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RSS2016 Vol. 28, No. 03
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2016,
28: 033001.
doi: 10.11884/HPLPB201628.033001
Abstract:
A high-power ultra-wideband feed is developed for large parabolic antenna. The feed consists of constant an impedance balun and a Chebyshev tapered transmission line TEM horn, and the impedance characteristics, transmission characteristics and radiation characteristics are studied based on numerical simulation. Then we make some experimental study. The results show that the feed has low reflection, wide band and high radiation efficiency. This feed has been successfully applied to large high-power parabolic antenna.
A high-power ultra-wideband feed is developed for large parabolic antenna. The feed consists of constant an impedance balun and a Chebyshev tapered transmission line TEM horn, and the impedance characteristics, transmission characteristics and radiation characteristics are studied based on numerical simulation. Then we make some experimental study. The results show that the feed has low reflection, wide band and high radiation efficiency. This feed has been successfully applied to large high-power parabolic antenna.
Suppression of parasitic oscillation in X-band long pulse multi-beam relativistic klystron amplifier
2016,
28: 033002.
doi: 10.11884/HPLPB201628.033002
Abstract:
An X-band multi-beam relativistic klystron amplifier is designed to increase the output microwave power and the operating frequency of the amplifier tube, and an experimental study is performed on the long pulse accelerator. The parasitic oscillation of relativistic klystron amplifier is explored in particle-in-cell code and experiment, and the results indicate that the parasitic oscillation is mainly excited by retrograde electrons. Special measures are introduced in the device to suppress the retrograde electrons and avoid parasitic oscillation. Output power of 0.98 GW is obtained in the experiment, the microwave frequency is 9.405 GHz, the pulse width is 95 ns, and the amplifier gain is about 43 dB.
An X-band multi-beam relativistic klystron amplifier is designed to increase the output microwave power and the operating frequency of the amplifier tube, and an experimental study is performed on the long pulse accelerator. The parasitic oscillation of relativistic klystron amplifier is explored in particle-in-cell code and experiment, and the results indicate that the parasitic oscillation is mainly excited by retrograde electrons. Special measures are introduced in the device to suppress the retrograde electrons and avoid parasitic oscillation. Output power of 0.98 GW is obtained in the experiment, the microwave frequency is 9.405 GHz, the pulse width is 95 ns, and the amplifier gain is about 43 dB.
2016,
28: 033003.
doi: 10.11884/HPLPB201628.033003
Abstract:
Based on a relativistic magnetron with six same cavities, the operating characteristics of transparent cathode are analyzed. A relativistic magnetron can work in 2 mode easily, when the number of metal strips of the transparent cathode is the same as resonant cavities. However, it can work in mode easily when the number is half of the resonant cavities. According to the theory, changing the position of angular orientation of the rotating sector transparent cathode can realize the frequency hopping in the relativistic magnetron. A transparent cathode is designed. Its outer radius is 15 mm. Meanwhile it has six sector metal strips, and each strips angular orientation is 20. The particle simulation software is used to calculate two models, the magnetic field is maintained in 0.75 T and the operating voltage changes from 600 kV to 800 kV. The results show that it can work in 2 mode when putting metal strips on angular position and anode blocks in alignment, while it can work in mode when making each metal strip and each resonant cavity in alignment. It demonstrates that the frequency hopping of the relativistic magnetron can be achieved by rotating the position of angular orientation of the sector transparent cathode.
Based on a relativistic magnetron with six same cavities, the operating characteristics of transparent cathode are analyzed. A relativistic magnetron can work in 2 mode easily, when the number of metal strips of the transparent cathode is the same as resonant cavities. However, it can work in mode easily when the number is half of the resonant cavities. According to the theory, changing the position of angular orientation of the rotating sector transparent cathode can realize the frequency hopping in the relativistic magnetron. A transparent cathode is designed. Its outer radius is 15 mm. Meanwhile it has six sector metal strips, and each strips angular orientation is 20. The particle simulation software is used to calculate two models, the magnetic field is maintained in 0.75 T and the operating voltage changes from 600 kV to 800 kV. The results show that it can work in 2 mode when putting metal strips on angular position and anode blocks in alignment, while it can work in mode when making each metal strip and each resonant cavity in alignment. It demonstrates that the frequency hopping of the relativistic magnetron can be achieved by rotating the position of angular orientation of the sector transparent cathode.
2016,
28: 033004.
doi: 10.11884/HPLPB201628.033004
Abstract:
Based on an independently developed large-scale parallel code NEPTUNE3D, a module of electromagnetic field finite-difference-time-domain method coupled with a plasma fluid model is programmed and built to investigate the physical phenomena of high power microwave (HPM) flashover and breakdown on the inner surface of the output window. By using improved NEPTUNE3D code, the 1.3 GHz HPM flashover and breakdown on the inner surface of the output window are simulated. The numerical results indicate that the plasma shape formed in flashover and breakdown is relevant to the initial seed electron distribution type. For the point source central distribution, the developing plasma configuration is like a mushroom; the shortening of the output microwave caused by plasma absorption is not serious. For the face-source distribution, the developing plasma configuration is like a hat; the shortening of the output microwave is intense, the plasma absorption effect is dominant at the initial stage, while the plasma reflection effect dominates when the plasma density is up to a high enough value. The output microwave pulse width could be prolonged by decreasing the microwave power, the outgassing rate and the initial seed electron density, respectively. The outgassing depth barely affects the width of the shortened microwave output pulse.
Based on an independently developed large-scale parallel code NEPTUNE3D, a module of electromagnetic field finite-difference-time-domain method coupled with a plasma fluid model is programmed and built to investigate the physical phenomena of high power microwave (HPM) flashover and breakdown on the inner surface of the output window. By using improved NEPTUNE3D code, the 1.3 GHz HPM flashover and breakdown on the inner surface of the output window are simulated. The numerical results indicate that the plasma shape formed in flashover and breakdown is relevant to the initial seed electron distribution type. For the point source central distribution, the developing plasma configuration is like a mushroom; the shortening of the output microwave caused by plasma absorption is not serious. For the face-source distribution, the developing plasma configuration is like a hat; the shortening of the output microwave is intense, the plasma absorption effect is dominant at the initial stage, while the plasma reflection effect dominates when the plasma density is up to a high enough value. The output microwave pulse width could be prolonged by decreasing the microwave power, the outgassing rate and the initial seed electron density, respectively. The outgassing depth barely affects the width of the shortened microwave output pulse.
2016,
28: 033005.
doi: 10.11884/HPLPB201628.033005
Abstract:
Cross-linked polystyrene (CLPS) was used as high voltage insulating material for its good electrical and mechanical properties. The flashover properties should be improved along with as the miniaturization of the impulse power system. The mica/CLPS composites were in-situ prepared with styrene、divinylbenzene (DVB), azodiisobutyronitrile (AIBN) and mica powder. The mica powder was dispersed in mix liquid of the precursors of CLPS. The components and morphology of the composites were tested by FT-IR and SEM, and the influence of mica powder on the flashover properties of CLPS was tested by high voltage impulse power. The result shows that the mica powder is well dispersed in the CLPS when its mass fraction is not more than 5%, while agglomerate happens with increase of the mica powder. The flashover voltage and resistance to discharge of CLPS are greatly improved with addition of 3.5%~5% mica.
