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RSS2021 Vol. 33, No. 5
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2021,
: 1-2.
2021,
33: 051001.
doi: 10.11884/HPLPB202133.210006
Abstract:
Stimulated Brillouin scattering (SBS) as a third-order optical effect is widely used in laser beam combination, distributed fiber sensing, Brillouin lasers and other fields. In recent years, SBS pulse compression has also received special attention. Based on the energy transfer characteristics of the Brillouin amplification process, SBS pulse compression technology can compress nanosecond pulses to sub-nanosecond levels, and the peak power can be increased by 1-2 orders of magnitude. This paper systematically introduces the basic theory of SBS pulse compression, comprehensively discusses the influence of SBS compressor structure, gain medium, pump pulse and other factors on pulse compression characteristics, and looks forward to the development trends of SBS pulse compression. It provides a useful reference for the future study of SBS characteristics and a feasible scheme for the acquisition of high repetition frequency and high energy laser.
2021,
33: 051002.
doi: 10.11884/HPLPB202133.200293
Abstract:
Precision polishing system for opticals based on bonnet polishing technology and industrial robot can not only meet the requirements of high efficiency and precision of rapid polishing, but also reduce the development cost, thus it is a potential development solution for polishing. Bonnet polishing requires stable and deterministic material removal characteristics, and the stability of polishing spot is usually around 90%. The influence of robot stiffness on the stability of robot bonnet polishing system in the process of multi-step discrete precession polishing was studied. The robot end deformation was analyzed by the stiffness matrix, and the removal function of bonnet polishing with deformation error was established based on Preston theory. Finally, a four-step discrete polishing experiment was designed. According to the results, the polishing spot was Gaussian on the xy section contour line, and the xy section contour line was basically the same, with a good coincidence degree. Comparison of the cross-section profiles at different polishing positions indicates, the relative errors are below 5%. The experiment proves that the robot bonnet polishing system has a good stability in discrete precast polishing.
Precision polishing system for opticals based on bonnet polishing technology and industrial robot can not only meet the requirements of high efficiency and precision of rapid polishing, but also reduce the development cost, thus it is a potential development solution for polishing. Bonnet polishing requires stable and deterministic material removal characteristics, and the stability of polishing spot is usually around 90%. The influence of robot stiffness on the stability of robot bonnet polishing system in the process of multi-step discrete precession polishing was studied. The robot end deformation was analyzed by the stiffness matrix, and the removal function of bonnet polishing with deformation error was established based on Preston theory. Finally, a four-step discrete polishing experiment was designed. According to the results, the polishing spot was Gaussian on the xy section contour line, and the xy section contour line was basically the same, with a good coincidence degree. Comparison of the cross-section profiles at different polishing positions indicates, the relative errors are below 5%. The experiment proves that the robot bonnet polishing system has a good stability in discrete precast polishing.
2021,
33: 053001.
doi: 10.11884/HPLPB202133.200335
Abstract:
The effect of the parameters (sintering temperature, pressure, holding time) of spark plasma sintering technique on the W porosity of Ba-W cathode was studied by orthogonal method. When the W porosity varied in the range of 23%−30%, the corresponding process parameters were obtained. On this basis, the spherical and traditional irregular W matrix with different porosity were sintered. The results show that the spherical porous W particles were packed and arranged orderly, and the pore size distribution was concentrated and uniform. When the porosity of spherical W was 26.3%, the size of the median pore was 1.41 μm. The vickers hardness of spherical tungsten matrix was lower than that of conventional irregular tungsten matrix. Under the condition of pulse width 10 μs and frequency 1000 Hz, the impulse current density of Ba-W cathode increased at first and then decreased with the increase in porosity. The maximum current density belonged to the Ba-W cathode with the matrix porosity of 26.3%. At 1050 ℃, the off-point emission current density of Ba-W cathode reached 24.62 A/cm2, the corresponding zero-field current density and workfunction were 7.62 A/cm2 and 1.95 eV, respectively.
The effect of the parameters (sintering temperature, pressure, holding time) of spark plasma sintering technique on the W porosity of Ba-W cathode was studied by orthogonal method. When the W porosity varied in the range of 23%−30%, the corresponding process parameters were obtained. On this basis, the spherical and traditional irregular W matrix with different porosity were sintered. The results show that the spherical porous W particles were packed and arranged orderly, and the pore size distribution was concentrated and uniform. When the porosity of spherical W was 26.3%, the size of the median pore was 1.41 μm. The vickers hardness of spherical tungsten matrix was lower than that of conventional irregular tungsten matrix. Under the condition of pulse width 10 μs and frequency 1000 Hz, the impulse current density of Ba-W cathode increased at first and then decreased with the increase in porosity. The maximum current density belonged to the Ba-W cathode with the matrix porosity of 26.3%. At 1050 ℃, the off-point emission current density of Ba-W cathode reached 24.62 A/cm2, the corresponding zero-field current density and workfunction were 7.62 A/cm2 and 1.95 eV, respectively.
