness in designing waveguide slot planar arrays. Simulation results indicate that antennas designed using the new method exhibit excellent matching performance. At the center frequency f = 2.458 GHz, the reflection coefficient for each port of antenna designed using the new method ranges from −37.2 dB to −27.7 dB. In comparison, antennas designed using the Stevenson formula for the same target parameters have reflection coefficients ranging from −11 dB to −8.7 dB, with the reflection coefficients of antennas designed with the new method being reduced by at least 19 dB. Moreover, the antennas designed with this new method achieve a low sidelobe level of −30.2 dB and a high power capacity of 332.6 MW.
, Available online ,
doi: 10.11884/HPLPB202537.240195
Abstract:
As one of important equipments for the linear injector of the Southern Light Source, the C-band photocathode electron gun is designed, In this paper, the RF and the coupler design are discussed. The working frequency of C-band electron gun is 5.712 GHz, using a 3.6-cell structure, π mode acceleration mode, and the coupler adopts a coaxial coupling method. The CST and Superfish are used to optimize the cavity microwave structure, reducing the surface electric field of the cavity to enhance the accelerating field strength and suppressing the multimode transmission. Furthermore, the Comsol is applied to analyze the cavity cooling system, reducing frequency drift caused by the cavity heating. Additionally, a water cooling design for the cavity ensures that the maximum temperature rise of the cavity is less than 20 degrees. Under an input power of 18.15MW, the acceleration gradient of 180 MV/m on the cathode surface is achieved, the ratio of the acceleration gradient to the cathode surface electric field is approximately 0.93, and the cavity quality factor is greater than 10000. For design of the coupler, suppresses the transmission of dipole and quadrupole modes is conducted, with the S11 parameter being less than −40 dB.
As one of important equipments for the linear injector of the Southern Light Source, the C-band photocathode electron gun is designed, In this paper, the RF and the coupler design are discussed. The working frequency of C-band electron gun is 5.712 GHz, using a 3.6-cell structure, π mode acceleration mode, and the coupler adopts a coaxial coupling method. The CST and Superfish are used to optimize the cavity microwave structure, reducing the surface electric field of the cavity to enhance the accelerating field strength and suppressing the multimode transmission. Furthermore, the Comsol is applied to analyze the cavity cooling system, reducing frequency drift caused by the cavity heating. Additionally, a water cooling design for the cavity ensures that the maximum temperature rise of the cavity is less than 20 degrees. Under an input power of 18.15MW, the acceleration gradient of 180 MV/m on the cathode surface is achieved, the ratio of the acceleration gradient to the cathode surface electric field is approximately 0.93, and the cavity quality factor is greater than 10000. For design of the coupler, suppresses the transmission of dipole and quadrupole modes is conducted, with the S11 parameter being less than −40 dB.
, Available online ,
doi: 10.11884/HPLPB202537.240334
Abstract:
Aiming at the pulse operating characteristics of voltage-controlled thyristors, a cascadable driving circuit is designed to realize the synchronous opening of multi-stage series-connected voltage-controlled thyristors. Firstly, the circuit topology and working principle is analysed. in which the coupled inductor is used to isolate the driver signal and transfer power to open the switch. Based on blumein PFN, an experimental test circuit is built, in which a 6-stage mos-controlled thyristor is series connected to be the discharge switch. A quasi-square-wave pulse current with an amplitude of 1.958 kA is obtained on a 4 Ω resistor.
Aiming at the pulse operating characteristics of voltage-controlled thyristors, a cascadable driving circuit is designed to realize the synchronous opening of multi-stage series-connected voltage-controlled thyristors. Firstly, the circuit topology and working principle is analysed. in which the coupled inductor is used to isolate the driver signal and transfer power to open the switch. Based on blumein PFN, an experimental test circuit is built, in which a 6-stage mos-controlled thyristor is series connected to be the discharge switch. A quasi-square-wave pulse current with an amplitude of 1.958 kA is obtained on a 4 Ω resistor.
, Available online ,
doi: 10.11884/HPLPB202537.240367
Abstract:
In this paper, a layout structure of the pulsed power generator based on the bipolar Linear Transformer Driver is proposed, achieving flexible stacking of the bipolar Linear Transformer Driver modules. The conduction time of the Metal-Oxide-Semiconductor Field Effect Transistor is regulated by adjusting the voltage of the driver circuit, enabling the precise control over the rise time of the pulsed voltage. An integrated core-copper pillar structure and a reverse overshoot discharge circuit are introduced in the Linear Transformer Driver structure, which optimizes the electromagnetic compatibility and reduces the reverse overshoot at the tail of the pulsed waveform. The developed bipolar Linear Transformer Driver device can stably output ±5 kV pulsed voltage with 1kHz in frequency and 1 μs in pulse width. The rise time of the pulsed voltage is continuously adjustable from 30 ns to 100 ns.The irreversible electroporation experiments on cells is carried out using the bipolar Linear Transformer Driver.
In this paper, a layout structure of the pulsed power generator based on the bipolar Linear Transformer Driver is proposed, achieving flexible stacking of the bipolar Linear Transformer Driver modules. The conduction time of the Metal-Oxide-Semiconductor Field Effect Transistor is regulated by adjusting the voltage of the driver circuit, enabling the precise control over the rise time of the pulsed voltage. An integrated core-copper pillar structure and a reverse overshoot discharge circuit are introduced in the Linear Transformer Driver structure, which optimizes the electromagnetic compatibility and reduces the reverse overshoot at the tail of the pulsed waveform. The developed bipolar Linear Transformer Driver device can stably output ±5 kV pulsed voltage with 1kHz in frequency and 1 μs in pulse width. The rise time of the pulsed voltage is continuously adjustable from 30 ns to 100 ns.The irreversible electroporation experiments on cells is carried out using the bipolar Linear Transformer Driver.
, Available online ,
doi: 10.11884/HPLPB202537.240168
Abstract:
The terahertz near-field high-throughput material physical property testing system (NFTHZ) integrates a wavelength-tunable terahertz free electron laser (THz-FEL). The instrument uses a linear accelerator with tunable electron energy of 10～18 MeV as the injector. A pre-bunched electron beam can be formed by adjusting the longitudinal/temporal structure of the driving laser. By matching the relationship between the bunching factor, energy of the electron beam at the undulator entrance and the K value of undulator, a terahertz free electron laser with megawatts peak power and an adjustable center wavelength of 0.5～5 THz can be achieved. The microwave system provides high-power microwave electric field, accelerating structure and microwave amplitude and phase control system to accelerate the electron beam to the target energy. This article will introduce the development of the microwave system of the NFTHZ facility and the construction progress of the electron linear accelerator.
The terahertz near-field high-throughput material physical property testing system (NFTHZ) integrates a wavelength-tunable terahertz free electron laser (THz-FEL). The instrument uses a linear accelerator with tunable electron energy of 10～18 MeV as the injector. A pre-bunched electron beam can be formed by adjusting the longitudinal/temporal structure of the driving laser. By matching the relationship between the bunching factor, energy of the electron beam at the undulator entrance and the K value of undulator, a terahertz free electron laser with megawatts peak power and an adjustable center wavelength of 0.5～5 THz can be achieved. The microwave system provides high-power microwave electric field, accelerating structure and microwave amplitude and phase control system to accelerate the electron beam to the target energy. This article will introduce the development of the microwave system of the NFTHZ facility and the construction progress of the electron linear accelerator.
, Available online ,
doi: 10.11884/HPLPB202537.240225
Abstract:
High power microwave is easy to enter the system through the main coupling path of interconnection cables between electronic devices, disrupting or even damaging sensitive circuits or devices. In order to guide the rational wiring in engineering and improve the survival ability of electronic system under high power microwave, the coupling effect between HPM and cable under different parameters(cable length, height from ground, terminal load resistance, radiation field incidence angle) is systematically studied by combining simulation analysis and test verification. The coupling response law is obtained and the internal reasons are analyzed. The results show that with the increase of cable length, the coupling signal oscillates first and then tends to be stable gradually, and the oscillation period is equal to the wavelength of the incident wave. The coupling signal oscillates with the change of the height from the cable to the ground, and the maximum and minimum values appear when the height from the ground is odd times of 1/4 wavelength and integer times of 1/2 wavelength of the incident wave respectively. The coupling signal decreases first and then increases with the increase of terminal load resistance. When the load resistance matches the cable characteristic impedance, the coupling signal is the smallest. The coupling signal increases with the increase of the angle between the incoming wave direction and the cable layout direction, and the coupling signal is the largest when the two are perpendicular. On this basis, some optimization suggestions of cable laying in practical engineering are given, which provides guidance for system-level electromagnetic compatibility and high-power microwave protection design.
High power microwave is easy to enter the system through the main coupling path of interconnection cables between electronic devices, disrupting or even damaging sensitive circuits or devices. In order to guide the rational wiring in engineering and improve the survival ability of electronic system under high power microwave, the coupling effect between HPM and cable under different parameters(cable length, height from ground, terminal load resistance, radiation field incidence angle) is systematically studied by combining simulation analysis and test verification. The coupling response law is obtained and the internal reasons are analyzed. The results show that with the increase of cable length, the coupling signal oscillates first and then tends to be stable gradually, and the oscillation period is equal to the wavelength of the incident wave. The coupling signal oscillates with the change of the height from the cable to the ground, and the maximum and minimum values appear when the height from the ground is odd times of 1/4 wavelength and integer times of 1/2 wavelength of the incident wave respectively. The coupling signal decreases first and then increases with the increase of terminal load resistance. When the load resistance matches the cable characteristic impedance, the coupling signal is the smallest. The coupling signal increases with the increase of the angle between the incoming wave direction and the cable layout direction, and the coupling signal is the largest when the two are perpendicular. On this basis, some optimization suggestions of cable laying in practical engineering are given, which provides guidance for system-level electromagnetic compatibility and high-power microwave protection design.
, Available online ,
doi: 10.11884/HPLPB202537.240199
Abstract:
In laser-driven inertial confinement fusion experiments, the CR-39 detector, a commonly - used recording medium for proton energy spectrum diagnosis, has timeliness and consistency flaws in energy spectrum measurement. However, the Timepix detector with the ability to obtain online signals can overcome these problems. To apply the Timepix detector to detect implosion proton energy spectra, it is essential to study the response of the Timepix detector to proton energies and incident angles. This work analyzes the response of the Timepix detector to proton beams in different energies and incident angles within the Allpix2 framework using Monte Carlo methods. The simulation results show that the response of the Timepix detector to proton beams in different energies and incident angles exhibits significant differences in cluster morphology, cluster size distribution, and cluster charge distribution. When incident proton beam energy is below 6 MeV, the Timepix detector exhibits high detection efficiency, and the angle of proton incidence does not significantly affect the energy response of the detector.
