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RSS2016 Vol. 28, No. 11
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2016,
28: 110201.
doi: 10.11884/HPLPB201628.160164
Abstract:
A multiterawatt facility Baikal is now under construction at Troitsk Institute for Innovation Fusion Research, Russia. Once finished, it will become the worlds largest pulsed-power driven facility for thermonuclear fusion and high energy density physics research. The technical scheme and output parameter of the facility Baikal have been revised several times since the project was proposed. The historical background of the conceptual design of the facility Baikal along with its development, evolution and present research progress are comprehensively reviewed. The structure of major parts of the facility as well as their parameters and capabilities are analyzed and evaluated in detail.
A multiterawatt facility Baikal is now under construction at Troitsk Institute for Innovation Fusion Research, Russia. Once finished, it will become the worlds largest pulsed-power driven facility for thermonuclear fusion and high energy density physics research. The technical scheme and output parameter of the facility Baikal have been revised several times since the project was proposed. The historical background of the conceptual design of the facility Baikal along with its development, evolution and present research progress are comprehensively reviewed. The structure of major parts of the facility as well as their parameters and capabilities are analyzed and evaluated in detail.
2016,
28: 111002.
doi: 10.11884/HPLPB201628.160097
Abstract:
According to characteristics of Gaussian beam scattering from the target, correlation function of the statistical characteristics of Gaussian beam scattering from the target is studied in this paper. Under the laser beam incidence，numerical methods are used to calculate the correlation function of a sphere changing with scattering angles in different radii, material, incident condition, and so on. The mutual correlation functions of metal film material have larger values than that of painted non-metal materials. There exist a stronger backward-scattering of metal film material sphere and a stronger forward-scattering of non-metallic paint sphere. Roughness of material film surface and dimension of sphere have bigger influences on the correlation functions of scattering fields, while mutual correlation functions have nearly the same distribution in different incident beam polarization. Our further works will be based on studying other high order statistical moments of laser beam scattering from target with rough surface.
According to characteristics of Gaussian beam scattering from the target, correlation function of the statistical characteristics of Gaussian beam scattering from the target is studied in this paper. Under the laser beam incidence，numerical methods are used to calculate the correlation function of a sphere changing with scattering angles in different radii, material, incident condition, and so on. The mutual correlation functions of metal film material have larger values than that of painted non-metal materials. There exist a stronger backward-scattering of metal film material sphere and a stronger forward-scattering of non-metallic paint sphere. Roughness of material film surface and dimension of sphere have bigger influences on the correlation functions of scattering fields, while mutual correlation functions have nearly the same distribution in different incident beam polarization. Our further works will be based on studying other high order statistical moments of laser beam scattering from target with rough surface.
2016,
28: 111003.
doi: 10.11884/HPLPB201628.160073
Abstract:
We investigated responsivity of photodiodes fabricated with silicon that was microstructured by femtosecond-laser pulses in a sulfur-containing atmosphere. In different temperature annealing, the aluminum electrodes were prepared using the electron evaporation method according to different spike height of microstructured silicon. The femtosecond laser microstructured photodiodes were made, and the opto-electronic responsivities of photodiodes was measured. Test results show that the responsivity of photodiodes depends on the height of spikes and annealing temperature, the responsivity can be as high as 0.55 A/W. For wavelengths of 1100 nm below the bandgap we obtained responsivities about 0.4 A/W, which is higher than that for standard silicon photodiodes.
We investigated responsivity of photodiodes fabricated with silicon that was microstructured by femtosecond-laser pulses in a sulfur-containing atmosphere. In different temperature annealing, the aluminum electrodes were prepared using the electron evaporation method according to different spike height of microstructured silicon. The femtosecond laser microstructured photodiodes were made, and the opto-electronic responsivities of photodiodes was measured. Test results show that the responsivity of photodiodes depends on the height of spikes and annealing temperature, the responsivity can be as high as 0.55 A/W. For wavelengths of 1100 nm below the bandgap we obtained responsivities about 0.4 A/W, which is higher than that for standard silicon photodiodes.
2016,
28: 112001.
doi: 10.11884/HPLPB201628.160133
Abstract:
The energy response curve of EJ232 without plating film was calibrated by the soft X-ray in Beijing Synchrotron Radiation Facility. The energy response curve of this type of EJ232 to less than 300 eV X-ray was obviously non-linear. According to the result, a new structure of EJ232 was designed and was achieved via vacuum magnetron sputtering. The calibration result of the designed EJ232 satisfied the request. The energy response of this kind of EJ232 to less than 1 keV X-ray has a good linearity, with a coefficient better than 99%. The simulation response result to Planckian spectrum indicates that the shape of output spectrum is similar to that of input spectrum. As a result, this designed EJ232 would be useful in the Z-pinch experiment.
The energy response curve of EJ232 without plating film was calibrated by the soft X-ray in Beijing Synchrotron Radiation Facility. The energy response curve of this type of EJ232 to less than 300 eV X-ray was obviously non-linear. According to the result, a new structure of EJ232 was designed and was achieved via vacuum magnetron sputtering. The calibration result of the designed EJ232 satisfied the request. The energy response of this kind of EJ232 to less than 1 keV X-ray has a good linearity, with a coefficient better than 99%. The simulation response result to Planckian spectrum indicates that the shape of output spectrum is similar to that of input spectrum. As a result, this designed EJ232 would be useful in the Z-pinch experiment.