2021,
33: 053002.
doi: 10.11884/HPLPB202133.210007
Abstract:
In this paper, a modeling method of actual bending random bundled wire harness is proposed. Firstly, based on image recognition technology, the three-dimensional coordinates of bending wire harness axis are reconstructed by using two photos of actual wire harness in side view and top view; then the random bundled wire harness is realized based on random transfer path method. Based on this modeling method, this paper analyzes the statistical characteristics of distribution parameters of bending random wire harness by Monte Carlo simulation, and finds that the variation trend of self inductance, mutual inductance and mutual capacitance along the line is consistent with the variation trend of wire harness height, while the trend of self capacitance is opposite; the coefficient of variation of self capacitance, self inductance and mutual inductance has negative correlation with wire harness height; the bundling randomness is not obvious It will change the mean value of self inductance and self capacitance, but reduce the mean value of mutual capacitance and mutual inductance.
In this paper, a modeling method of actual bending random bundled wire harness is proposed. Firstly, based on image recognition technology, the three-dimensional coordinates of bending wire harness axis are reconstructed by using two photos of actual wire harness in side view and top view; then the random bundled wire harness is realized based on random transfer path method. Based on this modeling method, this paper analyzes the statistical characteristics of distribution parameters of bending random wire harness by Monte Carlo simulation, and finds that the variation trend of self inductance, mutual inductance and mutual capacitance along the line is consistent with the variation trend of wire harness height, while the trend of self capacitance is opposite; the coefficient of variation of self capacitance, self inductance and mutual inductance has negative correlation with wire harness height; the bundling randomness is not obvious It will change the mean value of self inductance and self capacitance, but reduce the mean value of mutual capacitance and mutual inductance.
2021,
33: 053003.
doi: 10.11884/HPLPB202133.210048
Abstract:
The subgridding boundary condition (SGBC) based modeling of thin composite layer in Finite-Difference Time-Domain (FDTD) simulation of enclosures breaks the constraint that the mesh size should be less than the smallest dimension of thin composite layer to get more accurate results, and therefore greatly reduce the computational cost. A large-scale parallelization platform JASMIN based modeling method of SGBC-FDTD was developed. The thin composite layer can be automatically modeled and adaptively allocated in the developed parallelized SGBC-FDTD code. The parallelized SGBC-FDTD algorithm was used to analyze the electromagnetic shielding effectiveness of enclosures containing composite thin layers with different electromagnetic properties in the frequency range of 0.1−1.0 GHz. The results show that shielding effectiveness predicted using the parallelized SGBC-FDTD algorithm are in good agreement with the ones calculated by a full-wave analysis software, while the calculation efficiency is significantly improved.
The subgridding boundary condition (SGBC) based modeling of thin composite layer in Finite-Difference Time-Domain (FDTD) simulation of enclosures breaks the constraint that the mesh size should be less than the smallest dimension of thin composite layer to get more accurate results, and therefore greatly reduce the computational cost. A large-scale parallelization platform JASMIN based modeling method of SGBC-FDTD was developed. The thin composite layer can be automatically modeled and adaptively allocated in the developed parallelized SGBC-FDTD code. The parallelized SGBC-FDTD algorithm was used to analyze the electromagnetic shielding effectiveness of enclosures containing composite thin layers with different electromagnetic properties in the frequency range of 0.1−1.0 GHz. The results show that shielding effectiveness predicted using the parallelized SGBC-FDTD algorithm are in good agreement with the ones calculated by a full-wave analysis software, while the calculation efficiency is significantly improved.
2021,
33: 053004.
doi: 10.11884/HPLPB202133.210002
Abstract:
High frequency system is the key part of folded-waveguide (FW) traveling-wave tube (TWT), it will directly affect the operating frequency, bandwidth, gain and other indicators of TWT. In order to obtain larger output power and higher gain than a conventional single-beam FWTWT, the basic characteristics of the 0.34 THz high order mode two-beam FWTWT are studied. Firstly, the dispersion characteristics and interaction impedance of two-beam FW are calculated and compared with the results of simulation. The results show that the theory of dispersion characteristics is consistent with the simulation results and the interaction impedance matches well in high frequency band. CST studio suite is used to simulate the beam-wave interaction of the two-beam FW, and the output power is 41.68 W. In order to obtain high output, the height of the straight is increased. And the 63.12 W output is obtained with an increase of 52.7%. High frequency system is constituted by mode converter and output window structure, and good transmission characteristics are obtained within 25 GHz bandwidth. In the operating bandwidth, |S11| is greater than 15 dB, |S21| is less than 4.5 dB.