In laser-driven inertial confinement fusion experiments, the CR-39 detector, a commonly - used recording medium for proton energy spectrum diagnosis, has timeliness and consistency flaws in energy spectrum measurement. However, the Timepix detector with the ability to obtain online signals can overcome these problems. To apply the Timepix detector to detect implosion proton energy spectra, it is essential to study the response of the Timepix detector to proton energies and incident angles. This work analyzes the response of the Timepix detector to proton beams in different energies and incident angles within the Allpix2 framework using Monte Carlo methods. The simulation results show that the response of the Timepix detector to proton beams in different energies and incident angles exhibits significant differences in cluster morphology, cluster size distribution, and cluster charge distribution. When incident proton beam energy is below 6 MeV, the Timepix detector exhibits high detection efficiency, and the angle of proton incidence does not significantly affect the energy response of the detector.
, Available online ,
doi: 10.11884/HPLPB202537.240232
Abstract:
Stimulated Raman scattering is an effective non-linear frequency conversion method, and has received much attention. However, Raman lasers also have drawbacks, such as wavelength of Raman lasers could not be tuned continuously, therefore, the coverage of Raman laser wavelength is limited. So more Raman active media are required to improve the coverage of Raman lasers. In this work,1064 nm laser was used as pump source, and pressurized ethane was used as Raman active medium, and 1550 nm Raman laser was produced. No obvious backward Raman laser, nor higher orders of Stokes Raman lasers were observed in this experiment. By the optimization of experimental parameters, laser induced breakdown was meliorated; S1 Raman laser photon conversion efficiency was improved to 20.7%, and the maximum S1 energy was 21.2 mJ. Ethane was found having significant absorption at wavelength of 1550 nm, this was the major reason for the limited photon conversion efficiency and pulse energy of S1 Raman laser. The absorption coefficient of ethane at 1550 nm was measured to be 5.71\begin{document}$ \times {{10}}^{-{8}} $\end{document} ![]()
![]()
\begin{document}$ {2.3}{5} \times {{10}}^{-{24}}{\text{ cm}}^{{2}} $\end{document} ![]()
![]()
Stimulated Raman scattering is an effective non-linear frequency conversion method, and has received much attention. However, Raman lasers also have drawbacks, such as wavelength of Raman lasers could not be tuned continuously, therefore, the coverage of Raman laser wavelength is limited. So more Raman active media are required to improve the coverage of Raman lasers. In this work,
, Available online ,
doi: 10.11884/HPLPB202537.240154
Abstract:
In large current accelerator beam tubes, high-frequency fields are generated when charged particles circulate within the beam pipe. To mitigate the impact on beam current, it is essential to use high-order mode damper that convert the high-energy fields into heat, which can then be dissipated by a cooling system. This paper presents the research, fabrication, and key performance characteristics of a hybrid high-order mode damper. The absorbing materials utilized in the damper include ferrite and silicon carbide, which can be welded to metal substrates through metallization and welding techniques. Microwave performance simulations and thermal simulations were conducted using CST and COMSOL software, respectively, leading to an optimized damper structure. Test results demonstrate that the absorption efficiency of the hybrid damper aligns closely with calculated values in the frequency range below 1.7 GHz. However, while the simulated absorption efficiency exceeds the measured results above 1.7 GHz, significant discrepancies between the two sets of results were observed. Additionally, the vacuum leak rates, ultimate vacuum, and water resistance meet the design requirements for superconducting high-frequency cavities.
In large current accelerator beam tubes, high-frequency fields are generated when charged particles circulate within the beam pipe. To mitigate the impact on beam current, it is essential to use high-order mode damper that convert the high-energy fields into heat, which can then be dissipated by a cooling system. This paper presents the research, fabrication, and key performance characteristics of a hybrid high-order mode damper. The absorbing materials utilized in the damper include ferrite and silicon carbide, which can be welded to metal substrates through metallization and welding techniques. Microwave performance simulations and thermal simulations were conducted using CST and COMSOL software, respectively, leading to an optimized damper structure. Test results demonstrate that the absorption efficiency of the hybrid damper aligns closely with calculated values in the frequency range below 1.7 GHz. However, while the simulated absorption efficiency exceeds the measured results above 1.7 GHz, significant discrepancies between the two sets of results were observed. Additionally, the vacuum leak rates, ultimate vacuum, and water resistance meet the design requirements for superconducting high-frequency cavities.
, Available online ,
doi: 10.11884/HPLPB202537.240223
Abstract:
Due to the comprehensive performance advantages, GaN-based power devices are more suitable for the future development needs of RF power amplifier modules in the space equipment such as satellite electronic systems．Therefore, the degradation of electrical characteristics and damage mechanism of the enhancement-mode Cascode structure GaN HEMT devices were studied by irradiation experiments with 5 MeV, 60 MeV and 300 MeV protons at the irradiation dose of 2×1012～1×1014 p/cm2. The experimental results show that when the irradiation dose is 2×1012 p/cm2, the threshold voltage of Cascode structure GaN HEMT device is significantly reduced, the transconductance peak is negative drift and the peak transconductance is reduced, the saturated drain current is significantly increased, and the gate leakage current has no significant change. When the irradiation dose reaches 1×1013 p/cm2, the degradation of electrical properties is inhibited and tends to saturation. It is concluded that the existence of cascaded silicon MOSFET in Cascode structure GaN HEMT is the internal cause of threshold voltage negative drift and drain current increase after proton irradiation. Combined with low-frequency noise test analysis, it is found that the higher the proton irradiation dose, the larger the noise power spectral density of the device, indicating that the more defects introduced by irradiation, the more serious the irradiation damage. Compared with the results of 60 MeV and 300 MeV proton irradiation, the degradation of electrical characteristics of the device after 5 MeV proton irradiation is the most serious. SRIM simulation results show that the lower the proton irradiation energy, the greater the number of vacancies (gallium vacancy is dominated), and the more significant the degradation of electrical characteristics of the device.
Due to the comprehensive performance advantages, GaN-based power devices are more suitable for the future development needs of RF power amplifier modules in the space equipment such as satellite electronic systems．Therefore, the degradation of electrical characteristics and damage mechanism of the enhancement-mode Cascode structure GaN HEMT devices were studied by irradiation experiments with 5 MeV, 60 MeV and 300 MeV protons at the irradiation dose of 2×1012～1×1014 p/cm2. The experimental results show that when the irradiation dose is 2×1012 p/cm2, the threshold voltage of Cascode structure GaN HEMT device is significantly reduced, the transconductance peak is negative drift and the peak transconductance is reduced, the saturated drain current is significantly increased, and the gate leakage current has no significant change. When the irradiation dose reaches 1×1013 p/cm2, the degradation of electrical properties is inhibited and tends to saturation. It is concluded that the existence of cascaded silicon MOSFET in Cascode structure GaN HEMT is the internal cause of threshold voltage negative drift and drain current increase after proton irradiation. Combined with low-frequency noise test analysis, it is found that the higher the proton irradiation dose, the larger the noise power spectral density of the device, indicating that the more defects introduced by irradiation, the more serious the irradiation damage. Compared with the results of 60 MeV and 300 MeV proton irradiation, the degradation of electrical characteristics of the device after 5 MeV proton irradiation is the most serious. SRIM simulation results show that the lower the proton irradiation energy, the greater the number of vacancies (gallium vacancy is dominated), and the more significant the degradation of electrical characteristics of the device.
, Available online ,
doi: 10.11884/HPLPB202537.240209
Abstract:
Compared with high-pressure gas tanks, supersonic injection technology has significant advantages in pressure recovery of chemical laser weapons. Among them, the supersonic center injector has greater injection potential due to its smaller total pressure loss. Simulation and experimental studies were conducted on the supersonic center injector. The results show that for the supersonic center injector with a contraction-type mixing chamber, although it is easier to reach the working state, it is not superior to the straight-type injector under the condition of fixed injection coefficient and maintaining a lower blind cavity pressure. Under the condition of variable injection coefficient (fixed secondary mass flow rate), for every 0.05 increase in the area contraction ratio of the mixing chamber, the primary mass flow rate needs to be increased by approximately 0.3 kg/s to reach the critical start-up state. The overall injection performance of the supersonic injector reaches its highest when it is at the critical start-up state. In terms of blind cavity extraction capability, the single-stage supersonic center injector is significantly superior to other types of injectors, with a minimum of 1.3kPa achievable.
Compared with high-pressure gas tanks, supersonic injection technology has significant advantages in pressure recovery of chemical laser weapons. Among them, the supersonic center injector has greater injection potential due to its smaller total pressure loss. Simulation and experimental studies were conducted on the supersonic center injector. The results show that for the supersonic center injector with a contraction-type mixing chamber, although it is easier to reach the working state, it is not superior to the straight-type injector under the condition of fixed injection coefficient and maintaining a lower blind cavity pressure. Under the condition of variable injection coefficient (fixed secondary mass flow rate), for every 0.05 increase in the area contraction ratio of the mixing chamber, the primary mass flow rate needs to be increased by approximately 0.3 kg/s to reach the critical start-up state. The overall injection performance of the supersonic injector reaches its highest when it is at the critical start-up state. In terms of blind cavity extraction capability, the single-stage supersonic center injector is significantly superior to other types of injectors, with a minimum of 1.3kPa achievable.
, Available online ,
doi: 10.11884/HPLPB202537.240216
Abstract:
In the process of high energy and high power extreme ultraviolet (EUV) irradiation, carbon deposition and surface oxidation are easy to form on the surface of the EUV mirror, which will affect its reflectivity and shorten its service life. To solve this problem, technology of nitride and oxide capping coating on the surface of extreme ultraviolet multilayer film was studied experimentally and characterized. In the preparation process, based on DC reactive magnetron sputtering coating technology, the "hyperbola" relationship between process gas flow and sputtering voltage was studied, to optimize the control of the amount of reactive gas, and then reduce the influence of reactive gas on Mo/Si multilayer films during reactive sputtering. Based on this method, TiN, ZrN and TiO2 capping layer were plated on the surface of Mo/Si multilayer films and were characterized by grazing incident X-ray reflection (GIXR), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). It is proved that the nitride capping layer has certain performance advantages.
In the process of high energy and high power extreme ultraviolet (EUV) irradiation, carbon deposition and surface oxidation are easy to form on the surface of the EUV mirror, which will affect its reflectivity and shorten its service life. To solve this problem, technology of nitride and oxide capping coating on the surface of extreme ultraviolet multilayer film was studied experimentally and characterized. In the preparation process, based on DC reactive magnetron sputtering coating technology, the "hyperbola" relationship between process gas flow and sputtering voltage was studied, to optimize the control of the amount of reactive gas, and then reduce the influence of reactive gas on Mo/Si multilayer films during reactive sputtering. Based on this method, TiN, ZrN and TiO2 capping layer were plated on the surface of Mo/Si multilayer films and were characterized by grazing incident X-ray reflection (GIXR), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). It is proved that the nitride capping layer has certain performance advantages.
, Available online ,
doi: 10.11884/HPLPB202537.240153
Abstract:
The RF linac dedicated to boron neutron capture therapy clinic facility (BNCT02) in our institute is mainly composed of an ion source, a low energy beam transmission line, a radio frequency quadrupole accelerator and three high energy beam transmission lines. This study aims to ensure the safe operation of the BNCT02 accelerator. A machine protection system (MPS) was designed based on Yokogawa PLC and Experimental Physics and Industrial Control System (EPICS) software toolkit. In order to improve safety, the system adopts a redundant design, consisting of two completely independent subsystems with consistent main input and output signals. The test results show that the response time of the BNCT02 accelerator MPS is less than 1.6 ms, and it has the characteristics of high stability and reliability, which meets the operational requirements of the BNCT02 accelerator.
