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RSS2018 Vol. 30, No. 5
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2018,
30: 050000.
2018,
30: 050101.
doi: 10.11884/HPLPB201830.180046
Abstract:
On Shenguang Ⅲ laser facility, 32 laser beams were symmetrically injected a gas-filled hohlraum to create plasma situation which is close to the ignition condition. An X-ray framing camera on the polar station and an X-ray streak camera near the pole were utilized to obtain the temporal and spacial evolution X-ray images of the plasma from the hohlraum wall and near the laser entrance hole (LEH), which were used to analyse the LEH closure feature of the hohlraum with various LEH size. The experimental results clearly demonstrated the evolution of laser spot motion, plasma expanding near the LEH and closure of the LEH, which supplied the foundation to optimize the LEH dimension.
On Shenguang Ⅲ laser facility, 32 laser beams were symmetrically injected a gas-filled hohlraum to create plasma situation which is close to the ignition condition. An X-ray framing camera on the polar station and an X-ray streak camera near the pole were utilized to obtain the temporal and spacial evolution X-ray images of the plasma from the hohlraum wall and near the laser entrance hole (LEH), which were used to analyse the LEH closure feature of the hohlraum with various LEH size. The experimental results clearly demonstrated the evolution of laser spot motion, plasma expanding near the LEH and closure of the LEH, which supplied the foundation to optimize the LEH dimension.
2018,
30: 051001.
doi: 10.11884/HPLPB201830.170413
Abstract:
The plasma flow field of solid target in atmosphere under impulse laser irradiation was computed. The flow is governed by the 2-D Reynolds averaged Navier-Stokes (NS) equations. The k-ε turbulence model was used for turbulence simulations. To split the viscosity flux and the convective flux of the NS equations, the second order central scheme and the ROE scheme were adopted respectively. With the implicit Gauss-Seidel scheme, the code was advanced in time. The 2-D hydrokinetics process of laser plasma was presented in this paper by numerical simulation. The influence of target dimension and laser spot size on laser impulse was discussed. The results indicated that laser impulse increases generally with target dimension.
The plasma flow field of solid target in atmosphere under impulse laser irradiation was computed. The flow is governed by the 2-D Reynolds averaged Navier-Stokes (NS) equations. The k-ε turbulence model was used for turbulence simulations. To split the viscosity flux and the convective flux of the NS equations, the second order central scheme and the ROE scheme were adopted respectively. With the implicit Gauss-Seidel scheme, the code was advanced in time. The 2-D hydrokinetics process of laser plasma was presented in this paper by numerical simulation. The influence of target dimension and laser spot size on laser impulse was discussed. The results indicated that laser impulse increases generally with target dimension.
2018,
30: 051002.
doi: 10.11884/HPLPB201830.170521
Abstract:
Chromatic confocal 3D profiler has high precision, large measuring range and strong adaptability. The key component is the objective lens with axial dispersion. The nonlinear dispersion of axial dispersion and wavelength of the dispersion objective lens reduces the overall performance of theprofiler. In this paper, by analyzing the principle of confocal method to detect surface topography and the conditions for producing linear axial dispersion, the design indexes and requirements of confocal optical system are given, and a super-dispersive objective lens has been designed.The objective lens has four magnification structures in series dispersing the focus of wavelength between 400 and 700 nm to 30 mm longitudinal range. Through linear regression fitting of the defocusing amount and linearity of the wavelength, it is obtained that the coefficient of determination is 1, greatly improving the linearity of dispersion.
Chromatic confocal 3D profiler has high precision, large measuring range and strong adaptability. The key component is the objective lens with axial dispersion. The nonlinear dispersion of axial dispersion and wavelength of the dispersion objective lens reduces the overall performance of theprofiler. In this paper, by analyzing the principle of confocal method to detect surface topography and the conditions for producing linear axial dispersion, the design indexes and requirements of confocal optical system are given, and a super-dispersive objective lens has been designed.The objective lens has four magnification structures in series dispersing the focus of wavelength between 400 and 700 nm to 30 mm longitudinal range. Through linear regression fitting of the defocusing amount and linearity of the wavelength, it is obtained that the coefficient of determination is 1, greatly improving the linearity of dispersion.
2018,
30: 051003.
doi: 10.11884/HPLPB201830.170313
Abstract:
Based on the previous research, the study of the molecular sieve absorption technology for ground-state HF molecules in non-chain discharge-pumped high frequency HF laser was carried out, a new molecular sieve device was designed and a large number of absorption experiments were finished. The experiment results show that 3A molecular sieve is an effective sorbent to the ground-state HF molecules and using 3A molecular sieve absorption device could make the average HF laser energy reduction rate less than 5% when the laser was operating under 50 Hz/20 s, and 3A molecular sieve can greatly improve the stability of the laser energy and prolong the lifetime of HF laser media. The laser energy reduction rate was studied when the laser was operating under different frequencies with 3A molecular sieve absorption device. In addition, the method of activating treatment of 3A molecular sieve was obtained by experiments.
Based on the previous research, the study of the molecular sieve absorption technology for ground-state HF molecules in non-chain discharge-pumped high frequency HF laser was carried out, a new molecular sieve device was designed and a large number of absorption experiments were finished. The experiment results show that 3A molecular sieve is an effective sorbent to the ground-state HF molecules and using 3A molecular sieve absorption device could make the average HF laser energy reduction rate less than 5% when the laser was operating under 50 Hz/20 s, and 3A molecular sieve can greatly improve the stability of the laser energy and prolong the lifetime of HF laser media. The laser energy reduction rate was studied when the laser was operating under different frequencies with 3A molecular sieve absorption device. In addition, the method of activating treatment of 3A molecular sieve was obtained by experiments.
