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RSS2017 Vol. 29, No. 10
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2017,
29: 100101.
doi: 10.11884/HPLPB201729.170363
Abstract:
First lasing of the CAEP THz FEL (CTFEL) facility was obtained in August 29, 2017. The facility consists of a GaAs photocathode high-voltage DC gun, a superconducting RF linac, a planar undulator and a quasi-concentric optical resonator. The central frequency of the first saturated lasing was 2.56 THz, with the spectral width about 1.9%. The average output power in the macro pulse was larger than 5.7 W.
First lasing of the CAEP THz FEL (CTFEL) facility was obtained in August 29, 2017. The facility consists of a GaAs photocathode high-voltage DC gun, a superconducting RF linac, a planar undulator and a quasi-concentric optical resonator. The central frequency of the first saturated lasing was 2.56 THz, with the spectral width about 1.9%. The average output power in the macro pulse was larger than 5.7 W.
2017,
29: 100201.
doi: 10.11884/HPLPB201729.170181
Abstract:
The recent progress in fundamentals of high-average-power fiber lasers technology is summarized, the mutual-benefit process between high power fiber lasers technology and in-depth investigations into fundamental scientific issues such as oscillator cavity, mode and nonlinear effects is revealed. The consideration in writing this series of papers is briefly introduced.
The recent progress in fundamentals of high-average-power fiber lasers technology is summarized, the mutual-benefit process between high power fiber lasers technology and in-depth investigations into fundamental scientific issues such as oscillator cavity, mode and nonlinear effects is revealed. The consideration in writing this series of papers is briefly introduced.
2017,
29: 100202.
doi: 10.11884/HPLPB201729.170182
Abstract:
The basic setup, main components and their functions of a fiber laser oscillator are briefly introduced, and the current development status of fiber oscillator is presented. The temporal, spatial and spectral properties of the oscillator are analyzed based on the Fiber Bragg grating(FBG). The mechanism, method and progress in manipulation of the central wavelength, linewidth and shape of the output of the oscillator are introduced. The mechanism, method and progress in manipulation of the output mode of the oscillator are introduced via the relationship between the eigen mode and the reflection spectrum. Recent progress of the instantaneous temporal property modeling is shown, the relationship between temporal and spectral properties and their influence on the nonlinear effect are revealed. Two kinds of cavity-free high power fiber lasers are briefly discussed.
The basic setup, main components and their functions of a fiber laser oscillator are briefly introduced, and the current development status of fiber oscillator is presented. The temporal, spatial and spectral properties of the oscillator are analyzed based on the Fiber Bragg grating(FBG). The mechanism, method and progress in manipulation of the central wavelength, linewidth and shape of the output of the oscillator are introduced. The mechanism, method and progress in manipulation of the output mode of the oscillator are introduced via the relationship between the eigen mode and the reflection spectrum. Recent progress of the instantaneous temporal property modeling is shown, the relationship between temporal and spectral properties and their influence on the nonlinear effect are revealed. Two kinds of cavity-free high power fiber lasers are briefly discussed.
2017,
29: 101001.
doi: 10.11884/HPLPB201729.170107
Abstract:
In this paper, we studied the factors that affect the high frequency modulation performance of semiconductor laser in the process of direct modulation. The equivalent circuit model of LD is derived from the rate equation of semiconductor laser, which was established by using PSpice. We analyzed the effects of the parasitic parameters, the DC bias and the current modulation intensity on modulation characteristics of the laser, and put forward the corresponding methods to improve the performance of modulation. We designed a direct modulation system of semiconductor laser and simulated the system by OrCAD/PSpice. This system can output modulation semiconductor laser with frequency of 1 MHz and average power of 1.1 W.
In this paper, we studied the factors that affect the high frequency modulation performance of semiconductor laser in the process of direct modulation. The equivalent circuit model of LD is derived from the rate equation of semiconductor laser, which was established by using PSpice. We analyzed the effects of the parasitic parameters, the DC bias and the current modulation intensity on modulation characteristics of the laser, and put forward the corresponding methods to improve the performance of modulation. We designed a direct modulation system of semiconductor laser and simulated the system by OrCAD/PSpice. This system can output modulation semiconductor laser with frequency of 1 MHz and average power of 1.1 W.
2017,
29: 101002.
doi: 10.11884/HPLPB201729.170111
Abstract:
Through the analysis of the characteristics and development trend of the ultraviolet communication receiving optical system, a method of designing off-axial TMA ultraviolet communication receiving optical system is presented based on coaxial three-reflective optical system. The structural parameters of the system can be solved and optimized by ZEMAX. Then the off-axial three-mirror system with focal length of 998.192 mm, field of view of 4 and F-number of 4 is designed. The modulation transform function (MTF) of field of view is 0.4 at 50 lp/mm, and the full field diffusion plaque is controlled within 5 m. This system overcomes the central shielding problem which exists in coaxial TMA system, thus the image quality of the system is greatly improved. The system design meets the corresponding technical requirements, which is of great significance to successful development of ultraviolet communication system.
Through the analysis of the characteristics and development trend of the ultraviolet communication receiving optical system, a method of designing off-axial TMA ultraviolet communication receiving optical system is presented based on coaxial three-reflective optical system. The structural parameters of the system can be solved and optimized by ZEMAX. Then the off-axial three-mirror system with focal length of 998.192 mm, field of view of 4 and F-number of 4 is designed. The modulation transform function (MTF) of field of view is 0.4 at 50 lp/mm, and the full field diffusion plaque is controlled within 5 m. This system overcomes the central shielding problem which exists in coaxial TMA system, thus the image quality of the system is greatly improved. The system design meets the corresponding technical requirements, which is of great significance to successful development of ultraviolet communication system.