The RF linac dedicated to boron neutron capture therapy clinic facility (BNCT02) in our institute is mainly composed of an ion source, a low energy beam transmission line, a radio frequency quadrupole accelerator and three high energy beam transmission lines. This study aims to ensure the safe operation of the BNCT02 accelerator. A machine protection system (MPS) was designed based on Yokogawa PLC and Experimental Physics and Industrial Control System (EPICS) software toolkit. In order to improve safety, the system adopts a redundant design, consisting of two completely independent subsystems with consistent main input and output signals. The test results show that the response time of the BNCT02 accelerator MPS is less than 1.6 ms, and it has the characteristics of high stability and reliability, which meets the operational requirements of the BNCT02 accelerator.
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/HPLPB202537.240342
Abstract:
A new method of waveform reconstruction based on neural network is proposed to solve the problem of nano-second pulse distortion, which is caused by the existence of parasitic parameters and insufficient bandwidth in high-speed digital acquisition channels. The local mapping relationship between the distortion waveform acquired by the high-speed digital acquisition system and the reference waveform obtained from the oscilloscope is identified through single neural networks. Then, the global waveform is reconstructed by a series of neural networks. The experimental results show that the proposed method can obviously alleviate the problems such as the edge delay, overshoot of the distortion waveform, thus it can improve the power estimation accuracy by 32.5%, as well as improve the frequency response characteristics of the high-speed digital acquisition system.
A new method of waveform reconstruction based on neural network is proposed to solve the problem of nano-second pulse distortion, which is caused by the existence of parasitic parameters and insufficient bandwidth in high-speed digital acquisition channels. The local mapping relationship between the distortion waveform acquired by the high-speed digital acquisition system and the reference waveform obtained from the oscilloscope is identified through single neural networks. Then, the global waveform is reconstructed by a series of neural networks. The experimental results show that the proposed method can obviously alleviate the problems such as the edge delay, overshoot of the distortion waveform, thus it can improve the power estimation accuracy by 32.5%, as well as improve the frequency response characteristics of the high-speed digital acquisition system.
, Available online ,
doi: 10.11884/HPLPB202537.240296
Abstract:
Studying the transmission characteristics of high-frequency microwaves in plasma can effectively analyze and assess the information transfer process in microwave communication and radar technology. Numerical simulations were employed to analyze the effects of plasma electron density, thickness, and incident wave frequency on microwave reflection, absorption, and transmission. The results indicate that increased plasma thickness and electron density lead to enhanced absorption and reduced transmission; reflection increases slightly with decreased thickness and increased electron density. High-frequency microwaves are more easily transmitted through plasma, with transmission enhancing as frequency increases. Furthermore, the research shows that electron density not only affects energy transmission but also alters the electromagnetic wave shape, causing its broadening. High-density plasma significantly broadens microwave waveforms both spatially and temporally, with inelastic collisions contributing prominently to this broadening. The patterns of waveform changes can provide theoretical support for the restoration of information carried by radar echoes and microwave communications.
Studying the transmission characteristics of high-frequency microwaves in plasma can effectively analyze and assess the information transfer process in microwave communication and radar technology. Numerical simulations were employed to analyze the effects of plasma electron density, thickness, and incident wave frequency on microwave reflection, absorption, and transmission. The results indicate that increased plasma thickness and electron density lead to enhanced absorption and reduced transmission; reflection increases slightly with decreased thickness and increased electron density. High-frequency microwaves are more easily transmitted through plasma, with transmission enhancing as frequency increases. Furthermore, the research shows that electron density not only affects energy transmission but also alters the electromagnetic wave shape, causing its broadening. High-density plasma significantly broadens microwave waveforms both spatially and temporally, with inelastic collisions contributing prominently to this broadening. The patterns of waveform changes can provide theoretical support for the restoration of information carried by radar echoes and microwave communications.
, Available online ,
doi: 10.11884/HPLPB202537.240243
Abstract:
Accurate and fast solution of the electromagnetic characteristics problems is of great significance for the study of dynamic characteristics and reliability design of electromagnetic railguns. Based on the COMSOL moving mesh function, a new form of meshing—slip mesh combined with moving mesh—is proposed. The armature area and the track part where the pivot rail is in contact are meshed in to slip mesh, and the rest of the track part is dynamically meshed. This division method can not only solve the problems of low computational accuracy (coarse mesh) and high computational complexity (fine mesh) of “static mesh”, but also accurately solve the dynamic electromagnetic characteristics problems of transient and fast-moving models. The pulsed excitation current was used to simulate and analyze the established electromagnetic railgun model. The computing time and number of computational units of the three static meshes are compared with the meshing method proposed in this paper. The simulation results of different meshing methods on the armature motion velocity and the current density distribution at the armature center position are compared, and it is proved that the proposed meshing method is effective and efficient.
Accurate and fast solution of the electromagnetic characteristics problems is of great significance for the study of dynamic characteristics and reliability design of electromagnetic railguns. Based on the COMSOL moving mesh function, a new form of meshing—slip mesh combined with moving mesh—is proposed. The armature area and the track part where the pivot rail is in contact are meshed in to slip mesh, and the rest of the track part is dynamically meshed. This division method can not only solve the problems of low computational accuracy (coarse mesh) and high computational complexity (fine mesh) of “static mesh”, but also accurately solve the dynamic electromagnetic characteristics problems of transient and fast-moving models. The pulsed excitation current was used to simulate and analyze the established electromagnetic railgun model. The computing time and number of computational units of the three static meshes are compared with the meshing method proposed in this paper. The simulation results of different meshing methods on the armature motion velocity and the current density distribution at the armature center position are compared, and it is proved that the proposed meshing method is effective and efficient.
, Available online ,
doi: 10.11884/HPLPB202537.240158
Abstract:
To enhance the shock wave generated by underwater electrical wire explosion(UEWE), wires are connected in parallel to form wire-array, but wire-array’s low resistance results in low deposition power. To solve the problem, by using copper sheets, parallel-series wire-arrays with different resistance and same mass were designed, and it was proposed that resistance matching between wire-array and power source is the ideal discharge mode. By parallel-series wire-array, single wire discharge similarity was verified, and miniaturization verification of large devices with high voltage was achieved. With the help of discharge similarity and parallel-series wire-array, the optimal wire-array design of UEWE was proposed at a given energy and wire mass.
To enhance the shock wave generated by underwater electrical wire explosion(UEWE), wires are connected in parallel to form wire-array, but wire-array’s low resistance results in low deposition power. To solve the problem, by using copper sheets, parallel-series wire-arrays with different resistance and same mass were designed, and it was proposed that resistance matching between wire-array and power source is the ideal discharge mode. By parallel-series wire-array, single wire discharge similarity was verified, and miniaturization verification of large devices with high voltage was achieved. With the help of discharge similarity and parallel-series wire-array, the optimal wire-array design of UEWE was proposed at a given energy and wire mass.
, Available online ,
doi: 10.11884/HPLPB202537.240315
Abstract:
Pulsed power drive source is a key part of high power microwave technology. The quality of the output waveform of pulsed power drive source directly affects the output of high power microwave devices. Aiming at the oscillation problem of the flat-top output waveform of pulse power drive source, we designed and developed a compact pulsed power drive source based on PFN-Marx, and optimized the waveform. The parameters of PFN-Marx generators with different structures are analyzed by PSpice simulation, so as to determine the number of sections and levels of the PFN-Marx generator; the oscillation problem of the output waveform is converted into the degree of deviation of each extreme point from the reference value in the flat-top area of the waveform. The objective function is constructed with the root mean square error with the minimum flat-top ripple error as the goal, and the circuit model is established in Simulink. Combined with the MATLAB genetic algorithm, the inductance of the PFN is continuously iteratively optimized. Finally, a set of optimal values is determined, and the inductance structure is redesigned to adjust the inductance value conveniently and to achieve quick waveform optimization. The optimized single-stage PFN outputs a waveform with a leading edge of 24.4 ns and a pulse width of 93.6 ns on a 10 Ω load, and it has good flat-top performance. The assembled 7-stage PFN-Marx generator has an output quasi-square wave under a charging voltage of 53.8 kV and a load impedance of 75 Ω. The pulse peak amplitude is 189.2 kV, pulse width is 93.2 ns, rise time is 8.4 ns, decrease time is 33.6 ns, and the ripple coefficient is 3.5%.
Pulsed power drive source is a key part of high power microwave technology. The quality of the output waveform of pulsed power drive source directly affects the output of high power microwave devices. Aiming at the oscillation problem of the flat-top output waveform of pulse power drive source, we designed and developed a compact pulsed power drive source based on PFN-Marx, and optimized the waveform. The parameters of PFN-Marx generators with different structures are analyzed by PSpice simulation, so as to determine the number of sections and levels of the PFN-Marx generator; the oscillation problem of the output waveform is converted into the degree of deviation of each extreme point from the reference value in the flat-top area of the waveform. The objective function is constructed with the root mean square error with the minimum flat-top ripple error as the goal, and the circuit model is established in Simulink. Combined with the MATLAB genetic algorithm, the inductance of the PFN is continuously iteratively optimized. Finally, a set of optimal values is determined, and the inductance structure is redesigned to adjust the inductance value conveniently and to achieve quick waveform optimization. The optimized single-stage PFN outputs a waveform with a leading edge of 24.4 ns and a pulse width of 93.6 ns on a 10 Ω load, and it has good flat-top performance. The assembled 7-stage PFN-Marx generator has an output quasi-square wave under a charging voltage of 53.8 kV and a load impedance of 75 Ω. The pulse peak amplitude is 189.2 kV, pulse width is 93.2 ns, rise time is 8.4 ns, decrease time is 33.6 ns, and the ripple coefficient is 3.5%.
, Available online ,
doi: 10.11884/HPLPB202537.240159
Abstract:
To solve the problems of low inhibition of parasitic mode and measurement accuracy is susceptible to interference of parasitic modes in traditional high power microwave online measurement devices, a high-power TM01 mode coupling device is studied, which is applied to the Ku-band relativistic backward wave oscillator (RBWO) online measurement system. Due to the RBWO emission’s angular inhomogeneity, asymmetric modes is generated, and the traditional single-arm porous circular waveguide coupler cannot solve the competition problem between the TM01 mode and the asymmetric modes, which generally leads to the detection waveform distortion and coupling degree judgment deviation and seriously affects the accuracy of the online evaluation of the output power of TM01 mode of the RBWO. For this reason, combining the four-arm porous coupling structure with the TM01 mode selection network, a novel online mode-selective coupling device is proposed in this paper. Using the field structure difference of different waveguide modes, the proposed device realizes the differential coupling of TM01 mode and other parasitic modes and solves the problem of inaccurate online test power caused by parasitic mode interference. The simulation results show that the coupling degree of the proposed new coupler to TM01 mode is more than 20 dB higher than that of the other modes, and the on-line test waveform and power measured in the high-power experiment are in good agreement with the radiated field test waveform and power, and the coupling stability is significantly improved.