High frequency system is the key part of folded-waveguide (FW) traveling-wave tube (TWT), it will directly affect the operating frequency, bandwidth, gain and other indicators of TWT. In order to obtain larger output power and higher gain than a conventional single-beam FWTWT, the basic characteristics of the 0.34 THz high order mode two-beam FWTWT are studied. Firstly, the dispersion characteristics and interaction impedance of two-beam FW are calculated and compared with the results of simulation. The results show that the theory of dispersion characteristics is consistent with the simulation results and the interaction impedance matches well in high frequency band. CST studio suite is used to simulate the beam-wave interaction of the two-beam FW, and the output power is 41.68 W. In order to obtain high output, the height of the straight is increased. And the 63.12 W output is obtained with an increase of 52.7%. High frequency system is constituted by mode converter and output window structure, and good transmission characteristics are obtained within 25 GHz bandwidth. In the operating bandwidth, |S11| is greater than 15 dB, |S21| is less than 4.5 dB.
2021,
33: 053005.
doi: 10.11884/HPLPB202133.210044
Abstract:
A miniaturized dual-stopband frequency selective surface (FSS) is proposed in this paper to shield the sensitive electronic equipment from interference signals with closely spaced frequency bands. The proposed FSS composes of a dielectric layer and two metal strip layers printed on both sides of the dielectric substrate. Different from other dual-band FSSes, the coupling between the double metal strip layers of the proposed FSS is weakened intentionally by using the complementary design of the strip patterns. As a result, the proposed FSS has two independently tunable stopbands which are very closely spaced. The simulated results show that the operating bands of the proposed FSS structure can achieve a frequency ratio as low as 1.16. In addition, the miniaturized design by using the convoluted elements makes the dimension of the unit cell as small as 0.071λ, where λ is the wavelength of the lower resonant frequency in free space. This ensures that the proposed FSS has incident angular stability of up to 60° for both TE and TM polarizations, while keeping at least 24 dB shielding effectiveness at the same time. The prototypes of the proposed FSS are fabricated and tested. Good agreements are achieved between the measurement and simulation, which demonstrates the reliability of the simulation.
A miniaturized dual-stopband frequency selective surface (FSS) is proposed in this paper to shield the sensitive electronic equipment from interference signals with closely spaced frequency bands. The proposed FSS composes of a dielectric layer and two metal strip layers printed on both sides of the dielectric substrate. Different from other dual-band FSSes, the coupling between the double metal strip layers of the proposed FSS is weakened intentionally by using the complementary design of the strip patterns. As a result, the proposed FSS has two independently tunable stopbands which are very closely spaced. The simulated results show that the operating bands of the proposed FSS structure can achieve a frequency ratio as low as 1.16. In addition, the miniaturized design by using the convoluted elements makes the dimension of the unit cell as small as 0.071λ, where λ is the wavelength of the lower resonant frequency in free space. This ensures that the proposed FSS has incident angular stability of up to 60° for both TE and TM polarizations, while keeping at least 24 dB shielding effectiveness at the same time. The prototypes of the proposed FSS are fabricated and tested. Good agreements are achieved between the measurement and simulation, which demonstrates the reliability of the simulation.
2021,
33: 053006.
doi: 10.11884/HPLPB202133.210043
Abstract:
The frequency continuous extension to K/Ka band for electronic devices and wireless technology, as well the fast development of integrated electronic system have made the electromagnetic shielding design of electronic systems increasingly challenging. In this paper, a new shielding method which incorporates frequency selective surface (FSS) into electronic systems to replace the conventional heat dissipation holes array is proposed. The proposed shielding method can meet the requirements of both ventilation and electromagnetic shielding performance at 5G millimeter wave band. Based on the shielding effectiveness (SE) at the center point in the enclosure and the global shielding effectiveness, the influences of the arrangement of FSS cells and the polarization and incident angle of electromagnetic waves on SEs of the metallic enclosure are analyzed. The results show that the arrangement of FSS cells have little effects on the shielding performance of the metallic enclosure, and SE hardly changes with the polarization of the electromagnetic waves. The shielding effectiveness of the metallic enclosure with the FSS is about 30 dB in the frequency range of 23.0−25.5 GHz, which is 15 dB higher than that of the enclosure with the conventional heat dissipation holes array. This demonstrates that the method proposed in this paper has better electromagnetic shielding while keep good ventilation at the same time.