2017,
29: 103001.
doi: 10.11884/HPLPB201729.170116
Abstract:
In this paper, we present a new structure cathode named co-axis double annulus cathode. By modeling and solving the Laplace equation, we get the accurate distribution of potential in the diode, through which we have the connection of parameters to get the double annulus cathode emissions simultaneously. The CHIPIC particle-in-cell software was used to a simulate the electrons explosive emission of the double annulus cathode with appropriate parameters. The result verifies that, the emitting current density of the double annulus cathode is determined by both the original E-field distribution in the diode and the screening effect between two cathodes. The screening effect factor of one cathode has a linear relationship with the beam emitted from the other cathode and an exponential relationship with the distance between the two cathodes.
In this paper, we present a new structure cathode named co-axis double annulus cathode. By modeling and solving the Laplace equation, we get the accurate distribution of potential in the diode, through which we have the connection of parameters to get the double annulus cathode emissions simultaneously. The CHIPIC particle-in-cell software was used to a simulate the electrons explosive emission of the double annulus cathode with appropriate parameters. The result verifies that, the emitting current density of the double annulus cathode is determined by both the original E-field distribution in the diode and the screening effect between two cathodes. The screening effect factor of one cathode has a linear relationship with the beam emitted from the other cathode and an exponential relationship with the distance between the two cathodes.
2017,
29: 103002.
doi: 10.11884/HPLPB201729.170144
Abstract:
This paper presents a method for design a suitable two stage depressed collector of X band large duty ratio coupled-cavity traveling wave tube (CC-TWT). The axial, radial velocities and radius of 96 electron trajectories in the output potion of this TWT were simulated and analyzed by 2.5 dimensional interaction package owned by 772nd factory. A refocusing segment was designed to improve the flow of electron injection layer with the help of re-simulation of these parameters. Then a two stage depressed collector was designed with optical design, structural design and thermal analysis. Finally, a TWT was assembled for testing. The measured proportion of the current distribution in every collector electrode and the collector efficiency are close to the analytical full-band average results, which means that this analytical method is suitable for design of two stage depressed collector for high-power CC-TWT.
This paper presents a method for design a suitable two stage depressed collector of X band large duty ratio coupled-cavity traveling wave tube (CC-TWT). The axial, radial velocities and radius of 96 electron trajectories in the output potion of this TWT were simulated and analyzed by 2.5 dimensional interaction package owned by 772nd factory. A refocusing segment was designed to improve the flow of electron injection layer with the help of re-simulation of these parameters. Then a two stage depressed collector was designed with optical design, structural design and thermal analysis. Finally, a TWT was assembled for testing. The measured proportion of the current distribution in every collector electrode and the collector efficiency are close to the analytical full-band average results, which means that this analytical method is suitable for design of two stage depressed collector for high-power CC-TWT.
2017,
29: 103101.
doi: 10.11884/HPLPB201729.170118
Abstract:
Cross-linked polystyrene is a kind of thermosetting plastic with excellent dielectric properties and high breakdown voltage. We measured the terahertz spectra of cross-linked polystyrene and polystyrene using THz-TDS based on THz-ABCD(air biased coherent detector), and the absorption coefficients and refractive indexes in the range of 2-13 THz were obtained. The terahertz spectra of cross-linked polystyrene and polystyrene were similar, and there existed several absorption peaks such as 6.6 THz, 9.8 THz and 12.25 THz, the absorption coefficient of cross-linked polystyrene was higher than that of polystyrene below 12 THz but lower above 12 THz, the refractive index of cross-linked polystyrene (1.59-1.62) was higher than that of polystyrene (1.58-1.59).
Cross-linked polystyrene is a kind of thermosetting plastic with excellent dielectric properties and high breakdown voltage. We measured the terahertz spectra of cross-linked polystyrene and polystyrene using THz-TDS based on THz-ABCD(air biased coherent detector), and the absorption coefficients and refractive indexes in the range of 2-13 THz were obtained. The terahertz spectra of cross-linked polystyrene and polystyrene were similar, and there existed several absorption peaks such as 6.6 THz, 9.8 THz and 12.25 THz, the absorption coefficient of cross-linked polystyrene was higher than that of polystyrene below 12 THz but lower above 12 THz, the refractive index of cross-linked polystyrene (1.59-1.62) was higher than that of polystyrene (1.58-1.59).
2017,
29: 103102.
doi: 10.11884/HPLPB201729.170275
Abstract:
In order to realize the medium-range and long-distance detection in one radar, we studied and realized a kind of antenna array meeting the long- and medium-range radar demand. The simulation and measurement results show that the radar antenna array can meet the detection needs of 77 GHz vehicle millimeter-wave radar of large angle with medium distance and narrow angle with long distance.
In order to realize the medium-range and long-distance detection in one radar, we studied and realized a kind of antenna array meeting the long- and medium-range radar demand. The simulation and measurement results show that the radar antenna array can meet the detection needs of 77 GHz vehicle millimeter-wave radar of large angle with medium distance and narrow angle with long distance.
2017,
29: 103201.
doi: 10.11884/HPLPB201729.170187
Abstract:
Frequency sweep jamming is one of the main threats to the current frequency-modulated continuous-wave (FMCW) radio fuze while its jamming probability has certain randomness. To improve the jamming performance, an optimized narrow-band sweep jamming approach for single-channel FMCW Doppler radio fuze is proposed based on the analysis of the corresponding failure mechanism of the FMCW fuze. This approach is an unequal-interval frequency sweep jamming with optimized stepped-frequency points. The simulation and measurement results show that this approach enhances the effect of sweep jamming, and it also provides a reference to the design of jamming scheme for the FMCW fuze with multiple-channels or some other anti-jamming measures.