To solve the problems of low inhibition of parasitic mode and measurement accuracy is susceptible to interference of parasitic modes in traditional high power microwave online measurement devices, a high-power TM01 mode coupling device is studied, which is applied to the Ku-band relativistic backward wave oscillator (RBWO) online measurement system. Due to the RBWO emission’s angular inhomogeneity, asymmetric modes is generated, and the traditional single-arm porous circular waveguide coupler cannot solve the competition problem between the TM01 mode and the asymmetric modes, which generally leads to the detection waveform distortion and coupling degree judgment deviation and seriously affects the accuracy of the online evaluation of the output power of TM01 mode of the RBWO. For this reason, combining the four-arm porous coupling structure with the TM01 mode selection network, a novel online mode-selective coupling device is proposed in this paper. Using the field structure difference of different waveguide modes, the proposed device realizes the differential coupling of TM01 mode and other parasitic modes and solves the problem of inaccurate online test power caused by parasitic mode interference. The simulation results show that the coupling degree of the proposed new coupler to TM01 mode is more than 20 dB higher than that of the other modes, and the on-line test waveform and power measured in the high-power experiment are in good agreement with the radiated field test waveform and power, and the coupling stability is significantly improved.
, Available online ,
doi: 10.11884/HPLPB202537.240254
Abstract:
To reduce the threshold of using pulse power source, a compact pulse power source based on Marx generator is designed and implemented. The Marx generator is a 7-stage unipolar charging coaxial structure with low inductance ceramic capacitor and ultraviolet preionization output narrow pulse. It uses adjustable primary high voltage power supply and 2-way synchronous trigger switch, and metal shell as grounding shield and discharge circuit; it is filled with high pressure N2. Using the power source based on the above design, when the charging voltage is 26 kV and the charging voltage is 0.3 MPa, the high voltage pulse of 33 ns rise time, 59 ns pulse width and 109.2 kV amplitude is obtained on the 60 Ω load. The power source is housed in an aluminum alloy cylinder with a diameter of 0.2 m and a length of 1.1m. This paper provides a design idea and a reference prototype for compact and modular pulse power source, which can be used as flash X-ray radiography drive source.
To reduce the threshold of using pulse power source, a compact pulse power source based on Marx generator is designed and implemented. The Marx generator is a 7-stage unipolar charging coaxial structure with low inductance ceramic capacitor and ultraviolet preionization output narrow pulse. It uses adjustable primary high voltage power supply and 2-way synchronous trigger switch, and metal shell as grounding shield and discharge circuit; it is filled with high pressure N2. Using the power source based on the above design, when the charging voltage is 26 kV and the charging voltage is 0.3 MPa, the high voltage pulse of 33 ns rise time, 59 ns pulse width and 109.2 kV amplitude is obtained on the 60 Ω load. The power source is housed in an aluminum alloy cylinder with a diameter of 0.2 m and a length of 1.1m. This paper provides a design idea and a reference prototype for compact and modular pulse power source, which can be used as flash X-ray radiography drive source.
, Available online ,
doi: 10.11884/HPLPB202537.240211
Abstract:
The Monte Carlo (MC) method is one of the most widely applied methods in the simulation study of radiation damage and radiation shielding. When conducting radiation damage studies on large targets such as airports, railways, and ships, the focus is generally on 3D modeling and radiation calculations of these targets; however, the post-calculation data analysis often relies on manual methods, making this aspect of the research technically challenging and inefficient, thus becoming a bottleneck in related research efforts. In this paper, a visualization post-processing method for MC calculations of target particle irradiation is studied, and a post-processing model based on k-dimensional tree (KDtree) + inverse distance weighting (IDW) and genetic algorithm based backpropagation (GABP) neural network is established to realize the visualization analysis of data combined with the model. Compared with traditional data analysis methods, the method proposed in this paper can greatly reduce the difficulty of researchers’ work, improve the speed of data processing, realize the visual display of radiation effects, and enhance the efficiency of post-processing in radiation effects research.
The Monte Carlo (MC) method is one of the most widely applied methods in the simulation study of radiation damage and radiation shielding. When conducting radiation damage studies on large targets such as airports, railways, and ships, the focus is generally on 3D modeling and radiation calculations of these targets; however, the post-calculation data analysis often relies on manual methods, making this aspect of the research technically challenging and inefficient, thus becoming a bottleneck in related research efforts. In this paper, a visualization post-processing method for MC calculations of target particle irradiation is studied, and a post-processing model based on k-dimensional tree (KDtree) + inverse distance weighting (IDW) and genetic algorithm based backpropagation (GABP) neural network is established to realize the visualization analysis of data combined with the model. Compared with traditional data analysis methods, the method proposed in this paper can greatly reduce the difficulty of researchers’ work, improve the speed of data processing, realize the visual display of radiation effects, and enhance the efficiency of post-processing in radiation effects research.
, Available online ,
doi: 10.11884/HPLPB202537.240265
Abstract:
On the pulsed fusion sources such as laser ICF device, Z pinch facility and dense plasma focus device, the neutron activation method are widely applied, which can measure the neutron flux and diagnose the neutron yield from the source. Based on the inorganic scintillation detector, the 909 keV monoenergetic gammas, which are emitted from decay of the activated yttrium nuclei after the inelastic scattering on neutrons, can be measured, and the flux of the DD fusion neutrons can be diagnosed. In this work, an activation detection system using yttrium is developed, in which the LaBr3:Ce scintillator detector is chosen as the gamma sensitive material. The accumulation process of yttrium activation products under continuous irradiation has been physically analyzed, with respect to their half-life of only 15.663 s. An experimental method of calibrating the incident neutron detection efficiency by accelerator-based DD neutron source is thus established. In the experiments, the gamma detector is served as both neutron flux rate monitor and activation gamma measurements. The variation of radiation activity of the yttrium target with the neutron flux rate are simulated. Therefore, the in-situ calibration of the detection efficiency of this yttrium activation system for incident neutrons is achieved, with an accuracy of about 3.8%.
On the pulsed fusion sources such as laser ICF device, Z pinch facility and dense plasma focus device, the neutron activation method are widely applied, which can measure the neutron flux and diagnose the neutron yield from the source. Based on the inorganic scintillation detector, the 909 keV monoenergetic gammas, which are emitted from decay of the activated yttrium nuclei after the inelastic scattering on neutrons, can be measured, and the flux of the DD fusion neutrons can be diagnosed. In this work, an activation detection system using yttrium is developed, in which the LaBr3:Ce scintillator detector is chosen as the gamma sensitive material. The accumulation process of yttrium activation products under continuous irradiation has been physically analyzed, with respect to their half-life of only 15.663 s. An experimental method of calibrating the incident neutron detection efficiency by accelerator-based DD neutron source is thus established. In the experiments, the gamma detector is served as both neutron flux rate monitor and activation gamma measurements. The variation of radiation activity of the yttrium target with the neutron flux rate are simulated. Therefore, the in-situ calibration of the detection efficiency of this yttrium activation system for incident neutrons is achieved, with an accuracy of about 3.8%.
, Available online ,
doi: 10.11884/HPLPB202537.240228
Abstract:
To assess the susceptibility of road vehicles in complex electromagnetic environments, this paper proposes a radiation immunity testing method of vehicles based on actual electromagnetic environments in reverberation chambers (RCs), which records the actual electromagnetic signals, constructs a complex signal playback system in an RC, and gives the cumulative distribution function (CDF) of the received power. Moreover, this paper provides a field strength calibration method and the radiation immunity testing in an RC. The radiation immunity testing of vehicle was conducted, and the results show that in the complex RC electromagnetic environment, some vehicles have electromagnetic safety risks. The study method provides important support for enterprises to evaluate the electromagnetic compatibility quality of vehicles.
To assess the susceptibility of road vehicles in complex electromagnetic environments, this paper proposes a radiation immunity testing method of vehicles based on actual electromagnetic environments in reverberation chambers (RCs), which records the actual electromagnetic signals, constructs a complex signal playback system in an RC, and gives the cumulative distribution function (CDF) of the received power. Moreover, this paper provides a field strength calibration method and the radiation immunity testing in an RC. The radiation immunity testing of vehicle was conducted, and the results show that in the complex RC electromagnetic environment, some vehicles have electromagnetic safety risks. The study method provides important support for enterprises to evaluate the electromagnetic compatibility quality of vehicles.
, 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.
, Available online ,
doi: 10.11884/HPLPB202537.240224
Abstract:
In order to solve the problem of high voltage threshold, high linear slope, simple circuit and easy debugging of ramp signal in the scan control module of streak camera, we propose the advantages of high voltage generated by switching discharge and good linearity of constant current charging slope, and we design a simple circuit structure, higher voltage. The circuit can adjust and optimize the slope and linear rate of the linear slope signal by adjusting the resistance. The experimental results show that the linear high voltage ramp signal generated by the circuit can provide a voltage of up to 1 700 V, the nonlinear precision of the ramp is less than 3%, the scanning time is adjustable from 200 ns to 50 μs. Compared with the traditional high voltage ramp signal circuit, the circuit has a simple structure, convenient debugging, and the ramp time can be adjusted steplessly from nanoseconds to microseconds. This can effectively improve the scanning time accuracy of the fringe camera and effectively reduce problems such as circuit crosstalk.
In order to solve the problem of high voltage threshold, high linear slope, simple circuit and easy debugging of ramp signal in the scan control module of streak camera, we propose the advantages of high voltage generated by switching discharge and good linearity of constant current charging slope, and we design a simple circuit structure, higher voltage. The circuit can adjust and optimize the slope and linear rate of the linear slope signal by adjusting the resistance. The experimental results show that the linear high voltage ramp signal generated by the circuit can provide a voltage of up to 1 700 V, the nonlinear precision of the ramp is less than 3%, the scanning time is adjustable from 200 ns to 50 μs. Compared with the traditional high voltage ramp signal circuit, the circuit has a simple structure, convenient debugging, and the ramp time can be adjusted steplessly from nanoseconds to microseconds. This can effectively improve the scanning time accuracy of the fringe camera and effectively reduce problems such as circuit crosstalk.
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
Display Method:
2024, 36: 121001.
doi: 10.11884/HPLPB202436.240384
Abstract:
High-power ytterbium-doped fiber lasers have a wide range of applications in the maintenance of nuclear facilities owing to the advantages of high power, high efficiency, and flexible transmission. However, the irradiation effect in the nuclear facility environment can decrease the power of the fiber laser, which poses a big challenge to applications in such scenarios. Considering the self-bleaching effect of fiber lasers, we explore the relationship between darkening and self-bleaching effect under different irradiation dose rates. When the irradiation dose rate is relatively low, such as 0.1 rad/s, the output power of the 1 kW fiber laser is quite stable with the power fluctuation less than 1.79% during the whole experiment. We name such phenomenon as the self-bleaching and radiation equilibrium (SBRE). It is verified for the first time that under a certain irradiation dose rate, the laser power enhancement caused by the self-bleaching effect of the fiber laser can balance the power decrease caused by the irradiation effect, which provides effective support for the design of fiber lasers in related applications.