2018,
30: 052001.
doi: 10.11884/HPLPB201830.170383
Abstract:
Sol-gel SiO2 anti-reflective coatings were prepared with three different sol-gels, and their optic performance under atmosphere condition was studied in detail.Three AR coatings maintained reflective indexes of 1.15, 1.19, 1.25 respectively. The porous silica coatings can increase transmittance observably, but are very sensitive to contaminants and humidity in surroundings due to their strong adsorptive capacity resulting from the hydroxyl on the coatings surface and their porous structure with large specific surface area. The pores of silica coating can be filled with contaminants and humidity adsorbed on the coatings, which will increase the refractive index of the coatings and also absorb or scatter the light and therefore reduce the transmittance and increase the reflectance simultaneously. The fused silica coated with AR coatings were placed in ISO Class 5 cleanroom (ISO 14644-1) for 180 days. The results show that the optic performance change of all coatings is significant after 80 days. The AR coating with a refractive index of 1.19 is more stable comparatively.
Sol-gel SiO2 anti-reflective coatings were prepared with three different sol-gels, and their optic performance under atmosphere condition was studied in detail.Three AR coatings maintained reflective indexes of 1.15, 1.19, 1.25 respectively. The porous silica coatings can increase transmittance observably, but are very sensitive to contaminants and humidity in surroundings due to their strong adsorptive capacity resulting from the hydroxyl on the coatings surface and their porous structure with large specific surface area. The pores of silica coating can be filled with contaminants and humidity adsorbed on the coatings, which will increase the refractive index of the coatings and also absorb or scatter the light and therefore reduce the transmittance and increase the reflectance simultaneously. The fused silica coated with AR coatings were placed in ISO Class 5 cleanroom (ISO 14644-1) for 180 days. The results show that the optic performance change of all coatings is significant after 80 days. The AR coating with a refractive index of 1.19 is more stable comparatively.
2018,
30: 052002.
doi: 10.11884/HPLPB201830.170478
Abstract:
Different embeded-atom method potentials of gold were used in molecular dynamics simulation for shocked solid gold. Comparison between the simulation results and the experiment data of Hugoniot state for gold has been carried out. The potentials whose corresponding simulating shocked Hugoniot data are consistent with theoretical prediction were used in subsequent foamed gold simulations. The initial configuration of foamed gold has been constructed by means of randomly accumulating sphere shells in the simulation box. Three kinds of configuration have been obtained via changing the thickness, outer-radius of the sphere shell and potentials. Hugoniot states of porous polycrystal gold with 3-dimensional nanostructure under shock compression have been simulated by means of molecular dynamics(MD) method. Comparison between simulated results with porous equation of state(EOS) model and existing EOS database for Au has been done. The discrepancy suggests that experiments for the state of porous gold are necessary to verify the theory and the simulation method for porous gold.
Different embeded-atom method potentials of gold were used in molecular dynamics simulation for shocked solid gold. Comparison between the simulation results and the experiment data of Hugoniot state for gold has been carried out. The potentials whose corresponding simulating shocked Hugoniot data are consistent with theoretical prediction were used in subsequent foamed gold simulations. The initial configuration of foamed gold has been constructed by means of randomly accumulating sphere shells in the simulation box. Three kinds of configuration have been obtained via changing the thickness, outer-radius of the sphere shell and potentials. Hugoniot states of porous polycrystal gold with 3-dimensional nanostructure under shock compression have been simulated by means of molecular dynamics(MD) method. Comparison between simulated results with porous equation of state(EOS) model and existing EOS database for Au has been done. The discrepancy suggests that experiments for the state of porous gold are necessary to verify the theory and the simulation method for porous gold.
2018,
30: 053001.
doi: 10.11884/HPLPB201830.170407
Abstract:
This paper describes an experiment system of Ka-band extended interaction klystron (EIK) transmitter, whose core component is a domestic extended interaction klystron with 35.01 GHz of center frequency, 10 kW of output pulsed power and 0.5% of maximum duty cycle. The experiment system is an advanced research prototype of key component localization of Ka/W band dual frequency millimeter wave cloud-meter transmitter. The performance of the prototype EIK is tested completely, and analysis of potential application problems for EIK are also included in the experiment system. On the other hand, the electrocircuit of transmitter is optimized to meet optimum work requirement of EIK. Experimental results show that enormous progress has been made on domestic Ka-band extended interaction klystron technology and in some areas EIK transmitter has reached the practical stage.
This paper describes an experiment system of Ka-band extended interaction klystron (EIK) transmitter, whose core component is a domestic extended interaction klystron with 35.01 GHz of center frequency, 10 kW of output pulsed power and 0.5% of maximum duty cycle. The experiment system is an advanced research prototype of key component localization of Ka/W band dual frequency millimeter wave cloud-meter transmitter. The performance of the prototype EIK is tested completely, and analysis of potential application problems for EIK are also included in the experiment system. On the other hand, the electrocircuit of transmitter is optimized to meet optimum work requirement of EIK. Experimental results show that enormous progress has been made on domestic Ka-band extended interaction klystron technology and in some areas EIK transmitter has reached the practical stage.
2018,
30: 053002.
doi: 10.11884/HPLPB201830.170442
Abstract:
The wavelength of the waveguide of array antenna can be varied by mechanically adjusting the broadside size of the waveguide.Thereby adjusting the broadside size of the waveguide can achieve the same effect of beam scanning by varying feeding microwave frequency. In this paper, the beam scanning characteristics of narrow edge radiation waveguide traveling wave array antenna is analyzed. The maximum beam scanning range with the variation of the broadside size of the waveguide of array antenna under different spacing distance between adjacent radiation slots is analyzed. We designed an X-band waveguide slot array with variable broadside size of waveguide. We designed the beam scanning range point to waveguide feeding end and avoided array normal radiation (the radiation efficiency in normal radiation is low). The continuous beam scanning range is 29°. In the beam scanning range, the gain drop is less than 3 dB.The radiation efficiency is greater than 62%. The slot width of array is 3 mm, the waveguide length is about 1 m, and the number of slots in single waveguide is 40. The capacity of high power microwave of a single waveguide slots antenna can achieve 70 MW.