Frequency sweep jamming is one of the main threats to the current frequency-modulated continuous-wave (FMCW) radio fuze while its jamming probability has certain randomness. To improve the jamming performance, an optimized narrow-band sweep jamming approach for single-channel FMCW Doppler radio fuze is proposed based on the analysis of the corresponding failure mechanism of the FMCW fuze. This approach is an unequal-interval frequency sweep jamming with optimized stepped-frequency points. The simulation and measurement results show that this approach enhances the effect of sweep jamming, and it also provides a reference to the design of jamming scheme for the FMCW fuze with multiple-channels or some other anti-jamming measures.
2017,
29: 103202.
doi: 10.11884/HPLPB201729.170152
Abstract:
Random coupling model(RCM) for key parts of the complex electronic systems cavity to predict pulsed electromagnetic interfrence is a new method in studying high power microwave effects, while the damping of cavity is a key factor determining the effect of this statistical forecasting method. The effects that the cavity reactance varies with frequences is discussed in the first part of the paper. Then a new idea using the real part of cavity reactance vs radiation reactance to calculate the damping quickly is put forward. The method using matrix eigen values and comparison between radiation and scattering resistances is proposed to verify the feasibility of the new idea.
Random coupling model(RCM) for key parts of the complex electronic systems cavity to predict pulsed electromagnetic interfrence is a new method in studying high power microwave effects, while the damping of cavity is a key factor determining the effect of this statistical forecasting method. The effects that the cavity reactance varies with frequences is discussed in the first part of the paper. Then a new idea using the real part of cavity reactance vs radiation reactance to calculate the damping quickly is put forward. The method using matrix eigen values and comparison between radiation and scattering resistances is proposed to verify the feasibility of the new idea.
2017,
29: 103203.
doi: 10.11884/HPLPB201729.170094
Abstract:
The effect of the high-altitude nuclear explosion pulse on cable above ground is studied. Considering the effect of ground, Time Domain Integral Equation(TDIE) combined with reflection coefficient method are proposed to solve the transient current of the cable above ground. The time domain reflections of electromagnetic waves from half-space are obtained by eigenmodes method. The exact solution of time reflection coefficient could be obtained without calculating the infinite term of the Bessel function. Finally, the simulation results of the current induced by the cable above the ground are given. The results show that the reflection field always tries to cancel the incident field when the reflection pulse reaches the horizontal cable, the induced current on the cable is less than that only considering the incident pulse. The coupling current of the cable varies significantly with the height above ground, the overhead cable has a larger coupling current compared to the ground cable.
The effect of the high-altitude nuclear explosion pulse on cable above ground is studied. Considering the effect of ground, Time Domain Integral Equation(TDIE) combined with reflection coefficient method are proposed to solve the transient current of the cable above ground. The time domain reflections of electromagnetic waves from half-space are obtained by eigenmodes method. The exact solution of time reflection coefficient could be obtained without calculating the infinite term of the Bessel function. Finally, the simulation results of the current induced by the cable above the ground are given. The results show that the reflection field always tries to cancel the incident field when the reflection pulse reaches the horizontal cable, the induced current on the cable is less than that only considering the incident pulse. The coupling current of the cable varies significantly with the height above ground, the overhead cable has a larger coupling current compared to the ground cable.
2017,
29: 103204.
doi: 10.11884/HPLPB201729.170175
Abstract:
High intensity radiation field (HIRF) has been paid more and more attention and HIRF protection has become a necessary condition for aircraft design and equipment installation. This paper demonstrates a massively parallel 3D full-wave electromagnetic field simulation program software JEMS-FDTD and its application in HIRF simulation on a real aircraft. In order to ensure the accuracy of calculation, the non-uniform and conformal FDTD computing technology has been used. In addition, the spherical wave equivalent source is constructed to reflect the near field effect of the antenna. Finally, the simulation results are compared with the experimental results.
High intensity radiation field (HIRF) has been paid more and more attention and HIRF protection has become a necessary condition for aircraft design and equipment installation. This paper demonstrates a massively parallel 3D full-wave electromagnetic field simulation program software JEMS-FDTD and its application in HIRF simulation on a real aircraft. In order to ensure the accuracy of calculation, the non-uniform and conformal FDTD computing technology has been used. In addition, the spherical wave equivalent source is constructed to reflect the near field effect of the antenna. Finally, the simulation results are compared with the experimental results.
2017,
29: 103205.
doi: 10.11884/HPLPB201729.170156
Abstract:
To study the transient response of electrostatic discharge(ESD) protection device to the EMP with fast rise time, human-metal model (HMM) and transmission line pulse (TLP) current waveforms are widely used for ESD protection devices testing. In this paper, two testing systems were developed. One is an HMM tester, basing on IEC61000-4-2. The other can generate TLP waveform by transmission line charging and discharging. A type of ESD protection device was tested. Transient response waveforms, clamping voltage, clamping time, overshoot voltage were obtained, and the influence of transmission line length on the test results was studied and analyzed theoretically. The experiment results show that: The length of TL has a great impact on the performance testing of an ESD protection device, improper selection can lead to a wrong conclusion; When the ESD protection device is under test, TLP testing is preferred; The length of TL should be less than 8 meters when the ESD pulse testing is used.