High-power ytterbium-doped fiber lasers have a wide range of applications in the maintenance of nuclear facilities owing to the advantages of high power, high efficiency, and flexible transmission. However, the irradiation effect in the nuclear facility environment can decrease the power of the fiber laser, which poses a big challenge to applications in such scenarios. Considering the self-bleaching effect of fiber lasers, we explore the relationship between darkening and self-bleaching effect under different irradiation dose rates. When the irradiation dose rate is relatively low, such as 0.1 rad/s, the output power of the 1 kW fiber laser is quite stable with the power fluctuation less than 1.79% during the whole experiment. We name such phenomenon as the self-bleaching and radiation equilibrium (SBRE). It is verified for the first time that under a certain irradiation dose rate, the laser power enhancement caused by the self-bleaching effect of the fiber laser can balance the power decrease caused by the irradiation effect, which provides effective support for the design of fiber lasers in related applications.
2024, 36: 121002.
doi: 10.11884/HPLPB202436.240230
Abstract:
The radiation experiment on the seed stage of narrow line-width fiber lasers by γ ray radiation with total dose of 50 krad(Si) is conducted. The output properties of this seed laser are analyzed before and after γ radiation. Experimental results reveal that the output power declines over 70%, and the temperature of gain fiber rises significantly as the loss increases. The radiated seed source is amplified to kW power level, presenting little change of output power, central wavelength, and 3 dB bandwidth at different radiation dose. However, the SRS suppression slightly decreased with the increase of radiation dose. 793 nm and 524 nm LDs with the same power are applied as bleaching sources of radiated seed stage, and the bleaching effect is analyzed. Due to higher photon energy and closer to the absorption peak of radiation-induced defects, 524 nm LD presents a better bleaching effect. The output power of seed stage and 793 nm bleaching duration presents a linear relationship with a bleaching speed at 0.30 W/h, and the output power and 524 nm bleaching duration approximately presents a tensile-exponential function relationship with a bleaching speed at 1.65 W/h.
The radiation experiment on the seed stage of narrow line-width fiber lasers by γ ray radiation with total dose of 50 krad(Si) is conducted. The output properties of this seed laser are analyzed before and after γ radiation. Experimental results reveal that the output power declines over 70%, and the temperature of gain fiber rises significantly as the loss increases. The radiated seed source is amplified to kW power level, presenting little change of output power, central wavelength, and 3 dB bandwidth at different radiation dose. However, the SRS suppression slightly decreased with the increase of radiation dose. 793 nm and 524 nm LDs with the same power are applied as bleaching sources of radiated seed stage, and the bleaching effect is analyzed. Due to higher photon energy and closer to the absorption peak of radiation-induced defects, 524 nm LD presents a better bleaching effect. The output power of seed stage and 793 nm bleaching duration presents a linear relationship with a bleaching speed at 0.30 W/h, and the output power and 524 nm bleaching duration approximately presents a tensile-exponential function relationship with a bleaching speed at 1.65 W/h.
2024, 36: 121003.
doi: 10.11884/HPLPB202436.240008
Abstract:
In 1D particle-in-cell (PIC) simulation, it is found that a plasma grating is produced by the interaction of a single ultra-short laser pulse with a solid-density plasma carbon target. When the appropriate laser and plasma parameters are used, the incident laser and the laser reflected by the rear-surface of the plasma target can form a standing wave, resulting in a ponderomotive force and charge-separation field that can modulate the plasma density and form a plasma density grating. Under this mechanism, we have studied the plasma density gratings generated by the interaction between plasma and ultraviolet laser pulses with wavelengths ranging from 40nm to 130 nm. The results show that, using a single laser pulse and a under-critical plasma target, stable plasma gratings can last more than several tens of picoseconds, with the max peak density greater than twenty times that of the initial density. Compared with traditional generation of plasma gratings with two laser beams or density-gradient plasmas, this scheme with uniform plasma is easier to carry out.
In 1D particle-in-cell (PIC) simulation, it is found that a plasma grating is produced by the interaction of a single ultra-short laser pulse with a solid-density plasma carbon target. When the appropriate laser and plasma parameters are used, the incident laser and the laser reflected by the rear-surface of the plasma target can form a standing wave, resulting in a ponderomotive force and charge-separation field that can modulate the plasma density and form a plasma density grating. Under this mechanism, we have studied the plasma density gratings generated by the interaction between plasma and ultraviolet laser pulses with wavelengths ranging from 40nm to 130 nm. The results show that, using a single laser pulse and a under-critical plasma target, stable plasma gratings can last more than several tens of picoseconds, with the max peak density greater than twenty times that of the initial density. Compared with traditional generation of plasma gratings with two laser beams or density-gradient plasmas, this scheme with uniform plasma is easier to carry out.
2024, 36: 121004.
doi: 10.11884/HPLPB202436.240215
Abstract:
In vacuum and space environment, laser damage resistance of the optical film reduces greatly. This is mainly due to the coupling effect of organic pollution in the vacuum environment and the internal defect of the film, which results in the enhancement of the light field of film. The protective film technology is an effective measure to improve the ability of optical film to resist laser damage. Based on the finite-difference time-domain algorithm, the inhibition effect of the protective layer on the light field enhancement induced by the coupling of organic pollution droplet and defect was analyzed. The analysis result shows that the light field peak value of TiO2 film decreases with the increase of protective layer thickness. When the refractive index of the protective layer is the middle value of the organic pollution droplet refractive index and that of the film , the inhibition effect of light field enhancement is the greatest. The experimental results have verified the theoretical analysis. This study deepens the understanding of the mechanism of laser induced damage degradation of optical film in vacuum and has certain reference value for improving the laser damage resistance of optical film in vacuum environment.
In vacuum and space environment, laser damage resistance of the optical film reduces greatly. This is mainly due to the coupling effect of organic pollution in the vacuum environment and the internal defect of the film, which results in the enhancement of the light field of film. The protective film technology is an effective measure to improve the ability of optical film to resist laser damage. Based on the finite-difference time-domain algorithm, the inhibition effect of the protective layer on the light field enhancement induced by the coupling of organic pollution droplet and defect was analyzed. The analysis result shows that the light field peak value of TiO2 film decreases with the increase of protective layer thickness. When the refractive index of the protective layer is the middle value of the organic pollution droplet refractive index and that of the film , the inhibition effect of light field enhancement is the greatest. The experimental results have verified the theoretical analysis. This study deepens the understanding of the mechanism of laser induced damage degradation of optical film in vacuum and has certain reference value for improving the laser damage resistance of optical film in vacuum environment.
2024, 36: 122001.
doi: 10.11884/HPLPB202436.240379
Abstract:
The investigation of hydrodynamic instability growth in convergent geometry is crucial for optimizing the design of inertial confinement fusion capsules, which aims to mitigate the growth of hydrodynamic instability and mixing. Experiments about the hydrodynamic instability of the decelerated inner interface in radiation-driven cylindrical implosions were conducted at 100 kJ laser facility. Mode coupling of perturbations and the Bell-Plesset (BP) effect unique to convergent geometry were observed. The theoretical predictions of the growth induced by the BP effect are consistent with the experimental results. Additionally, these experiments identified a second-order mode introduced by an M2 drive asymmetry. The drive asymmetry is about 11%. To mitigate the drive asymmetry, a method of extending the length of the hohlraum was proposed. Researches of the hydrodynamic instability in cylindrical geometry contribute to a better understanding of how convergent geometry affects hydrodynamic instability growth at high energy density, thereby aiding in optimizing the design of inertial confinement fusion capsules.
The investigation of hydrodynamic instability growth in convergent geometry is crucial for optimizing the design of inertial confinement fusion capsules, which aims to mitigate the growth of hydrodynamic instability and mixing. Experiments about the hydrodynamic instability of the decelerated inner interface in radiation-driven cylindrical implosions were conducted at 100 kJ laser facility. Mode coupling of perturbations and the Bell-Plesset (BP) effect unique to convergent geometry were observed. The theoretical predictions of the growth induced by the BP effect are consistent with the experimental results. Additionally, these experiments identified a second-order mode introduced by an M2 drive asymmetry. The drive asymmetry is about 11%. To mitigate the drive asymmetry, a method of extending the length of the hohlraum was proposed. Researches of the hydrodynamic instability in cylindrical geometry contribute to a better understanding of how convergent geometry affects hydrodynamic instability growth at high energy density, thereby aiding in optimizing the design of inertial confinement fusion capsules.
2024, 36: 122002.
doi: 10.11884/HPLPB202436.240218
Abstract:
There are several issues with traditional microchannel plate (MCP) gated framing cameras used for inertial confinement fusion diagnostic, such as large volume, incapable single line-of-sight (SLOS), and so on. The MCP can be instead by a CMOS chips with time resolution of picosecond-scale to achieve the image with SLOS. This paper presents a SLOS four-frame picosecond CMOS circuit consisting of 8×8×4 pixel arrays, and its performance is simulated. The CMOS circuit includes the design of unit pixel which contains four-frame, delay and control circuitry, binary clock tree, circuitry of row and column selector by using 0.18 μm CMOS process and 5T (5 transistors) unit pixel. The signals in the pixel array of the CMOS circuit are analyzed, ans the simulation results show that the CMOS circuit has the capability to obtain four images with a single exposure. The temporal resolution is 100 ps, the interval between two adjacent images is 300 ps, and the uniformity of intra-pixel signals is better than 90%.
There are several issues with traditional microchannel plate (MCP) gated framing cameras used for inertial confinement fusion diagnostic, such as large volume, incapable single line-of-sight (SLOS), and so on. The MCP can be instead by a CMOS chips with time resolution of picosecond-scale to achieve the image with SLOS. This paper presents a SLOS four-frame picosecond CMOS circuit consisting of 8×8×4 pixel arrays, and its performance is simulated. The CMOS circuit includes the design of unit pixel which contains four-frame, delay and control circuitry, binary clock tree, circuitry of row and column selector by using 0.18 μm CMOS process and 5T (5 transistors) unit pixel. The signals in the pixel array of the CMOS circuit are analyzed, ans the simulation results show that the CMOS circuit has the capability to obtain four images with a single exposure. The temporal resolution is 100 ps, the interval between two adjacent images is 300 ps, and the uniformity of intra-pixel signals is better than 90%.
2024, 36: 122003.
doi: 10.11884/HPLPB202436.240025
Abstract:
To obtain the equation of state (EOS) of tantalum-niobium alloy (Ta-Nb) materials under high pressure, a type of Al/Ta-Nb impedance matching target for laser EOS experiments was fabricated. The processes of precision rolling and femtosecond laser cutting of Ta-Nb alloy foil were studied. A step sample of Ta-Nb alloy with a thickness of 13 μm and a width of 400 μm was obtained. Ta-Nb alloy step was assembled with Al standard material using polyvinyl alcohol (PVA) hydrosol. The surface morphology, step thickness and sample density of the target were measured by white light interferometer and electronic densitometer. The results show that the Al/Ta-Nb alloy impedance matching target fabricated can meet the requirements of laser EOS experiments.