Analysis of deviation sources and precision of cylindrical foam assembly in Z-pinch dynamic hohlraum
2016,
28: 112002.
doi: 10.11884/HPLPB201628.160118
Abstract:
Based on the analysis of moving platform and vision identification techniques, error source model was proposed to enhance the assembly precision of low density foam column belonged to dynamic hohlraum. Error sources transmission models of design, machining and assembling processes were established, respectively. Moreover, the impact factor of assembly precision influenced by error sources was captured from the prediction model of coaxial degree and axial angle of low density foam column. Finally, a type of dynamic hohlraum was given for demonstrating the effectiveness of the prediction model. When the adhesive random position error of foam column was relatively small, coaxial deviation between predicted value and measured value was from 0.01 mm to 0.03 mm, and axial angle deviation was from 0.05 to 0.34. It is proved that the methods can provide theoretical foundation for assembly precision prediction and error sources control in the assembly process of low density foam column.
Based on the analysis of moving platform and vision identification techniques, error source model was proposed to enhance the assembly precision of low density foam column belonged to dynamic hohlraum. Error sources transmission models of design, machining and assembling processes were established, respectively. Moreover, the impact factor of assembly precision influenced by error sources was captured from the prediction model of coaxial degree and axial angle of low density foam column. Finally, a type of dynamic hohlraum was given for demonstrating the effectiveness of the prediction model. When the adhesive random position error of foam column was relatively small, coaxial deviation between predicted value and measured value was from 0.01 mm to 0.03 mm, and axial angle deviation was from 0.05 to 0.34. It is proved that the methods can provide theoretical foundation for assembly precision prediction and error sources control in the assembly process of low density foam column.
2016,
28: 112003.
doi: 10.11884/HPLPB201628.160074
Abstract:
Two-stage proton acceleration scheme by laser radiation pressure is investigated. When an ultra-intense laser interacts with a solid foil with backside underdense plasma, the laser ponderomotive force pushes the electrons in the foil forward and an electron-ion double layer is produced. As the laser continuously pushes the double layer into the backside plasma, the double layer acts like an intense moving electric field propagating through the underdense plasma with an almost steady speed. The protons at the backside plasma can be reflected and trapped by this moving field and be accelerated to high energies. The proposed scheme is studied by both two-dimensional particle-in-cell simulation and theoretical analysis. The proton energy spectrum shows a good profile with maximum energy above 20 GeV even after a long time. Proton acceleration with this scheme is more effective than that by the simple radiation pressure acceleration. The simulation results agree well with that of the theoretical analysis.
Two-stage proton acceleration scheme by laser radiation pressure is investigated. When an ultra-intense laser interacts with a solid foil with backside underdense plasma, the laser ponderomotive force pushes the electrons in the foil forward and an electron-ion double layer is produced. As the laser continuously pushes the double layer into the backside plasma, the double layer acts like an intense moving electric field propagating through the underdense plasma with an almost steady speed. The protons at the backside plasma can be reflected and trapped by this moving field and be accelerated to high energies. The proposed scheme is studied by both two-dimensional particle-in-cell simulation and theoretical analysis. The proton energy spectrum shows a good profile with maximum energy above 20 GeV even after a long time. Proton acceleration with this scheme is more effective than that by the simple radiation pressure acceleration. The simulation results agree well with that of the theoretical analysis.
2016,
28: 112004.
doi: 10.11884/HPLPB201628.160087
Abstract:
Three dimensional models of spatially smoothing beam propagating in hohlraum are established in a laser plasma simulation code named LAP3D to investigate laser filamentation. Simulation results of spatially smoothing beam produced by continuous phase plates (CPP) with a given f number (f=11) propagating in a 2000 laser wavelength long homogeneous slab plasma, corresponding to plasma density at tenth of the critical density, electron and ion temperature at 3 and 1 keV, respectively, are presented in this paper. The influence of parameters associated with the beam power and intensities on developing of laser filamentation instability is analyzed. Features of laser filamentation instability are found with simulation results, including beam spay and laser energy spreading to higher wave numbers in the Fourier space. It is found that there is a clear correlation between onset of the beam filamentation and the value of the average laser intensity. Based on simulation results, it is suggested that with high hot spot intensities, bigger size hot spots or other smoothing methods should be applied to suppress laser filamentation.
Three dimensional models of spatially smoothing beam propagating in hohlraum are established in a laser plasma simulation code named LAP3D to investigate laser filamentation. Simulation results of spatially smoothing beam produced by continuous phase plates (CPP) with a given f number (f=11) propagating in a 2000 laser wavelength long homogeneous slab plasma, corresponding to plasma density at tenth of the critical density, electron and ion temperature at 3 and 1 keV, respectively, are presented in this paper. The influence of parameters associated with the beam power and intensities on developing of laser filamentation instability is analyzed. Features of laser filamentation instability are found with simulation results, including beam spay and laser energy spreading to higher wave numbers in the Fourier space. It is found that there is a clear correlation between onset of the beam filamentation and the value of the average laser intensity. Based on simulation results, it is suggested that with high hot spot intensities, bigger size hot spots or other smoothing methods should be applied to suppress laser filamentation.
2016,
28: 112005.
doi: 10.11884/HPLPB201628.160100
Abstract:
This article presents a technique to restore X-ray bremsstrahlung spectrum. Through restoring the bremsstrahlung spectrum of the imploded capsule, we can obtain the information of the pellet. Assuming the energy density in each energy band is equal, we divided the energy range into 5 parts, and with a specially-made multi-pinhole camera and an algebraic transformation, we recorded images of the hot-spots. The images were produced on the imaging plate. In this way, five different linear equations were obtained and through this equation group, we could restore the spectrum. This approach was applied to hot-spot bremsstrahlung spectrum reconstruction of Shenguang Ⅲ prototype Facility. Based on the spectrum reconstruction, we deduced the temperature of the hot-spot, which is in line with the result obtained from the characteristic spectral line of the tracer element.
