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RSS2014 Vol. 26, No. 06
Recommend Articles
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2014,
26: 063001.
doi: 10.11884/HPLPB201426.063001
Abstract:
In order to further improve and optimize the topological structure of the high-power radial line array antenna, increase the power capacity, and satisfy the demand of the vacuum sealing of feed source, a microwave output window suitable for high-power radial line array antenna was designed. The material of the high-power radial line output window is circular ceramic, whose permittivity is 9.4, the thickness of the window is 3 mm, and inner radius of the window is 36 mm. It can realize vacuum sealing of the radial line array antenna feed system between the input coaxial waveguide and the output coaxial waveguide. Under the center frequency of 2.856 GHz, this radial line output windows standing-wave ratio is 1.03, insertion loss is 0.17 dB and power capacity attain about 150 MW.
In order to further improve and optimize the topological structure of the high-power radial line array antenna, increase the power capacity, and satisfy the demand of the vacuum sealing of feed source, a microwave output window suitable for high-power radial line array antenna was designed. The material of the high-power radial line output window is circular ceramic, whose permittivity is 9.4, the thickness of the window is 3 mm, and inner radius of the window is 36 mm. It can realize vacuum sealing of the radial line array antenna feed system between the input coaxial waveguide and the output coaxial waveguide. Under the center frequency of 2.856 GHz, this radial line output windows standing-wave ratio is 1.03, insertion loss is 0.17 dB and power capacity attain about 150 MW.
2014,
26: 063002.
doi: 10.11884/HPLPB201426.063002
Abstract:
A compact low impedance pulse forming module in long pulse linear transformer driver(LTD) working repeatedly is designed by integrating Blumlein pulse forming network（PFN）, switch and linear transformer. In order to optimize configuration, reduce distribution parameters and improve waveform, each module consists of two 20 Blumlein PFN which is designed in L-type. A coaxial switch drives two PFNs, and high voltage pulse feeds symmetrically primary coil of LT. A built-in laser trigger switch is developed for cutting down inductance and decreasing risetime of pulse. Comparatively this switch shortens its down-lead by 50%, and risetime is reduced by 10%. The LTD experimental device of two stages produces pulses with voltage of 240 kV and duration of 180 ns at 25 Hz repetitive rate in a resistance load of 18.5 .
A compact low impedance pulse forming module in long pulse linear transformer driver(LTD) working repeatedly is designed by integrating Blumlein pulse forming network（PFN）, switch and linear transformer. In order to optimize configuration, reduce distribution parameters and improve waveform, each module consists of two 20 Blumlein PFN which is designed in L-type. A coaxial switch drives two PFNs, and high voltage pulse feeds symmetrically primary coil of LT. A built-in laser trigger switch is developed for cutting down inductance and decreasing risetime of pulse. Comparatively this switch shortens its down-lead by 50%, and risetime is reduced by 10%. The LTD experimental device of two stages produces pulses with voltage of 240 kV and duration of 180 ns at 25 Hz repetitive rate in a resistance load of 18.5 .
2014,
26: 063003.
doi: 10.11884/HPLPB201426.063003
Abstract:
In recent experiment about air breakdown induced by high power microwave, when the incident microwave value is set near the breakdown threshold, it can be found that although all the other external conditions are the same, it is not certain that the air breakdown will occur. To solve this problem, the mechanism of air breakdown was studied and we divided air breakdown into two stages, one stage was the appearance of the first free electron in the breakdown region, the other was the avalanche induced by microwave electric field accelerate electron. A novel model combining average electron generation rate model and avalanche breakdown model was proposed to simulate the probability distribution of high power microwave breakdown in air. The air breakdown probability distribution was simulated under conditions similar to the experiments, and the simulated results agreed well with the experiment data.
In recent experiment about air breakdown induced by high power microwave, when the incident microwave value is set near the breakdown threshold, it can be found that although all the other external conditions are the same, it is not certain that the air breakdown will occur. To solve this problem, the mechanism of air breakdown was studied and we divided air breakdown into two stages, one stage was the appearance of the first free electron in the breakdown region, the other was the avalanche induced by microwave electric field accelerate electron. A novel model combining average electron generation rate model and avalanche breakdown model was proposed to simulate the probability distribution of high power microwave breakdown in air. The air breakdown probability distribution was simulated under conditions similar to the experiments, and the simulated results agreed well with the experiment data.
2014,
26: 063004.
doi: 10.11884/HPLPB201426.063004
Abstract:
The design of a separate and plate-inserted mode converter for rectangular TM11-TE10 was presented. A metal flashboard, paralleling the wide edge, was inserted at the middle of the narrow edge, separating the rectangular waveguide into two equal parts, which transformed TE10 modes with reverse phases. A group of metal plates, paralleling the narrow edge, were inserted with the same space, both in two parts. While the difference of metal plates coaxial length between different parts was suitable, the TE10 modes of the two parts got 180 phase difference. Thereafter, the TE10modes from different parts were transformed with the same phase and compounded into one single TE10 mode by an impedance degression part. The mode converter could keep the same axis and transverse size of output port of high-power microwave source driven by sheet election beam. Its axial length was short and had simple and compact structure. The design was validated and preliminarily optimized by software with finite element algorithm. The transmission efficiency reached -0.45 dB, while bandwidth exceeded 10%, meeting the needs of high-power microwave source driven by sheet electron beams. All the results above offer a new technology for the design of high-power microwave generators with sheet electron beams and its radiation system.
The design of a separate and plate-inserted mode converter for rectangular TM11-TE10 was presented. A metal flashboard, paralleling the wide edge, was inserted at the middle of the narrow edge, separating the rectangular waveguide into two equal parts, which transformed TE10 modes with reverse phases. A group of metal plates, paralleling the narrow edge, were inserted with the same space, both in two parts. While the difference of metal plates coaxial length between different parts was suitable, the TE10 modes of the two parts got 180 phase difference. Thereafter, the TE10modes from different parts were transformed with the same phase and compounded into one single TE10 mode by an impedance degression part. The mode converter could keep the same axis and transverse size of output port of high-power microwave source driven by sheet election beam. Its axial length was short and had simple and compact structure. The design was validated and preliminarily optimized by software with finite element algorithm. The transmission efficiency reached -0.45 dB, while bandwidth exceeded 10%, meeting the needs of high-power microwave source driven by sheet electron beams. All the results above offer a new technology for the design of high-power microwave generators with sheet electron beams and its radiation system.
2014,
26: 063005.
doi: 10.11884/HPLPB201426.063005
Abstract:
The integrodifferential equation of instantaneous current and beam kinetic energy are presented. The relationship among the normalized beam current, the kinetic energy of the beam and the normalized distance are calculated using the Matlab-based numerical method including the progressive deduction method, the central difference method and the trapezoidal integration. The normalized factor based on conservation of charge is introduced as well. Finally, the mode strength versus the propagation distance is included.
The integrodifferential equation of instantaneous current and beam kinetic energy are presented. The relationship among the normalized beam current, the kinetic energy of the beam and the normalized distance are calculated using the Matlab-based numerical method including the progressive deduction method, the central difference method and the trapezoidal integration. The normalized factor based on conservation of charge is introduced as well. Finally, the mode strength versus the propagation distance is included.