The frequency continuous extension to K/Ka band for electronic devices and wireless technology, as well the fast development of integrated electronic system have made the electromagnetic shielding design of electronic systems increasingly challenging. In this paper, a new shielding method which incorporates frequency selective surface (FSS) into electronic systems to replace the conventional heat dissipation holes array is proposed. The proposed shielding method can meet the requirements of both ventilation and electromagnetic shielding performance at 5G millimeter wave band. Based on the shielding effectiveness (SE) at the center point in the enclosure and the global shielding effectiveness, the influences of the arrangement of FSS cells and the polarization and incident angle of electromagnetic waves on SEs of the metallic enclosure are analyzed. The results show that the arrangement of FSS cells have little effects on the shielding performance of the metallic enclosure, and SE hardly changes with the polarization of the electromagnetic waves. The shielding effectiveness of the metallic enclosure with the FSS is about 30 dB in the frequency range of 23.0−25.5 GHz, which is 15 dB higher than that of the enclosure with the conventional heat dissipation holes array. This demonstrates that the method proposed in this paper has better electromagnetic shielding while keep good ventilation at the same time.
2021,
33: 053007.
doi: 10.11884/HPLPB202133.200307
Abstract:
An accelerator-based boron neutron capture therapy (BNCT) experimental facility has been built by Institute of High Energy Physics, Chinese Academy of Sciences. The radio frequency (RF) power source system provides 352.2 MHz pulse power for radio-frequency quadrupole (RFQ) cavity and the beam energy reaches 3.5 MeV through RFQ cavity. The RF power source system includes klystron power source, digital low-level RF (LLRF) control system, and RF transmission system. This paper will introduce the BNCT RF system including physical requirements, system composition, key equipment, installation and commissioning work. At present, the therapy facility operates for animal tests with the target beam power higher than 4.3 kW. The RF power source system runs stably and reliably in the long-term operation.
An accelerator-based boron neutron capture therapy (BNCT) experimental facility has been built by Institute of High Energy Physics, Chinese Academy of Sciences. The radio frequency (RF) power source system provides 352.2 MHz pulse power for radio-frequency quadrupole (RFQ) cavity and the beam energy reaches 3.5 MeV through RFQ cavity. The RF power source system includes klystron power source, digital low-level RF (LLRF) control system, and RF transmission system. This paper will introduce the BNCT RF system including physical requirements, system composition, key equipment, installation and commissioning work. At present, the therapy facility operates for animal tests with the target beam power higher than 4.3 kW. The RF power source system runs stably and reliably in the long-term operation.
2021,
33: 053008.
doi: 10.11884/HPLPB202133.200350
Abstract:
Aiming at the problem that the impedance of the probe is prone to non-linear changes when applied to the bulk current injection test replacing high field intensity radiation, the linearity test of the existing commercial current probe is carried out by analyzing the method of large current injection. The test results show that as the injected power increases, the linearity error at different frequencies also increases. A plan for the development of a high-power and high-linearity current probe was proposed, and the probe was developed and passed the test. The self-developed current injection probe has a maximum withstand power of 500 W. The insertion loss varies with the injected power and has good linearity (0.3 dB @ 1−500 W). The probe can meet the technical requirements of carrying out bulk current injection (equivalent high field electromagnetic radiation effect) test.
Aiming at the problem that the impedance of the probe is prone to non-linear changes when applied to the bulk current injection test replacing high field intensity radiation, the linearity test of the existing commercial current probe is carried out by analyzing the method of large current injection. The test results show that as the injected power increases, the linearity error at different frequencies also increases. A plan for the development of a high-power and high-linearity current probe was proposed, and the probe was developed and passed the test. The self-developed current injection probe has a maximum withstand power of 500 W. The insertion loss varies with the injected power and has good linearity (0.3 dB @ 1−500 W). The probe can meet the technical requirements of carrying out bulk current injection (equivalent high field electromagnetic radiation effect) test.