This article presents a technique to restore X-ray bremsstrahlung spectrum. Through restoring the bremsstrahlung spectrum of the imploded capsule, we can obtain the information of the pellet. Assuming the energy density in each energy band is equal, we divided the energy range into 5 parts, and with a specially-made multi-pinhole camera and an algebraic transformation, we recorded images of the hot-spots. The images were produced on the imaging plate. In this way, five different linear equations were obtained and through this equation group, we could restore the spectrum. This approach was applied to hot-spot bremsstrahlung spectrum reconstruction of Shenguang Ⅲ prototype Facility. Based on the spectrum reconstruction, we deduced the temperature of the hot-spot, which is in line with the result obtained from the characteristic spectral line of the tracer element.
2016,
28: 112006.
doi: 10.11884/HPLPB201628.160360
Abstract:
In this paper, a novel hybrid plasmonic nanolaser with a metal ridge and a MgF2 dielectric layer at ultraviolet band is demonstrated. The electric field distribution, the modal properties, the quality factor and the lasing threshold are investigated by using the finite-element method on the basis of the COMSOL Multiphysics platform. At the 390 nm working wavelength, the structure of the nanolaser can reach good deep-subwavelength mode confinement by optimizing its geometric parameters, while maintaining high quality factor and low propagation loss and low gain threshold. Compared to the previously reported structure with a metal plate, this structure has stronger capacity of field confinement and microcavity bound with the same geometric parameters. The structure shows potential to promote miniaturization and integration of lasers.
In this paper, a novel hybrid plasmonic nanolaser with a metal ridge and a MgF2 dielectric layer at ultraviolet band is demonstrated. The electric field distribution, the modal properties, the quality factor and the lasing threshold are investigated by using the finite-element method on the basis of the COMSOL Multiphysics platform. At the 390 nm working wavelength, the structure of the nanolaser can reach good deep-subwavelength mode confinement by optimizing its geometric parameters, while maintaining high quality factor and low propagation loss and low gain threshold. Compared to the previously reported structure with a metal plate, this structure has stronger capacity of field confinement and microcavity bound with the same geometric parameters. The structure shows potential to promote miniaturization and integration of lasers.
2016,
28: 112007.
doi: 10.11884/HPLPB201628.160170
Abstract:
With the help of 1-D radiation hydrodynamic code MULTI, we simulated the ablation process of a pulsed CO2 laser irradiation on a tin planar target. We studied the influence of pulse duration, peak power intensity and initial target density on electron temperature and density distribution at different time. Also, the optimum pulse duration for 13.5 nm extreme-ultraviolet (EUV) emission was obtained by statistical analysis. It is found that long pulse duration , for example, 100-200 ns, is better for EUV emission. In this paper, the mechanism is discussed combining electron temperature and density distribution. Laser energy is effectively absorbed in the critical density area, while absorption of laser energy and EUV in the underdense corona can be negligible. Using a long CO2 laser pulse to prolong the EUV emission time can improve conversion efficiency effectively. Meanwhile, the initial target density has little influence on tin plasma parameters.
With the help of 1-D radiation hydrodynamic code MULTI, we simulated the ablation process of a pulsed CO2 laser irradiation on a tin planar target. We studied the influence of pulse duration, peak power intensity and initial target density on electron temperature and density distribution at different time. Also, the optimum pulse duration for 13.5 nm extreme-ultraviolet (EUV) emission was obtained by statistical analysis. It is found that long pulse duration , for example, 100-200 ns, is better for EUV emission. In this paper, the mechanism is discussed combining electron temperature and density distribution. Laser energy is effectively absorbed in the critical density area, while absorption of laser energy and EUV in the underdense corona can be negligible. Using a long CO2 laser pulse to prolong the EUV emission time can improve conversion efficiency effectively. Meanwhile, the initial target density has little influence on tin plasma parameters.
2016,
28: 113001.
doi: 10.11884/HPLPB201628.160098
Abstract:
To measure the energy within the transmission line of the high power microwave source, liquid absorption energy calorimeter with full absorption is developed. The mixture of ethanol and deionized water is used as absorbing liquid, the liquid level of the detector rises when the microwave energy is absorbed, and it is detected by the control system as the voltage variation, thus the microwave energy is accurately measured. The structure of the energy calorimeter is simple and has high accuracy. Measurements show that the reflection coefficient of the energy calorimeter is less than -20 dB, the range of the energy calorimeter is 10-600 J, the standard deviation of the five measurements is less than 5%. It can meet the requirements of HPM sources within the transmission line or space radiation energy measurements.
To measure the energy within the transmission line of the high power microwave source, liquid absorption energy calorimeter with full absorption is developed. The mixture of ethanol and deionized water is used as absorbing liquid, the liquid level of the detector rises when the microwave energy is absorbed, and it is detected by the control system as the voltage variation, thus the microwave energy is accurately measured. The structure of the energy calorimeter is simple and has high accuracy. Measurements show that the reflection coefficient of the energy calorimeter is less than -20 dB, the range of the energy calorimeter is 10-600 J, the standard deviation of the five measurements is less than 5%. It can meet the requirements of HPM sources within the transmission line or space radiation energy measurements.