2014,
26: 063006.
doi: 10.11884/HPLPB201426.063006
Abstract:
In this paper, on the basis of numerical simulation, an X-band dichroic plate for high power microwave combination is designed. With an incidence angle of 45, the reflection efficiency for the dichroic plate is more than 99% from 9 GHz to 9.3 GHz; The transmission efficiency is more than 99% from 9.7 GHz to 10 GHz. The dichroic plate can be used in combination of HPMs with identical polarization. Making use of full wave analysis software, a numerical model of the dichroic plate is established. The field enhancement factor and power handling capacity is also analyzed.
In this paper, on the basis of numerical simulation, an X-band dichroic plate for high power microwave combination is designed. With an incidence angle of 45, the reflection efficiency for the dichroic plate is more than 99% from 9 GHz to 9.3 GHz; The transmission efficiency is more than 99% from 9.7 GHz to 10 GHz. The dichroic plate can be used in combination of HPMs with identical polarization. Making use of full wave analysis software, a numerical model of the dichroic plate is established. The field enhancement factor and power handling capacity is also analyzed.
2014,
26: 063007.
doi: 10.11884/HPLPB201426.063007
Abstract:
The paper presents several ways about antenna gain measurement. Based on high power microwave(HPM) antenna particularity, the change of antenna gain was studied under different pulse widths. The experiments were conducted using narrow pulse signal resource. The antenna gain values under narrow pulse were tested by the way of demarcating the received power under different pulse widths. The experiment shows that the test results are uniform in the cases of continued wave and narrow pulse wave. The experiment proves that HPM antenna gain measurement with pulse width more than 25 ns is as effective as continue wave measurement.
The paper presents several ways about antenna gain measurement. Based on high power microwave(HPM) antenna particularity, the change of antenna gain was studied under different pulse widths. The experiments were conducted using narrow pulse signal resource. The antenna gain values under narrow pulse were tested by the way of demarcating the received power under different pulse widths. The experiment shows that the test results are uniform in the cases of continued wave and narrow pulse wave. The experiment proves that HPM antenna gain measurement with pulse width more than 25 ns is as effective as continue wave measurement.
2014,
26: 063008.
doi: 10.11884/HPLPB201426.063008
Abstract:
The major factor that leads to the damage of electron beam collector in relativistic backward wave oscillators with high magnetic field is analyzed. By tapering stainless steel collectors, the ability of collectors to bear the impact of high current electron beams is improved. In single shot experiment, the effects of electron beam energy density on the surface damage of stainless steel collectors and the generation of microwave are studied. Based on the experimental results, damage threshold range of stainless steel collectors with respect to electron beam energy density is brought forward with the research on the space density distribution of intense electron beams in the foilless diode.
The major factor that leads to the damage of electron beam collector in relativistic backward wave oscillators with high magnetic field is analyzed. By tapering stainless steel collectors, the ability of collectors to bear the impact of high current electron beams is improved. In single shot experiment, the effects of electron beam energy density on the surface damage of stainless steel collectors and the generation of microwave are studied. Based on the experimental results, damage threshold range of stainless steel collectors with respect to electron beam energy density is brought forward with the research on the space density distribution of intense electron beams in the foilless diode.
2014,
26: 063009.
doi: 10.11884/HPLPB201426.063009
Abstract:
A 94 GHz TE11-HE11 mode converter using an iterative synthesis method based on mode-matching technology is presented. The commercial electromagnetic simulation software is used to validate the design. The simulation results meet the requirements of design. The purity of output mode of the converter is over 98% at 88 GHz to 102 GHz, and the highest is 99.1%. The structure of smooth circular waveguide based on waveguide deformation is easy to process, avoiding the disadvantage that corrugated waveguide is easy to breakdown.
A 94 GHz TE11-HE11 mode converter using an iterative synthesis method based on mode-matching technology is presented. The commercial electromagnetic simulation software is used to validate the design. The simulation results meet the requirements of design. The purity of output mode of the converter is over 98% at 88 GHz to 102 GHz, and the highest is 99.1%. The structure of smooth circular waveguide based on waveguide deformation is easy to process, avoiding the disadvantage that corrugated waveguide is easy to breakdown.
2014,
26: 063010.
doi: 10.11884/HPLPB201426.063010
Abstract:
In relativistic backward-wave oscillator(RBWO), electrons bomb on the collector surface under the guiding of magnetic field at some incident angle after the beam-wave interaction. Restriction from guiding magnetic field to electrons was analyzed theoretically, and condition for backscattering electrons escaping from the collector surface was derived. Using Monte Carlo method, energy deposition of electrons was calculated. It was found that restriction from guiding magnetic field to electrons moving inside materials was quite weak, but was extremely strong out of materials. Most of the backscattering electrons strike again on the collector surface due to Larmor precession. Electrons escaping enter into beam-wave interaction area, reducing the efficiency of energy transformation and output of microwave. When enlarging the incident angle of spent electrons, reduction of beam current density and re-bombardment of backscattering electrons result in the drop of the maximum energy deposition density and improvement of bombard-resistance of collectors.
In relativistic backward-wave oscillator(RBWO), electrons bomb on the collector surface under the guiding of magnetic field at some incident angle after the beam-wave interaction. Restriction from guiding magnetic field to electrons was analyzed theoretically, and condition for backscattering electrons escaping from the collector surface was derived. Using Monte Carlo method, energy deposition of electrons was calculated. It was found that restriction from guiding magnetic field to electrons moving inside materials was quite weak, but was extremely strong out of materials. Most of the backscattering electrons strike again on the collector surface due to Larmor precession. Electrons escaping enter into beam-wave interaction area, reducing the efficiency of energy transformation and output of microwave. When enlarging the incident angle of spent electrons, reduction of beam current density and re-bombardment of backscattering electrons result in the drop of the maximum energy deposition density and improvement of bombard-resistance of collectors.
2014,
26: 063011.
doi: 10.11884/HPLPB201426.063011
Abstract:
A novel broadband W-band Flaps antenna phase-shifting element which the crossed-dipole with annulus patches is proposed in this paper. Compared to the conventional sing-layer Flaps antenna element, the novel elements can realize much larger phase variation range and higher precision of phase shift as well as expand the bandwidth of the antennae effectively. Based on this element, a single-layer reflectarray antenna operating at 94 GHz is designed. The simulation exhibits perfect performance in the bandwidth and directivity, the 1-dB gain bandwidth which is close to 10.6% is obtained and the peak gain of the center frequency is 18.2 dBi. This proposed element offers a new way to design single-layer millimeter-wave reflectarray antenna.
A novel broadband W-band Flaps antenna phase-shifting element which the crossed-dipole with annulus patches is proposed in this paper. Compared to the conventional sing-layer Flaps antenna element, the novel elements can realize much larger phase variation range and higher precision of phase shift as well as expand the bandwidth of the antennae effectively. Based on this element, a single-layer reflectarray antenna operating at 94 GHz is designed. The simulation exhibits perfect performance in the bandwidth and directivity, the 1-dB gain bandwidth which is close to 10.6% is obtained and the peak gain of the center frequency is 18.2 dBi. This proposed element offers a new way to design single-layer millimeter-wave reflectarray antenna.