Cross-linked polystyrene (CLPS) was used as high voltage insulating material for its good electrical and mechanical properties. The flashover properties should be improved along with as the miniaturization of the impulse power system. The mica/CLPS composites were in-situ prepared with styrene、divinylbenzene (DVB), azodiisobutyronitrile (AIBN) and mica powder. The mica powder was dispersed in mix liquid of the precursors of CLPS. The components and morphology of the composites were tested by FT-IR and SEM, and the influence of mica powder on the flashover properties of CLPS was tested by high voltage impulse power. The result shows that the mica powder is well dispersed in the CLPS when its mass fraction is not more than 5%, while agglomerate happens with increase of the mica powder. The flashover voltage and resistance to discharge of CLPS are greatly improved with addition of 3.5%~5% mica.
2016,
28: 033006.
doi: 10.11884/HPLPB201628.033006
Abstract:
A compact output structure with TE11 radiated mode in a relativistic magnetron with axial output is proposed. In the device, through adopting a basic structure of 6 resonant cavities operating in the -mode and designing an axial output structure between the structure of resonant cavities and the cylindrical waveguide properly, a TE11 radiated mode can be obtained in the cylindrical waveguide. Compared with the relativistic magnetron with diffraction output, the structure proposed in this paper provides a much purer radiated mode in the output waveguide, and makes the diameter of the device minimized. In the three-dimensional particle-in-cell (PIC) simulation, the power conversion efficiency can reach 21.9%, corresponding to an output power of 247.0 MW and a resonant frequency of 4.18 GHz, under the condition of the applied voltage of 280 kV and the applied magnetic field of 0.5 T.
A compact output structure with TE11 radiated mode in a relativistic magnetron with axial output is proposed. In the device, through adopting a basic structure of 6 resonant cavities operating in the -mode and designing an axial output structure between the structure of resonant cavities and the cylindrical waveguide properly, a TE11 radiated mode can be obtained in the cylindrical waveguide. Compared with the relativistic magnetron with diffraction output, the structure proposed in this paper provides a much purer radiated mode in the output waveguide, and makes the diameter of the device minimized. In the three-dimensional particle-in-cell (PIC) simulation, the power conversion efficiency can reach 21.9%, corresponding to an output power of 247.0 MW and a resonant frequency of 4.18 GHz, under the condition of the applied voltage of 280 kV and the applied magnetic field of 0.5 T.
2016,
28: 033007.
doi: 10.11884/HPLPB201628.033007
Abstract:
The development on a parallel 2.5D electromagnetic and particle-in-cell code named NEPTUNE2D is introduced preliminarily. The code is developed on the J parallel adaptive structured mesh applications infrastructure (JASMIN), with high parallel efficiency, strong expansibility and adaptive load-balance. A new PIC method is used instead of the classical one, which is more suitable for massively parallel simulation. This code can construct and simulate devices in the R-Z coordinate, and it is capable of fast simulation and design of high power microwave (HPM) devices and electron-vacuum tubes. At present, basic physical function modules are accomplished, such as electromagnetic field update, particle movement, electromagnetic wave input/output and particle injection/absorption. This code is verified and validated by simulations of a coaxial-line, a cylindrical waveguide, a coaxial diode and a foilless diode. Finally, by using this code, a CRBWO (coaxial relativistic backward wave oscillator) with high efficiency is designed and simulated. The physical figures are presented and parallel efficiency is given.
The development on a parallel 2.5D electromagnetic and particle-in-cell code named NEPTUNE2D is introduced preliminarily. The code is developed on the J parallel adaptive structured mesh applications infrastructure (JASMIN), with high parallel efficiency, strong expansibility and adaptive load-balance. A new PIC method is used instead of the classical one, which is more suitable for massively parallel simulation. This code can construct and simulate devices in the R-Z coordinate, and it is capable of fast simulation and design of high power microwave (HPM) devices and electron-vacuum tubes. At present, basic physical function modules are accomplished, such as electromagnetic field update, particle movement, electromagnetic wave input/output and particle injection/absorption. This code is verified and validated by simulations of a coaxial-line, a cylindrical waveguide, a coaxial diode and a foilless diode. Finally, by using this code, a CRBWO (coaxial relativistic backward wave oscillator) with high efficiency is designed and simulated. The physical figures are presented and parallel efficiency is given.
2016,
28: 033008.
doi: 10.11884/HPLPB201628.033008
Abstract:
By resorting to numerical simulation, an S-band split-cavity oscillator (SCO) is designed. The cathode model of explosive emission is built, and the SCO with a real diode is simulated. The typical simulation results are that when the electron beam voltage is 495 kV and the current is about 3.93 kA, an SCO can generate about 640 MW of HPM with a frequency of 2.85 GHz. The power efficiency is about 33.0%. At the same time, we also investigate the influence of the input voltage amplitude and its waveform, the anode-cathode gap and the cathode radius on the output high power microwave of the SCO. The preliminary results show that besides the rate of the grid, the diode impedance and the cathode radius have obvious influence on the output microwave of the SCO, the diode impedance is needed to match the voltage, and the triangle voltage will decrease the power efficiency of the SCO obviously.
By resorting to numerical simulation, an S-band split-cavity oscillator (SCO) is designed. The cathode model of explosive emission is built, and the SCO with a real diode is simulated. The typical simulation results are that when the electron beam voltage is 495 kV and the current is about 3.93 kA, an SCO can generate about 640 MW of HPM with a frequency of 2.85 GHz. The power efficiency is about 33.0%. At the same time, we also investigate the influence of the input voltage amplitude and its waveform, the anode-cathode gap and the cathode radius on the output high power microwave of the SCO. The preliminary results show that besides the rate of the grid, the diode impedance and the cathode radius have obvious influence on the output microwave of the SCO, the diode impedance is needed to match the voltage, and the triangle voltage will decrease the power efficiency of the SCO obviously.
2016,
28: 033009.
doi: 10.11884/HPLPB201628.033009
Abstract:
In order to study the space charge limited current and its related physical quantities, considering the infinitely long radial direction and the current density being constant in axial direction, the Poisson equation for electrical potential is solved theoretically and the expression of the space charge limited current of the beam is obtained. Then the non-linear Poisson equation which takes into consideration the non-uniform distribution of the charge density in axial direction is solved numerically. The numerical results and analytical results are compared. The results show that the radial beam has a higher space charge limited current in radial transmission line. When the beam value approaches to the space charge limited current, the non-uniform distribution of the charge density increases significantly. The relevant conclusion can provide guidance on the design of radial high power microwave devices.
In order to study the space charge limited current and its related physical quantities, considering the infinitely long radial direction and the current density being constant in axial direction, the Poisson equation for electrical potential is solved theoretically and the expression of the space charge limited current of the beam is obtained. Then the non-linear Poisson equation which takes into consideration the non-uniform distribution of the charge density in axial direction is solved numerically. The numerical results and analytical results are compared. The results show that the radial beam has a higher space charge limited current in radial transmission line. When the beam value approaches to the space charge limited current, the non-uniform distribution of the charge density increases significantly. The relevant conclusion can provide guidance on the design of radial high power microwave devices.