The wavelength of the waveguide of array antenna can be varied by mechanically adjusting the broadside size of the waveguide.Thereby adjusting the broadside size of the waveguide can achieve the same effect of beam scanning by varying feeding microwave frequency. In this paper, the beam scanning characteristics of narrow edge radiation waveguide traveling wave array antenna is analyzed. The maximum beam scanning range with the variation of the broadside size of the waveguide of array antenna under different spacing distance between adjacent radiation slots is analyzed. We designed an X-band waveguide slot array with variable broadside size of waveguide. We designed the beam scanning range point to waveguide feeding end and avoided array normal radiation (the radiation efficiency in normal radiation is low). The continuous beam scanning range is 29°. In the beam scanning range, the gain drop is less than 3 dB.The radiation efficiency is greater than 62%. The slot width of array is 3 mm, the waveguide length is about 1 m, and the number of slots in single waveguide is 40. The capacity of high power microwave of a single waveguide slots antenna can achieve 70 MW.
2018,
30: 053003.
doi: 10.11884/HPLPB201830.170433
Abstract:
The polarization mismatch caused by variation of signal polarization angle and base gesture often leads to accuracy decrease in high power microwave(HPM) radiation precise measurement. It is commonly difficult to realize polarization match with linearly polarized antenna. Based on analysis of trapezoidal circularly polarized antenna, method of sequentially 90° rotation and phase shift with power divider and phase shifters as feedwork, a novel circularly polarized microstrip array antenna with low axial ratio feature was designed. The experimental behavior of this antenna shows its gain is 9.4 dB, 1 dB angular width is 17.4°, and axial ratio is as low as 0.4 dB. The application of the designed circularly polarized antenna is able to effectively reduce polarization mismatch uncertainty to less than 0.2 dB, which satisfies the requirement of airborne HPM radiation measurement.
The polarization mismatch caused by variation of signal polarization angle and base gesture often leads to accuracy decrease in high power microwave(HPM) radiation precise measurement. It is commonly difficult to realize polarization match with linearly polarized antenna. Based on analysis of trapezoidal circularly polarized antenna, method of sequentially 90° rotation and phase shift with power divider and phase shifters as feedwork, a novel circularly polarized microstrip array antenna with low axial ratio feature was designed. The experimental behavior of this antenna shows its gain is 9.4 dB, 1 dB angular width is 17.4°, and axial ratio is as low as 0.4 dB. The application of the designed circularly polarized antenna is able to effectively reduce polarization mismatch uncertainty to less than 0.2 dB, which satisfies the requirement of airborne HPM radiation measurement.
2018,
30: 053004.
doi: 10.11884/HPLPB201830.170470
Abstract:
Increasing the single pulse energy is always one of the development targets in high power microwave (HPM) domain. Pulse shortening should be emphatically focused on and solved. Combining the classical theory and particle-in-cell simulation, a long-pulse C-band relativistic backward wave oscillator (RBWO) was designed and optimized. Using the space charge effect of the intense relativistic electron beam, the maximum field strength on the electrodynamic structure surface was no more than 700 kV/cm with about 3 GW output. Further, the related experiment was carried out based on the 700L high voltage pulse generator in our laboratory. As demonstrated by the studies, pulse shortening of the RBWO can be effectively suppressed at about 3 GW level through rational design. With a 760 keV, 9.0 kA beam in the experiment, a 2.8 GW, 4.23 GHz microwave was obtained in the far-field measurement. The pulse width was about 101 ns and the device efficiency was 41%. The experimental result agrees well with that obtained in the simulation.
Increasing the single pulse energy is always one of the development targets in high power microwave (HPM) domain. Pulse shortening should be emphatically focused on and solved. Combining the classical theory and particle-in-cell simulation, a long-pulse C-band relativistic backward wave oscillator (RBWO) was designed and optimized. Using the space charge effect of the intense relativistic electron beam, the maximum field strength on the electrodynamic structure surface was no more than 700 kV/cm with about 3 GW output. Further, the related experiment was carried out based on the 700L high voltage pulse generator in our laboratory. As demonstrated by the studies, pulse shortening of the RBWO can be effectively suppressed at about 3 GW level through rational design. With a 760 keV, 9.0 kA beam in the experiment, a 2.8 GW, 4.23 GHz microwave was obtained in the far-field measurement. The pulse width was about 101 ns and the device efficiency was 41%. The experimental result agrees well with that obtained in the simulation.
2018,
30: 053005.
doi: 10.11884/HPLPB201830.170448
Abstract:
A radome with polarization conversion for high power radial spiral array antenna is designed. Three-layer dielectric substrate are used to sandwich double-layer metal meander line to form sealed and embedded structure. The power capacity can be improved by avoiding the contact between the metal and the air while the conversion between the circular polarization and the linear polarization is realized. The influence of each parameter of the embedded meander-line grid unit is analyzed, and the unit parameters are optimized. An embedded meander-line radome with polarization conversion is made and loaded into an X-band high power helical array antenna. The basic performance and power capacity of the antenna are analyzed. The simulation results show that the matching performance of the antenna is good, the axial ratio of the center frequency is changed from 1.16 dB to 40 dB, and the circular polarization is converted to linear polarization. Through preliminary analysis, the power capacity of the embedded radome with polarization conversion is 121 MW, and the high power application of the radome with polarization conversion is realized.
A radome with polarization conversion for high power radial spiral array antenna is designed. Three-layer dielectric substrate are used to sandwich double-layer metal meander line to form sealed and embedded structure. The power capacity can be improved by avoiding the contact between the metal and the air while the conversion between the circular polarization and the linear polarization is realized. The influence of each parameter of the embedded meander-line grid unit is analyzed, and the unit parameters are optimized. An embedded meander-line radome with polarization conversion is made and loaded into an X-band high power helical array antenna. The basic performance and power capacity of the antenna are analyzed. The simulation results show that the matching performance of the antenna is good, the axial ratio of the center frequency is changed from 1.16 dB to 40 dB, and the circular polarization is converted to linear polarization. Through preliminary analysis, the power capacity of the embedded radome with polarization conversion is 121 MW, and the high power application of the radome with polarization conversion is realized.