2014,
26: 063012.
doi: 10.11884/HPLPB201426.063012
Abstract:
Based on the particle-in-cell (PIC) simulation method of the first principle, this paper studies the situation about formation and development of the electron process on the dielectric window surface in high power microwave (HPM) devices. We establish a simple two-dimensional model that the TEM wave irradiates the dielectric window surface vertically with the PIC simulation software VORPAL, employ the Vaughans secondary electron emission model, utilize Monte Carlo collision model to deal with the elastic collision, the excitation collision and the ionization collision between electron and background gas, and acquire the electron multipactor images on the dielectric window surface. The simulation results show that the electron number on the dielectric window surface reaches saturation in a period of time and its oscillation frequency is twice as much as that of the incident electric field. Changing the initial emissive number of the seed electrons, the amplitude of the incident electric field and the pressure of the background gas, we can obtain the variation of the electron number on the dielectric window surface in different conditions.
Based on the particle-in-cell (PIC) simulation method of the first principle, this paper studies the situation about formation and development of the electron process on the dielectric window surface in high power microwave (HPM) devices. We establish a simple two-dimensional model that the TEM wave irradiates the dielectric window surface vertically with the PIC simulation software VORPAL, employ the Vaughans secondary electron emission model, utilize Monte Carlo collision model to deal with the elastic collision, the excitation collision and the ionization collision between electron and background gas, and acquire the electron multipactor images on the dielectric window surface. The simulation results show that the electron number on the dielectric window surface reaches saturation in a period of time and its oscillation frequency is twice as much as that of the incident electric field. Changing the initial emissive number of the seed electrons, the amplitude of the incident electric field and the pressure of the background gas, we can obtain the variation of the electron number on the dielectric window surface in different conditions.
2014,
26: 063013.
doi: 10.11884/HPLPB201426.063013
Abstract:
This paper introduces a type of microwave source based on power combining of conventional klystrons and pulse compression. In order to achieve power combing of two high peak power klystrons, a compact planar power combiner was designed. The reflection losses of each ports and the isolation of opposite ports are both more than 45 dB at 2.856 GHz. Combining two 50 MW microwaves, the max surface field of four-port power combiner is about 9.6 MV/m, and the power combing efficiency is more than 99%. A type of eight-port combiner was realized based on two-stage combining of the four-port power combiner, when combining four 50 MW microwaves, the max surface field of the eight-port power combiner is about 13.5 MV/m.
This paper introduces a type of microwave source based on power combining of conventional klystrons and pulse compression. In order to achieve power combing of two high peak power klystrons, a compact planar power combiner was designed. The reflection losses of each ports and the isolation of opposite ports are both more than 45 dB at 2.856 GHz. Combining two 50 MW microwaves, the max surface field of four-port power combiner is about 9.6 MV/m, and the power combing efficiency is more than 99%. A type of eight-port combiner was realized based on two-stage combining of the four-port power combiner, when combining four 50 MW microwaves, the max surface field of the eight-port power combiner is about 13.5 MV/m.
2014,
26: 063014.
doi: 10.11884/HPLPB201426.063014
Abstract:
The damage process and mechanism of the typical AlGaAs/InGaAs structure high electron mobility transistor by injection of 1 GHz microwave signals from the gate were studied with TCAD based on the distribution of the space charge density, electric field, current density and temperature. The results showed that the gate current rapidly increased because of avalanche breakdown which was 4 orders higher than the gate leakage current under small signals and the gate finger was extremely easy to burn and melt by such high current in the positive semi-cycle of microwave signals; the internal peak temperature of the device appeared between the InGaAs channel and gate near the source below the gate; when the amplitude of the microwave signals was high enough, during the fall time of the positive semi-cycle, the second breakdown occurred below the central gate inclining to the drain which caused double-peak phenomenon of the gate current, and the internal peak temperature of the device shifted to the above position and surpassed the GaAs melting point. Failure analysis of high electron mobility transistor devices damaged by microwaves was carried out with scanning electron microscope and the simulation results were well consistent with the experiment results.
The damage process and mechanism of the typical AlGaAs/InGaAs structure high electron mobility transistor by injection of 1 GHz microwave signals from the gate were studied with TCAD based on the distribution of the space charge density, electric field, current density and temperature. The results showed that the gate current rapidly increased because of avalanche breakdown which was 4 orders higher than the gate leakage current under small signals and the gate finger was extremely easy to burn and melt by such high current in the positive semi-cycle of microwave signals; the internal peak temperature of the device appeared between the InGaAs channel and gate near the source below the gate; when the amplitude of the microwave signals was high enough, during the fall time of the positive semi-cycle, the second breakdown occurred below the central gate inclining to the drain which caused double-peak phenomenon of the gate current, and the internal peak temperature of the device shifted to the above position and surpassed the GaAs melting point. Failure analysis of high electron mobility transistor devices damaged by microwaves was carried out with scanning electron microscope and the simulation results were well consistent with the experiment results.
2014,
26: 063015.
doi: 10.11884/HPLPB201426.063015
Abstract:
This paper constructs a two-stages PIN limiter with high power microwave(HPM) effect circuit model based on PIN diode electro-thermal self-consistent coupling model. According to the simulation model we design and fabricate two-stage PIN limiter experiment samples, the injected experimental data of input and output characteristics of limiter are basically identical to simulation results which have verified the effectiveness of the multi-stage limiter model and showed that multi-stage PIN limiter model established in this paper can be applied to HPM effect simulation. Simulated using different HPM waveform parameters for the HPM effect, the calculated results indicate that the junction temperature of pre-stage thick I layer PIN diode is higher than that of the post-stage thin I layer PIN diode with the increase of injected power and pulse width, so the thick I layer PIN diode is more susceptible to damage; the frequency and pulse rising time have less influence on junction temperature. Research results have a certain reference for HPM protection of PIN limiter.
This paper constructs a two-stages PIN limiter with high power microwave(HPM) effect circuit model based on PIN diode electro-thermal self-consistent coupling model. According to the simulation model we design and fabricate two-stage PIN limiter experiment samples, the injected experimental data of input and output characteristics of limiter are basically identical to simulation results which have verified the effectiveness of the multi-stage limiter model and showed that multi-stage PIN limiter model established in this paper can be applied to HPM effect simulation. Simulated using different HPM waveform parameters for the HPM effect, the calculated results indicate that the junction temperature of pre-stage thick I layer PIN diode is higher than that of the post-stage thin I layer PIN diode with the increase of injected power and pulse width, so the thick I layer PIN diode is more susceptible to damage; the frequency and pulse rising time have less influence on junction temperature. Research results have a certain reference for HPM protection of PIN limiter.
2014,
26: 063016.
doi: 10.11884/HPLPB201426.063016
Abstract:
According to the working principle of switching power supply, an external circuit model of bus bar was built. The simulation of field-circuit coupling with the model of bus bar was carried out, and the current density distribution and ohmic loss distribution under the conditions of the bus bar in the actual excitation were obtained, using the finite-element simulation. The concentrated areas of ohmic loss of the bus bar was analyzed, and the structure of the bus bar was optimized on the basis of the analysis, and the current density and the ohmic losses were decreased.