2016,
28: 113002.
doi: 10.11884/HPLPB201628.160065
Abstract:
A new type of magnetically insulated transmission line oscillator (MILO)-planar MILO is put forward to solve the low frequency and low efficiency problems of MILO. The new device can be expanded along the x direction of the plane and it is also a microwave tube with low impedance and high power. The planar MILO uses a low external magnetic field to take the place of conventional magnetic insulation magnetic field so that we can enhance the efficiency of the microwave output. Through numerical calculation, the impacts of several structure parameters of the planar MILO coaxial SWS with plane-wrinkle surface on its high frequency characteristic are analyzed. Then the external magnetic is further optimized with 2.5 dimensional particle-in-cell simulation. High power microwaves generated from the planar MILO have the average output power of 1.22 GW, central frequency of 6.56 GHz and efficiency of 30%, when the beam voltage is 800 kV.
A new type of magnetically insulated transmission line oscillator (MILO)-planar MILO is put forward to solve the low frequency and low efficiency problems of MILO. The new device can be expanded along the x direction of the plane and it is also a microwave tube with low impedance and high power. The planar MILO uses a low external magnetic field to take the place of conventional magnetic insulation magnetic field so that we can enhance the efficiency of the microwave output. Through numerical calculation, the impacts of several structure parameters of the planar MILO coaxial SWS with plane-wrinkle surface on its high frequency characteristic are analyzed. Then the external magnetic is further optimized with 2.5 dimensional particle-in-cell simulation. High power microwaves generated from the planar MILO have the average output power of 1.22 GW, central frequency of 6.56 GHz and efficiency of 30%, when the beam voltage is 800 kV.
2016,
28: 113003.
doi: 10.11884/HPLPB201628.160069
Abstract:
A high power microwave antenna was developed based on longitudinal shunt slots of rectangular waveguides. The antenna consists of 4 route rectangular waveguides and a Teflon window. To obtain high power capacity, the high power microwaves inside antenna transmit in vacuum system. To restrain the high power microwave breakdown in surface of window on the vacuum side, the window surface at vacuum side is notched periodically with triangle grooves. There are support planks between waveguides and window. The support planks not only support the window but restrain the mutual coupling of the slots of neighboring waveguides. The antenna was optimized by HFSS software. The antenna works at 1.575 GHz. With a gain of 22.7 dBi and aperture efficiency of 98.3%. The active reflection coefficients of 4 route rectangular waveguides are less than -25 dB, the reflection bandwidth is 5% and the fluctuation of gain of antenna is no more than 0.4 dB over the reflection bandwidth. The aperture efficiency of antenna is no less than 98% and the deviation of direction of main lobe is no more than 1.2 over the reflection bandwidth. The high power capacity of antenna is 1.92 GW.
A high power microwave antenna was developed based on longitudinal shunt slots of rectangular waveguides. The antenna consists of 4 route rectangular waveguides and a Teflon window. To obtain high power capacity, the high power microwaves inside antenna transmit in vacuum system. To restrain the high power microwave breakdown in surface of window on the vacuum side, the window surface at vacuum side is notched periodically with triangle grooves. There are support planks between waveguides and window. The support planks not only support the window but restrain the mutual coupling of the slots of neighboring waveguides. The antenna was optimized by HFSS software. The antenna works at 1.575 GHz. With a gain of 22.7 dBi and aperture efficiency of 98.3%. The active reflection coefficients of 4 route rectangular waveguides are less than -25 dB, the reflection bandwidth is 5% and the fluctuation of gain of antenna is no more than 0.4 dB over the reflection bandwidth. The aperture efficiency of antenna is no less than 98% and the deviation of direction of main lobe is no more than 1.2 over the reflection bandwidth. The high power capacity of antenna is 1.92 GW.
2016,
28: 113005.
doi: 10.11884/HPLPB201628.160139
Abstract:
Nonlinear response of cable irradiated by X-ray is simulated using numerical method. The physical processes of the X-ray irradiating to cable are analyzed. Norton-equivalent driver model is built up for coaxial cable or shielded multi-cable based on 2-dimension finite-element method, focusing on dielectrics radiation-induced conductivity effect. The nonlinear responses of Norton-equivalent driver are calculated and their regularities are concluded in detail. The simulation result showed that the current amplitude would reach a saturation value as the X-ray fluence increased when induced conductivity existed. For some types of cable, there would be 3 different current peaks appearing successively at different point on the waveform while the X-ray fluence increased.
Nonlinear response of cable irradiated by X-ray is simulated using numerical method. The physical processes of the X-ray irradiating to cable are analyzed. Norton-equivalent driver model is built up for coaxial cable or shielded multi-cable based on 2-dimension finite-element method, focusing on dielectrics radiation-induced conductivity effect. The nonlinear responses of Norton-equivalent driver are calculated and their regularities are concluded in detail. The simulation result showed that the current amplitude would reach a saturation value as the X-ray fluence increased when induced conductivity existed. For some types of cable, there would be 3 different current peaks appearing successively at different point on the waveform while the X-ray fluence increased.
2016,
28: 113006.
doi: 10.11884/HPLPB201628.160165
Abstract:
This paper presents a self-consistent nolinear theory and gives the integrodifferential equations of the instantaneous current and the beam kinetic energy. For two groups of typical parameters, the coefficients of current modulation versus the propagation distance were calculated by the numerical method and 2D-PIC code. The kinetic energy of the beam and the mode strength Cn versus the propagation distance were also calculated and analyzed. The results of the simulation are consistent with the results of the nonlinear theory.
This paper presents a self-consistent nolinear theory and gives the integrodifferential equations of the instantaneous current and the beam kinetic energy. For two groups of typical parameters, the coefficients of current modulation versus the propagation distance were calculated by the numerical method and 2D-PIC code. The kinetic energy of the beam and the mode strength Cn versus the propagation distance were also calculated and analyzed. The results of the simulation are consistent with the results of the nonlinear theory.