2018,
30: 053006.
doi: 10.11884/HPLPB201830.170459
Abstract:
Charging power based on HF AC-Link technology can be used as a primary power source for high-power microwave systems. In order to improve the adaptability of the power supply in the power grid with non-ideal input, this paper adopts the three-phase phase-locked loop in the decoupled double synchronous coordinate system to obtain the phase and frequency information of the positive sequence voltage. To extract the input line voltage amplitude of the fundamental wave, this paper uses the FIR filter to provide timely and accurate control parameters for the power supply. The model was established by Matlab/Simulink software, and the simulation was carried out under the condition of three-phase input imbalance, frequency change and voltage distortion. Lastly, a control program was written and tested based on DSP2812. The simulation and experimental results show that the method can accurately extract the amplitude, phase and frequency information of the input line voltage in all kinds of grid input, and provide a guarantee for good operation of the power supply.
Charging power based on HF AC-Link technology can be used as a primary power source for high-power microwave systems. In order to improve the adaptability of the power supply in the power grid with non-ideal input, this paper adopts the three-phase phase-locked loop in the decoupled double synchronous coordinate system to obtain the phase and frequency information of the positive sequence voltage. To extract the input line voltage amplitude of the fundamental wave, this paper uses the FIR filter to provide timely and accurate control parameters for the power supply. The model was established by Matlab/Simulink software, and the simulation was carried out under the condition of three-phase input imbalance, frequency change and voltage distortion. Lastly, a control program was written and tested based on DSP2812. The simulation and experimental results show that the method can accurately extract the amplitude, phase and frequency information of the input line voltage in all kinds of grid input, and provide a guarantee for good operation of the power supply.
2018,
30: 053007.
doi: 10.11884/HPLPB201830.170447
Abstract:
Gas discharge plasmas generated by μs-pulse focused microwaves are investigated. The model is based on a self-consistent solution to Helmholtz equation for microwave field, particle continuity equations, and the energy balance equations, coupled with plasma kinetics. Two recent experiments are studied: a. sub-megawatt (MW) X-band 9.4 GHz microwave breakdown in nitrogen; b. MW-class W-band 110 GHz microwave breakdown in 100-10 000 Pa air. In experiment a, the tracked density of electronic states N2(C3Πu) agreed with the measured intensity from second positive system (SPS) of optical emission spectroscopy (OES). In experiment b, the simulation results reproduced the dependence of nitrogen vibrational and translational temperature on air pressure measured by OES. The underlying mechanisms for the above coincidences are unveiled.
Gas discharge plasmas generated by μs-pulse focused microwaves are investigated. The model is based on a self-consistent solution to Helmholtz equation for microwave field, particle continuity equations, and the energy balance equations, coupled with plasma kinetics. Two recent experiments are studied: a. sub-megawatt (MW) X-band 9.4 GHz microwave breakdown in nitrogen; b. MW-class W-band 110 GHz microwave breakdown in 100-10 000 Pa air. In experiment a, the tracked density of electronic states N2(C3Πu) agreed with the measured intensity from second positive system (SPS) of optical emission spectroscopy (OES). In experiment b, the simulation results reproduced the dependence of nitrogen vibrational and translational temperature on air pressure measured by OES. The underlying mechanisms for the above coincidences are unveiled.
2018,
30: 053008.
doi: 10.11884/HPLPB201830.170445
Abstract:
Beam-wave interaction for a W band traveling wave tube(TWT) based on staggered double rectangular waveguide structure(SDRWS) is calculated by CST PIC, showing that the TWT has over 35 W output power and over 30 dB gain and about 5% electron efficiency from 92 GHz to 97 GHz on the condition of a 10 kV, 70 mA beam. Even if the beam voltage of 10 kV is relatively low, the sizes of SDRWS still remain relatively large, meaning that SDRWS is in favor of evading the difficulties in manufacturing. A process based on wire electrical discharge machining(wire-EDM) is proposed to manufacture SDRWS for W band TWT, and an SDRWS assembly is successfully obtained. Besides, box-shaped window and electron gun are also simulated by computer, and correspondent parts are manufactured and then put together into assemblies. Then "cold test" is performed on an SDRWS assembly put together with two box-shaped windows, showing that voltage standing wave ratio is lower than 2.067 from 92 GHz to 100 GHz.
Beam-wave interaction for a W band traveling wave tube(TWT) based on staggered double rectangular waveguide structure(SDRWS) is calculated by CST PIC, showing that the TWT has over 35 W output power and over 30 dB gain and about 5% electron efficiency from 92 GHz to 97 GHz on the condition of a 10 kV, 70 mA beam. Even if the beam voltage of 10 kV is relatively low, the sizes of SDRWS still remain relatively large, meaning that SDRWS is in favor of evading the difficulties in manufacturing. A process based on wire electrical discharge machining(wire-EDM) is proposed to manufacture SDRWS for W band TWT, and an SDRWS assembly is successfully obtained. Besides, box-shaped window and electron gun are also simulated by computer, and correspondent parts are manufactured and then put together into assemblies. Then "cold test" is performed on an SDRWS assembly put together with two box-shaped windows, showing that voltage standing wave ratio is lower than 2.067 from 92 GHz to 100 GHz.
2018,
30: 053009.
doi: 10.11884/HPLPB201830.170375
Abstract:
In this paper, first the geometrical factor is derived and the integrodifferential equation of the instantaneous current and the beam kinetic energy in two-cavity klystrons is given. Then a nonlinear theory of cavity excitation by modulated electron beam is applied to calculate the amplitude and the phase of the gap voltage of the middle cavity, the relativistic error of the amplitude is 0.07%, the error of the phase is 2.15°. The coupling coefficient of the gap of the coaxial cavity is obtained. With electron beam voltage of 715.2 kV, electron beam current of 8 kA, and the gap voltages of the input cavity and the middle cavity of 14 kV and 315.2 kV respectively, the fundamental harmonic current modulation coefficient versus distance z is calculated by both the two dimensional particle in cell (PIC) simulation and the code of nonlinear theory. The results of the theory and the simulation agree remarkably well. With the beam propagation distance of 60.8 cm, the fundamental harmonic current modulation coefficient and the kinetic versus the normalized time are calculated, the normalization constant and the nth harmonic current modulation coefficient versus distance z are also calculated.