According to the working principle of switching power supply, an external circuit model of bus bar was built. The simulation of field-circuit coupling with the model of bus bar was carried out, and the current density distribution and ohmic loss distribution under the conditions of the bus bar in the actual excitation were obtained, using the finite-element simulation. The concentrated areas of ohmic loss of the bus bar was analyzed, and the structure of the bus bar was optimized on the basis of the analysis, and the current density and the ohmic losses were decreased.
2014,
26: 063017.
doi: 10.11884/HPLPB201426.063017
Abstract:
A new-type of electromagnetic modeling technology for high power microwave (HPM) transmission and radiation structures with large electrical-size and thick radome is studied. Hybrid equations are established by combining mode-matching and integral equation method. Multilevel fast multipole algorithm and preconditioners are used to accelerate this method. Some numerical examples are given out to validate the accuracy and the applicability, including flare-angle-tapered feed horn, power-combined antenna, beam waveguide and beam-waveguide antenna system. Far-field patterns and near-field power density distributions are simulated. The simulation results show that this new technology can fit the boundaries and model the feeding mode accurately. Computer memory cost is reduced using this method. Applicability and ascendant of this method are validated. Some aspects which can be improved are also discussed in this paper.
A new-type of electromagnetic modeling technology for high power microwave (HPM) transmission and radiation structures with large electrical-size and thick radome is studied. Hybrid equations are established by combining mode-matching and integral equation method. Multilevel fast multipole algorithm and preconditioners are used to accelerate this method. Some numerical examples are given out to validate the accuracy and the applicability, including flare-angle-tapered feed horn, power-combined antenna, beam waveguide and beam-waveguide antenna system. Far-field patterns and near-field power density distributions are simulated. The simulation results show that this new technology can fit the boundaries and model the feeding mode accurately. Computer memory cost is reduced using this method. Applicability and ascendant of this method are validated. Some aspects which can be improved are also discussed in this paper.
2014,
26: 063018.
doi: 10.11884/HPLPB201426.063018
Abstract:
The electromagnetic pulse effect mechanism of PIN limiter is analyzed，and the devices multi-physical field model is established with software Sentaurus-TCAD. The input/output power curve, indicating the increase in flat leakage with increasing input power, is studied, and the simulation results are in good agreement with the experimental ones. The influence of electromagnetic pulse width on the diodes damage is simulated. Adopting the data analysis software, the relation equation between the device damage power and the pulse width under different injecting power is obtained. It is analyzed using Wunsch and Bell developed semi-empirical relationships.
The electromagnetic pulse effect mechanism of PIN limiter is analyzed，and the devices multi-physical field model is established with software Sentaurus-TCAD. The input/output power curve, indicating the increase in flat leakage with increasing input power, is studied, and the simulation results are in good agreement with the experimental ones. The influence of electromagnetic pulse width on the diodes damage is simulated. Adopting the data analysis software, the relation equation between the device damage power and the pulse width under different injecting power is obtained. It is analyzed using Wunsch and Bell developed semi-empirical relationships.
2014,
26: 063019.
doi: 10.11884/HPLPB201426.063019
Abstract:
To meet the needs for assembling, a kind of TE01 miter bend structure is designed and analyzed, which is composed of two perpendicular mode converting circular waveguides and a metal mirror that has a 45 angle with the center line of each circular waveguide. The whole structure is equivalent to a combination of two mode converting parts with a gap in the middle, where the length of the gap is equal to the diameter of the circular waveguide. The mode converting part converts TE01 mode into the mixed mode of TE01 and TE02, whose E-field has a symmetry distribution when propagating through the gap. As a result, the transmission loss is reduced and the efficiency is increased. A Ka band TE01 miter bend circular waveguide was designed, the simulation results obtained from CST match the measured results well. They both show that the transmission efficiency is above 98 % at the center frequency, the insert loss is below 0.2 dB and the VSWR is below 1.2 with the transmission efficiency greater than 95 % in 2 GHz band.
To meet the needs for assembling, a kind of TE01 miter bend structure is designed and analyzed, which is composed of two perpendicular mode converting circular waveguides and a metal mirror that has a 45 angle with the center line of each circular waveguide. The whole structure is equivalent to a combination of two mode converting parts with a gap in the middle, where the length of the gap is equal to the diameter of the circular waveguide. The mode converting part converts TE01 mode into the mixed mode of TE01 and TE02, whose E-field has a symmetry distribution when propagating through the gap. As a result, the transmission loss is reduced and the efficiency is increased. A Ka band TE01 miter bend circular waveguide was designed, the simulation results obtained from CST match the measured results well. They both show that the transmission efficiency is above 98 % at the center frequency, the insert loss is below 0.2 dB and the VSWR is below 1.2 with the transmission efficiency greater than 95 % in 2 GHz band.
2014,
26: 063020.
doi: 10.11884/HPLPB201426.063020
Abstract:
In order to achieve beam scanning of mechanical phased array antenna, the stepper motor is adopted to drive a helical antenna element to rotate to a predetermined radiation phase. In order to optimize the open-loop control strategy of stepper, and improve the control speed and accuracy, the influence of running curve on the stepper motor control performance was studied. According to operating principle of stepper motor control system, a simulation model of stepper motor open-loop control system was constituted based on Simulink, and on this basis, the two trapezoidal and parabolic running curves were simulated. The simulation results show that, the control of running curve to the stepper motor was achieved accurately in the simulation model. Using trapezoidal running curve in the control cycle of 100 ms, the maximum rotation angle of the stepper motor can reach 270. Using parabolic running curve, the maximum rotation angle of the stepper motor can reach 360. Parabolic running curve has better control velocity in open-loop control system.
In order to achieve beam scanning of mechanical phased array antenna, the stepper motor is adopted to drive a helical antenna element to rotate to a predetermined radiation phase. In order to optimize the open-loop control strategy of stepper, and improve the control speed and accuracy, the influence of running curve on the stepper motor control performance was studied. According to operating principle of stepper motor control system, a simulation model of stepper motor open-loop control system was constituted based on Simulink, and on this basis, the two trapezoidal and parabolic running curves were simulated. The simulation results show that, the control of running curve to the stepper motor was achieved accurately in the simulation model. Using trapezoidal running curve in the control cycle of 100 ms, the maximum rotation angle of the stepper motor can reach 270. Using parabolic running curve, the maximum rotation angle of the stepper motor can reach 360. Parabolic running curve has better control velocity in open-loop control system.
2014,
26: 063021.
doi: 10.11884/HPLPB201426.063021
Abstract:
The influences of key parameters on the width of output pulses generated by a semiconductor opening switch (SOS) with p+-p-n-n+ structure were numerically studied using Silvaco TCAD tools, including diffusion depth of n+ region, effective cross-sectional area, external circuit parameters, etc. The simulation results show that the width of output pulses decrease with the increasing of the diffusion depth of n+ region, effective cross-sectional area and the resistance of external circuits. After a series of parameter optimizations, the output pulse with 4 ns width could be obtained.