To study the transient response of electrostatic discharge(ESD) protection device to the EMP with fast rise time, human-metal model (HMM) and transmission line pulse (TLP) current waveforms are widely used for ESD protection devices testing. In this paper, two testing systems were developed. One is an HMM tester, basing on IEC61000-4-2. The other can generate TLP waveform by transmission line charging and discharging. A type of ESD protection device was tested. Transient response waveforms, clamping voltage, clamping time, overshoot voltage were obtained, and the influence of transmission line length on the test results was studied and analyzed theoretically. The experiment results show that: The length of TL has a great impact on the performance testing of an ESD protection device, improper selection can lead to a wrong conclusion; When the ESD protection device is under test, TLP testing is preferred; The length of TL should be less than 8 meters when the ESD pulse testing is used.
2017,
29: 104001.
doi: 10.11884/HPLPB201729.170062
Abstract:
In order to get optimization results of the emission current and the focal spot size of the micro X-ray tube, the geometric structure of the cathode emitter is simulated. Firstly, the relationship among the direct thermal cathode emitter, the emission current density and the geometry structure is derived theoretically. Secondly, the discretization of the finite integral algorithm in solving the numerical solution of the electric field distribution is discussed. Finally, the geometric model is built by using the CST particle Studio software, and the geometric structure of the cathode emitter is optimized. When the distance between the filament and the control pole is 0.4 mm, and at the position the aperture diameter of the control pole is 0.6 mm, smaller focal spot and higher charge density distribution are attainable. The emitter fabricated has a maximum emission current of 85 A.
In order to get optimization results of the emission current and the focal spot size of the micro X-ray tube, the geometric structure of the cathode emitter is simulated. Firstly, the relationship among the direct thermal cathode emitter, the emission current density and the geometry structure is derived theoretically. Secondly, the discretization of the finite integral algorithm in solving the numerical solution of the electric field distribution is discussed. Finally, the geometric model is built by using the CST particle Studio software, and the geometric structure of the cathode emitter is optimized. When the distance between the filament and the control pole is 0.4 mm, and at the position the aperture diameter of the control pole is 0.6 mm, smaller focal spot and higher charge density distribution are attainable. The emitter fabricated has a maximum emission current of 85 A.
2017,
29: 104002.
doi: 10.11884/HPLPB201729.170119
Abstract:
The weighted nonlinear least squares iterative fitting method is an important method to solve the -particle spectra. The appropriate spectrum peak shape function model and the initial values of the parameters are the key to the nonlinear least squares iterative fitting. Based on the shaping mechanism of -ray spectrum, a kind of -ray spectrum peak shape function was established, and the method of determining the initial values of the peak shape function based on the moment estimation was proposed. The mathematical statistics, the mean, variance and third-order central moments of the peak shape function and the discrete spectral peak data were calculated respectively. The initial values of the parameters were obtained by the established equations. The radon daughters alpha spectra detected by a continuous aerosol detector and 238Pu surface-source -energy spectra detected by a low-background -ray spectrometer were used to test the peak shape function model and the initial values acquisition method. The results show that the peak shape function model can be well applied from high-degree overlapping to low-degree overlapping. The initial values of the parameters of the peak shape function obtained by the moment estimation method can make the peak shape function well fit the alpha spectrum data. The method has strong practicability in the computer automatic analysis of alpha spectrum.
The weighted nonlinear least squares iterative fitting method is an important method to solve the -particle spectra. The appropriate spectrum peak shape function model and the initial values of the parameters are the key to the nonlinear least squares iterative fitting. Based on the shaping mechanism of -ray spectrum, a kind of -ray spectrum peak shape function was established, and the method of determining the initial values of the peak shape function based on the moment estimation was proposed. The mathematical statistics, the mean, variance and third-order central moments of the peak shape function and the discrete spectral peak data were calculated respectively. The initial values of the parameters were obtained by the established equations. The radon daughters alpha spectra detected by a continuous aerosol detector and 238Pu surface-source -energy spectra detected by a low-background -ray spectrometer were used to test the peak shape function model and the initial values acquisition method. The results show that the peak shape function model can be well applied from high-degree overlapping to low-degree overlapping. The initial values of the parameters of the peak shape function obtained by the moment estimation method can make the peak shape function well fit the alpha spectrum data. The method has strong practicability in the computer automatic analysis of alpha spectrum.
2017,
29: 104102.
doi: 10.11884/HPLPB201729.170115
Abstract:
Laser surface melting technology can effectively reduce nano optical waveguide sidewall roughness for scattering loss reduction. To clarify the temperature field evolution law of KrF excimer laser surface melting on waveguide sidewall, a two dimensional finite element numerical model is established, which has taken into account the effects of temperature dependences of material parameters and latent heat. Several investigations have been made about the relationships between the carry behavior forward of melting pool boundary and different processing parameters. Simulation results indicate that melting pool begins developing in the corner between the upper surface of waveguide and the laser-facing sidewall surface. At a given laser incidence angle, the depth of melting pool is correlated positively with the average energy density. Melting pool shape is mainly controlled by laser incident angle: with the decreasing incidence angle, the melting pool appears firstly single-edge U-shaped, then single-edge V-shaped, and finally single-edge V-shaped with an obtuse angle. Analysis shows that melting pool shape induced by a larger laser incidence angle is more favourable to the finishing process of waveguide sidewall. On this basis, a new process method is proposed for determinating laser incident angle to optimize the shapes of melting pool and then selecting the appropriate laser energy density to obtain sufficient melting depth.