2016,
28: 113007.
doi: 10.11884/HPLPB201628.151066
Abstract:
As measurement function of evaluation of uncertainty in peak detector calibration for HPM test is an implicit function and transfer of the probability distribution of measurements is complicated, this paper evaluates the uncertainty in peak detector calibration based on Monte-Carlo method. A time-domain response calculation model of detector calibration system was founded by band-limited scatter parameters. The model contains the direct measurements, such as S-parameters of microwave devices, demodulation voltage, peak power and so on. The model can also calculate the pulse reflection, pulse superposition and time delay. This paper imports probability distribution of direct measurements into the model based on Monte-Carlo principle, and then gives the uncertainty and probability distribution of detector calibration curve by repeated calculation.
As measurement function of evaluation of uncertainty in peak detector calibration for HPM test is an implicit function and transfer of the probability distribution of measurements is complicated, this paper evaluates the uncertainty in peak detector calibration based on Monte-Carlo method. A time-domain response calculation model of detector calibration system was founded by band-limited scatter parameters. The model contains the direct measurements, such as S-parameters of microwave devices, demodulation voltage, peak power and so on. The model can also calculate the pulse reflection, pulse superposition and time delay. This paper imports probability distribution of direct measurements into the model based on Monte-Carlo principle, and then gives the uncertainty and probability distribution of detector calibration curve by repeated calculation.
2016,
28: 113101.
doi: 10.11884/HPLPB201628.160142
Abstract:
In multiple-input multiple-output (MIMO) radar imaging systems, the configuration of antenna array as one of the key techniques has great effects on image quality. Based on the imaging model of MIMO radar, the sparse array design method taking advantage of the equivalent virtual array concept was discussed, and the near field effects on imaging results were analyzed. Short range two-dimensional imaging experiments for small targets were carried out by the constructed imaging system. The experiment results confirm the validity of this array design method for MIMO radar operating at 120~150 GHz, and the imaging ability of MIMO array in the near field is verified.
In multiple-input multiple-output (MIMO) radar imaging systems, the configuration of antenna array as one of the key techniques has great effects on image quality. Based on the imaging model of MIMO radar, the sparse array design method taking advantage of the equivalent virtual array concept was discussed, and the near field effects on imaging results were analyzed. Short range two-dimensional imaging experiments for small targets were carried out by the constructed imaging system. The experiment results confirm the validity of this array design method for MIMO radar operating at 120~150 GHz, and the imaging ability of MIMO array in the near field is verified.
2016,
28: 113201.
doi: 10.11884/HPLPB201628.160154
Abstract:
The equipment circuit method is introduced to obtain the transient response of the lossy non-uniform transmission line network with nonlinear terminations. After modifying the equipment circuit model of the lossy transmission line, a lossy non-uniform transmission line equivalent circuit model is introduced in this paper. Meanwhile, the transient responses for a lossy microstrip line with linear and nonlinear terminations excited by the designed electromagnetic pulse source are simulated. The results of the simulations and the experiments are consistent with each other, which verifies that the models are correct. A typical lossy non-uniform transmission line, a typical unequal length lossy non-uniform transmission line, and a typical lossy non-uniform transmission line network are simulated. The simulation results are in good agreement with those of the finite difference time domain(FDTD) method and the conventional lumped method.
The equipment circuit method is introduced to obtain the transient response of the lossy non-uniform transmission line network with nonlinear terminations. After modifying the equipment circuit model of the lossy transmission line, a lossy non-uniform transmission line equivalent circuit model is introduced in this paper. Meanwhile, the transient responses for a lossy microstrip line with linear and nonlinear terminations excited by the designed electromagnetic pulse source are simulated. The results of the simulations and the experiments are consistent with each other, which verifies that the models are correct. A typical lossy non-uniform transmission line, a typical unequal length lossy non-uniform transmission line, and a typical lossy non-uniform transmission line network are simulated. The simulation results are in good agreement with those of the finite difference time domain(FDTD) method and the conventional lumped method.
2016,
28: 113202.
doi: 10.11884/HPLPB201628.160129
Abstract:
The multiphysics algorithm in this paper is based on semiconductors physical model to realize the simulation of electromagnetic effects on semiconductor devices and circuits. The model is constituted of a set of partial differential equations, including electromagnetic equations, semiconductor physics and thermal equations. For accurately simulating temperature distributions in semiconductor devices, the thermal boundary conditions are researched in this paper. A commercial Schottky diode with model number HSMS-282c is excited by a 2 V step pulse generator. Its temperature variation under different thermal boundary conditions are compared. The diodes surface temperature under different forward voltage is also measured and compared with the simulation result. The results show that the temperature of semiconductor devices can be accurately simulated by the multiphysics algorithm with convection boundary condition.
The multiphysics algorithm in this paper is based on semiconductors physical model to realize the simulation of electromagnetic effects on semiconductor devices and circuits. The model is constituted of a set of partial differential equations, including electromagnetic equations, semiconductor physics and thermal equations. For accurately simulating temperature distributions in semiconductor devices, the thermal boundary conditions are researched in this paper. A commercial Schottky diode with model number HSMS-282c is excited by a 2 V step pulse generator. Its temperature variation under different thermal boundary conditions are compared. The diodes surface temperature under different forward voltage is also measured and compared with the simulation result. The results show that the temperature of semiconductor devices can be accurately simulated by the multiphysics algorithm with convection boundary condition.