2016,
28: 033010.
doi: 10.11884/HPLPB201628.033010
Abstract:
We designed a double negative medium structure for 12.5 GHz based on the principle of negative dielectric constant and permeability, using metal wires and a split ring resonator. The S-parameter was calculated in special boundary conditions. Equivalent parameters were obtained by using the Nicolson-Ross-Weir method. We achieved the characteristics of the left-handed material, that is that the dielectric constant, permeability and refractive index were all negative and the refractive index approximately zero. The double negative medium structure was optimized numerically which applied in Ku-band cone horn antenna. Antenna gains were improved from 11 GHz to 13 GHz and increased 2.17 dB at 12.5 GHz. In the experiments, the antenna gain increased 1.51 dB with the double negative medium loaded, and simultaneously the backward radiation decreased 5.7 dB. The radiation characteristics were improved obviously.
We designed a double negative medium structure for 12.5 GHz based on the principle of negative dielectric constant and permeability, using metal wires and a split ring resonator. The S-parameter was calculated in special boundary conditions. Equivalent parameters were obtained by using the Nicolson-Ross-Weir method. We achieved the characteristics of the left-handed material, that is that the dielectric constant, permeability and refractive index were all negative and the refractive index approximately zero. The double negative medium structure was optimized numerically which applied in Ku-band cone horn antenna. Antenna gains were improved from 11 GHz to 13 GHz and increased 2.17 dB at 12.5 GHz. In the experiments, the antenna gain increased 1.51 dB with the double negative medium loaded, and simultaneously the backward radiation decreased 5.7 dB. The radiation characteristics were improved obviously.
2016,
28: 033011.
doi: 10.11884/HPLPB201628.033011
Abstract:
In order to achieve the phase control of array antenna efficiently, miniaturization, high-speed and parallel control, according to the Nios Ⅱs Avalon bus specification, the paper introduces the design of an IP core for DC-Micromotor controller based on FPGA, and the completion of simulation and experimental verification using Verilog hardware description language. In order to meet the high-speed and parallel control requirements, the controller uses a method of finite-state machine, achieving hardware control functions by several modules. Based on DC micromotor driving characteristics, is uses a PID algorithm, sectional control and start-stop monitoring and other control strategies. Experiments show that the position control system has the characteristics of fast response, high precision, high reliability, small size, and portability; it independently controls multiple axis DC micromotor, and has good control performance, which can meet the requirements of fast and accurate phase control of the antenna.
In order to achieve the phase control of array antenna efficiently, miniaturization, high-speed and parallel control, according to the Nios Ⅱs Avalon bus specification, the paper introduces the design of an IP core for DC-Micromotor controller based on FPGA, and the completion of simulation and experimental verification using Verilog hardware description language. In order to meet the high-speed and parallel control requirements, the controller uses a method of finite-state machine, achieving hardware control functions by several modules. Based on DC micromotor driving characteristics, is uses a PID algorithm, sectional control and start-stop monitoring and other control strategies. Experiments show that the position control system has the characteristics of fast response, high precision, high reliability, small size, and portability; it independently controls multiple axis DC micromotor, and has good control performance, which can meet the requirements of fast and accurate phase control of the antenna.
2016,
28: 033012.
doi: 10.11884/HPLPB201628.033012
Abstract:
The ferroelectric phase shifter is studied for high-power microwave in order to expand beam scanning range. The operating principle of the ferroelectric-lens phase-scanning antenna is briefly introduced and several problems are discussed for high-power microwave application. The high-power microwave propagation in ferroelectrics is analyzed by means of finite difference time domain. In the end, the conclusion about the feasibility of ferroelectric phase shifter applying for high-power microwave is given. The results show that a phase shift of 180 can be achieved in this phase shifter with a length of 10 cm and the transmission efficiency is above 90% without dielectric loss at L wave band.
The ferroelectric phase shifter is studied for high-power microwave in order to expand beam scanning range. The operating principle of the ferroelectric-lens phase-scanning antenna is briefly introduced and several problems are discussed for high-power microwave application. The high-power microwave propagation in ferroelectrics is analyzed by means of finite difference time domain. In the end, the conclusion about the feasibility of ferroelectric phase shifter applying for high-power microwave is given. The results show that a phase shift of 180 can be achieved in this phase shifter with a length of 10 cm and the transmission efficiency is above 90% without dielectric loss at L wave band.
2016,
28: 033013.
doi: 10.11884/HPLPB201628.033013
Abstract:
An L band all cavity axial extraction relativistic magnetron is designed in this paper. The microwave from two adjacent cavities is coupled into an axially oriented coaxial sector waveguide through radial slots on the cavities. And two neighboring slots locate symmetrically about the center axis of the inner wall of the sector waveguide. When the magnetron operates in the ode, the fundamental mode (TE11) will be excited in the sector waveguide. In an N cavity magnetron, N/2 coaxial sector waveguides are employed to extract microwave power. Particle-in-cell simulation is carried out to optimize the parameters of the magnetron. By employing an electron beam of 600 kV and 6.3 kA, the magnetron could generate a microwave output power of 1.89 GW, corresponding to a power conversion efficiency of 50%, and the frequency is 1.57 GHz. This is a preferred structure for a compact relativistic magnetron because only three sector waveguides are needed to be added outside the magnetron cavity.
An L band all cavity axial extraction relativistic magnetron is designed in this paper. The microwave from two adjacent cavities is coupled into an axially oriented coaxial sector waveguide through radial slots on the cavities. And two neighboring slots locate symmetrically about the center axis of the inner wall of the sector waveguide. When the magnetron operates in the ode, the fundamental mode (TE11) will be excited in the sector waveguide. In an N cavity magnetron, N/2 coaxial sector waveguides are employed to extract microwave power. Particle-in-cell simulation is carried out to optimize the parameters of the magnetron. By employing an electron beam of 600 kV and 6.3 kA, the magnetron could generate a microwave output power of 1.89 GW, corresponding to a power conversion efficiency of 50%, and the frequency is 1.57 GHz. This is a preferred structure for a compact relativistic magnetron because only three sector waveguides are needed to be added outside the magnetron cavity.
2016,
28: 033014.
doi: 10.11884/HPLPB201628.033014
Abstract:
Overmoded Ka-band high power microwave (HPM) sources with high energy efficiency can not ensure the output modes purity, which are generally mixedTM0n modes. However, it is necessary for high radiation efficiency that the microwave input to the ready-made radiation terminal is a certain single mode. So it is hard to put these HPM sources into application. In this paper, a hybrid modes converter, utilizing outer and inner coaxial waveguides to purify TM0n mixed modes with high power handing capacity, is proposed. With this method, the TM0n(n5) mixed modes can be converted into pure TEM mode with high conversion efficiency, reducing the modes purification difficulty in the design of the overmoded HPM sources.
Overmoded Ka-band high power microwave (HPM) sources with high energy efficiency can not ensure the output modes purity, which are generally mixedTM0n modes. However, it is necessary for high radiation efficiency that the microwave input to the ready-made radiation terminal is a certain single mode. So it is hard to put these HPM sources into application. In this paper, a hybrid modes converter, utilizing outer and inner coaxial waveguides to purify TM0n mixed modes with high power handing capacity, is proposed. With this method, the TM0n(n5) mixed modes can be converted into pure TEM mode with high conversion efficiency, reducing the modes purification difficulty in the design of the overmoded HPM sources.