Laser surface melting technology can effectively reduce nano optical waveguide sidewall roughness for scattering loss reduction. To clarify the temperature field evolution law of KrF excimer laser surface melting on waveguide sidewall, a two dimensional finite element numerical model is established, which has taken into account the effects of temperature dependences of material parameters and latent heat. Several investigations have been made about the relationships between the carry behavior forward of melting pool boundary and different processing parameters. Simulation results indicate that melting pool begins developing in the corner between the upper surface of waveguide and the laser-facing sidewall surface. At a given laser incidence angle, the depth of melting pool is correlated positively with the average energy density. Melting pool shape is mainly controlled by laser incident angle: with the decreasing incidence angle, the melting pool appears firstly single-edge U-shaped, then single-edge V-shaped, and finally single-edge V-shaped with an obtuse angle. Analysis shows that melting pool shape induced by a larger laser incidence angle is more favourable to the finishing process of waveguide sidewall. On this basis, a new process method is proposed for determinating laser incident angle to optimize the shapes of melting pool and then selecting the appropriate laser energy density to obtain sufficient melting depth.
2017,
29: 104104.
doi: 10.11884/HPLPB201729.170141
Abstract:
In order to ensure the normal operation of mobile devices in the Wi-Fi band without interference from adjacent frequency bands, a bulk acoustic wave (BAW) filter for the Wi-Fi 802.11b band (2401-2482 MHz) is designed. An initial structure ladder filter based on a one-dimensional Mason equivalent circuit model using thin-film bulk acoustic resonators (FBARs) is designed. The resonance area value of series FBARs and the ratio of resonance area value of parallel FBARs to series FBARs were made into two types of optimization parameters reasonably. Using the required insertion loss and out of band rejection of filter as the optimization objectives, the optimized values were obtained by the algorithm based on gradient and genetics in ADS software. In order to make the simulation results more accurate, the combined acoustic-electromagnetic method is used to simulate and compare with the simulation results of the Mason equivalent circuit model in the filter design process. The results show that the performance of the filter is decreased, with 1.6 dB insertion loss increase and 1.1 dB ripple increase, while out of band rejection is basically the same. The designed Wi-Fi band BAW filter has low insertion loss (less than 3 dB) and high out of band rejection (more than 40 dB) performance.
In order to ensure the normal operation of mobile devices in the Wi-Fi band without interference from adjacent frequency bands, a bulk acoustic wave (BAW) filter for the Wi-Fi 802.11b band (2401-2482 MHz) is designed. An initial structure ladder filter based on a one-dimensional Mason equivalent circuit model using thin-film bulk acoustic resonators (FBARs) is designed. The resonance area value of series FBARs and the ratio of resonance area value of parallel FBARs to series FBARs were made into two types of optimization parameters reasonably. Using the required insertion loss and out of band rejection of filter as the optimization objectives, the optimized values were obtained by the algorithm based on gradient and genetics in ADS software. In order to make the simulation results more accurate, the combined acoustic-electromagnetic method is used to simulate and compare with the simulation results of the Mason equivalent circuit model in the filter design process. The results show that the performance of the filter is decreased, with 1.6 dB insertion loss increase and 1.1 dB ripple increase, while out of band rejection is basically the same. The designed Wi-Fi band BAW filter has low insertion loss (less than 3 dB) and high out of band rejection (more than 40 dB) performance.
2017,
29: 105001.
doi: 10.11884/HPLPB201729.170166
Abstract:
Magnetic switch is the key part of magnetic pulse compression system. The performance parameters of magnetic switch core directly affect the overall performance of the magnetic pulse compression system. According to the physical properties and application features of the ferrite core, a loop oscillation circuit is designed to test the dynamic characteristics of the magnetic cores under fast pulse excitations, and the hysteresis loops of the ferrite cores under hundreds of nanoseconds excitations are obtained. The diagnosis of the winding current and the change rate of magnetic flux on the magnetic core provides necessary value for determining the hysteresis loop, saturated magnetic flux intensity and coercivity of magnetic core. A magnetic pulse compression circuit model with dynamic hysteresis loop is established based on the experimental measurement parameters, and the effect of the dynamic characteristics of the magnetic switch on the voltage transfer is studied.
Magnetic switch is the key part of magnetic pulse compression system. The performance parameters of magnetic switch core directly affect the overall performance of the magnetic pulse compression system. According to the physical properties and application features of the ferrite core, a loop oscillation circuit is designed to test the dynamic characteristics of the magnetic cores under fast pulse excitations, and the hysteresis loops of the ferrite cores under hundreds of nanoseconds excitations are obtained. The diagnosis of the winding current and the change rate of magnetic flux on the magnetic core provides necessary value for determining the hysteresis loop, saturated magnetic flux intensity and coercivity of magnetic core. A magnetic pulse compression circuit model with dynamic hysteresis loop is established based on the experimental measurement parameters, and the effect of the dynamic characteristics of the magnetic switch on the voltage transfer is studied.
2017,
29: 105002.
doi: 10.11884/HPLPB201729.170161
Abstract:
The electromagnetic driven solid liner implosion is one of the high energy density (HEDP) experimental techniques. Some drivers have been constructed in the past years, these drivers are varied in peak current and current rise time. This paper analyzes the effect of current rise time on the solid liner implosion, in order to provide some advice on the choice of the existed drivers which will be appropriate for solid liner implosion experiment. Calculations were performed under uncompressible zero dimension model, the effects of liner size, current amplitude and current rise time on implosion velocity were obtained. The results indicate that drivers with current rise time above 2 microsecond would be appropriate for solid liner implosion experiment. The analysis also lays the theoretical foundation for the future design of high capacity drivers used for solid liner implosion experiment.