The influences of key parameters on the width of output pulses generated by a semiconductor opening switch (SOS) with p+-p-n-n+ structure were numerically studied using Silvaco TCAD tools, including diffusion depth of n+ region, effective cross-sectional area, external circuit parameters, etc. The simulation results show that the width of output pulses decrease with the increasing of the diffusion depth of n+ region, effective cross-sectional area and the resistance of external circuits. After a series of parameter optimizations, the output pulse with 4 ns width could be obtained.
2014,
26: 063022.
doi: 10.11884/HPLPB201426.063022
Abstract:
The traceability and uncertainty of ultra-wideband short pulse(UWB-SP) electric-field standard device was researched in this paper. There is no UWB-SP E-field national primary standard, we got the traceability of E-field from pulse parameters, S parameters and dimension parameters national primary standard. The mathematic model of the E-field was established. We evaluated the uncertainty of the source output, the uncertainty of transmission and the uncertainty of structure dimensions, than we calculated the combined standard uncertainty. Finally, the expanded uncertainty of the E-field produced by the standard device was 8.4%.
The traceability and uncertainty of ultra-wideband short pulse(UWB-SP) electric-field standard device was researched in this paper. There is no UWB-SP E-field national primary standard, we got the traceability of E-field from pulse parameters, S parameters and dimension parameters national primary standard. The mathematic model of the E-field was established. We evaluated the uncertainty of the source output, the uncertainty of transmission and the uncertainty of structure dimensions, than we calculated the combined standard uncertainty. Finally, the expanded uncertainty of the E-field produced by the standard device was 8.4%.
2014,
26: 063023.
doi: 10.11884/HPLPB201426.063023
Abstract:
Carbon nanotube (CNT) which has excellent field emission characteristics can be an ideal cathode material for the field emission devices. Based on experimental test results, the field emission properties of large area carbon nanotube cold cathode are investigated using the three dimensional PIC simulation software. The impact on field emission characteristic and the pass rate of electron beam with different dimensions of planar mesh grid structure are studied. On this basis of optimized mesh grid structure, a sheet beam electron gun with carbon nanotube cold cathode is designed, whose compression ratio of area is 18 and the output current density is 14.9 A/cm2.
Carbon nanotube (CNT) which has excellent field emission characteristics can be an ideal cathode material for the field emission devices. Based on experimental test results, the field emission properties of large area carbon nanotube cold cathode are investigated using the three dimensional PIC simulation software. The impact on field emission characteristic and the pass rate of electron beam with different dimensions of planar mesh grid structure are studied. On this basis of optimized mesh grid structure, a sheet beam electron gun with carbon nanotube cold cathode is designed, whose compression ratio of area is 18 and the output current density is 14.9 A/cm2.
2014,
26: 063024.
doi: 10.11884/HPLPB201426.063024
Abstract:
Combing 2-port network theory with Mixed Potentials Integral Equation and Method of Moments (MPIE-MoM), the equivalent source of electromagnetic pulse coupling effects of shielding with cables is modeled. Taking a Gaussian pulse for example, the electromagnetic sensitivity of the internal circuits is analyzed using the field-circuit method. The simulated results of the presented method tallies well with that with the commercial software in the frequency range of 0.1-7.5 GHz, which provides theory reference to the quantitative analysis of the electromagnetic pulse coupling effect and the circuit safety protection in complex electromagnetic interference irradiation environment.
Combing 2-port network theory with Mixed Potentials Integral Equation and Method of Moments (MPIE-MoM), the equivalent source of electromagnetic pulse coupling effects of shielding with cables is modeled. Taking a Gaussian pulse for example, the electromagnetic sensitivity of the internal circuits is analyzed using the field-circuit method. The simulated results of the presented method tallies well with that with the commercial software in the frequency range of 0.1-7.5 GHz, which provides theory reference to the quantitative analysis of the electromagnetic pulse coupling effect and the circuit safety protection in complex electromagnetic interference irradiation environment.
2014,
26: 063025.
doi: 10.11884/HPLPB201426.063025
Abstract:
In this paper, the V-band circular TE01 mode transducer consisting of a TE10-TE20 mode converter and a TE20-TE01 mode converter is studied. This paper describes a novel TE10-TE20 mode transducer utilizing an H-plane right-angled corner composed of a standard waveguide and an overmoded one. According to the electric field characteristic of the TE0,1 mode, we achieve TE20 rectangular waveguide mode to a TE01 circular waveguide mode by oval-waveguide. The calculation results obtained from the HFSS show that the transducer maximum conversion efficiency could reach 99.08% at 43.4 GHz with a purity of 99.20%，the bandwidth for conversion efficiency beyond than 95% with mode purity over than 98% is about 4.2 GHz. The transducer has high conversion efficiency, simple structure, and it is easy to fabricate. a design can be applied to the low-power test for the high-power microwave devices.
In this paper, the V-band circular TE01 mode transducer consisting of a TE10-TE20 mode converter and a TE20-TE01 mode converter is studied. This paper describes a novel TE10-TE20 mode transducer utilizing an H-plane right-angled corner composed of a standard waveguide and an overmoded one. According to the electric field characteristic of the TE0,1 mode, we achieve TE20 rectangular waveguide mode to a TE01 circular waveguide mode by oval-waveguide. The calculation results obtained from the HFSS show that the transducer maximum conversion efficiency could reach 99.08% at 43.4 GHz with a purity of 99.20%，the bandwidth for conversion efficiency beyond than 95% with mode purity over than 98% is about 4.2 GHz. The transducer has high conversion efficiency, simple structure, and it is easy to fabricate. a design can be applied to the low-power test for the high-power microwave devices.
2014,
26: 063026.
doi: 10.11884/HPLPB201426.063026
Abstract:
Air-breakdown is a key problem for high power microwave(HPM) propagating. On one hand, field distribution of HPM antenna at near-field region exists in oscillating wave style, and some peak points will occur at local area, thus a series of problems occur, such as air-breakdown at near-field region, dielectric surface breakdown, etc. On the other hand, air-breakdown at far-field region must be considered for the improvement of single HPM sources and the development of power combining technology. The method and criterion to judge the air-breakdown should be studied. This paper presents the way based on the curves regular of air-breakdown threshold and antenna field distribution with the altitude. When initial field value is less than the air-breakdown threshold in the corresponding, and two curves exist at the intersection point, then air-breakdown may be in the propagating route while it will not occur in the near field region of antenna. The result is proved in related experiments.
Air-breakdown is a key problem for high power microwave(HPM) propagating. On one hand, field distribution of HPM antenna at near-field region exists in oscillating wave style, and some peak points will occur at local area, thus a series of problems occur, such as air-breakdown at near-field region, dielectric surface breakdown, etc. On the other hand, air-breakdown at far-field region must be considered for the improvement of single HPM sources and the development of power combining technology. The method and criterion to judge the air-breakdown should be studied. This paper presents the way based on the curves regular of air-breakdown threshold and antenna field distribution with the altitude. When initial field value is less than the air-breakdown threshold in the corresponding, and two curves exist at the intersection point, then air-breakdown may be in the propagating route while it will not occur in the near field region of antenna. The result is proved in related experiments.