To obtain the equation of state (EOS) of tantalum-niobium alloy (Ta-Nb) materials under high pressure, a type of Al/Ta-Nb impedance matching target for laser EOS experiments was fabricated. The processes of precision rolling and femtosecond laser cutting of Ta-Nb alloy foil were studied. A step sample of Ta-Nb alloy with a thickness of 13 μm and a width of 400 μm was obtained. Ta-Nb alloy step was assembled with Al standard material using polyvinyl alcohol (PVA) hydrosol. The surface morphology, step thickness and sample density of the target were measured by white light interferometer and electronic densitometer. The results show that the Al/Ta-Nb alloy impedance matching target fabricated can meet the requirements of laser EOS experiments.
2024, 36: 122004.
doi: 10.11884/HPLPB202436.240015
Abstract:
High-resolution flow field data has important applications in meteorology, aerospace engineering, high-energy physics and other fields. Experiments and numerical simulations are two main ways to obtain high-resolution flow field data, while the high experiment cost and computing resources for simulation hinder the specific analysis of flow field evolution. With the development of deep learning technology, convolutional neural networks are used to achieve high-resolution reconstruction of the flow field. In this paper, an ordinary convolutional neural network and a multi-time-path convolutional neural network are established for the ablative Rayleigh-Taylor instability. These two methods can reconstruct the high-resolution flow field in just a few seconds, and further greatly enrich the application of high-resolution reconstruction technology in fluid instability. Compared with the ordinary convolutional neural network, the multi-time-path convolutional neural network model has smaller error and can restore more details of the flow field. The influence of low-resolution flow field data obtained by the two pooling methods on the convolutional neural networks model is also discussed.
2024, 36: 123001.
doi: 10.11884/HPLPB202436.240219
Abstract:
To enhance the protective effectiveness of the Beidou Navigation Satellite System (BDS) and the Global Positioning System (GPS) against high-power microwave, we adopted the method of field-circuit collaborative simulation design to analyze the response characteristics of the BDS/GPS antenna under high-power microwave irradiation. The coupling voltage was obtained by simulation. To achieve protection against high-power microwave, a two-stage protection circuit was designed. By constructing steady-state and transient circuit models, the insertion loss and leakage voltage were analyzed according to simulation, and the circuit was processed. The test results show that the leakage power of the protective circuit was less than 0.5 W under HPM-NS injection of 2 kW, the leakage voltage was less than 12 V under HPM-UWS injection of 1 411 V, and this proposed circuit structure can achieve effective suppression of high-power microwave. The protection circuit was assembled into the BDS/GPS antenna, and the test results show that the navigation systems can operate normally.
To enhance the protective effectiveness of the Beidou Navigation Satellite System (BDS) and the Global Positioning System (GPS) against high-power microwave, we adopted the method of field-circuit collaborative simulation design to analyze the response characteristics of the BDS/GPS antenna under high-power microwave irradiation. The coupling voltage was obtained by simulation. To achieve protection against high-power microwave, a two-stage protection circuit was designed. By constructing steady-state and transient circuit models, the insertion loss and leakage voltage were analyzed according to simulation, and the circuit was processed. The test results show that the leakage power of the protective circuit was less than 0.5 W under HPM-NS injection of 2 kW, the leakage voltage was less than 12 V under HPM-UWS injection of 1 411 V, and this proposed circuit structure can achieve effective suppression of high-power microwave. The protection circuit was assembled into the BDS/GPS antenna, and the test results show that the navigation systems can operate normally.
2024, 36: 123002.
doi: 10.11884/HPLPB202436.240104
Abstract:
The influence of boundary deformation on the resonant frequency drift of a reverberation chamber was analyzed, and a design of a reverberation chamber reflector with controllable boundary deformation was proposed. Transforming the traditional mechanical stirrer into a wrinkled wall, the goal is to change the boundary conditions by controlling the angle between adjacent reflection modules. A simulation model of a 5 m×4 m×3 m reverberation chamber was constructed, and the effectiveness of the controllable boundary deformation reverberation chamber was analyzed from three aspects: field uniformity, stirring efficiency, and field distribution. The results show that the standard deviation of the electric field in the test area was less than 3 dB, the stirring efficiency was higher than that of traditional mechanical mixers, and the electric field in the test area followed the ideal distribution pattern of the reverberation chamber. This method can effectively increase the testing area space of the reverberation chamber.
The influence of boundary deformation on the resonant frequency drift of a reverberation chamber was analyzed, and a design of a reverberation chamber reflector with controllable boundary deformation was proposed. Transforming the traditional mechanical stirrer into a wrinkled wall, the goal is to change the boundary conditions by controlling the angle between adjacent reflection modules. A simulation model of a 5 m×4 m×3 m reverberation chamber was constructed, and the effectiveness of the controllable boundary deformation reverberation chamber was analyzed from three aspects: field uniformity, stirring efficiency, and field distribution. The results show that the standard deviation of the electric field in the test area was less than 3 dB, the stirring efficiency was higher than that of traditional mechanical mixers, and the electric field in the test area followed the ideal distribution pattern of the reverberation chamber. This method can effectively increase the testing area space of the reverberation chamber.
2024, 36: 123003.
doi: 10.11884/HPLPB202436.240007
Abstract:
Aiming to address the bottleneck of low output power in terahertz band traveling wave tubes and responding to the distinct demand for compact design, this paper proposes a 0.34 THz folded waveguide traveling wave tube structure with power combination inside the tube. Firstly, the high-frequency characteristics of the folded waveguide slow-wave structure are investigated. Electromagnetic full-wave simulations are used to obtain its dispersion characteristics and coupling impedance. The normalized phase velocity at 0.34 THz is 0.248 and the coupling impedance is 0.46 Ω. Secondly, a 3 dB directional coupler structure for in-tube power combination is designed. The analysis indicates that its amplitude balance is within ±0.19 dB in the range of 0.31–0.368 THz, and the isolation exceeds 24 dB. Finally, the basic structure of the folded waveguide traveling wave tube based on the in-tube combination of the 3 dB directional coupler is demonstrated. The simulation model is constructed, and the results show a maximum output power of 9.16 W, a gain of 26.6 dB, and a 3 dB bandwidth of 21 GHz. For comparison, the output power of a single folded waveguide traveling wave tube is 6.18 W. The output power of the in-tube synthesized folded waveguide traveling wave tube is 1.48 times that of the single traveling wave tube. Moreover, compared with the design of a dual-tube assembly using conventional external power combination structure, the lateral size is reduced by at least 56.5%.
Aiming to address the bottleneck of low output power in terahertz band traveling wave tubes and responding to the distinct demand for compact design, this paper proposes a 0.34 THz folded waveguide traveling wave tube structure with power combination inside the tube. Firstly, the high-frequency characteristics of the folded waveguide slow-wave structure are investigated. Electromagnetic full-wave simulations are used to obtain its dispersion characteristics and coupling impedance. The normalized phase velocity at 0.34 THz is 0.248 and the coupling impedance is 0.46 Ω. Secondly, a 3 dB directional coupler structure for in-tube power combination is designed. The analysis indicates that its amplitude balance is within ±0.19 dB in the range of 0.31–0.368 THz, and the isolation exceeds 24 dB. Finally, the basic structure of the folded waveguide traveling wave tube based on the in-tube combination of the 3 dB directional coupler is demonstrated. The simulation model is constructed, and the results show a maximum output power of 9.16 W, a gain of 26.6 dB, and a 3 dB bandwidth of 21 GHz. For comparison, the output power of a single folded waveguide traveling wave tube is 6.18 W. The output power of the in-tube synthesized folded waveguide traveling wave tube is 1.48 times that of the single traveling wave tube. Moreover, compared with the design of a dual-tube assembly using conventional external power combination structure, the lateral size is reduced by at least 56.5%.
Design and verification of electron optical system for 140 GHz folded waveguide travelling wave tube
2024, 36: 123004.
doi: 10.11884/HPLPB202436.240134
Abstract:
In this paper, the electron optical system for 140 GHz folded waveguide travelling wave tube (FTWT) is designed. The electron beam considering the thermal velocity effect in periodic permanent magnetic (PPM) focusing system is simulated and optimized by using the particle simulation software Opera-3D. The magnetic field is optimized to improve the matching effect between electron beam and PPM. The current of electron optical system is 60 mA when the anode voltage is 20 kV, and the simulation shows that the transmission efficiency is improved to 99.9%. In the experiment of sample tube, the parameters of the electron gun are in agreement with the design results. When the travelling wave tube (TWT) works in DC mode, about 97.2% of the electron beam reaches the collector.
In this paper, the electron optical system for 140 GHz folded waveguide travelling wave tube (FTWT) is designed. The electron beam considering the thermal velocity effect in periodic permanent magnetic (PPM) focusing system is simulated and optimized by using the particle simulation software Opera-3D. The magnetic field is optimized to improve the matching effect between electron beam and PPM. The current of electron optical system is 60 mA when the anode voltage is 20 kV, and the simulation shows that the transmission efficiency is improved to 99.9%. In the experiment of sample tube, the parameters of the electron gun are in agreement with the design results. When the travelling wave tube (TWT) works in DC mode, about 97.2% of the electron beam reaches the collector.
2024, 36: 123005.
doi: 10.11884/HPLPB202436.240198
Abstract:
The power division network is one of the key components of high power microwave (HPM) phased array antenna. It is used to divide HPM into several paths and feed them into phase shifter and element antenna. In such a network, the over-mode circular waveguide to multi-channel rectangular waveguide power divider has the function of mode conversion and power distribution. It is the front end of the power division network and requires high power handling capability, high transmission efficiency and low reflection. In this paper, the design, simulation, fabrication, and small signal test of the power divider from Ku-band GW-level over-mode circular waveguide to 8-channel rectangular waveguide were carried out. Subsequently, the power handling capacity of the power divider was evaluated utilizing the established power capacity testing facility. The experimental outcomes demonstrated that within the frequency band of 14.7 GHz±200 MHz, the reflection coefficient was consistently below −20 dB, the transmission coefficient exceeded −9.1 dB, the port imbalance was maintained at less the 0.4 dB, and the power handling capacity exceeded 900 MW.
The power division network is one of the key components of high power microwave (HPM) phased array antenna. It is used to divide HPM into several paths and feed them into phase shifter and element antenna. In such a network, the over-mode circular waveguide to multi-channel rectangular waveguide power divider has the function of mode conversion and power distribution. It is the front end of the power division network and requires high power handling capability, high transmission efficiency and low reflection. In this paper, the design, simulation, fabrication, and small signal test of the power divider from Ku-band GW-level over-mode circular waveguide to 8-channel rectangular waveguide were carried out. Subsequently, the power handling capacity of the power divider was evaluated utilizing the established power capacity testing facility. The experimental outcomes demonstrated that within the frequency band of 14.7 GHz±200 MHz, the reflection coefficient was consistently below −20 dB, the transmission coefficient exceeded −9.1 dB, the port imbalance was maintained at less the 0.4 dB, and the power handling capacity exceeded 900 MW.