In this paper, first the geometrical factor is derived and the integrodifferential equation of the instantaneous current and the beam kinetic energy in two-cavity klystrons is given. Then a nonlinear theory of cavity excitation by modulated electron beam is applied to calculate the amplitude and the phase of the gap voltage of the middle cavity, the relativistic error of the amplitude is 0.07%, the error of the phase is 2.15°. The coupling coefficient of the gap of the coaxial cavity is obtained. With electron beam voltage of 715.2 kV, electron beam current of 8 kA, and the gap voltages of the input cavity and the middle cavity of 14 kV and 315.2 kV respectively, the fundamental harmonic current modulation coefficient versus distance z is calculated by both the two dimensional particle in cell (PIC) simulation and the code of nonlinear theory. The results of the theory and the simulation agree remarkably well. With the beam propagation distance of 60.8 cm, the fundamental harmonic current modulation coefficient and the kinetic versus the normalized time are calculated, the normalization constant and the nth harmonic current modulation coefficient versus distance z are also calculated.
2018,
30: 053201.
doi: 10.11884/HPLPB201830.170301
Abstract:
In order to study the absorption characteristics of 10 GHz electromagnetic (EM) waves by femtosecond filaments array, the interaction model of electromagnetic wave and femtosecond filaments array is established, and the absorption coefficients with electron temperature, electron density, filament diameter, and EM polarization are calculated by the finite element method (FEM). The results indicate that the plasma filaments array becomes transparent for EM wave when the polarization of the EM waves is perpendicular to the filaments axis. The absorption coefficient increases first and then decreases with the increasing of the filaments electron density or electron temperature, when skin depth of EM wave is equal to the diameter of the filament, the absorption coefficient reaches the maximum. For the S-polarized EM wave, the absorption coefficient increases with incident angle when the diameter of the filament is 50 μm. There is an absorption peak at large angle when the filament diameter is between 100 μm to 200 μm, and the incident angle responding to the peak absorption is decreasing with the diameter of the filaments. For the P-polarized EM wave, the absorption coefficient is decreasing with the incidence angle of the EM wave.
In order to study the absorption characteristics of 10 GHz electromagnetic (EM) waves by femtosecond filaments array, the interaction model of electromagnetic wave and femtosecond filaments array is established, and the absorption coefficients with electron temperature, electron density, filament diameter, and EM polarization are calculated by the finite element method (FEM). The results indicate that the plasma filaments array becomes transparent for EM wave when the polarization of the EM waves is perpendicular to the filaments axis. The absorption coefficient increases first and then decreases with the increasing of the filaments electron density or electron temperature, when skin depth of EM wave is equal to the diameter of the filament, the absorption coefficient reaches the maximum. For the S-polarized EM wave, the absorption coefficient increases with incident angle when the diameter of the filament is 50 μm. There is an absorption peak at large angle when the filament diameter is between 100 μm to 200 μm, and the incident angle responding to the peak absorption is decreasing with the diameter of the filaments. For the P-polarized EM wave, the absorption coefficient is decreasing with the incidence angle of the EM wave.
2018,
30: 053202.
doi: 10.11884/HPLPB201830.170354
Abstract:
The source signal recovery model for underdetermined blind source separation based on compressed sensing(CS) is constructed, and the recovery effect of three algorithms separately based on the complementary matching pursuit(CMP), the L1 based complementary matching pursuit(L1CMP) and modified Newton radial basis function(NRASR) are compared by simulation. Results show that as to the completely sparse source signals in time domain, the recovery effect of the three algorithms are similar, while the calculation complexity of L1CMP is the lowest. As to the completely sparse source signals in transformation domain, the recovery effects of CMP and L1CMP are similar, but that of NRASR is worse. When the source signals are incompletely sparse in time domain, the recovery effect of CMP is worse, and those of L1CMP and NRASR are similar. So based on comprehensive consideration, the L1CMP algorithm is the best in the three algorithms. As to the case of the source signal number and observation signal number are small, the recovery effect would decline in time domain. The sparse representation method combined with the CS reconstruction algorithms can get good source signal recovery effect.
The source signal recovery model for underdetermined blind source separation based on compressed sensing(CS) is constructed, and the recovery effect of three algorithms separately based on the complementary matching pursuit(CMP), the L1 based complementary matching pursuit(L1CMP) and modified Newton radial basis function(NRASR) are compared by simulation. Results show that as to the completely sparse source signals in time domain, the recovery effect of the three algorithms are similar, while the calculation complexity of L1CMP is the lowest. As to the completely sparse source signals in transformation domain, the recovery effects of CMP and L1CMP are similar, but that of NRASR is worse. When the source signals are incompletely sparse in time domain, the recovery effect of CMP is worse, and those of L1CMP and NRASR are similar. So based on comprehensive consideration, the L1CMP algorithm is the best in the three algorithms. As to the case of the source signal number and observation signal number are small, the recovery effect would decline in time domain. The sparse representation method combined with the CS reconstruction algorithms can get good source signal recovery effect.
2018,
30: 053203.
doi: 10.11884/HPLPB201830.170430
Abstract:
Intermittent sampling repeater jamming is a new kind of jamming means to wideband imaging radar. According to the principle of intermittent sampling repeater jamming, under its common application strategy, the jamming can add a string of bogus scatters to high resolution range profile(HRRP) of wideband imaging radar. Combing with process of imaging, it is found that the string of bogus scatters improves the quality of envelope alignment in the process of imaging. In order to solve the problem caused by intermittent sampling repeater jamming under common strategy, a new application strategy for intermittent sampling repeater jamming is put forward, which aims to disturb envelope alignment. In the new application strategy, period of intermittent sampling is changed according to some predefined random sequence. Simulation is executed, and the result shows that the new application strategy can degrade imaging quality obviously.