2014,
26: 063027.
doi: 10.11884/HPLPB201426.063027
Abstract:
Direct-quadrature(D-Q) coordinate transformation is an effective circuit modeling method which is often used in three-phase circuit equivalent transformation. In this paper, a method which constructs a virtual orthogonal circuit is used to derivate the D-Q equivalent circuit of the single-phase parallel resonant converter in D-Q rotating coordinate. The transfer function of the equivalent circuit is solved. And it is verified that the derived D-Q equivalent circuit can accurately represent the original converter circuit by simulation. Based on this conclusion, by the transfer function of the D-Q equivalent circuit, the output LC filter parameters of a single-phase parallel resonant converter is designed, meeting the output voltage pulse less than 50 s edge, less than 5% overshoot, less than 100 s settling time and less than 5% ripple. It is proved that the method used to design the parallel resonant converter output LC filter parameters is feasible.
Direct-quadrature(D-Q) coordinate transformation is an effective circuit modeling method which is often used in three-phase circuit equivalent transformation. In this paper, a method which constructs a virtual orthogonal circuit is used to derivate the D-Q equivalent circuit of the single-phase parallel resonant converter in D-Q rotating coordinate. The transfer function of the equivalent circuit is solved. And it is verified that the derived D-Q equivalent circuit can accurately represent the original converter circuit by simulation. Based on this conclusion, by the transfer function of the D-Q equivalent circuit, the output LC filter parameters of a single-phase parallel resonant converter is designed, meeting the output voltage pulse less than 50 s edge, less than 5% overshoot, less than 100 s settling time and less than 5% ripple. It is proved that the method used to design the parallel resonant converter output LC filter parameters is feasible.
2014,
26: 063029.
doi: 10.11884/HPLPB201426.063029
Abstract:
Using plasma fluid theory, from linear perturbation equations, the effect of the beam current size on the dispersion relation of plasma-filled dielectric Cherenkov maser is examined when the beam current is complete, or not effectively neutralized by the return current in the background plasma. The dispersion relation and the wave growth of the TM0n are solved under both cases. Based on this, a discussion on the effect of the beam current on the dispersion relation and wave growth is given. Both of the cases of plasma return current can or not effectively neutralized electron beams current has different dispersion relation and wave growth. When the parameters of waveguide and plasma are fixed, the electron beam current is not the bigger the better, too large electron beam current is harmful for improving the efficiency of the device, and there has an optimal matching relationship between them.
Using plasma fluid theory, from linear perturbation equations, the effect of the beam current size on the dispersion relation of plasma-filled dielectric Cherenkov maser is examined when the beam current is complete, or not effectively neutralized by the return current in the background plasma. The dispersion relation and the wave growth of the TM0n are solved under both cases. Based on this, a discussion on the effect of the beam current on the dispersion relation and wave growth is given. Both of the cases of plasma return current can or not effectively neutralized electron beams current has different dispersion relation and wave growth. When the parameters of waveguide and plasma are fixed, the electron beam current is not the bigger the better, too large electron beam current is harmful for improving the efficiency of the device, and there has an optimal matching relationship between them.
2014,
26: 063030.
doi: 10.11884/HPLPB201426.063030
Abstract:
A Ku-band helix traveling-wave tube (TWT) is designed using theoretical analysis and simulation. The effect of the variation in inner radius on dispersion and coupled impedance is analyzed to optimize the slow-wave structure of helix TWT. The input and output structure of TWT is simulated, the input reflecting coefficient is less than -19 dB and the voltage standing wave ratio (VSWR) is less than 1.24. Periodic permanent-magnetic field is used as electromagnetic focusing system, the magnetic system period is 8.5 mm and the magnetic peak value is 0.17 T. The slow-wave circuit with property of dynamic velocity tapper (DVT) is used to increase the interaction efficiency, it can provide enough time for the interaction of beam and high-frequency field and make electrons continuously transport energy to high-frequency field. The helix TWT is simulated using a three-dimensional particle-in-cell (PIC) code. The simulation results demonstrate that the output power is bigger than 88.7 W, the electron efficiency is bigger than 14.8% and the saturated gain is bigger than 34.6 dB in the frequency range from 12.5 to 16.0 GHz.
A Ku-band helix traveling-wave tube (TWT) is designed using theoretical analysis and simulation. The effect of the variation in inner radius on dispersion and coupled impedance is analyzed to optimize the slow-wave structure of helix TWT. The input and output structure of TWT is simulated, the input reflecting coefficient is less than -19 dB and the voltage standing wave ratio (VSWR) is less than 1.24. Periodic permanent-magnetic field is used as electromagnetic focusing system, the magnetic system period is 8.5 mm and the magnetic peak value is 0.17 T. The slow-wave circuit with property of dynamic velocity tapper (DVT) is used to increase the interaction efficiency, it can provide enough time for the interaction of beam and high-frequency field and make electrons continuously transport energy to high-frequency field. The helix TWT is simulated using a three-dimensional particle-in-cell (PIC) code. The simulation results demonstrate that the output power is bigger than 88.7 W, the electron efficiency is bigger than 14.8% and the saturated gain is bigger than 34.6 dB in the frequency range from 12.5 to 16.0 GHz.
2014,
26: 063031.
doi: 10.11884/HPLPB201426.063031
Abstract:
When the operating frequency goes into higher band, the traditional high power microwave (HPM) generators are of smaller size and can support less power capacity and space-charge limiting. In order to solve these difficulties, a Ku-band coaxial transit-time oscillator was proposed. Using a coaxial structure, the space-charge limiting current and power capacity of the proposed device can be increased significantly. In comparison with a dual-cavity buncher, this proposed device with a trinal-cavity buncher can lead to a higher degree of beam current modulation. By using high frequency field software, the cold-cavity analysis was performed for buncher and extractor. The proposed oscillator was designed and optimized by a particle-in-cell (PIC) code. With the voltage 392 kV, the current 15.2 kA and the guiding magnetic field 0.6 T, the output power was 1.2 GW at the main frequency 14.184 GHz, and the efficiency of beam-to-microwave power conversion was about 20%.
When the operating frequency goes into higher band, the traditional high power microwave (HPM) generators are of smaller size and can support less power capacity and space-charge limiting. In order to solve these difficulties, a Ku-band coaxial transit-time oscillator was proposed. Using a coaxial structure, the space-charge limiting current and power capacity of the proposed device can be increased significantly. In comparison with a dual-cavity buncher, this proposed device with a trinal-cavity buncher can lead to a higher degree of beam current modulation. By using high frequency field software, the cold-cavity analysis was performed for buncher and extractor. The proposed oscillator was designed and optimized by a particle-in-cell (PIC) code. With the voltage 392 kV, the current 15.2 kA and the guiding magnetic field 0.6 T, the output power was 1.2 GW at the main frequency 14.184 GHz, and the efficiency of beam-to-microwave power conversion was about 20%.