2024, 36: 124001.
doi: 10.11884/HPLPB202436.240044
Abstract:
In synchrotrons, the high-frequency ripple error of magnet excitation current causes magnetic field ripple, which leads to decreased beam acceptance. The low-frequency tracking error of the excitation current would affect the matching degree of magnetic field and beam energy, which would cause the closed orbit distortion of the beam. The correlation between magnetic field ripple and excitation current ripple of HIAF BRing dipole magnet is studied in this paper. The current quality quantification methods based on high and low-frequency separation are proposed, which evaluate the effect of excitation current error on the beam. The low-frequency tracking error and high-frequency ripple error of the excitation current are obtained by Gaussian smoothing. Three times the standard deviation is used as the quantification indicator of the excitation current in terms of ripple and tracking error. Since parameters of the low-pass filter are determined by the response relationship between magnetic field ripple and excitation current ripple, this method could accurately quantify the magnetic field ripple. Th current tracking error waveform could be used to adjust the reference waveform of synchrotron pulse power supplies, improving the matching degree of magnetic field and beam energy.
In synchrotrons, the high-frequency ripple error of magnet excitation current causes magnetic field ripple, which leads to decreased beam acceptance. The low-frequency tracking error of the excitation current would affect the matching degree of magnetic field and beam energy, which would cause the closed orbit distortion of the beam. The correlation between magnetic field ripple and excitation current ripple of HIAF BRing dipole magnet is studied in this paper. The current quality quantification methods based on high and low-frequency separation are proposed, which evaluate the effect of excitation current error on the beam. The low-frequency tracking error and high-frequency ripple error of the excitation current are obtained by Gaussian smoothing. Three times the standard deviation is used as the quantification indicator of the excitation current in terms of ripple and tracking error. Since parameters of the low-pass filter are determined by the response relationship between magnetic field ripple and excitation current ripple, this method could accurately quantify the magnetic field ripple. Th current tracking error waveform could be used to adjust the reference waveform of synchrotron pulse power supplies, improving the matching degree of magnetic field and beam energy.
2024, 36: 124002.
doi: 10.11884/HPLPB202436.240205
Abstract:
In recent years, off-axis injection schemes based on nonlinear kicker magnets have emerged as a new research focus, particularly suitable for storage rings with small dynamic apertures. This scheme is characterized by a strong magnetic field generated by the nonlinear kicker magnet at the injection point to deflect the injected beam, while maintaining a near-zero magnetic field near the central orbit, significantly reducing interference with the stored beam. This paper presents the design of a nonlinear kicker magnet with an eight-conductor layout, conducting an in-depth study on the impact of key parameters—such as conductor layout, edge fields at the magnet ends, and ceramic vacuum coatings—on magnetic field performance, followed by optimization of these parameters. Results indicate that this nonlinear kicker magnet design meets the injection system requirements for the high-brightness electron-positron collider and synchrotron radiation ring under development.
In recent years, off-axis injection schemes based on nonlinear kicker magnets have emerged as a new research focus, particularly suitable for storage rings with small dynamic apertures. This scheme is characterized by a strong magnetic field generated by the nonlinear kicker magnet at the injection point to deflect the injected beam, while maintaining a near-zero magnetic field near the central orbit, significantly reducing interference with the stored beam. This paper presents the design of a nonlinear kicker magnet with an eight-conductor layout, conducting an in-depth study on the impact of key parameters—such as conductor layout, edge fields at the magnet ends, and ceramic vacuum coatings—on magnetic field performance, followed by optimization of these parameters. Results indicate that this nonlinear kicker magnet design meets the injection system requirements for the high-brightness electron-positron collider and synchrotron radiation ring under development.
2024, 36: 125001.
doi: 10.11884/HPLPB202436.240070
Abstract:
The study of measurement methods for strong electric fields in small spaces is a challenge. By utilizing the Stark effect of spectral lines and selecting reasonable atoms or ions, measurements can be completed without interference. This article designs a set of atmospheric pressure nanosecond pulse discharge experimental device, which generates a strong electric field through needle electrode discharge, and tests the splitting of He 447.1nm spectral lines under strong electric fields generated at different discharge voltages. When the spectral line broadening is difficult to obtain directly by observing the spectral line, by using the non-linear least squares, the allowable component, the prohibited component and the field independent component of the spectral line are analyzed and the corresponding wavelength offset is calculated to obtain the electric field size. According to Mason’s formula, based on energy equivalence, the experimental results meet theoretical expectations, and this method can be used to measure strong electric fields in small spaces. Analysis indicates that the discrepancy between theoretical and experimental results may be attributed to the shielding effect caused by the plasma produced when helium gas undergoes breakdown.
The study of measurement methods for strong electric fields in small spaces is a challenge. By utilizing the Stark effect of spectral lines and selecting reasonable atoms or ions, measurements can be completed without interference. This article designs a set of atmospheric pressure nanosecond pulse discharge experimental device, which generates a strong electric field through needle electrode discharge, and tests the splitting of He 447.1nm spectral lines under strong electric fields generated at different discharge voltages. When the spectral line broadening is difficult to obtain directly by observing the spectral line, by using the non-linear least squares, the allowable component, the prohibited component and the field independent component of the spectral line are analyzed and the corresponding wavelength offset is calculated to obtain the electric field size. According to Mason’s formula, based on energy equivalence, the experimental results meet theoretical expectations, and this method can be used to measure strong electric fields in small spaces. Analysis indicates that the discrepancy between theoretical and experimental results may be attributed to the shielding effect caused by the plasma produced when helium gas undergoes breakdown.
2024, 36: 126001.
doi: 10.11884/HPLPB202436.240320
Abstract:
In experimental validations of fusion blanket neutronics performance, tritium production rate is one of the most crucial measurement parameters. The number of 6Li atoms in the detector, as a normalization factor for calculating the tritium production rate, is a key factor determining the accuracy of measurement results and must be accurately calibrated. This paper specifically introduces the principles of calibrating the number of 6Li, the experimental setup and procedure, and the methods for quantifying uncertainties. For the first time, the number of 6Li atoms in a small lithium glass detector was calibrated using a germanium monocrystal monochromator to obtain 32.36 meV neutrons at the M5 horizontal channel of the China Mianyang Research Reactor (CMRR), with an uncertainty of 2.62%.
In experimental validations of fusion blanket neutronics performance, tritium production rate is one of the most crucial measurement parameters. The number of 6Li atoms in the detector, as a normalization factor for calculating the tritium production rate, is a key factor determining the accuracy of measurement results and must be accurately calibrated. This paper specifically introduces the principles of calibrating the number of 6Li, the experimental setup and procedure, and the methods for quantifying uncertainties. For the first time, the number of 6Li atoms in a small lithium glass detector was calibrated using a germanium monocrystal monochromator to obtain 32.36 meV neutrons at the M5 horizontal channel of the China Mianyang Research Reactor (CMRR), with an uncertainty of 2.62%.
2024, 36: 126002.
doi: 10.11884/HPLPB202436.240359
Abstract:
To enhance the corrosion resistance of depleted uranium surfaces, a comparative analysis was conducted to evaluate the efficacy of three plasma nitriding technologies: Plasma Source Ion Implantation (PSII), Glow Discharge Plasma Nitriding (GDPN), and Hollow Cathode Plasma Nitriding (GDPN). The composition, structure and chemical state of the nitrided layers were analysed using a range of material analysis methods. The nitrides present in the three nitrided layers are predominantly α-U2N3. Due to the strong affinity between uranium metal and oxygen, all three plasma nitriding processes have introduced oxygen impurities to varying degrees. PSII is capable of breaking through the thermodynamic equilibrium and converting some of the oxides into nitrides, while GDPN and HCPN can form nitrides through surface reactions and thermal diffusion. HCPN technology has certain advantages in controlling the oxygen impurities, and can significantly reduce the oxygen impurities in the nitrided layer. The results of the wet heat corrosion and electrochemical tests demonstrate that plasma nitriding can markedly enhance the corrosion resistance of depleted uranium. The degree of improvement achieved by HCPN and GDPN is superior to that of PSII, with HCPN technology exhibiting the most favourable outcome. The findings of this study could provide a reference for plasma nitriding treatment of reactive metals..
To enhance the corrosion resistance of depleted uranium surfaces, a comparative analysis was conducted to evaluate the efficacy of three plasma nitriding technologies: Plasma Source Ion Implantation (PSII), Glow Discharge Plasma Nitriding (GDPN), and Hollow Cathode Plasma Nitriding (GDPN). The composition, structure and chemical state of the nitrided layers were analysed using a range of material analysis methods. The nitrides present in the three nitrided layers are predominantly α-U2N3. Due to the strong affinity between uranium metal and oxygen, all three plasma nitriding processes have introduced oxygen impurities to varying degrees. PSII is capable of breaking through the thermodynamic equilibrium and converting some of the oxides into nitrides, while GDPN and HCPN can form nitrides through surface reactions and thermal diffusion. HCPN technology has certain advantages in controlling the oxygen impurities, and can significantly reduce the oxygen impurities in the nitrided layer. The results of the wet heat corrosion and electrochemical tests demonstrate that plasma nitriding can markedly enhance the corrosion resistance of depleted uranium. The degree of improvement achieved by HCPN and GDPN is superior to that of PSII, with HCPN technology exhibiting the most favourable outcome. The findings of this study could provide a reference for plasma nitriding treatment of reactive metals..
2024, 36: 126003.
doi: 10.11884/HPLPB202436.240156
Abstract:
In the field of neutron radiation, the problem of neutron spectrum unfolding has attracted much attention. The Bonner sphere spectrometer is often used for neutron spectrum detection, and the maximum entropy method can be used to analyze the neutron spectrum of the Bonner sphere spectrometer. Based on this principle, this paper establishes a simulation model including the Bonner sphere spectrometer with reference to the neutron shielding experiment in 2014. The simulation results of Monte Carlo method are used as the prior spectrum, and the maximum entropy deconvolution code (MAXED) based on the principle of maximum entropy is used for neutron spectrum unfolding. The effectiveness and accuracy of the method are verified by comparing with the literature data. By increasing the number of random particles in Monte Carlo method, multiple groups of prior spectrum with different accuracy are obtained. For different prior spectrum, the final spectral solution results can be statistically significant and the spectral solution results are effective. After comparison, the more accurate the prior spectrum is, the higher the accuracy of the final spectral solution results, indicating that it is important to obtain accurate Monte Carlo calculation results through appropriate variance reduction method, which can provide reference for subsequent research and experiments. In this paper, the GRAVEL method based on iterative algorithm is used to solve the neutron spectrum simultaneously, and the comparison of the calculation results of the two methods further proves the superior performance of the solution spectrum of the MAXED method.
In the field of neutron radiation, the problem of neutron spectrum unfolding has attracted much attention. The Bonner sphere spectrometer is often used for neutron spectrum detection, and the maximum entropy method can be used to analyze the neutron spectrum of the Bonner sphere spectrometer. Based on this principle, this paper establishes a simulation model including the Bonner sphere spectrometer with reference to the neutron shielding experiment in 2014. The simulation results of Monte Carlo method are used as the prior spectrum, and the maximum entropy deconvolution code (MAXED) based on the principle of maximum entropy is used for neutron spectrum unfolding. The effectiveness and accuracy of the method are verified by comparing with the literature data. By increasing the number of random particles in Monte Carlo method, multiple groups of prior spectrum with different accuracy are obtained. For different prior spectrum, the final spectral solution results can be statistically significant and the spectral solution results are effective. After comparison, the more accurate the prior spectrum is, the higher the accuracy of the final spectral solution results, indicating that it is important to obtain accurate Monte Carlo calculation results through appropriate variance reduction method, which can provide reference for subsequent research and experiments. In this paper, the GRAVEL method based on iterative algorithm is used to solve the neutron spectrum simultaneously, and the comparison of the calculation results of the two methods further proves the superior performance of the solution spectrum of the MAXED method.