Intermittent sampling repeater jamming is a new kind of jamming means to wideband imaging radar. According to the principle of intermittent sampling repeater jamming, under its common application strategy, the jamming can add a string of bogus scatters to high resolution range profile(HRRP) of wideband imaging radar. Combing with process of imaging, it is found that the string of bogus scatters improves the quality of envelope alignment in the process of imaging. In order to solve the problem caused by intermittent sampling repeater jamming under common strategy, a new application strategy for intermittent sampling repeater jamming is put forward, which aims to disturb envelope alignment. In the new application strategy, period of intermittent sampling is changed according to some predefined random sequence. Simulation is executed, and the result shows that the new application strategy can degrade imaging quality obviously.
2018,
30: 054001.
doi: 10.11884/HPLPB201830.170283
Abstract:
By performing a Monte Carlo simulation, energy spectra as a function of surface structure for slow highly charged Arq+ ions in grazing incidence on a single-crystal copper surface were studied. Four possible mechanisms were taken into account in energy loss calculation. The energy loss spectrum consisting of two peak structure with an obvious small peak at higher energy loss side was found for Ar atoms grazing along low-index direction. The channeling effect observed in the energy loss of Arq+ ions grazing from surface was discussed. The calculated energy loss spectra agree reasonably well with those of experiment.
By performing a Monte Carlo simulation, energy spectra as a function of surface structure for slow highly charged Arq+ ions in grazing incidence on a single-crystal copper surface were studied. Four possible mechanisms were taken into account in energy loss calculation. The energy loss spectrum consisting of two peak structure with an obvious small peak at higher energy loss side was found for Ar atoms grazing along low-index direction. The channeling effect observed in the energy loss of Arq+ ions grazing from surface was discussed. The calculated energy loss spectra agree reasonably well with those of experiment.
2018,
30: 054002.
doi: 10.11884/HPLPB201830.170307
Abstract:
The principle of magnetic mass spectrometer is briefly introduced. According to types of equipment included in the magnetic mass spectrometer, a two-layer structure of control system based on Ethernet is designed. The basic functions of remote adjustment and monitor of parameters and interlock protection are realized. A set of trigger system is designed for a continuously adjustable delay time of 0~20 μs.Through the test, the system has obtained the spectral graph which satisfies the physical experiment requirements. After dozens of hours of experimental test, the system is stable and operable, which satisfactorily meets the user's experimental needs.
The principle of magnetic mass spectrometer is briefly introduced. According to types of equipment included in the magnetic mass spectrometer, a two-layer structure of control system based on Ethernet is designed. The basic functions of remote adjustment and monitor of parameters and interlock protection are realized. A set of trigger system is designed for a continuously adjustable delay time of 0~20 μs.Through the test, the system has obtained the spectral graph which satisfies the physical experiment requirements. After dozens of hours of experimental test, the system is stable and operable, which satisfactorily meets the user's experimental needs.
2018,
30: 055001.
doi: 10.11884/HPLPB201830.170385
Abstract:
"Yingguang-1" is a multi-bank program-discharged pulsed power device to investigate the formation, confinement and instability of the high temperature and high density field reversed configuration (FRC) plasma injector for the magnetized target fusion (MTF), which was constructed at the Institute of Fluid Physics (IFP) in 2014. This paper discusses the influence of the crowbar switch on the load current in "Yingguang-1" device by function modeling the crowbar switch with the software Pspice and conducting the preliminary test experiment. The function circuit modeling of the crowbar switch employed in the program-discharged power system, is accurately presented for the first time. The simulation and experiment results show that the crowbar switch can improve the load current's duration effectively and both its closed resistance and inductances can affect the load current's amplitude and duration obviously. As the closing resistance decreases, the current's duration becomes broader, however, the current's amplitude remains the same. As the coupling inductance connecting to the theta pinch main power system decreases, the duration becomes broader. The approximate 4 mΩ closing resistance and 60 nH with 125 nH coupling inductances in the actual crowbar switch have been determined by the simulation based on the measured current. The test results prove that the function modeling of the crowbar switch is correct and it broadens the current duration effectively.
"Yingguang-1" is a multi-bank program-discharged pulsed power device to investigate the formation, confinement and instability of the high temperature and high density field reversed configuration (FRC) plasma injector for the magnetized target fusion (MTF), which was constructed at the Institute of Fluid Physics (IFP) in 2014. This paper discusses the influence of the crowbar switch on the load current in "Yingguang-1" device by function modeling the crowbar switch with the software Pspice and conducting the preliminary test experiment. The function circuit modeling of the crowbar switch employed in the program-discharged power system, is accurately presented for the first time. The simulation and experiment results show that the crowbar switch can improve the load current's duration effectively and both its closed resistance and inductances can affect the load current's amplitude and duration obviously. As the closing resistance decreases, the current's duration becomes broader, however, the current's amplitude remains the same. As the coupling inductance connecting to the theta pinch main power system decreases, the duration becomes broader. The approximate 4 mΩ closing resistance and 60 nH with 125 nH coupling inductances in the actual crowbar switch have been determined by the simulation based on the measured current. The test results prove that the function modeling of the crowbar switch is correct and it broadens the current duration effectively.
2018,
30: 055002.
doi: 10.11884/HPLPB201830.170373
Abstract:
The paper presents a high power wide band oscillator with nonmatched transmission line which is charged by low impedance forming line. The designs of low impedance forming line and nonmatched transmission line are completed accordingly and high voltage experiments are conducted on the 1 MV Marx generation. The wide band oscillator can output wide-spectrum pulse with center frequency 260 MHz, repeat rate 20 Hz when the gap of main switch is 14 mm with 1.5 MPa SF6, the gap of chopping switch is 6 mm with 1.0 MPa SF6, and the gap of peaking switch is 4 mm with 1.1 MPa SF6. The technology of nonmatched transmission line charged by low impedance forming line can output high power wide band pulse and increase center frequency.