2014,
26: 063032.
doi: 10.11884/HPLPB201426.063032
Abstract:
The O-type Cerenkov devices usually use a section of finite-length slow wave structure (SWS) as the core region of beam-wave interaction, the longitudinal resonances occur when the electromagnetic wave is reflected at the terminal of SWS and affect the beam-wave interaction of the device, and as a result investigating the high-frequency characteristics of finite-length slow-wave structure is important for the designing of O-type Cerenkov devices structure. Using the field-matching method, the expression for the reflection coefficient of electromagnetic wave reflected at the intersection face of straight waveguide and SWS was derived, and the relationships between the reflection coefficient and the longitudinal wave number and SWS terminal phase were acquired. Then using the transmission line theory and the calculation results of reflection coefficient, the longitudinal resonant condition in finite-length SWS was brought forward, and using this method we analyzed the longitudinal resonances in finite-length SWS. We calculated the longitudinal resonant frequencies of a section of finite-length SWS. Theoretical and simulation results were close to each other. The resonant frequencies of a type of nonuniform SWS cold cavity were simulated; the frequencies and field distribution of the resonant mode in nonuniform SWS were close to the relevant uniform SWS. Consequently the longitudinal resonant condition could also be used for the analysis of nonuniform SWS with finite length.
The O-type Cerenkov devices usually use a section of finite-length slow wave structure (SWS) as the core region of beam-wave interaction, the longitudinal resonances occur when the electromagnetic wave is reflected at the terminal of SWS and affect the beam-wave interaction of the device, and as a result investigating the high-frequency characteristics of finite-length slow-wave structure is important for the designing of O-type Cerenkov devices structure. Using the field-matching method, the expression for the reflection coefficient of electromagnetic wave reflected at the intersection face of straight waveguide and SWS was derived, and the relationships between the reflection coefficient and the longitudinal wave number and SWS terminal phase were acquired. Then using the transmission line theory and the calculation results of reflection coefficient, the longitudinal resonant condition in finite-length SWS was brought forward, and using this method we analyzed the longitudinal resonances in finite-length SWS. We calculated the longitudinal resonant frequencies of a section of finite-length SWS. Theoretical and simulation results were close to each other. The resonant frequencies of a type of nonuniform SWS cold cavity were simulated; the frequencies and field distribution of the resonant mode in nonuniform SWS were close to the relevant uniform SWS. Consequently the longitudinal resonant condition could also be used for the analysis of nonuniform SWS with finite length.
2014,
26: 063033.
doi: 10.11884/HPLPB201426.063033
Abstract:
The preliminary design of a Ka-band extended interaction klystron is presented with three-dimensional particle-in-cell(PIC) code. The extended interaction technology is widely adopted in resonant cavities used for high power, high gain, and bandwith applications. The electron gun and the focusing system are separately designed and optimized, where a permanent magnetic focusing scheme is introduced. The klystron is driven by a 0.15 A, 9 kV round-electron beam. An output average power of 355 W is achieved with an input power of 200 mW, corresponding to the gain of 32.5 dB , the efficiency of 26%, and the bandwith of 410 MHz at the centeral frequency.
The preliminary design of a Ka-band extended interaction klystron is presented with three-dimensional particle-in-cell(PIC) code. The extended interaction technology is widely adopted in resonant cavities used for high power, high gain, and bandwith applications. The electron gun and the focusing system are separately designed and optimized, where a permanent magnetic focusing scheme is introduced. The klystron is driven by a 0.15 A, 9 kV round-electron beam. An output average power of 355 W is achieved with an input power of 200 mW, corresponding to the gain of 32.5 dB , the efficiency of 26%, and the bandwith of 410 MHz at the centeral frequency.
2014,
26: 063034.
doi: 10.11884/HPLPB201426.063034
Abstract:
Uniform magnetic focusing system adopts three coil and a pureironto realize gradient uniform magnetic field distribution. The model of magnetic field is built and analyzed by utilizing FEMM (Finite Element Method Magnetics) simulation software, according to the theoretical calculation of the electrostatic gun with uniform focusing magnetic field. CST simulation of the electron gun shows that the perveance of the electron gun is 0.175 P and the cathode emission current density is less than 10 A/cm2 and the anode voltage is 17 kV, under conditions of the magnetic field 0.7 T. CST simulation software optimizes the transmission of electron beam to get the results. The results shows that gun parameter compression ratio is about 32, the beam current density is 343.17 A/cm2, and the electronic beam transverse longitudinal velocity ratio is 7.2%.
Uniform magnetic focusing system adopts three coil and a pureironto realize gradient uniform magnetic field distribution. The model of magnetic field is built and analyzed by utilizing FEMM (Finite Element Method Magnetics) simulation software, according to the theoretical calculation of the electrostatic gun with uniform focusing magnetic field. CST simulation of the electron gun shows that the perveance of the electron gun is 0.175 P and the cathode emission current density is less than 10 A/cm2 and the anode voltage is 17 kV, under conditions of the magnetic field 0.7 T. CST simulation software optimizes the transmission of electron beam to get the results. The results shows that gun parameter compression ratio is about 32, the beam current density is 343.17 A/cm2, and the electronic beam transverse longitudinal velocity ratio is 7.2%.
2014,
26: 063035.
doi: 10.11884/HPLPB201426.063035
Abstract:
For the leakage model of high-power radial line array antenna in no pressure difference conditions, equivalent area method is used to equal the seal structure. Numerical simulations are carried out on the leakage process by using software which is based on the finite volume method, and the results are verified by the tightness experiment. Researches show that the numerical simulations are consistent with the experimental trends, proving the correctness of the numerical simulation. The numerical simulation is faster, more cost-effective and can obtain internal gas parameter distribution.
For the leakage model of high-power radial line array antenna in no pressure difference conditions, equivalent area method is used to equal the seal structure. Numerical simulations are carried out on the leakage process by using software which is based on the finite volume method, and the results are verified by the tightness experiment. Researches show that the numerical simulations are consistent with the experimental trends, proving the correctness of the numerical simulation. The numerical simulation is faster, more cost-effective and can obtain internal gas parameter distribution.
2014,
26: 063036.
doi: 10.11884/HPLPB201426.063036
Abstract:
A new beam premodulation structure of the coaxial virtual cathode oscillator is proposed and numerically studied. Radial beam premodulation type coaxial virtual cathode oscillator has a metal ring in beam-wave interaction region forming a resonant cavity which changes the electric field distribution of the beam-wave interaction region and modulates the electron beam. The electric field generated by the buncher both modulates the electron beam, and locks the microwave frequency. The resonant frequency is dominated by the length of the metal cylinder and the radial distance between the two cylinders. Through optimization, applying a 600 kV voltage at 73 kA current without external guiding magnetic field, the generated microwave has an average power of 6.00 GW at 2.575 GHz operating frequency, the conversion efficiency reaches 13.94%.
A new beam premodulation structure of the coaxial virtual cathode oscillator is proposed and numerically studied. Radial beam premodulation type coaxial virtual cathode oscillator has a metal ring in beam-wave interaction region forming a resonant cavity which changes the electric field distribution of the beam-wave interaction region and modulates the electron beam. The electric field generated by the buncher both modulates the electron beam, and locks the microwave frequency. The resonant frequency is dominated by the length of the metal cylinder and the radial distance between the two cylinders. Through optimization, applying a 600 kV voltage at 73 kA current without external guiding magnetic field, the generated microwave has an average power of 6.00 GW at 2.575 GHz operating frequency, the conversion efficiency reaches 13.94%.