2021,
33: 054001.
doi: 10.11884/HPLPB202133.200311
Abstract:
This article presents, the research about the vibration of the space environment simulation and research infrastructure (SESRI) scanning magnet for Harbin Institute of Technology (HIT), which uses laser displacement sensors to measure the amplitudes at the key test points. The purpose of the test is to analyze the factors that influence the vibration and the way to block or absorb vibration. The collected data show that when I＝450 A, f＜140 Hz, the magnet has no obvious vibration. Current and its frequency, especially frequency, are the main factors affecting the vibration. The scanning magnet for SESRI is resin casted with coil and iron core designed to be integrated. Compared with the previous design, the vibration is obviously reduced. As the conclusion, the rational design inside the magnet can block vibration, which can provide a reference for designing new magnets.
This article presents, the research about the vibration of the space environment simulation and research infrastructure (SESRI) scanning magnet for Harbin Institute of Technology (HIT), which uses laser displacement sensors to measure the amplitudes at the key test points. The purpose of the test is to analyze the factors that influence the vibration and the way to block or absorb vibration. The collected data show that when I＝450 A, f＜140 Hz, the magnet has no obvious vibration. Current and its frequency, especially frequency, are the main factors affecting the vibration. The scanning magnet for SESRI is resin casted with coil and iron core designed to be integrated. Compared with the previous design, the vibration is obviously reduced. As the conclusion, the rational design inside the magnet can block vibration, which can provide a reference for designing new magnets.
2021,
33: 054002.
doi: 10.11884/HPLPB202133.200300
Abstract:
High energy electron radiography is a useful nondestructive method for density material diagnosis. The higher the kinetic energy, the stronger penetrability the electron has. Thus electron with GeV energy is considered for probing the density material. This paper aims at 2.5 GeV electron radiography. The key processes of radiography are studied by Monte Carlo simulation. All simulations are carried out by Geant4 code. Firstly, basic physical processes including the transport of electrons in the quadrupole lens group and the attenuation of the interaction between electrons and matter are constructed by Geant4 code. Some details about the physics setup are given. Four samples of different materials and thickness, with voids inside, are designed as the object of simulation radiography. Other necessary geometries for electronic photography such as quadrupole and pixel detector are built as well. Then a large-scale electronic photography is simulated. In addition to this, two step samples made of copper and tungsten, respectively, are employed as object for the radiography simulation. In the simulation, collimated line electron source radiates objects, then the line spread function of the electron beam passing through the different area density is obtained. Based on the simulated results, evaluation about the detection and resolution ability of 2.5 GeV electron radiography is shown.
High energy electron radiography is a useful nondestructive method for density material diagnosis. The higher the kinetic energy, the stronger penetrability the electron has. Thus electron with GeV energy is considered for probing the density material. This paper aims at 2.5 GeV electron radiography. The key processes of radiography are studied by Monte Carlo simulation. All simulations are carried out by Geant4 code. Firstly, basic physical processes including the transport of electrons in the quadrupole lens group and the attenuation of the interaction between electrons and matter are constructed by Geant4 code. Some details about the physics setup are given. Four samples of different materials and thickness, with voids inside, are designed as the object of simulation radiography. Other necessary geometries for electronic photography such as quadrupole and pixel detector are built as well. Then a large-scale electronic photography is simulated. In addition to this, two step samples made of copper and tungsten, respectively, are employed as object for the radiography simulation. In the simulation, collimated line electron source radiates objects, then the line spread function of the electron beam passing through the different area density is obtained. Based on the simulated results, evaluation about the detection and resolution ability of 2.5 GeV electron radiography is shown.
2021,
33: 054003.
doi: 10.11884/HPLPB202133.210015
Abstract:
Shanghai Soft X-ray Free Electron Laser (SXFEL) is the first fourth-generation light source in China that can work in soft X-ray band. With the advantages of short wavelength, full coherence, ultra-high brightness, and ultra-short pulse, it is expected to play an important role in basic science research. Based on the characteristics of the linear accelerator, the stripline beam position monitor (SBPM) was selected as the beam position measurement tool in the injection section and the straight section. The system is mainly composed of the probe, the front-end electronics system, and the digital beam position monitor (DBPM). The design draws on the same type of device from Shanghai Synchrotron Radiation Facility (SSRF) and is further optimized according to the characteristics of SXFEL. Finally, the beam experiment results show that the resolution reaches 5.7 μm@188 pC, which meets the requirements for beam position resolution of SXFEL.