The paper presents a high power wide band oscillator with nonmatched transmission line which is charged by low impedance forming line. The designs of low impedance forming line and nonmatched transmission line are completed accordingly and high voltage experiments are conducted on the 1 MV Marx generation. The wide band oscillator can output wide-spectrum pulse with center frequency 260 MHz, repeat rate 20 Hz when the gap of main switch is 14 mm with 1.5 MPa SF6, the gap of chopping switch is 6 mm with 1.0 MPa SF6, and the gap of peaking switch is 4 mm with 1.1 MPa SF6. The technology of nonmatched transmission line charged by low impedance forming line can output high power wide band pulse and increase center frequency.
2018,
30: 055003.
doi: 10.11884/HPLPB201830.170432
Abstract:
In order to explore the feasibility of low density imaging of rod pinch diode (RPD) under impact loading, a simulation study on physical properties of RPD under low voltage operation (≤500 kV) is carried out. Based on particle-in-cell (PIC) simulation method, a simulation is carried out on amplitude of loading voltage of diode, thickness of cathode plate, aperture ratio of cathode and anode, etc. The physical process of pinch is analyzed according to the angle of electron pinch efficiency, proton flow, electron utilization, electric field and magnetic field distribution. The simulation results show that the current of RPD is low under low voltage operation, and can't provide enough magnetic force for the electron, resulting in low electron pinch efficiency. It is a technical approach to realize high dose and small focal spot light source under low voltage condition by using composite rod-pinch diode and optimizing design of the transition region of anode rod to bremsstrahlung target region.
In order to explore the feasibility of low density imaging of rod pinch diode (RPD) under impact loading, a simulation study on physical properties of RPD under low voltage operation (≤500 kV) is carried out. Based on particle-in-cell (PIC) simulation method, a simulation is carried out on amplitude of loading voltage of diode, thickness of cathode plate, aperture ratio of cathode and anode, etc. The physical process of pinch is analyzed according to the angle of electron pinch efficiency, proton flow, electron utilization, electric field and magnetic field distribution. The simulation results show that the current of RPD is low under low voltage operation, and can't provide enough magnetic force for the electron, resulting in low electron pinch efficiency. It is a technical approach to realize high dose and small focal spot light source under low voltage condition by using composite rod-pinch diode and optimizing design of the transition region of anode rod to bremsstrahlung target region.
2018,
30: 055004.
doi: 10.11884/HPLPB201830.170411
Abstract:
Electromagnetic rail launcher (EMRL) is one of the new propulsor based on impulse discharge with pulsed high current technique. In recent years, the research of EMRL has attracted the attention of domestic and foreign institutions, such as China laboratories, the United States Navy Laboratory, the Franco-German Joint Laboratory, and has made great progress. In order to solve the fracture problem between bus-bar and rail connections caused by strong recoil. In experiments, base on the study of mechanical properties, this paper studies a bus-bar structure with high flow capacity, long life, and operational characteristics. The high current causes the bus-bar to be subjected to a strong recoil, in order to weaken the influence of the recoil, geometric design and simulation analysis are done according to the different angles between the bus-bar and the track. A highly reliable, easy to operate bus-bar optimization structure is obtained through the force analysis and initial velocity calculation. This structure can be used in laboratory.
Electromagnetic rail launcher (EMRL) is one of the new propulsor based on impulse discharge with pulsed high current technique. In recent years, the research of EMRL has attracted the attention of domestic and foreign institutions, such as China laboratories, the United States Navy Laboratory, the Franco-German Joint Laboratory, and has made great progress. In order to solve the fracture problem between bus-bar and rail connections caused by strong recoil. In experiments, base on the study of mechanical properties, this paper studies a bus-bar structure with high flow capacity, long life, and operational characteristics. The high current causes the bus-bar to be subjected to a strong recoil, in order to weaken the influence of the recoil, geometric design and simulation analysis are done according to the different angles between the bus-bar and the track. A highly reliable, easy to operate bus-bar optimization structure is obtained through the force analysis and initial velocity calculation. This structure can be used in laboratory.
2018,
30: 055005.
doi: 10.11884/HPLPB201830.170422
Abstract:
Solving the problem of ablation of track and armature is the key to the practical application of the six-pole electromagnetic launcher. One of the causes of the ablation of track and armature is the uneven distribution of current between the rails and the armature.In this paper, the finite element simulation software Ansoft Maxwell is used to simulate the three different orbits, and the distribution of the armature contact surface current density and the armature stress are obtained. The results show: the rectangular orbit maximum current density is the minimum of the three orbits; the concave-semicircle-orbit current distribution is the most uniform, and during the launch process the concave armature contact surface can effectively reduce the erosion of the rail and armature; the convex-orbit armature has the maximum stress and it can be used for high quality objects launch.
Solving the problem of ablation of track and armature is the key to the practical application of the six-pole electromagnetic launcher. One of the causes of the ablation of track and armature is the uneven distribution of current between the rails and the armature.In this paper, the finite element simulation software Ansoft Maxwell is used to simulate the three different orbits, and the distribution of the armature contact surface current density and the armature stress are obtained. The results show: the rectangular orbit maximum current density is the minimum of the three orbits; the concave-semicircle-orbit current distribution is the most uniform, and during the launch process the concave armature contact surface can effectively reduce the erosion of the rail and armature; the convex-orbit armature has the maximum stress and it can be used for high quality objects launch.
2018,
30: 055006.
doi: 10.11884/HPLPB201830.170327
Abstract:
This paper aims to improve the output waveform of pulse forming network (PFN) -Marx generator and get output waveform of short rise time and small ripple factor. Firstly, characteristics of the single stage PFN are studied by simulation, including the impact of single stage PFN terminal capacitance, inductance and PFN terminal impedance on output waveform. The complete simulation model of PFN-Marx generator is established. Using coupled inductor as isolating inductor and using discrete inductor as isolation inductor are studied. The simulation result shows that using coupled inductor as isolating inductor can make charging waveform of PFN more consistent. A small PFN-Marx generator is built. The difference of output waveform of gas switch in PFN-Marx generator under different atmospheric pressure is studied. The result shows that increasing air pressure is beneficial to decrease the rise time of output waveform of PFN-Marx generator.