2016,
28: 033015.
doi: 10.11884/HPLPB201628.033015
Abstract:
A novel ellipse cylindrical dielectric lens antenna array is designed in this paper. In order to improve antenna radiation properties, considering high voltage breakdown based on high power application, this paper proposes filling transformer oil in a nylon radome structure of an elliptical cross-section and rectangular combination, then sealing a knife-shape antenna array in the structure, and eventually forming a dielectric lens antenna array. The geometric focusing capability of ellipse and shrinkage of wavelength helps to enhance the main lobe gain and the electric size of the antenna array. Compared with the traditional antenna array, it shows that the peak-to-peak voltage value along the antenna axis in the far field pattern increases by 41% via changing the array distance, while the far field beam width decreases obviously, and the gain enhancement is 4.96 dB. Furthermore, the front to back ratio gets better, the power capacity is up to 9.63 GW, 338 times greater than that of the former structure.
A novel ellipse cylindrical dielectric lens antenna array is designed in this paper. In order to improve antenna radiation properties, considering high voltage breakdown based on high power application, this paper proposes filling transformer oil in a nylon radome structure of an elliptical cross-section and rectangular combination, then sealing a knife-shape antenna array in the structure, and eventually forming a dielectric lens antenna array. The geometric focusing capability of ellipse and shrinkage of wavelength helps to enhance the main lobe gain and the electric size of the antenna array. Compared with the traditional antenna array, it shows that the peak-to-peak voltage value along the antenna axis in the far field pattern increases by 41% via changing the array distance, while the far field beam width decreases obviously, and the gain enhancement is 4.96 dB. Furthermore, the front to back ratio gets better, the power capacity is up to 9.63 GW, 338 times greater than that of the former structure.
2016,
28: 033016.
doi: 10.11884/HPLPB201628.033016
Abstract:
This paper simulates the coupled signals on a PCB circuit, which includes a PIN limiter, generated by high power microwave (HPM) with different frequencies by using a hybrid simulation method. This hybrid method is based on the transient electromagnetic topology method and device/circuit mixed simulation. It realizes the hybrid simulation of fields, circuits, and devices. It can be employed to simulate the coupled signals on a PCB circuit within a shielding enclosure illuminated by HPM. This method is employed to obtain the coupled signals on the PCB circuit generated by HPM with the frequencies of 1 GHz, 1.25 GHz and 2.5 GHz. The coupled signal generated by 1 GHz HPM is the largest when the PCB circuit has no shielding enclosures. However, the coupled signal generated by 2.5 GHz HPM is the largest when the PCB circuit has its enclosure. The results show that the PIN limiter has a good protection effect when the coupled signal is large.
This paper simulates the coupled signals on a PCB circuit, which includes a PIN limiter, generated by high power microwave (HPM) with different frequencies by using a hybrid simulation method. This hybrid method is based on the transient electromagnetic topology method and device/circuit mixed simulation. It realizes the hybrid simulation of fields, circuits, and devices. It can be employed to simulate the coupled signals on a PCB circuit within a shielding enclosure illuminated by HPM. This method is employed to obtain the coupled signals on the PCB circuit generated by HPM with the frequencies of 1 GHz, 1.25 GHz and 2.5 GHz. The coupled signal generated by 1 GHz HPM is the largest when the PCB circuit has no shielding enclosures. However, the coupled signal generated by 2.5 GHz HPM is the largest when the PCB circuit has its enclosure. The results show that the PIN limiter has a good protection effect when the coupled signal is large.
2016,
28: 033017.
doi: 10.11884/HPLPB201628.033017
Abstract:
A permanent magnet (PM) is one of the guiding magnet systems of high power microwave (HPM) sources. A relativistic backward wave oscillator (RBWO) packaged by the PM system has the advantages of compact structure, high efficiency and high repetition frequency. On the basis of the Halbach array, the theoretical design and the manufacture structure of the PM are proposed. The simulated magnetic flux density reaches 0.98 T, within a diameter of 50 mm. By employing the PIC simulation, the integrated design is carried out combining the PM and the RBWO. The output power of the RBWO is larger than 1 GW. Furthermore, the PM is manufactured and tested. The uniform length is 110 mm, the weight is 306 kg and the measured magnetic flux density is 0.88 T in center.
A permanent magnet (PM) is one of the guiding magnet systems of high power microwave (HPM) sources. A relativistic backward wave oscillator (RBWO) packaged by the PM system has the advantages of compact structure, high efficiency and high repetition frequency. On the basis of the Halbach array, the theoretical design and the manufacture structure of the PM are proposed. The simulated magnetic flux density reaches 0.98 T, within a diameter of 50 mm. By employing the PIC simulation, the integrated design is carried out combining the PM and the RBWO. The output power of the RBWO is larger than 1 GW. Furthermore, the PM is manufactured and tested. The uniform length is 110 mm, the weight is 306 kg and the measured magnetic flux density is 0.88 T in center.
2016,
28: 033018.
doi: 10.11884/HPLPB201628.033018
Abstract:
With the electromagnetic code, a frequency-tuned relativistic klystron amplifier (RKA) is designed and calculated. It is found that the operation frequency of the RKA can jump across S-band and C-band by adjusting the feeding frequency and the length of the output cavity. A 1 GW averaged power over the oscillator period is generated by simulation, with 700 kV electron beam voltage, 4 kA current, and 340 kW feeding power. The frequency of the output microwave is 3.2 GHz. The efficiency is about 35%. Meanwhile, a C-band microwave with a frequency of 5.6 GHz and a power level of above 490 MW is generated when the feeding frequency is 2.8 GHz and the output cavity length is 3.7 cm. The efficiency is about 17%.
With the electromagnetic code, a frequency-tuned relativistic klystron amplifier (RKA) is designed and calculated. It is found that the operation frequency of the RKA can jump across S-band and C-band by adjusting the feeding frequency and the length of the output cavity. A 1 GW averaged power over the oscillator period is generated by simulation, with 700 kV electron beam voltage, 4 kA current, and 340 kW feeding power. The frequency of the output microwave is 3.2 GHz. The efficiency is about 35%. Meanwhile, a C-band microwave with a frequency of 5.6 GHz and a power level of above 490 MW is generated when the feeding frequency is 2.8 GHz and the output cavity length is 3.7 cm. The efficiency is about 17%.
2016,
28: 033019.
doi: 10.11884/HPLPB201628.033019
Abstract:
The influence of field enhancement factors on the power capacity of relativistic backward wave oscillators is preliminarily investigated in the paper. Under the conditions of strong field, positive asperity and burr on the surface of high frequency structures will lead to field electron emission and RF breakdown, which can further generate plasma and lead to pulse shortening and reduction of power limit. By precisely polishing the surface of a kind of X band RBWO, the surface roughness can be reduced to less than 1/40 of the initial value, where the power limit will increase by at least 25%.
The influence of field enhancement factors on the power capacity of relativistic backward wave oscillators is preliminarily investigated in the paper. Under the conditions of strong field, positive asperity and burr on the surface of high frequency structures will lead to field electron emission and RF breakdown, which can further generate plasma and lead to pulse shortening and reduction of power limit. By precisely polishing the surface of a kind of X band RBWO, the surface roughness can be reduced to less than 1/40 of the initial value, where the power limit will increase by at least 25%.
2016,
28: 033020.
doi: 10.11884/HPLPB201628.033020
Abstract:
The charge conserving emission technique is presented in this paper. Based on the relationship between the charge and current distributions and Gauss law preservation, the emitting surface is triangulated, and the charged particle is initially located at the nearest conductor node to the conformal emission triangle. The motion trajectory of the charged particle is decided by two components: the normal component and the transversal component. The normal component is the displacement under the normal electric field of the emission triangle within one step; the transversal component is a random displacement parallel to the emission triangle, whose step size is constrained by the shape of the emission triangle. Currents generated by the movement of charged particles are distributed to the discrete grid according to the charge conserving law. As the charged particle starts from the conductor node, the conformal emission is free of nonphysical electrostatic accumulation. Finally a cylindrical diode is simulated to validate the technique.