Shanghai Soft X-ray Free Electron Laser (SXFEL) is the first fourth-generation light source in China that can work in soft X-ray band. With the advantages of short wavelength, full coherence, ultra-high brightness, and ultra-short pulse, it is expected to play an important role in basic science research. Based on the characteristics of the linear accelerator, the stripline beam position monitor (SBPM) was selected as the beam position measurement tool in the injection section and the straight section. The system is mainly composed of the probe, the front-end electronics system, and the digital beam position monitor (DBPM). The design draws on the same type of device from Shanghai Synchrotron Radiation Facility (SSRF) and is further optimized according to the characteristics of SXFEL. Finally, the beam experiment results show that the resolution reaches 5.7 μm@188 pC, which meets the requirements for beam position resolution of SXFEL.
2021,
33: 054004.
doi: 10.11884/HPLPB202133.200352
Abstract:
Orbit correction is one of the most fundamental processes used for beam control in accelerators. Algorithms have been developed at various laboratories to meet specific demands. Typically, linear algebraic tools are applied to various response matrices to solve related problems. However, there are still many problems faced by orbit correction algorithms such as lengthy measurement and computation time. A new approach based on machine learning to develop an orbit correction program is introduced. In this method a machine learning program is trained with correctors data and BPMs data for applying to orbit correction. Mathematical formulation, algorithms prototyped and tested on simulated and real data, and future possibilities are discussed.
Orbit correction is one of the most fundamental processes used for beam control in accelerators. Algorithms have been developed at various laboratories to meet specific demands. Typically, linear algebraic tools are applied to various response matrices to solve related problems. However, there are still many problems faced by orbit correction algorithms such as lengthy measurement and computation time. A new approach based on machine learning to develop an orbit correction program is introduced. In this method a machine learning program is trained with correctors data and BPMs data for applying to orbit correction. Mathematical formulation, algorithms prototyped and tested on simulated and real data, and future possibilities are discussed.
2021,
33: 054005.
doi: 10.11884/HPLPB202133.210046
Abstract:
Aiming to control the rising failure rate of electronics system for BEPC II linac’s beam position measurement, considering the physical design parameters of BEPC II and the requirements of band-pass sampling of BPM electronics ADC chip, a digital BPM RF front-end electronics with high isolation degree and good amplitude and phase consistency is designed. The digital BPM electronics system adopts MicroTCA 4.0 system architecture, takes FPGA as the main controller, and is designed based on EDA software. This paper mainly introduces RF power amplifier, digital adjustable attenuator and bandpass filter in RF front-end electronics module, as well as the laboratory and online test results. In the collision mode of BEPC II, positron beam was used to complete the electronic system online test, and the measurement accuracy of x-direction was about 38.46 μm, while that of y-direction was about 26.16 μm. The measurement accuracy and system stability of the proposed method are better than that of commercial analog BPM electronics module, and can meet the beam position measurement requirements of BEPC II linac.
Aiming to control the rising failure rate of electronics system for BEPC II linac’s beam position measurement, considering the physical design parameters of BEPC II and the requirements of band-pass sampling of BPM electronics ADC chip, a digital BPM RF front-end electronics with high isolation degree and good amplitude and phase consistency is designed. The digital BPM electronics system adopts MicroTCA 4.0 system architecture, takes FPGA as the main controller, and is designed based on EDA software. This paper mainly introduces RF power amplifier, digital adjustable attenuator and bandpass filter in RF front-end electronics module, as well as the laboratory and online test results. In the collision mode of BEPC II, positron beam was used to complete the electronic system online test, and the measurement accuracy of x-direction was about 38.46 μm, while that of y-direction was about 26.16 μm. The measurement accuracy and system stability of the proposed method are better than that of commercial analog BPM electronics module, and can meet the beam position measurement requirements of BEPC II linac.
2021,
33: 055001.
doi: 10.11884/HPLPB202133.200329
Abstract:
The material parameters and functional modules of LiF are added to the two-dimensional magnetically driven simulation code (MDSC2), which makes MDSC2 code have the ability to simulate the magnetically driven quasi-isentropic compression experiments with windows. Magnetically driven experiments with windows, shots of exp-3-window and exp-6-window, which were carried out in a large pulsed power device, are simulated and analyzed by the MDSC2 code. The simulated flyer plate/window interface velocities agree well with the experimental records by Velocity Interferometry System for Any Reflector (VISAR). The magneto-hydrodynamic code can correctly simulate the magnetically driven experiments with windows, which is helpful to understand the physical mechanism of sample material behaviors in magnetically driven experiments with windows.