2016,
28: 113203.
doi: 10.11884/HPLPB201628.160116
Abstract:
Evaluating the shielding effectiveness of cabins is important for verifying the susceptibility of systems against high altitude electromagnetic pulses. To quantitatively estimate the uncertainty introduced by experiment designs and data analysis, the method of evaluation is studied, which focuses on the selection of frequency or time domain measurement, the determination of test frequencies, the design of pass/fail curve, and the criteria to deal with unqualified points. A group of pass/fail curves for cabins with low shielding effectiveness are proposed. Based on the approximation of two order resonance systems, the uncertainty introduced by test frequencies, pass/fail curve, and the criteria are estimated, which provide sustainment for the experiment design, data analysis and the uncertainty estimation for evaluating the shield effectiveness of cabins.
Evaluating the shielding effectiveness of cabins is important for verifying the susceptibility of systems against high altitude electromagnetic pulses. To quantitatively estimate the uncertainty introduced by experiment designs and data analysis, the method of evaluation is studied, which focuses on the selection of frequency or time domain measurement, the determination of test frequencies, the design of pass/fail curve, and the criteria to deal with unqualified points. A group of pass/fail curves for cabins with low shielding effectiveness are proposed. Based on the approximation of two order resonance systems, the uncertainty introduced by test frequencies, pass/fail curve, and the criteria are estimated, which provide sustainment for the experiment design, data analysis and the uncertainty estimation for evaluating the shield effectiveness of cabins.
2016,
28: 114001.
doi: 10.11884/HPLPB201628.160045
Abstract:
The backprojection filtered (BPF) algorithm, which can provide a good reconstruction with data truncation, plays an important role in reconstruction of region of interest for circular cone-beam CT. However, when the cone-angle increases, there will be serious artifacts in the top and the bottom of the reconstruction image. Aiming for solving this problem, the paper rederives the cone-beam BPF algorithm based on fan-beam circle BPF algorithm, then purposes a new weighting function through analyzing the cause of the artifacts. The weighting function based on cone-angle and the axial distance can restrain the artifacts by modifying the solution of the differential backprojection image in the reconstruction process. The experimental results show that the proposed algorithm can inhibit the artifacts and improve the image quality compared with the BPF algorithm at a large cone-angle.
The backprojection filtered (BPF) algorithm, which can provide a good reconstruction with data truncation, plays an important role in reconstruction of region of interest for circular cone-beam CT. However, when the cone-angle increases, there will be serious artifacts in the top and the bottom of the reconstruction image. Aiming for solving this problem, the paper rederives the cone-beam BPF algorithm based on fan-beam circle BPF algorithm, then purposes a new weighting function through analyzing the cause of the artifacts. The weighting function based on cone-angle and the axial distance can restrain the artifacts by modifying the solution of the differential backprojection image in the reconstruction process. The experimental results show that the proposed algorithm can inhibit the artifacts and improve the image quality compared with the BPF algorithm at a large cone-angle.
2016,
28: 114101.
doi: 10.11884/HPLPB201628.160140
Abstract:
As the structure of discriminator in the current micro-electromechanical system combination lock is complex and the reliability of electronic combination locks is poor, we designed an N bit in-situ sputtering single-try discrimination circuit to solve these problems. The N bit discrimination circuit is composed of 2N (N-stage, two switches per stage) sputtering type OFF-ON switches and formed by alternative logic of each stage and N-stage series. The sputtering type OFF-ON switches (the one-way switch of the OFF state to ON state is irreversible) and the fuse having a fusing characteristic are connected by the corresponding relationship between setting password and the circuit to form in-situ sputtering and single-try solid combination lock which can be used in high security key systems and facilities. In order to ensure a space between the metal exploding foil and the interdigital electrode, three different micromachining process methods of the discrimination circuit are presented.
As the structure of discriminator in the current micro-electromechanical system combination lock is complex and the reliability of electronic combination locks is poor, we designed an N bit in-situ sputtering single-try discrimination circuit to solve these problems. The N bit discrimination circuit is composed of 2N (N-stage, two switches per stage) sputtering type OFF-ON switches and formed by alternative logic of each stage and N-stage series. The sputtering type OFF-ON switches (the one-way switch of the OFF state to ON state is irreversible) and the fuse having a fusing characteristic are connected by the corresponding relationship between setting password and the circuit to form in-situ sputtering and single-try solid combination lock which can be used in high security key systems and facilities. In order to ensure a space between the metal exploding foil and the interdigital electrode, three different micromachining process methods of the discrimination circuit are presented.
2016,
28: 115001.
doi: 10.11884/HPLPB201628.151056
Abstract:
Due to high withstand voltage, high flow capacity, stable trigger and small size, the pulse power thyristor has been widely used in pulse power system. However, the thyristor reverse recovery characteristics may cause overvoltage damage in the turn-off process of the thyristor, therefore establishing an effective thyristor model to simulate thyristor overvoltage is needed to decrease thyristor overvoltage damage probability. In this paper, pulse thyristors as the research object, with a maximum flow capacity of 150 kA and a withstand voltage of 5.2 kV, were tested in a pulse forming circuit as the prepositive switch. Then the experimental data were analyzed to find out the relationship between on-state current and related parameters in turn-off process such as reverse recovery charge Qrr, reverse recovery current peak value, and cut-off time. The experimental results show that the reverse recovery time decreases with the increase of the on-state current peak value IF; Qrr increases along with the augment of IF, and when the current drop rate di/dt changes among 50~1000 A/s, di/dt and IF has a good linear relationship, so does reverse current peak value IRM and IF. Therefore, under the condition of large pulse current, di/dt and IF can be used as the same parameter when analyzing and deducing relationship between on-state current parameters and reverse recovery parameters. Applying relations fitted from experimental data to the thyristor modeling, a thyristor model with reverse recovery process was established based on Matlab.