The charge conserving emission technique is presented in this paper. Based on the relationship between the charge and current distributions and Gauss law preservation, the emitting surface is triangulated, and the charged particle is initially located at the nearest conductor node to the conformal emission triangle. The motion trajectory of the charged particle is decided by two components: the normal component and the transversal component. The normal component is the displacement under the normal electric field of the emission triangle within one step; the transversal component is a random displacement parallel to the emission triangle, whose step size is constrained by the shape of the emission triangle. Currents generated by the movement of charged particles are distributed to the discrete grid according to the charge conserving law. As the charged particle starts from the conductor node, the conformal emission is free of nonphysical electrostatic accumulation. Finally a cylindrical diode is simulated to validate the technique.
2016,
28: 033021.
doi: 10.11884/HPLPB201628.033021
Abstract:
In order to get higher output power and higher efficiency, a new L band magnetically insulated transmission line oscillator(MILO) with a high operation voltage (700 kV) is designed based on the theoretical analysis and PIC simulation. From the simulation, an average output power of 11.2 GW with an efficiency 20.1% is got with an input power of 55.7 GW. The efficiency of the MILO is higher than that of traditional MILO with a lower operation voltage. Different from the lower operation voltage MILO, the new MILOs efficiency is not highest at its operation voltage but increases as the input voltage rises. This phenomenon is explained and it is concluded that with a proper design, high operation voltage MILOs would achieve higher efficiency and higher power along with increasing the voltage.
In order to get higher output power and higher efficiency, a new L band magnetically insulated transmission line oscillator(MILO) with a high operation voltage (700 kV) is designed based on the theoretical analysis and PIC simulation. From the simulation, an average output power of 11.2 GW with an efficiency 20.1% is got with an input power of 55.7 GW. The efficiency of the MILO is higher than that of traditional MILO with a lower operation voltage. Different from the lower operation voltage MILO, the new MILOs efficiency is not highest at its operation voltage but increases as the input voltage rises. This phenomenon is explained and it is concluded that with a proper design, high operation voltage MILOs would achieve higher efficiency and higher power along with increasing the voltage.
2016,
28: 033022.
doi: 10.11884/HPLPB201628.033022
Abstract:
A Monte Carlo model is proposed to simulate the process of HPM single and mixed gas breakdowns, and a three-dimensional Monte Carlo code (3D-MCC) is compiled by analyzing the collision process between electrons and background gases. Aiming at Ar, N2 and N2/O2 mixture (air), the electron cloud formation process and the electron energy distribution function (EEDF) can be obtained by simulating the process of gas breakdown using 3D-MCC. The gas breakdown time, derived by analyzing the variation trend of the EEDF and the electron density along with time, has an intense dependence on the EEDF for Ar, but not for N2. The correctness of this model is verified by comparing with the fluid model. An experimental system allowing the air breakdown to be triggered in vacuum by a focused HPM is established. The air breakdown time is measured under different pressures at S-band when the electric field is 6.38 kV/cm. The simulation results are consistent with the experimental data.
A Monte Carlo model is proposed to simulate the process of HPM single and mixed gas breakdowns, and a three-dimensional Monte Carlo code (3D-MCC) is compiled by analyzing the collision process between electrons and background gases. Aiming at Ar, N2 and N2/O2 mixture (air), the electron cloud formation process and the electron energy distribution function (EEDF) can be obtained by simulating the process of gas breakdown using 3D-MCC. The gas breakdown time, derived by analyzing the variation trend of the EEDF and the electron density along with time, has an intense dependence on the EEDF for Ar, but not for N2. The correctness of this model is verified by comparing with the fluid model. An experimental system allowing the air breakdown to be triggered in vacuum by a focused HPM is established. The air breakdown time is measured under different pressures at S-band when the electric field is 6.38 kV/cm. The simulation results are consistent with the experimental data.
2016,
28: 033023.
doi: 10.11884/HPLPB201628.033023
Abstract:
The commutation phenomena produced by cathode outgassing ionization is a possible factor limiting MILOs work performance, and also is the main obstacle to the MILOs repeat frequency. In this paper, the physical modeling technology for cathode outgassing ionization phenomena of the high-power microwave device MILO and the particle simulation techniques to achieve the desired three-dimensional self-consistent calculation are analyzed by three dimensional PIC code. According to the simulation and computing results of different relative outgassing rate, when the outgassing rate exceeds a certain threshold, the plasma caused by the ionization will make the microwave output power rapidly.
The commutation phenomena produced by cathode outgassing ionization is a possible factor limiting MILOs work performance, and also is the main obstacle to the MILOs repeat frequency. In this paper, the physical modeling technology for cathode outgassing ionization phenomena of the high-power microwave device MILO and the particle simulation techniques to achieve the desired three-dimensional self-consistent calculation are analyzed by three dimensional PIC code. According to the simulation and computing results of different relative outgassing rate, when the outgassing rate exceeds a certain threshold, the plasma caused by the ionization will make the microwave output power rapidly.
2016,
28: 033024.
doi: 10.11884/HPLPB201628.033024
Abstract:
The response of MOSFET to HPM is numerically studied by a simulator based on semiconductor drift-diffusion model. The response characteristics of ESD device under the action of HPM and the physical image of the device are simulated. The results of numerical simulation show that the amplitude and the frequency of the HPM signal are the factors that affect the ESD device, and the maximum temperature and the signal amplitude are positive exponential relationship with the HPM pulse width of the 30ns pulse. When the HPM signal is injected into the same amplitude ESD signal, the larger the frequency is, the longer the device can achieve the failure temperature. The results of this paper can provide a theoretical reference for the research of the damage mechanism of MOS device and the reinforcement design of the HPM device.
The response of MOSFET to HPM is numerically studied by a simulator based on semiconductor drift-diffusion model. The response characteristics of ESD device under the action of HPM and the physical image of the device are simulated. The results of numerical simulation show that the amplitude and the frequency of the HPM signal are the factors that affect the ESD device, and the maximum temperature and the signal amplitude are positive exponential relationship with the HPM pulse width of the 30ns pulse. When the HPM signal is injected into the same amplitude ESD signal, the larger the frequency is, the longer the device can achieve the failure temperature. The results of this paper can provide a theoretical reference for the research of the damage mechanism of MOS device and the reinforcement design of the HPM device.
2016,
28: 033025.
doi: 10.11884/HPLPB201628.033025
Abstract:
The energy loss mechanism and the influence of the kinetic energy on the energy deposition of incident electrons in collectors were analyzed theoretically. Using Monte Carlo method, the energy deposition in collectors of electron beams with different kinetic energies was calculated. The influence of kinetic energy on the energy deposition was analyzed, and two ways were proposed to improve the resistance of collectors to electron beam impact. It was found that excitation and ionization was the major mechanism leading to electrons losing energy. Electrons with higher kinetic energy penetrated further in the collector, but the maximum energy density deposited was lower. Considering the influence of beam distribution on the energy deposition, two ways were put forward to improve the collectors: one was to enlarge the collecting area through structure optimization, and the other was to design HPM generators with higher resistance.