The material parameters and functional modules of LiF are added to the two-dimensional magnetically driven simulation code (MDSC2), which makes MDSC2 code have the ability to simulate the magnetically driven quasi-isentropic compression experiments with windows. Magnetically driven experiments with windows, shots of exp-3-window and exp-6-window, which were carried out in a large pulsed power device, are simulated and analyzed by the MDSC2 code. The simulated flyer plate/window interface velocities agree well with the experimental records by Velocity Interferometry System for Any Reflector (VISAR). The magneto-hydrodynamic code can correctly simulate the magnetically driven experiments with windows, which is helpful to understand the physical mechanism of sample material behaviors in magnetically driven experiments with windows.
2021,
33: 055002.
doi: 10.11884/HPLPB202133.200289
Abstract:
Epoxy/Al2O3 composite is widely used as insulating material in power equipment. However, its performance in SF6 gas under fast-rising pulse is little studied, which limits its application in guiding insulation design of pulse power devices. To investigate the insulation characteristics of epoxy/Al2O3 composite under nanosecond pulses, the flashover characteristics of this material are studied under pulse voltage with rise time of about 52 ns. The results show that its electric field of flashover is much higher than pure epoxy’s, and the flashover voltage is in accordance with Weibull distribution. The experiment shows that the flashover voltage increases significantly with the increase of the pulse steepness, from 108 kV at 5.8 kV/ns to 226 kV at 20.5 kV/ns. As pulse steepness increases, the flashover delay time decreases rapidly first, then tends to be flat. The surface morphology of the flashover area of the samples shows that the flashover channel is obviously carbonized and flashover discharge has a destructive effect on the composite material.
Epoxy/Al2O3 composite is widely used as insulating material in power equipment. However, its performance in SF6 gas under fast-rising pulse is little studied, which limits its application in guiding insulation design of pulse power devices. To investigate the insulation characteristics of epoxy/Al2O3 composite under nanosecond pulses, the flashover characteristics of this material are studied under pulse voltage with rise time of about 52 ns. The results show that its electric field of flashover is much higher than pure epoxy’s, and the flashover voltage is in accordance with Weibull distribution. The experiment shows that the flashover voltage increases significantly with the increase of the pulse steepness, from 108 kV at 5.8 kV/ns to 226 kV at 20.5 kV/ns. As pulse steepness increases, the flashover delay time decreases rapidly first, then tends to be flat. The surface morphology of the flashover area of the samples shows that the flashover channel is obviously carbonized and flashover discharge has a destructive effect on the composite material.
2021,
33: 055003.
doi: 10.11884/HPLPB202133.210014
Abstract:
Aiming at the difficult problems of trigger delay, jitter and short life of triggered vacuum switch, A new type of triggered vacuum switch based on a gas-breathing electrode was designed to carry out life test and conduction characteristic experiment under different trigger polarity, main gap voltage and trigger energy. The experimental results show that compared with the pure metal electrode switch, the gas-breathing electrode switch has shorter trigger delay, shorter jitter and longer working life. The trigger delay and jitter of negative polarity trigger are lower than that of positive polarity trigger. The trigger delay of positive polarity trigger is 1.7−3.0 μs, and the delay jitter is 300−700 ns. The trigger delay of negative polarity trigger is 400−600 ns, and the jitter is 30−70 ns. The trigger delay and jitter decrease with the increase of trigger energy, but when the energy is higher than a certain value, the influence of trigger energy on the conduction characteristics tends to be saturated.
Aiming at the difficult problems of trigger delay, jitter and short life of triggered vacuum switch, A new type of triggered vacuum switch based on a gas-breathing electrode was designed to carry out life test and conduction characteristic experiment under different trigger polarity, main gap voltage and trigger energy. The experimental results show that compared with the pure metal electrode switch, the gas-breathing electrode switch has shorter trigger delay, shorter jitter and longer working life. The trigger delay and jitter of negative polarity trigger are lower than that of positive polarity trigger. The trigger delay of positive polarity trigger is 1.7−3.0 μs, and the delay jitter is 300−700 ns. The trigger delay of negative polarity trigger is 400−600 ns, and the jitter is 30−70 ns. The trigger delay and jitter decrease with the increase of trigger energy, but when the energy is higher than a certain value, the influence of trigger energy on the conduction characteristics tends to be saturated.
2021,
33: 055004.
doi: 10.11884/HPLPB202133.210067
Abstract:
To evaluate the vibration environmental adaptability of Tesla-type pulse generator under vehicle transportation condition, simulation and verification test were carried out for the coaxial pulse forming line (PFL) with cantilever support insulators. An equivalent modeling was proposed for the inner and outer magnetic cores with laminated structure. The finite element model was modified according to the modal test results. Thus the effect of insulating oil on the modal frequency and damping of the PFL was studied, the stress and response of PFL under typical transportation conditions were obtained by simulation, and the vibration test of PFL equivalent parts was conducted to verify the simulation result. It was found that the structure of the PFL were nonlinear in the vibration test. The simulation analysis and the vibration test of equivalent parts verify that the existing structure of the coaxial PFL meets the requirements of vehicle transportation vibration environmental adaptability.