This paper aims to improve the output waveform of pulse forming network (PFN) -Marx generator and get output waveform of short rise time and small ripple factor. Firstly, characteristics of the single stage PFN are studied by simulation, including the impact of single stage PFN terminal capacitance, inductance and PFN terminal impedance on output waveform. The complete simulation model of PFN-Marx generator is established. Using coupled inductor as isolating inductor and using discrete inductor as isolation inductor are studied. The simulation result shows that using coupled inductor as isolating inductor can make charging waveform of PFN more consistent. A small PFN-Marx generator is built. The difference of output waveform of gas switch in PFN-Marx generator under different atmospheric pressure is studied. The result shows that increasing air pressure is beneficial to decrease the rise time of output waveform of PFN-Marx generator.
2018,
30: 055101.
doi: 10.11884/HPLPB201830.170384
Abstract:
The phase one project of the China Spallation Neutron Source (CSNS) is in the stage of beam commissioning. In the future, the pi-mode structure (PIMS) will be used to upgrade the energy of linac from 80 MeV to 300 MeV. Some preliminarily study was done. The dimension of the PIMS was designed with 2D code SUPERFISH, where the operating frequency was 324 MHz and the β value was 0.4. Coupling coefficient, number of coupling slots and the shape of them were optimized by 3D code CST Microwave studio. The coupling coefficient was chosen to be 6.53%. Field flatness was tuned to 2.18% with slug tuners, which meet the operational requirements.
The phase one project of the China Spallation Neutron Source (CSNS) is in the stage of beam commissioning. In the future, the pi-mode structure (PIMS) will be used to upgrade the energy of linac from 80 MeV to 300 MeV. Some preliminarily study was done. The dimension of the PIMS was designed with 2D code SUPERFISH, where the operating frequency was 324 MHz and the β value was 0.4. Coupling coefficient, number of coupling slots and the shape of them were optimized by 3D code CST Microwave studio. The coupling coefficient was chosen to be 6.53%. Field flatness was tuned to 2.18% with slug tuners, which meet the operational requirements.
2018,
30: 055102.
doi: 10.11884/HPLPB201830.170339
Abstract:
As the light source to provide multi-time radiography, multi-pulse linear induction accelerator (LIA) needs each of its accelerating module to produce several induction pulses in ~μs, with ~100 ns pulse width and ~200 kV pulse voltage. Two kinds of multi-pulse accelerating modules are introduced and compared in this paper, one is based on pulse forming line (PFL) parallel connection method, the other is based on pulse transmission line (PTL) time-delay method. A new design of double-pulse acceleration module is advanced, and the principle experiments' results are discussed.
As the light source to provide multi-time radiography, multi-pulse linear induction accelerator (LIA) needs each of its accelerating module to produce several induction pulses in ~μs, with ~100 ns pulse width and ~200 kV pulse voltage. Two kinds of multi-pulse accelerating modules are introduced and compared in this paper, one is based on pulse forming line (PFL) parallel connection method, the other is based on pulse transmission line (PTL) time-delay method. A new design of double-pulse acceleration module is advanced, and the principle experiments' results are discussed.
2018,
30: 055103.
doi: 10.11884/HPLPB201830.170439
Abstract:
The evaluation of the uncertainty of accelerator industrial CT has always been one of the difficulties in the research and application of industrial CT. In order to evaluate the uncertainty of linear dimension measurement of accelerator industrial CT, an industrial CT size measurement model was established, and the main sources of uncertainty in the measurement were analyzed. Based on the Guide to the Expression of Uncertainty in Measurement (GUM) method, the evaluation of the uncertainty of industrial CT linear dimension was studied. Taking 6 MeV high-energy industrial CT system size measurement as an example, the main uncertainty components of linear dimension measurement of length samples were analyzed, and the uncertainty of the dimension measurement was evaluated. The result is an extended uncertainty of 0.09 mm with an inclusion probability of 0.99, which reflects the accuracy and reliability of industrial CT dimensional measurements. This paper provides a reference for the reliability of the size measurement results of industrial CT.
The evaluation of the uncertainty of accelerator industrial CT has always been one of the difficulties in the research and application of industrial CT. In order to evaluate the uncertainty of linear dimension measurement of accelerator industrial CT, an industrial CT size measurement model was established, and the main sources of uncertainty in the measurement were analyzed. Based on the Guide to the Expression of Uncertainty in Measurement (GUM) method, the evaluation of the uncertainty of industrial CT linear dimension was studied. Taking 6 MeV high-energy industrial CT system size measurement as an example, the main uncertainty components of linear dimension measurement of length samples were analyzed, and the uncertainty of the dimension measurement was evaluated. The result is an extended uncertainty of 0.09 mm with an inclusion probability of 0.99, which reflects the accuracy and reliability of industrial CT dimensional measurements. This paper provides a reference for the reliability of the size measurement results of industrial CT.
2018,
30: 056001.
doi: 10.11884/HPLPB201830.170345
Abstract:
In this research, MCNP code and ORIGEN code are used to calculate the control rod reactivity worth effects by simulating the 3D core model of CMRR reactor. The integral and differential behaviors of reactivity worth effects are measured by rod-drop experiments and digital inverse kinetic method with each other. The calculated and measured results are well accorded. The integral reactivity worth of one safety rod is about 4%Δk/k. Even in an accident when one safety rod gets stuck, the CMRR shutdown margin is still greater than 10%Δk/k, and CMRR is totally safe. So the physical design of CMRR is highly reliable and the operation could be safe.
In this research, MCNP code and ORIGEN code are used to calculate the control rod reactivity worth effects by simulating the 3D core model of CMRR reactor. The integral and differential behaviors of reactivity worth effects are measured by rod-drop experiments and digital inverse kinetic method with each other. The calculated and measured results are well accorded. The integral reactivity worth of one safety rod is about 4%Δk/k. Even in an accident when one safety rod gets stuck, the CMRR shutdown margin is still greater than 10%Δk/k, and CMRR is totally safe. So the physical design of CMRR is highly reliable and the operation could be safe.