The energy loss mechanism and the influence of the kinetic energy on the energy deposition of incident electrons in collectors were analyzed theoretically. Using Monte Carlo method, the energy deposition in collectors of electron beams with different kinetic energies was calculated. The influence of kinetic energy on the energy deposition was analyzed, and two ways were proposed to improve the resistance of collectors to electron beam impact. It was found that excitation and ionization was the major mechanism leading to electrons losing energy. Electrons with higher kinetic energy penetrated further in the collector, but the maximum energy density deposited was lower. Considering the influence of beam distribution on the energy deposition, two ways were put forward to improve the collectors: one was to enlarge the collecting area through structure optimization, and the other was to design HPM generators with higher resistance.
2016,
28: 033026.
doi: 10.11884/HPLPB201628.033026
Abstract:
In order to realize the multi-node communication between the main control system of array antenna and the other systems based on VxWorks, a communication protocol based on UDP is used in this paper. In the application layer, a unified communication protocol is designed, which can ensure communication between both parties. At the same time, the buffer mechanism is designed to store the command and ensure that the information is not lost during the transmission, so that the order task can be executed normally and orderly. Experimental results show that the protocol and buffer queue can achieve the multi-node communication between the main control system and the other systems.
In order to realize the multi-node communication between the main control system of array antenna and the other systems based on VxWorks, a communication protocol based on UDP is used in this paper. In the application layer, a unified communication protocol is designed, which can ensure communication between both parties. At the same time, the buffer mechanism is designed to store the command and ensure that the information is not lost during the transmission, so that the order task can be executed normally and orderly. Experimental results show that the protocol and buffer queue can achieve the multi-node communication between the main control system and the other systems.
2016,
28: 033027.
doi: 10.11884/HPLPB201628.033027
Abstract:
To meet the demands of compactness and miniaturization of the wideband high power microwave radiation system, an electric-magnetic vibrator combined antenna with an aperture of 20 cm20 cm is designed. By applying the 3D full wave electromagnetic field simulation tool, it is proved that the antenna voltage standing wave ratio is less than 3 and the antenna gain is larger than 2 within the bandwidth of 0.3-1.7 GHz. Meanwhile, the influences of the size of the antenna structure, the length of the current loop and the angle of the antenna aperture on the antenna impedance bandwidth and the gain are investigated. On this basis, fed by the wideband signal with a peak voltage of 226 kV for simulation, the maximum radiation factor reaches 150 kV, the equivalent radiation power reaches 358.8 MW and the radiation efficiency is 70.6%. The results indicate that the electric-magnetic vibrator combined antenna can meet the radiation requirements of the high power wideband microwave, the compactness of the radiation system and high radiation efficiency.
To meet the demands of compactness and miniaturization of the wideband high power microwave radiation system, an electric-magnetic vibrator combined antenna with an aperture of 20 cm20 cm is designed. By applying the 3D full wave electromagnetic field simulation tool, it is proved that the antenna voltage standing wave ratio is less than 3 and the antenna gain is larger than 2 within the bandwidth of 0.3-1.7 GHz. Meanwhile, the influences of the size of the antenna structure, the length of the current loop and the angle of the antenna aperture on the antenna impedance bandwidth and the gain are investigated. On this basis, fed by the wideband signal with a peak voltage of 226 kV for simulation, the maximum radiation factor reaches 150 kV, the equivalent radiation power reaches 358.8 MW and the radiation efficiency is 70.6%. The results indicate that the electric-magnetic vibrator combined antenna can meet the radiation requirements of the high power wideband microwave, the compactness of the radiation system and high radiation efficiency.
2016,
28: 033028.
doi: 10.11884/HPLPB201628.033028
Abstract:
The high power microwave(HPM) measurement diagnoses technology is an important content of the study of HPM technology. For the realistic demand, the study found a measurement system using the microwave photonics technology, expatiating the elements of the system, and analysing the performance of the measurement system via simulation. The measurement system uses the ultra-wideband large-dynamic Mach-Zehnder-modulator and photodetector, uses the optical fiber to carry on the remote telecontrol measurement, thus to avoid the radiation and transmission interference, and finally the measurement bandwidth can be achieved 40 GHz and the spurious free dynamic range(SFDR) can be achieved 100 dB/Hz2/3.
The high power microwave(HPM) measurement diagnoses technology is an important content of the study of HPM technology. For the realistic demand, the study found a measurement system using the microwave photonics technology, expatiating the elements of the system, and analysing the performance of the measurement system via simulation. The measurement system uses the ultra-wideband large-dynamic Mach-Zehnder-modulator and photodetector, uses the optical fiber to carry on the remote telecontrol measurement, thus to avoid the radiation and transmission interference, and finally the measurement bandwidth can be achieved 40 GHz and the spurious free dynamic range(SFDR) can be achieved 100 dB/Hz2/3.
2016,
28: 033029.
doi: 10.11884/HPLPB201628.033029
Abstract:
In order to satisfy the demand of microwave amplifier tube for wide-band input window, a coaxial input window suitable for wide-band microwave device is designed. The material of the coaxial input window is tapered circular ceramic, whose permittivity is 9.3. The structure and size of coaxial and tapered ceramic are simulated by three-dimensional simulation software. Simulation results show that this coaxial input window can work in 10-45 GHz range with a less than 0.5 dB insertion loss.
In order to satisfy the demand of microwave amplifier tube for wide-band input window, a coaxial input window suitable for wide-band microwave device is designed. The material of the coaxial input window is tapered circular ceramic, whose permittivity is 9.3. The structure and size of coaxial and tapered ceramic are simulated by three-dimensional simulation software. Simulation results show that this coaxial input window can work in 10-45 GHz range with a less than 0.5 dB insertion loss.
2016,
28: 033030.
doi: 10.11884/HPLPB201628.033030
Abstract:
This paper studies a Ku-band rectangular radial line sub-array feed system. In order to meet the requirement of specific coupling, this paper proposes a new type of coupling probe with superposition structure, and on this basis, the center frequency of 12.5 GHz 28 unit sub-array rectangular grid radial line feed system is designed and analyzed. Simulation results show that: The diameter of 61.6 mm125.2 mm feed system in the center frequency of 12.5 GHz has a reflection coefficient of 0.015, and a roughness of 1.05 dB. At the same time, within the scope of 12.2-12.7 GHz frequency band, the reflection coefficient is less than 0.1, and the maximum roughness of amplitude is 2. 62 dB, and the feed system basically meets the requirements of continuous feed output for 28 ports.
This paper studies a Ku-band rectangular radial line sub-array feed system. In order to meet the requirement of specific coupling, this paper proposes a new type of coupling probe with superposition structure, and on this basis, the center frequency of 12.5 GHz 28 unit sub-array rectangular grid radial line feed system is designed and analyzed. Simulation results show that: The diameter of 61.6 mm125.2 mm feed system in the center frequency of 12.5 GHz has a reflection coefficient of 0.015, and a roughness of 1.05 dB. At the same time, within the scope of 12.2-12.7 GHz frequency band, the reflection coefficient is less than 0.1, and the maximum roughness of amplitude is 2. 62 dB, and the feed system basically meets the requirements of continuous feed output for 28 ports.
2016,
28: 033101.
doi: 10.11884/HPLPB201628.033101
Abstract:
Effects of the structure parameters, including the ratio of b/a, the height of the folded waveguide, the width of the beam tunnel, on the output characteristics of the terahertz band folded waveguide traveling wave tube are analyzed. Calculation results show that there exists an optimal value of b/a for the maximum small signal gain and the coupling impedance. With the increasing of the width of the beam tunnel, the attenuation constant will increase markedly. Thus the small signal gain and the coupling impedance will decreased markedly. Both the attenuation constant and the small signal gain are relatively insensitive to the height of the folded waveguide. The results are useful to the design of the folded waveguide tube in practical applications.