To evaluate the vibration environmental adaptability of Tesla-type pulse generator under vehicle transportation condition, simulation and verification test were carried out for the coaxial pulse forming line (PFL) with cantilever support insulators. An equivalent modeling was proposed for the inner and outer magnetic cores with laminated structure. The finite element model was modified according to the modal test results. Thus the effect of insulating oil on the modal frequency and damping of the PFL was studied, the stress and response of PFL under typical transportation conditions were obtained by simulation, and the vibration test of PFL equivalent parts was conducted to verify the simulation result. It was found that the structure of the PFL were nonlinear in the vibration test. The simulation analysis and the vibration test of equivalent parts verify that the existing structure of the coaxial PFL meets the requirements of vehicle transportation vibration environmental adaptability.
2021,
33: 055005.
doi: 10.11884/HPLPB202133.210136
Abstract:
Rod pinch diode (RPD) has the characteristics of small focal spot and high brightness, which is a research hotspot in the field of flash radiography. In this paper, based on the Marx generator and pulse forming line technology route, 1 MV high voltage pulse driving RPD is generated, and the experimental research of diode with different structure parameters is carried out. Based on the numerical model of RPD physical process, the ratio of cathode to anode aperture is a complex variable related to the average diffusion velocity of cathode and anode plasma, which is also the main parameter affecting the radiation performance of RPD. The results show that the average diffusion velocity of RPD anode plasma is about 0.6 cm/μs at 1 MV voltage. When the anode rod diameter is fixed, the diode numerical model shows that reducing the cathode aperture can make the diode enter the strong pinch state faster, but too small cathode aperture will lead to premature closure of the diode gap.
Rod pinch diode (RPD) has the characteristics of small focal spot and high brightness, which is a research hotspot in the field of flash radiography. In this paper, based on the Marx generator and pulse forming line technology route, 1 MV high voltage pulse driving RPD is generated, and the experimental research of diode with different structure parameters is carried out. Based on the numerical model of RPD physical process, the ratio of cathode to anode aperture is a complex variable related to the average diffusion velocity of cathode and anode plasma, which is also the main parameter affecting the radiation performance of RPD. The results show that the average diffusion velocity of RPD anode plasma is about 0.6 cm/μs at 1 MV voltage. When the anode rod diameter is fixed, the diode numerical model shows that reducing the cathode aperture can make the diode enter the strong pinch state faster, but too small cathode aperture will lead to premature closure of the diode gap.
2021,
33: 059001.
doi: 10.11884/HPLPB202133.210039
Abstract:
Having a new generation of selective laser melting process, surface exposure selective laser melting technology has the advantages of high forming efficiency and uniform temperature field, and is becoming a research focus in additive manufacturing field. The influence of laser spot overlap rate and electric current on the shape accuracy of single-layer laser melting with surface exposure was investigated. The effects of overlap rate, exposure time and electric current on the forming of laser spot, track, circular ring and sharp angle were studied by the control variable method. The experimental results show that: within a certain range, the larger the electric current is, the more uniform the laser spot is, and the more conducive to forming; The lowest shape error can be obtained with overlap rate of 38.4%. The forming error of the circular ring increases with the increase of electric current. The forming error of sharp angle increases first and then decreases with the increase of electric current. The shape error caused by zero-order diffraction can be reduced when the overlap rate is 46.1% and 38.4%.
Having a new generation of selective laser melting process, surface exposure selective laser melting technology has the advantages of high forming efficiency and uniform temperature field, and is becoming a research focus in additive manufacturing field. The influence of laser spot overlap rate and electric current on the shape accuracy of single-layer laser melting with surface exposure was investigated. The effects of overlap rate, exposure time and electric current on the forming of laser spot, track, circular ring and sharp angle were studied by the control variable method. The experimental results show that: within a certain range, the larger the electric current is, the more uniform the laser spot is, and the more conducive to forming; The lowest shape error can be obtained with overlap rate of 38.4%. The forming error of the circular ring increases with the increase of electric current. The forming error of sharp angle increases first and then decreases with the increase of electric current. The shape error caused by zero-order diffraction can be reduced when the overlap rate is 46.1% and 38.4%.