The electromagnetic driven solid liner implosion is one of the high energy density (HEDP) experimental techniques. Some drivers have been constructed in the past years, these drivers are varied in peak current and current rise time. This paper analyzes the effect of current rise time on the solid liner implosion, in order to provide some advice on the choice of the existed drivers which will be appropriate for solid liner implosion experiment. Calculations were performed under uncompressible zero dimension model, the effects of liner size, current amplitude and current rise time on implosion velocity were obtained. The results indicate that drivers with current rise time above 2 microsecond would be appropriate for solid liner implosion experiment. The analysis also lays the theoretical foundation for the future design of high capacity drivers used for solid liner implosion experiment.
2017,
29: 105003.
doi: 10.11884/HPLPB201729.170039
Abstract:
This paper presents the principle and methods for measuring brightness of high-density and high-current electron beam. Measurement were performed on a 4 MeV LIA injector with a time-resolved measurement system using three methods: the emittance measurement method, beam collimator without magnetic field method, and beam collimator with magnetic field method. This paper describes the concept of the high current beam brightness and typical theoretic analysis of beam measurement. A time-resolved framing photography has been set up for triple-pulsed beam emittance measuring, which can capture beam divergence image and obtain electron beam root mean square emittance. A series of beam emittance data has been obtained in the 4 MeV LIA injector, the normalized beam emittance is about 114 mmmrad and the double pulse normalized emittance is 456 mmmrad. According to the electron beams Gaussian distribution, a primary analysis is carried out, which gives the numerical relations between beam root mean square emittance, measured emittance and edge emittance.
This paper presents the principle and methods for measuring brightness of high-density and high-current electron beam. Measurement were performed on a 4 MeV LIA injector with a time-resolved measurement system using three methods: the emittance measurement method, beam collimator without magnetic field method, and beam collimator with magnetic field method. This paper describes the concept of the high current beam brightness and typical theoretic analysis of beam measurement. A time-resolved framing photography has been set up for triple-pulsed beam emittance measuring, which can capture beam divergence image and obtain electron beam root mean square emittance. A series of beam emittance data has been obtained in the 4 MeV LIA injector, the normalized beam emittance is about 114 mmmrad and the double pulse normalized emittance is 456 mmmrad. According to the electron beams Gaussian distribution, a primary analysis is carried out, which gives the numerical relations between beam root mean square emittance, measured emittance and edge emittance.
2017,
29: 105004.
doi: 10.11884/HPLPB201729.160551
Abstract:
A fiber system was constructed to trigger photoconductive semiconductor switch(PCSS) at MHz operation frequency. The fibers in fiber system are arranged in alveolate position and each group has different lengths to make stable time delay. This paper focuses on the calculation of fiber system, group division and program design. Calculation program approves: With the increases of ratio of division radius to beam radius, the efficiency of fiber splitter increases until it reaches a certain point. With stable beam diameter the efficiency of fiber splitter decreases with the increasing of number of plies of fiber; With the stable of radical of fiber system, the maximum variance in the energy contained in each pulse of laser decreases versus the increasing of number of plies of fiber. Experiment has proved that the 10 MHz fiber splitter in output 4 laser pulse bursts and the maximum variance in the energy contained in each pulse is 6.80% while the efficiency of system is 38.07%.
A fiber system was constructed to trigger photoconductive semiconductor switch(PCSS) at MHz operation frequency. The fibers in fiber system are arranged in alveolate position and each group has different lengths to make stable time delay. This paper focuses on the calculation of fiber system, group division and program design. Calculation program approves: With the increases of ratio of division radius to beam radius, the efficiency of fiber splitter increases until it reaches a certain point. With stable beam diameter the efficiency of fiber splitter decreases with the increasing of number of plies of fiber; With the stable of radical of fiber system, the maximum variance in the energy contained in each pulse of laser decreases versus the increasing of number of plies of fiber. Experiment has proved that the 10 MHz fiber splitter in output 4 laser pulse bursts and the maximum variance in the energy contained in each pulse is 6.80% while the efficiency of system is 38.07%.
2017,
29: 105005.
doi: 10.11884/HPLPB201729.170069
Abstract:
In order to obtain high current high frequency square wave pulse used in industry, we analyzed and improved the semiconductor full controlled Marx, in charge of the implementation and truncated function. Using the new semi-floating-gate SFGT transistor structure as main switch, the design can produce kV high voltage, high current and high frequency square wave pulse. At the same time, the circuit structure is optimized, and the stability of DC power supply to the pulse power supply is also optimized. The main work of this paper is as follows: first, we develop a square wave pulse generator with current 100 A, frequency 4 kHz, pulse width 4 s, 6 kV negative high voltage and rising edge falling in 80 ns. Second, study the SFGT core isolation of the corresponding driving circuit with half bridge SFGT grid parallel independent capacitance isolation drive and IR2110 drive circuit, the equivalent circuit of half bridge gate and the MOS tube was analyzed, with strong anti-interference ability and wide pulse width modulation characteristics.
In order to obtain high current high frequency square wave pulse used in industry, we analyzed and improved the semiconductor full controlled Marx, in charge of the implementation and truncated function. Using the new semi-floating-gate SFGT transistor structure as main switch, the design can produce kV high voltage, high current and high frequency square wave pulse. At the same time, the circuit structure is optimized, and the stability of DC power supply to the pulse power supply is also optimized. The main work of this paper is as follows: first, we develop a square wave pulse generator with current 100 A, frequency 4 kHz, pulse width 4 s, 6 kV negative high voltage and rising edge falling in 80 ns. Second, study the SFGT core isolation of the corresponding driving circuit with half bridge SFGT grid parallel independent capacitance isolation drive and IR2110 drive circuit, the equivalent circuit of half bridge gate and the MOS tube was analyzed, with strong anti-interference ability and wide pulse width modulation characteristics.