Effects of the structure parameters, including the ratio of b/a, the height of the folded waveguide, the width of the beam tunnel, on the output characteristics of the terahertz band folded waveguide traveling wave tube are analyzed. Calculation results show that there exists an optimal value of b/a for the maximum small signal gain and the coupling impedance. With the increasing of the width of the beam tunnel, the attenuation constant will increase markedly. Thus the small signal gain and the coupling impedance will decreased markedly. Both the attenuation constant and the small signal gain are relatively insensitive to the height of the folded waveguide. The results are useful to the design of the folded waveguide tube in practical applications.
2016,
28: 033102.
doi: 10.11884/HPLPB201628.033102
Abstract:
Broadband wireless access over short distances with fixed THz wireless links is very promising. A new model of atmospheric transmission of terahertz communication is developed based on the radiation transmission theory and the continuum absorption phenomenon using data from the HITRAN database. The attenuation, the path loss and the channel capacity of THz atmospheric propagation are investigated by means of numerical simulation. The THz wave atmospheric attenuation experimental results obtained with the THz-time domain spectroscopy (THz-TDS) technique is analyzed by this new model. The intensity and the location of the observed absorption lines are in good agreement with the spectral databases. Five channels ranging from 100 to 900 GHz are analyzed. Nevertheless, contrary to the wireless links in the lower GHz-bands, the transmittable data rates are reduced in this frequency range because of the high free-space path loss and attenuation due to molecules in air or water droplets. As demonstrated here, high transmission data rates larger than 10 Gbps can be reached via these channels within short distances if antennas with high gains are used.
Broadband wireless access over short distances with fixed THz wireless links is very promising. A new model of atmospheric transmission of terahertz communication is developed based on the radiation transmission theory and the continuum absorption phenomenon using data from the HITRAN database. The attenuation, the path loss and the channel capacity of THz atmospheric propagation are investigated by means of numerical simulation. The THz wave atmospheric attenuation experimental results obtained with the THz-time domain spectroscopy (THz-TDS) technique is analyzed by this new model. The intensity and the location of the observed absorption lines are in good agreement with the spectral databases. Five channels ranging from 100 to 900 GHz are analyzed. Nevertheless, contrary to the wireless links in the lower GHz-bands, the transmittable data rates are reduced in this frequency range because of the high free-space path loss and attenuation due to molecules in air or water droplets. As demonstrated here, high transmission data rates larger than 10 Gbps can be reached via these channels within short distances if antennas with high gains are used.
2016,
28: 033103.
doi: 10.11884/HPLPB201628.033103
Abstract:
A terahertz overmoded surface wave oscillator (SWO) with tapered slow wave structures (SWS) added after the uniform SWSs is investigated, and the notable enhancement of output power and mode purity is obtained. At first, the resonant characteristics of the multiple high frequency structure are studied and analyzed by using the S-parameters method. Then a 2.5 dimensional particle-in-cell (PIC) code UNIPIC is employed to simulate and research the variation relations between the output performance of the oscillator and the length of tapered SWSs. The results show that the power ratio of TM01 mode in the output terahertz wave increases to be over 80% with the increase of period number, while ratios of TM02 and TM03 higher modes are suppressed efficiently; and the output power of the oscillator with appropriate length of tapered SWSs is 50% more than that from SWO with uniform SWSs.
A terahertz overmoded surface wave oscillator (SWO) with tapered slow wave structures (SWS) added after the uniform SWSs is investigated, and the notable enhancement of output power and mode purity is obtained. At first, the resonant characteristics of the multiple high frequency structure are studied and analyzed by using the S-parameters method. Then a 2.5 dimensional particle-in-cell (PIC) code UNIPIC is employed to simulate and research the variation relations between the output performance of the oscillator and the length of tapered SWSs. The results show that the power ratio of TM01 mode in the output terahertz wave increases to be over 80% with the increase of period number, while ratios of TM02 and TM03 higher modes are suppressed efficiently; and the output power of the oscillator with appropriate length of tapered SWSs is 50% more than that from SWO with uniform SWSs.
2016,
28: 033201.
doi: 10.11884/HPLPB201628.033201
Abstract:
This article made a review of methods used in capturing electronic system high power electromagnetic(HPEM ) effects tested on IC, PCB, and system level, and proposed that by monitoring voltage waveform at critical nodes of electrical circuits, various error effects could be monitored, classified, traced and determined for unmanned aircraft HPEM susceptibility test. A voltage probe with high input impedance as well as fiber optical output port was designed and achieved to satisfy special requirements of this application, which showed tested characteristics of 1 M input impedance, DC-450 MHz bandwidth and compact size. Working voltage waveforms at nodes of rudder control circuit, RF link circuit et al of an unmanned aircraft were remotely monitored with this voltage probe. Coupled pulse voltage waveforms at circuit nodes were successfully probed in high field strength HEMP range test of an unmanned aircraft, which showed reasonable characteristics.
This article made a review of methods used in capturing electronic system high power electromagnetic(HPEM ) effects tested on IC, PCB, and system level, and proposed that by monitoring voltage waveform at critical nodes of electrical circuits, various error effects could be monitored, classified, traced and determined for unmanned aircraft HPEM susceptibility test. A voltage probe with high input impedance as well as fiber optical output port was designed and achieved to satisfy special requirements of this application, which showed tested characteristics of 1 M input impedance, DC-450 MHz bandwidth and compact size. Working voltage waveforms at nodes of rudder control circuit, RF link circuit et al of an unmanned aircraft were remotely monitored with this voltage probe. Coupled pulse voltage waveforms at circuit nodes were successfully probed in high field strength HEMP range test of an unmanned aircraft, which showed reasonable characteristics.
2016,
28: 033202.
doi: 10.11884/HPLPB201628.033202
Abstract:
Building a physical semiconductor model is a technical difficulty in numerical simulation of EMP effect on semiconductor device. As an example, one type TVS diode is tested to obtain parameters for model building. Area and depth of PN junction are obtained by X-ray imaging, SEM scanning and doping impurity staining. Breakdown voltage and capacitance curve of the diode are surveyed and be used for educing doping concentration of the diode combining with numerical results. The semiconductor model of this type diode is built by using parameters from this test, and is used for numerical simulation. Numerical result tallies with the test. This test method can be used in PN junction modeling, and can be referenced for modeling of other device. It could be applied in HPM effect numerical study.
Building a physical semiconductor model is a technical difficulty in numerical simulation of EMP effect on semiconductor device. As an example, one type TVS diode is tested to obtain parameters for model building. Area and depth of PN junction are obtained by X-ray imaging, SEM scanning and doping impurity staining. Breakdown voltage and capacitance curve of the diode are surveyed and be used for educing doping concentration of the diode combining with numerical results. The semiconductor model of this type diode is built by using parameters from this test, and is used for numerical simulation. Numerical result tallies with the test. This test method can be used in PN junction modeling, and can be referenced for modeling of other device. It could be applied in HPM effect numerical study.