Due to high withstand voltage, high flow capacity, stable trigger and small size, the pulse power thyristor has been widely used in pulse power system. However, the thyristor reverse recovery characteristics may cause overvoltage damage in the turn-off process of the thyristor, therefore establishing an effective thyristor model to simulate thyristor overvoltage is needed to decrease thyristor overvoltage damage probability. In this paper, pulse thyristors as the research object, with a maximum flow capacity of 150 kA and a withstand voltage of 5.2 kV, were tested in a pulse forming circuit as the prepositive switch. Then the experimental data were analyzed to find out the relationship between on-state current and related parameters in turn-off process such as reverse recovery charge Qrr, reverse recovery current peak value, and cut-off time. The experimental results show that the reverse recovery time decreases with the increase of the on-state current peak value IF; Qrr increases along with the augment of IF, and when the current drop rate di/dt changes among 50~1000 A/s, di/dt and IF has a good linear relationship, so does reverse current peak value IRM and IF. Therefore, under the condition of large pulse current, di/dt and IF can be used as the same parameter when analyzing and deducing relationship between on-state current parameters and reverse recovery parameters. Applying relations fitted from experimental data to the thyristor modeling, a thyristor model with reverse recovery process was established based on Matlab.
2016,
28: 115002.
doi: 10.11884/HPLPB201628.160090
Abstract:
To test character of ZnO ceramics resistor undergoing high-voltage, a high-voltage pulse generator whose output pulse is approximately square and voltage amplitude varies between 10-80 kV was designed adopting pulse transformer and pulse forming net (PFN). The article introduces the principle, simulation, circuits of the high-voltage pulse generator, and elaborates output states of the power supply with a standard ZnO load. Test results show that the fall on the top of the waveform is less than 3 percent, the pulse top fluctuation is less than 1.5%, and pulse rising edge and falling edge all meet the requirements. The results show that the high voltage pulse source can be used for performance testing of ZnO ceramics.
To test character of ZnO ceramics resistor undergoing high-voltage, a high-voltage pulse generator whose output pulse is approximately square and voltage amplitude varies between 10-80 kV was designed adopting pulse transformer and pulse forming net (PFN). The article introduces the principle, simulation, circuits of the high-voltage pulse generator, and elaborates output states of the power supply with a standard ZnO load. Test results show that the fall on the top of the waveform is less than 3 percent, the pulse top fluctuation is less than 1.5%, and pulse rising edge and falling edge all meet the requirements. The results show that the high voltage pulse source can be used for performance testing of ZnO ceramics.
2016,
28: 115003.
doi: 10.11884/HPLPB201628.160077
Abstract:
A compact module based on arc-type pulse forming network(PFN) for long-pulse power generator is designed. Four Blumlein PFNs with 24 impedance are symmetrically connected with the LTDs primary coil and driven by two high voltage gas switches. The Blumlein PFNs use arc configuration. The design ensures small horizontal size of the module and compact connection of PFNs and gas switches. On this basis, a two-module long-pulse power generator is developed. At the repetition frequency of 5 Hz, the output pulse of the long-pulse module connected with 12 load is about 260 kV in amplitude, 170 ns in duration with power of 5.2 GW.
A compact module based on arc-type pulse forming network(PFN) for long-pulse power generator is designed. Four Blumlein PFNs with 24 impedance are symmetrically connected with the LTDs primary coil and driven by two high voltage gas switches. The Blumlein PFNs use arc configuration. The design ensures small horizontal size of the module and compact connection of PFNs and gas switches. On this basis, a two-module long-pulse power generator is developed. At the repetition frequency of 5 Hz, the output pulse of the long-pulse module connected with 12 load is about 260 kV in amplitude, 170 ns in duration with power of 5.2 GW.
2016,
28: 115101.
doi: 10.11884/HPLPB201628.160009
Abstract:
The THz source based on free-electron laser (FEL) has many remarkable performance, such as tunability, high power, high efficiency and flexible picosecond-pulse time structure of coherent radiation. A low-cost, compact FEL facility can also be built on THz region to provide monochromatic, tunable, high power and high quality radiation. Due to the space limitation, the quadrupole magnets on the FEL should reduce their size as much as possible while meeting the performance requirement. The size of the magnetic yokes aperture and length are 64 mm100 mm for two quadrupoles, and 45 mm100 mm for the other three. The quadrupole magnets magnetic field gradient can reach 0.6-1.9 Tm-1. The Poisson codes and Opera-3D codes have been used to calculate the magnetic field. This paper presents the design, analysis and measurement procedure of the magnets.
The THz source based on free-electron laser (FEL) has many remarkable performance, such as tunability, high power, high efficiency and flexible picosecond-pulse time structure of coherent radiation. A low-cost, compact FEL facility can also be built on THz region to provide monochromatic, tunable, high power and high quality radiation. Due to the space limitation, the quadrupole magnets on the FEL should reduce their size as much as possible while meeting the performance requirement. The size of the magnetic yokes aperture and length are 64 mm100 mm for two quadrupoles, and 45 mm100 mm for the other three. The quadrupole magnets magnetic field gradient can reach 0.6-1.9 Tm-1. The Poisson codes and Opera-3D codes have been used to calculate the magnetic field. This paper presents the design, analysis and measurement procedure of the magnets.
2016,
28: 115102.
doi: 10.11884/HPLPB201527.160119
Abstract:
A Faraday cup used for measuring the beam currents downstream from strong electric fields was designed. The strong electric field was screened by a grid. The electrons were prohibited by the positive voltage on the collector. The shape of the grid was equilateral hexagon distributed because of its lowest saturation electric field at the same grid widths and the same grid transmission rates. The beam current of a vacuum arc ion source was measured by the designed beam current measuring device and the peak value of the beam current was about 550 mA. The secondary electron yield of the Cu collector bombarded by the hybrid ion beams was calculated to be 2.0.