2017,
29: 106001.
doi: 10.11884/HPLPB201729.170224
Abstract:
One of the important performance indexes of the neutron monitor is the detection efficiency for different energy neutrons, which would directly affect the credibility and use of measured value. High sensitivity area neutron monitor produced by the Institute of High Energy Physics, Chinese Academy of Sciences was used to simulate its detection efficiency curve by Monte Carlo software, which shows detection efficiency firstly rises then decreases with the increase in energy, and the highest efficiency is at around 1 MeV. To verify the reliability and to compare trend changes of the detection efficiency curve, ray incident direction used in the simulation was changed. Based on this, 2.5 MeV single-energy neutron and 14 MeV single-energy neutron respectively generated by D-D neutron tube and D-T neutron tube were used to calibrate and verify the detection efficiency curve, and finally the detection efficiency curve of the neutron monitor was made.
One of the important performance indexes of the neutron monitor is the detection efficiency for different energy neutrons, which would directly affect the credibility and use of measured value. High sensitivity area neutron monitor produced by the Institute of High Energy Physics, Chinese Academy of Sciences was used to simulate its detection efficiency curve by Monte Carlo software, which shows detection efficiency firstly rises then decreases with the increase in energy, and the highest efficiency is at around 1 MeV. To verify the reliability and to compare trend changes of the detection efficiency curve, ray incident direction used in the simulation was changed. Based on this, 2.5 MeV single-energy neutron and 14 MeV single-energy neutron respectively generated by D-D neutron tube and D-T neutron tube were used to calibrate and verify the detection efficiency curve, and finally the detection efficiency curve of the neutron monitor was made.
2017,
29: 106002.
doi: 10.11884/HPLPB201729.170108
Abstract:
In the process of -source spectrum measurement, influence factors of the detector efficiency of the PIPS- spectrometer are the geometric factor, air layer absorption, dead layer absorption, the intrinsic detection efficiency, and so on. In order to calculate the activity of sources more accurately, to analyse the type and concentration of the parent nuclide, it is of great significance to explore the influence of these factors on the detection efficiency. Monte Carlo software was used to simulate the energy spectrum measurement of different source-detector distance and vacuum degree, SRIM was used to simulate the range and distribution of alpha particles in the air and dead layer with 5 MeV alpha particles, and PIPS- spectrometer was used to measure the actual spectra of three standard radioactive sources 241Am, 238Pu，239Pu. According to the results of experiments and simulation, the influence of various factors on the detection efficiency was analyzed, the intrinsic detection efficiency of spectrum of different -sources was calculated. The results show that: in the PIPS- spectrometer measurement process, the main factors affecting the detection efficiency of the spectrometer is geometric factor and intrinsic detection efficiency; the absorption of alpha particles by air and dead layer is negligible; the intrinsic detection efficiencies of the spectrometer for 241Am, 238Pu, 239Pu standard sources are 64.84%, 49.95%, 51.55% respectively.
In the process of -source spectrum measurement, influence factors of the detector efficiency of the PIPS- spectrometer are the geometric factor, air layer absorption, dead layer absorption, the intrinsic detection efficiency, and so on. In order to calculate the activity of sources more accurately, to analyse the type and concentration of the parent nuclide, it is of great significance to explore the influence of these factors on the detection efficiency. Monte Carlo software was used to simulate the energy spectrum measurement of different source-detector distance and vacuum degree, SRIM was used to simulate the range and distribution of alpha particles in the air and dead layer with 5 MeV alpha particles, and PIPS- spectrometer was used to measure the actual spectra of three standard radioactive sources 241Am, 238Pu，239Pu. According to the results of experiments and simulation, the influence of various factors on the detection efficiency was analyzed, the intrinsic detection efficiency of spectrum of different -sources was calculated. The results show that: in the PIPS- spectrometer measurement process, the main factors affecting the detection efficiency of the spectrometer is geometric factor and intrinsic detection efficiency; the absorption of alpha particles by air and dead layer is negligible; the intrinsic detection efficiencies of the spectrometer for 241Am, 238Pu, 239Pu standard sources are 64.84%, 49.95%, 51.55% respectively.
2017,
29: 106003.
doi: 10.11884/HPLPB201729.170197
Abstract:
For critical nuclear cases including radioactive material leakage, illegal freight of special nuclear material, this paper proposes a research on an energy spectrometer with neutron/gamma discrimination via a single probe to achieve detection and monitor of special nuclear materials and radioactive materials. Several difficult research points have been triggered and expanded to tackle the challenging studies on FPGA and EJ299-33A including the data acquisition circuit design of nuclear pulses, nuclear signal process, pulse discrimination and offline analysis of energy spectra. The host machine software is able to process the real-time energy spectra for offering reference information in making a correct decision of nuclear emergency response. The application of novel detector and the fractural theory based processing method enables rays discrimination via FPGA, which effectively solves discrimination difficulties of particles via traditional detectors and analog circuits and also justifies the viability of the fractural-frequency spectrum based method application to nuclear signal processing. The n/ detector is developed with versatile capacities in particle discrimination, energy spectrum measurement, and radioactive element identification. In a mixed radioactive field of neutron and gamma, the proposed detector not only can perform ray discrimination and energy spectra measurement, but also handles the challenges in energy spectrum analysis of different particle and nuclei identification.