2024, 36: 126004.
doi: 10.11884/HPLPB202436.240292
Abstract:
In nuclear radiation environment, the radiation protection of vehicles such as ships and tanks is crucial for nuclear safety, radiation protection, radiation damage assessment, response and decision-making. This paper does research on ships’ radiation shielding performance. Using ship materials and typical structures, neutron-photon coupling transportation method is adopted to quantitatively simulate ship’s radiation shielding performance, under neutron and γ’ simultaneous irradiation. By utilizing large-scale parallel technology, efficient simulation has been achieved for deep-penetrating problem. The simulation of radiation transportation process considers incident neutrons, γ and even secondary particles. For basic shape models such as plate, cavity with different thicknesses and materials, it simulates neutron and γ's transportation in gas and materials, monitors particles flux, dose, and energy spectrum. The radiation protection factors(RPF) for neutrons, γ rays, and both are simulated and analyzed. It studies RPF influence rules with key parameter such as plate thicknesses, incident angles. The materials researched include Fe, Al, Pb, HSLA100 steel, and the radiation sources include single energy neutron, and nuclear leaked neutron and γ spectra. These results will contribute to the analysis of vehicles’ radiation protection performance, and provide theoretical support for nuclear radiation effect assessment, emergency response, etc.
In nuclear radiation environment, the radiation protection of vehicles such as ships and tanks is crucial for nuclear safety, radiation protection, radiation damage assessment, response and decision-making. This paper does research on ships’ radiation shielding performance. Using ship materials and typical structures, neutron-photon coupling transportation method is adopted to quantitatively simulate ship’s radiation shielding performance, under neutron and γ’ simultaneous irradiation. By utilizing large-scale parallel technology, efficient simulation has been achieved for deep-penetrating problem. The simulation of radiation transportation process considers incident neutrons, γ and even secondary particles. For basic shape models such as plate, cavity with different thicknesses and materials, it simulates neutron and γ's transportation in gas and materials, monitors particles flux, dose, and energy spectrum. The radiation protection factors(RPF) for neutrons, γ rays, and both are simulated and analyzed. It studies RPF influence rules with key parameter such as plate thicknesses, incident angles. The materials researched include Fe, Al, Pb, HSLA100 steel, and the radiation sources include single energy neutron, and nuclear leaked neutron and γ spectra. These results will contribute to the analysis of vehicles’ radiation protection performance, and provide theoretical support for nuclear radiation effect assessment, emergency response, etc.
2024, 36: 129001.
doi: 10.11884/HPLPB202436.240333
Abstract:
This article employs Fourier transform infrared spectroscopy to investigate radiometric calibration methods and the measurement of continuous atmospheric transmittance across the shortwave infrared band. The presence of multiple strong absorption bands within the shortwave infrared spectrum (0.9−2.2 μm) leads to significant errors in the commonly used Langley method, and even the improved Langley method struggles to yield accurate results for the calibration of these strong absorption bands. To fulfill the high-precision measurement demands for atmospheric transmittance across the entire shortwave infrared band, this paper introduces an enhanced method for calculating atmospheric transmittance. Initially, the Langley calibration technique is utilized to determine the instrument calibration value and response function K in the non-absorption band. Subsequently, the instrument response function in the absorption band is derived by interpolating the wavelength based on the instrument response function calibrated in the non-absorption band. Ultimately, the instrument calibration value is established by correlating it with the solar irradiance at the atmosphere’s top, thereby obtaining the atmospheric transmittance across the entire shortwave infrared band. Compared to results calculated by the medium-resolution atmospheric radiative transfer model software CART, the atmospheric transmittance values obtained using this method within the 0.9−2.2 μm band exhibit an average error of less than 2.5%.
This article employs Fourier transform infrared spectroscopy to investigate radiometric calibration methods and the measurement of continuous atmospheric transmittance across the shortwave infrared band. The presence of multiple strong absorption bands within the shortwave infrared spectrum (0.9−2.2 μm) leads to significant errors in the commonly used Langley method, and even the improved Langley method struggles to yield accurate results for the calibration of these strong absorption bands. To fulfill the high-precision measurement demands for atmospheric transmittance across the entire shortwave infrared band, this paper introduces an enhanced method for calculating atmospheric transmittance. Initially, the Langley calibration technique is utilized to determine the instrument calibration value and response function K in the non-absorption band. Subsequently, the instrument response function in the absorption band is derived by interpolating the wavelength based on the instrument response function calibrated in the non-absorption band. Ultimately, the instrument calibration value is established by correlating it with the solar irradiance at the atmosphere’s top, thereby obtaining the atmospheric transmittance across the entire shortwave infrared band. Compared to results calculated by the medium-resolution atmospheric radiative transfer model software CART, the atmospheric transmittance values obtained using this method within the 0.9−2.2 μm band exhibit an average error of less than 2.5%.
2024, 36: 129002.
doi: 10.11884/HPLPB202436.240069
Abstract:
To improve the radiation measurement efficiency of nuclear retirement facilities and reduce the risk of radiation exposure to measurement personnel, a radiation patrol control system for multiple unmanned vehicle formations has been designed. Firstly, the navigation following formation strategy is adopted to control the robots to move in a predetermined formation, while collecting real-time radiation intensity information and their respective position data measured by each unmanned vehicle during the formation process, to preliminarily analyze the radiation distribution inside the environment. Secondly, utilizing radiation intensity and location information, the Markov chain Monte Carlo method is employed to estimate the parameters of the radiation source. The simulation results show that the unmanned vehicle formation can move along the automatically planned path in radiation environment, with advantages such as fast response speed, high control accuracy, and it can estimate the parameters of the radiation source position coordinates.
To improve the radiation measurement efficiency of nuclear retirement facilities and reduce the risk of radiation exposure to measurement personnel, a radiation patrol control system for multiple unmanned vehicle formations has been designed. Firstly, the navigation following formation strategy is adopted to control the robots to move in a predetermined formation, while collecting real-time radiation intensity information and their respective position data measured by each unmanned vehicle during the formation process, to preliminarily analyze the radiation distribution inside the environment. Secondly, utilizing radiation intensity and location information, the Markov chain Monte Carlo method is employed to estimate the parameters of the radiation source. The simulation results show that the unmanned vehicle formation can move along the automatically planned path in radiation environment, with advantages such as fast response speed, high control accuracy, and it can estimate the parameters of the radiation source position coordinates.
2024, 36: 124003.
doi: 10.11884/HPLPB202436.240175
Abstract:
Bremsstrahlung diode is an important device for obtaining large area uniform bremsstrahlung field in laboratory. In this paper, based on Monte Carlo method, a model of single and double ring parallel electron beam bombarding tantalum target is established to simulate the process of bremsstrahlung field generated by ring diode. The electron beam energy is 1.5 MeV, the tantalum target thickness is 200 μm, and the dose of bremsstrahlung field generated by a single ring electron beam 10 cm behind the target is simulated by detector counting method. For single-ring diode structure, the inner diameter of the ring is the main factor affecting the bremsstrahlung field uniformity behind the target, and the larger the inner diameter, the worse the central dose uniformity. Compared with the inner diameter of the ring, the ring width mainly affects the dose of the radiation field, but has little influence on the uniformity. When the inner diameter of a single ring is 19 cm and the outer diameter is 20 cm, a uniform radiation field with a maximum area of2290.221 cm2 can be obtained. When the inner diameter of a single ring is 19 cm and the outer diameter is 20 cm, a uniform radiation field with a maximum area of 2290.221 cm2 can be obtained. The double-loop diode structure can obtain a larger area of uniform radiation field than the single-loop structure. However, the variation of the outer ring diameter leads to multi-level peaks in the dose distribution of the radiation field, which also affects the homogeneity of each region of the radiation field. The simulation results show that by adding a concentric outer ring with an inner diameter of 43.5 cm and an outer diameter of 44.167 cm to the outside of the single ring structure, the radiation field area meeting the uniformity requirement can be increased to 7238.229 cm2.
Bremsstrahlung diode is an important device for obtaining large area uniform bremsstrahlung field in laboratory. In this paper, based on Monte Carlo method, a model of single and double ring parallel electron beam bombarding tantalum target is established to simulate the process of bremsstrahlung field generated by ring diode. The electron beam energy is 1.5 MeV, the tantalum target thickness is 200 μm, and the dose of bremsstrahlung field generated by a single ring electron beam 10 cm behind the target is simulated by detector counting method. For single-ring diode structure, the inner diameter of the ring is the main factor affecting the bremsstrahlung field uniformity behind the target, and the larger the inner diameter, the worse the central dose uniformity. Compared with the inner diameter of the ring, the ring width mainly affects the dose of the radiation field, but has little influence on the uniformity. When the inner diameter of a single ring is 19 cm and the outer diameter is 20 cm, a uniform radiation field with a maximum area of
2024, 36: 126005.
doi: 10.11884/HPLPB202436.240095
Abstract:
FLASH radiotherapy delivers the entire dose to the target area within milliseconds using ultra-high dose rates, rendering existing online dosimeters essentially ineffective. Currently, radiation-sensitive films are commonly employed for dose measurement. Utilizing an electron accelerator developed by the Institute of Applied Electronics of CAEP, an electron FLASH radiotherapy platform was established to investigate the dose rate range and dose distribution using the EBT3 film’s rapid readout method. Experimental results indicate that the rapid readout method of EBT3 films is applicable for dose measurement in electron FLASH radiotherapy, with dose rates ranging from 240 Gy/s to 290 Gy/s at a source-to-skin distance of 100 cm and a depth of 1 cm. Fluctuations in the average energy of the electron beam reaching the surface of the phantom result in dose fluctuations of approximately ±5% in the target area. The surface dose distribution meets the requirements of flatness within ±5% and symmetry within ±3%.
FLASH radiotherapy delivers the entire dose to the target area within milliseconds using ultra-high dose rates, rendering existing online dosimeters essentially ineffective. Currently, radiation-sensitive films are commonly employed for dose measurement. Utilizing an electron accelerator developed by the Institute of Applied Electronics of CAEP, an electron FLASH radiotherapy platform was established to investigate the dose rate range and dose distribution using the EBT3 film’s rapid readout method. Experimental results indicate that the rapid readout method of EBT3 films is applicable for dose measurement in electron FLASH radiotherapy, with dose rates ranging from 240 Gy/s to 290 Gy/s at a source-to-skin distance of 100 cm and a depth of 1 cm. Fluctuations in the average energy of the electron beam reaching the surface of the phantom result in dose fluctuations of approximately ±5% in the target area. The surface dose distribution meets the requirements of flatness within ±5% and symmetry within ±3%.