A Faraday cup used for measuring the beam currents downstream from strong electric fields was designed. The strong electric field was screened by a grid. The electrons were prohibited by the positive voltage on the collector. The shape of the grid was equilateral hexagon distributed because of its lowest saturation electric field at the same grid widths and the same grid transmission rates. The beam current of a vacuum arc ion source was measured by the designed beam current measuring device and the peak value of the beam current was about 550 mA. The secondary electron yield of the Cu collector bombarded by the hybrid ion beams was calculated to be 2.0.
2016,
28: 115103.
doi: 10.11884/HPLPB201628.160057
Abstract:
In the HLS-Ⅱstorage ring, a swept-frequency excitation(SFE) based tune measurement system has been developed and running well. This paper presents the construction and commissioning of the SFE-based tune measurement system. The system hardware includes spectrum analyzer with tracking, excitation module, strip-line kicker, signal processing module and beam position monitor(BPM) as signal pickup. The control software of the tune measurement system is developed using EPICS software. The control software consists of three parts: input/output controller, operation personal interface and channel access. The on-line test of the system is performed to investigate the system statistical resolutions in the two transverse directions. Test results reveal that the statistical resolutions are better than 0.0003/0.000 2 in the swept range from 2.1 MHz to 4.1 MHz.
In the HLS-Ⅱstorage ring, a swept-frequency excitation(SFE) based tune measurement system has been developed and running well. This paper presents the construction and commissioning of the SFE-based tune measurement system. The system hardware includes spectrum analyzer with tracking, excitation module, strip-line kicker, signal processing module and beam position monitor(BPM) as signal pickup. The control software of the tune measurement system is developed using EPICS software. The control software consists of three parts: input/output controller, operation personal interface and channel access. The on-line test of the system is performed to investigate the system statistical resolutions in the two transverse directions. Test results reveal that the statistical resolutions are better than 0.0003/0.000 2 in the swept range from 2.1 MHz to 4.1 MHz.
2016,
28: 119001.
doi: 10.11884/HPLPB201628.160081
Abstract:
The relationship between the size and gray distribution of the halo in the output image of LLL(low light level) TV system and the parameters of the system was studied and a feature quantitative model of the halo was established. Firstly, the mechanism of the halo in the output image of the system was analyzed; Then, according to imaging theory, the feature quantitative method of the halo was realized by analyzing the number and the initial angular distribution of photoelectrons generated by photocathode, the movement of the photoelectrons between the photocathode and the MCP, and the collision law of the photoelectrons with non-opening wall of the MCP. Finally, the digital simulation model of the halo was built on the basis of the theories mentioned above. The experimental results show that: the results of the proposed halo effect model agree well that of experiment in gray distribution and size; the halo effect will be more obvious with the stronger of the light energy, which will generate greater impact on the imaging quality.
The relationship between the size and gray distribution of the halo in the output image of LLL(low light level) TV system and the parameters of the system was studied and a feature quantitative model of the halo was established. Firstly, the mechanism of the halo in the output image of the system was analyzed; Then, according to imaging theory, the feature quantitative method of the halo was realized by analyzing the number and the initial angular distribution of photoelectrons generated by photocathode, the movement of the photoelectrons between the photocathode and the MCP, and the collision law of the photoelectrons with non-opening wall of the MCP. Finally, the digital simulation model of the halo was built on the basis of the theories mentioned above. The experimental results show that: the results of the proposed halo effect model agree well that of experiment in gray distribution and size; the halo effect will be more obvious with the stronger of the light energy, which will generate greater impact on the imaging quality.
2016,
28: 111001.
doi: 10.11884/HPLPB201628.151166
Abstract:
Based on the Design-Expert V8, the experiments of autogenous laser welding for 3 mm-thick 5A90 aluminum-lithium alloys were implemented. The effects of shielding gas on porosity were investigated. The plots of pore count as a function of side-blowing angle and gas flow rate fitted well as its mathematical model, and the shielding gas parameters were optimized. The results show that the shielding gas can suppress the porosity well, and the gas flow rate is a significant factor, while the side-blowing angle and interaction are not significant. With the increase of gas flow rate, the pore count increased at first then decreased. A minimum value is reached in the range of 5~7 L/min while the optimal blowing angle is in the range of 20~30. The optimal response model for pore count is cubic, and the model has been inspected by validation tests in which the error range is smaller than 10%. The gas flow rate, blowing angle in the ranges of 3~9 L/min, 15~52 respectively are identified as the optimal parameters for grade Ⅰ weld seam.
Based on the Design-Expert V8, the experiments of autogenous laser welding for 3 mm-thick 5A90 aluminum-lithium alloys were implemented. The effects of shielding gas on porosity were investigated. The plots of pore count as a function of side-blowing angle and gas flow rate fitted well as its mathematical model, and the shielding gas parameters were optimized. The results show that the shielding gas can suppress the porosity well, and the gas flow rate is a significant factor, while the side-blowing angle and interaction are not significant. With the increase of gas flow rate, the pore count increased at first then decreased. A minimum value is reached in the range of 5~7 L/min while the optimal blowing angle is in the range of 20~30. The optimal response model for pore count is cubic, and the model has been inspected by validation tests in which the error range is smaller than 10%. The gas flow rate, blowing angle in the ranges of 3~9 L/min, 15~52 respectively are identified as the optimal parameters for grade Ⅰ weld seam.