2016,
28: 033203.
doi: 10.11884/HPLPB201628.033203
Abstract:
Verification validation (VV) approach attracts more and more focus since numerical simulation becomes more and more important in computational electromagnetics research. In this paper, the basic concepts, research method and current progress of VV are introduced. Development and focuses in VV research in computational electromagnetics are briefly summarized. Standards for validation of computational electromagnetics computer modeling and simulations and the recommended practice are also referred to. In the end of this paper, a terse analysis for the possible role and development of VV in computational electromagnetics is given.
Verification validation (VV) approach attracts more and more focus since numerical simulation becomes more and more important in computational electromagnetics research. In this paper, the basic concepts, research method and current progress of VV are introduced. Development and focuses in VV research in computational electromagnetics are briefly summarized. Standards for validation of computational electromagnetics computer modeling and simulations and the recommended practice are also referred to. In the end of this paper, a terse analysis for the possible role and development of VV in computational electromagnetics is given.
2016,
28: 035001.
doi: 10.11884/HPLPB201628.035001
Abstract:
The vibrational degree of nitrogen is highly excited in low temperature plasma generated by air discharges. Based on harmonic oscillator model and the assumption of Boltzmann distribution of vibrational levels, the behavior of vibrational temperature during repetitively pulsed air discharges is investigated. The results show that the determinant factor of vibrational temperature is the competition between electron-vibrational (e-V) excitation process and vibrational-translational (V-T) relaxation process, while the chemical-vibrational (Chem-V) process involving oxygen atom also influences in highly excited vibrational state. For the e-V process, the characteristic relaxation time deduced from an empirical reciprocal law of transition rates agrees well with that from kinetic modeling. For the V-T process, the dominant role is played by oxygen atoms in dry air and water moleculars in humid air. If the density of oxygen atom is 1014 cm-3 and the vibrational temperature is 5000 K, the relaxation time during initial Chem-V process is in the order of 0.1~1 s.
The vibrational degree of nitrogen is highly excited in low temperature plasma generated by air discharges. Based on harmonic oscillator model and the assumption of Boltzmann distribution of vibrational levels, the behavior of vibrational temperature during repetitively pulsed air discharges is investigated. The results show that the determinant factor of vibrational temperature is the competition between electron-vibrational (e-V) excitation process and vibrational-translational (V-T) relaxation process, while the chemical-vibrational (Chem-V) process involving oxygen atom also influences in highly excited vibrational state. For the e-V process, the characteristic relaxation time deduced from an empirical reciprocal law of transition rates agrees well with that from kinetic modeling. For the V-T process, the dominant role is played by oxygen atoms in dry air and water moleculars in humid air. If the density of oxygen atom is 1014 cm-3 and the vibrational temperature is 5000 K, the relaxation time during initial Chem-V process is in the order of 0.1~1 s.
2016,
28: 035003.
doi: 10.11884/HPLPB201628.035003
Abstract:
In order to research the surface flashover characteristics of two typical insulating materials (nylon and synthetic glass) under hundred-nanosecond pulse in nitrogen gas, experimental device of surface flashover under hundred-nanosecond pulse was designed. The variation laws of the flashover voltage of the insulating material with air pressure and flashover distance have been researched via experimentation. The experimental results showed that the flashover voltage increased with the increasing of the air pressure. However, the flashover electric field intensity decreased with the increasing of the distance. In the same condition, the flashover voltage of PMMA is higher than that of nylon. The flashover voltage of the materials with different gas pressure and distance under hundred-nanosecond pulse were obtained via the surface flashover experiment.
In order to research the surface flashover characteristics of two typical insulating materials (nylon and synthetic glass) under hundred-nanosecond pulse in nitrogen gas, experimental device of surface flashover under hundred-nanosecond pulse was designed. The variation laws of the flashover voltage of the insulating material with air pressure and flashover distance have been researched via experimentation. The experimental results showed that the flashover voltage increased with the increasing of the air pressure. However, the flashover electric field intensity decreased with the increasing of the distance. In the same condition, the flashover voltage of PMMA is higher than that of nylon. The flashover voltage of the materials with different gas pressure and distance under hundred-nanosecond pulse were obtained via the surface flashover experiment.
2016,
28: 035004.
doi: 10.11884/HPLPB201628.035004
Abstract:
As for pulse generators based on gas-switch and SOS-switch, the output of the avalanche transistor pulse is relatively low. To increase its output, the method of power-combining is used. The key point is that the pulse-generator-units must have high stability and time-coherence. The reason why the trigger pulse affects the pulse-generator based on avalanche transistor is analyzed in the paper. And the key influence factors, which are the slope of the trigger pulse, the difference of avalanche transistors and the noise of circuits, are found out. In experiment, the jitter of the pulse-generator and the time-coherence between units are less than 20 ps through increasing the extent and slope of the trigger pulse.
As for pulse generators based on gas-switch and SOS-switch, the output of the avalanche transistor pulse is relatively low. To increase its output, the method of power-combining is used. The key point is that the pulse-generator-units must have high stability and time-coherence. The reason why the trigger pulse affects the pulse-generator based on avalanche transistor is analyzed in the paper. And the key influence factors, which are the slope of the trigger pulse, the difference of avalanche transistors and the noise of circuits, are found out. In experiment, the jitter of the pulse-generator and the time-coherence between units are less than 20 ps through increasing the extent and slope of the trigger pulse.
2016,
28: 035002.
doi: 10.11884/HPLPB201628.035002
Abstract:
In this paper, in the case of considering the mutual inductance, the linear, L and U1 connecting structures of the pulse forming network are simulated by PSpice software. At the same time, a three-dimensional model of five different connecting structures of pulse forming network are established and simulated with the transient field-circuit synchronous collaborative simulation methodology. Then, the experiments of the PFNs with the five different connecting structures are carried out. The experimental results reveal that the rise time of PFNs with five different connecting structures is about 45 ns, the pulse half-high widths of the PFNs with U1-type, U2-type and U3-type structures are 166 ns, 158 ns and 154 ns, respectively. And the flat-tops of the output waveform are more fluctuant. Finally, the simulation results obtained by the circuit and transient field-circuit synchronous collaborative simulation methods and the experimental results are analyzed and compared. The results show that the working process and output waveform of the pulse forming network are well simulated with the transient field-circuit synchronous collaborative simulation methodology, and the matching load and the switch inductance in the experiment are bigger than that in the simulation, and it is of great significance that the U-type structure of PFN is conducive to the compact structure and miniaturization of the pulsed power source system in engineering applications.
In this paper, in the case of considering the mutual inductance, the linear, L and U1 connecting structures of the pulse forming network are simulated by PSpice software. At the same time, a three-dimensional model of five different connecting structures of pulse forming network are established and simulated with the transient field-circuit synchronous collaborative simulation methodology. Then, the experiments of the PFNs with the five different connecting structures are carried out. The experimental results reveal that the rise time of PFNs with five different connecting structures is about 45 ns, the pulse half-high widths of the PFNs with U1-type, U2-type and U3-type structures are 166 ns, 158 ns and 154 ns, respectively. And the flat-tops of the output waveform are more fluctuant. Finally, the simulation results obtained by the circuit and transient field-circuit synchronous collaborative simulation methods and the experimental results are analyzed and compared. The results show that the working process and output waveform of the pulse forming network are well simulated with the transient field-circuit synchronous collaborative simulation methodology, and the matching load and the switch inductance in the experiment are bigger than that in the simulation, and it is of great significance that the U-type structure of PFN is conducive to the compact structure and miniaturization of the pulsed power source system in engineering applications.