For critical nuclear cases including radioactive material leakage, illegal freight of special nuclear material, this paper proposes a research on an energy spectrometer with neutron/gamma discrimination via a single probe to achieve detection and monitor of special nuclear materials and radioactive materials. Several difficult research points have been triggered and expanded to tackle the challenging studies on FPGA and EJ299-33A including the data acquisition circuit design of nuclear pulses, nuclear signal process, pulse discrimination and offline analysis of energy spectra. The host machine software is able to process the real-time energy spectra for offering reference information in making a correct decision of nuclear emergency response. The application of novel detector and the fractural theory based processing method enables rays discrimination via FPGA, which effectively solves discrimination difficulties of particles via traditional detectors and analog circuits and also justifies the viability of the fractural-frequency spectrum based method application to nuclear signal processing. The n/ detector is developed with versatile capacities in particle discrimination, energy spectrum measurement, and radioactive element identification. In a mixed radioactive field of neutron and gamma, the proposed detector not only can perform ray discrimination and energy spectra measurement, but also handles the challenges in energy spectrum analysis of different particle and nuclei identification.
2017,
29: 104103.
doi: 10.11884/HPLPB201729.170128
Abstract:
The research and testing technique of friction sensor is an important support for hypersonic aircraft. Compared with the conventional skin friction sensor, the micro shear stress sensor has the advantages of small size, high sensitivity, good stability, and good dynamic response. The micro shear stress sensor can be integrated with other flow field sensors whose process is compatible with that of the micro shear stress sensor to achieve multi-physical measurement of the flow field; and the micro-friction balance sensor array enables large area and accurate measurement for the near-wall flow. A micro shear stress sensor structure is proposed, whose sensing element does not directly contact with the flow field. The MEMS fabrication process of the sensing element is described in detail. The thermal silicon oxide is used as the mask to solve the selection ratio problem of silicon deep reactive ion etching(DRIE). The optimized process parameters of DRIE are etching power 1600 W/LF power 100 W, SF6 flux 360 cm3/min, C4F8 flux 300 cm3/min, O2 flux 300 cm3/min. With Cr/Au mask, etching depth of glass shallow groove can be controlled at 30 ℃ and low concentration HF solution; spray etching and wafer rotating improve the corrosion surface quality of glass shallow groove. The micro shear stress sensor samples were fabricated by the above MEMS process, and results show that the error of the length and width of the elastic cantilever is within 2 m, the depth error of the shallow groove is less than 0.03 m, and the static capacitance error is within 0.2 pF, which satisfy the design requirements.
The research and testing technique of friction sensor is an important support for hypersonic aircraft. Compared with the conventional skin friction sensor, the micro shear stress sensor has the advantages of small size, high sensitivity, good stability, and good dynamic response. The micro shear stress sensor can be integrated with other flow field sensors whose process is compatible with that of the micro shear stress sensor to achieve multi-physical measurement of the flow field; and the micro-friction balance sensor array enables large area and accurate measurement for the near-wall flow. A micro shear stress sensor structure is proposed, whose sensing element does not directly contact with the flow field. The MEMS fabrication process of the sensing element is described in detail. The thermal silicon oxide is used as the mask to solve the selection ratio problem of silicon deep reactive ion etching(DRIE). The optimized process parameters of DRIE are etching power 1600 W/LF power 100 W, SF6 flux 360 cm3/min, C4F8 flux 300 cm3/min, O2 flux 300 cm3/min. With Cr/Au mask, etching depth of glass shallow groove can be controlled at 30 ℃ and low concentration HF solution; spray etching and wafer rotating improve the corrosion surface quality of glass shallow groove. The micro shear stress sensor samples were fabricated by the above MEMS process, and results show that the error of the length and width of the elastic cantilever is within 2 m, the depth error of the shallow groove is less than 0.03 m, and the static capacitance error is within 0.2 pF, which satisfy the design requirements.
2017,
29: 104101.
doi: 10.11884/HPLPB201729.170113
Abstract:
The resonant sensors based on aluminum nitride double-ended tuning fork (AlN DETF) have the characteristics of small size, good stability and reliability, and fast response. In order to improve the sensitivity and resolution, it is necessary to analyze the influence of the structure parameters of vibrating beam on the sensitivity and signal power of AlN resonator. The multi-physics model of AlN DETF resonator was established to verify effect of single parameter on the sensitivity by pre-stressed eigenfrequency analysis. The relationships between signal power and length, width of vibrating beam were obtained by post-processing data of simulation results when the thickness remained constant. The results show that relative sensitivity and signal power are growing in opposite directions with the width or the length of the beam. Therefore, there is a design tradeoff between signal power and relative sensitivity of AlN resonator according to process and structure strength. The optimized AlN DETF resonator was simulated, and its sensitivity, signal power and Q value are 56 Hz/N, 6.810-4 nW and 958, respectively.
The resonant sensors based on aluminum nitride double-ended tuning fork (AlN DETF) have the characteristics of small size, good stability and reliability, and fast response. In order to improve the sensitivity and resolution, it is necessary to analyze the influence of the structure parameters of vibrating beam on the sensitivity and signal power of AlN resonator. The multi-physics model of AlN DETF resonator was established to verify effect of single parameter on the sensitivity by pre-stressed eigenfrequency analysis. The relationships between signal power and length, width of vibrating beam were obtained by post-processing data of simulation results when the thickness remained constant. The results show that relative sensitivity and signal power are growing in opposite directions with the width or the length of the beam. Therefore, there is a design tradeoff between signal power and relative sensitivity of AlN resonator according to process and structure strength. The optimized AlN DETF resonator was simulated, and its sensitivity, signal power and Q value are 56 Hz/N, 6.810-4 nW and 958, respectively.