2014,
26: 063037.
doi: 10.11884/HPLPB201426.063037
Abstract:
An relativistic backward wave oscillator (RBWO) with trapezium slow wave structure is studied. Properties of the RBWO are investigated and optimized by the 2.5-dimensional fully electromagnetic PIC software. An external microwave signal is injected into the RBWO from diode area. When the injected power is 50 kW, and the injected power ratio is －48.3 dB, the relative phase between the RBWO output microwave and the injected signal is less than 20. The formula that describes the relationship between the RBWO output microwave phase jitter and the injected power is given. When the injected power is increased to 120 MW, and the injected power ratio is increased to －14.5 dB, the frequency of the RBWO output microwave is locked.
An relativistic backward wave oscillator (RBWO) with trapezium slow wave structure is studied. Properties of the RBWO are investigated and optimized by the 2.5-dimensional fully electromagnetic PIC software. An external microwave signal is injected into the RBWO from diode area. When the injected power is 50 kW, and the injected power ratio is －48.3 dB, the relative phase between the RBWO output microwave and the injected signal is less than 20. The formula that describes the relationship between the RBWO output microwave phase jitter and the injected power is given. When the injected power is increased to 120 MW, and the injected power ratio is increased to －14.5 dB, the frequency of the RBWO output microwave is locked.
2014,
26: 063038.
doi: 10.11884/HPLPB201426.063038
Abstract:
Multiple-beam relativistic klystrons use multiple parallel beamlets that propagate in individual channels but interact in common cavity gaps. Multiple-beam operation takes advantage of the low current and small radius of individual beamlet to avoid non-working mode oscillation and enable more efficient bunching and consequently higher efficiency. A small-signal theory of multiple-beam relativistic klystrons is developed and validated by simulation. The method of calculating the beam coupling coefficient is studied, assuming that the electric field is a function of gap distance. Properties of current modulation are investigated, obtaining a expression of scaling law for the fundamental component of the bunching current. The results indicate that the amplitude of the beam coupling coefficient is higher in the coaxial cavity, which is better for beam-wave interaction. The influences of potential energy of individual beamlet on current modulation are crucial, using more annular electron beams helps to have a bigger amplitude of ac current. Making use of electron beams of 600 kV/5 kA, gap voltage of 30 kV, the ac current of multiple beamlets can reach 800 A behind the input cavity.
Multiple-beam relativistic klystrons use multiple parallel beamlets that propagate in individual channels but interact in common cavity gaps. Multiple-beam operation takes advantage of the low current and small radius of individual beamlet to avoid non-working mode oscillation and enable more efficient bunching and consequently higher efficiency. A small-signal theory of multiple-beam relativistic klystrons is developed and validated by simulation. The method of calculating the beam coupling coefficient is studied, assuming that the electric field is a function of gap distance. Properties of current modulation are investigated, obtaining a expression of scaling law for the fundamental component of the bunching current. The results indicate that the amplitude of the beam coupling coefficient is higher in the coaxial cavity, which is better for beam-wave interaction. The influences of potential energy of individual beamlet on current modulation are crucial, using more annular electron beams helps to have a bigger amplitude of ac current. Making use of electron beams of 600 kV/5 kA, gap voltage of 30 kV, the ac current of multiple beamlets can reach 800 A behind the input cavity.
2014,
26: 063039.
doi: 10.11884/HPLPB201426.063039
Abstract:
The high power microwave system simulation platform produces large scale of complex time-varying data that bring forward new needs of data storage and process. But the existed data management methods can not provide the abilities that satisfy the platforms requirements for data storage, accessing and analysis. After deep researching on scientific data representation, metadata management, high performance I/O, parallel processing and quick searching, we have developed scientific data management software tools to integrate these technologies. As a result, data generated by the high power microwave virtual experiments could be efficiently stored, organized and managed, which have good supporting effects in promoting sub-system data exchanging, accelerating data I/O efficiency and exploring important physical problems.
The high power microwave system simulation platform produces large scale of complex time-varying data that bring forward new needs of data storage and process. But the existed data management methods can not provide the abilities that satisfy the platforms requirements for data storage, accessing and analysis. After deep researching on scientific data representation, metadata management, high performance I/O, parallel processing and quick searching, we have developed scientific data management software tools to integrate these technologies. As a result, data generated by the high power microwave virtual experiments could be efficiently stored, organized and managed, which have good supporting effects in promoting sub-system data exchanging, accelerating data I/O efficiency and exploring important physical problems.
2014,
26: 063040.
doi: 10.11884/HPLPB201426.063040
Abstract:
The paper introduces the design, calibration, test and application of the circular directional couplers. Taking X-band directional coupler as an example, the structure parameters are numerically optimized based on the small-aperture coupling theory. Its coupling coefficient can be stabilized within (552) dB and the corresponding isolating coefficient is greater than 80 dB. According to the numerical result, the X-band directional coupler is machined and tested. The result agrees well with that of simulation. Further high power microwave (HPM) experiment demonstrates that the coupler is of high power handle capacity and can satisfy the experimental requirements. Such directional couplers have been widely used in our online measurement of the HPM devices.
The paper introduces the design, calibration, test and application of the circular directional couplers. Taking X-band directional coupler as an example, the structure parameters are numerically optimized based on the small-aperture coupling theory. Its coupling coefficient can be stabilized within (552) dB and the corresponding isolating coefficient is greater than 80 dB. According to the numerical result, the X-band directional coupler is machined and tested. The result agrees well with that of simulation. Further high power microwave (HPM) experiment demonstrates that the coupler is of high power handle capacity and can satisfy the experimental requirements. Such directional couplers have been widely used in our online measurement of the HPM devices.
2014,
26: 063041.
doi: 10.11884/HPLPB201426.063041
Abstract:
An iterative method based on coupled mode theory is proposed in this paper, also structural controlling and multi-frequency design techniques are proposed to satisfy the structural property and frequency response property requirements. The iteration method can be used to design many kinds of waveguide components. A TE01-TE11 mode converter is designed, the working frequency of which is 35 GHz, and the radius is 13.6 mm. The multi-frequency technique is utilized. The bandwidth reaches 13.6%, which is the 2.3 times of conventional method.
An iterative method based on coupled mode theory is proposed in this paper, also structural controlling and multi-frequency design techniques are proposed to satisfy the structural property and frequency response property requirements. The iteration method can be used to design many kinds of waveguide components. A TE01-TE11 mode converter is designed, the working frequency of which is 35 GHz, and the radius is 13.6 mm. The multi-frequency technique is utilized. The bandwidth reaches 13.6%, which is the 2.3 times of conventional method.
2014,
26: 063042.
doi: 10.11884/HPLPB201426.063042
Abstract:
The paper studies an X-band 16-element square helical array antenna. It introduces the background of the rectangular array antenna and the working principle, analyzes coupling characteristics of two kinds of electromagnetic coupling probes in the X-band. A collaborative design of the choke structure and the electromagnetic coupling probe was conducted, the 16-element square helical array antenna with a center frequency of 9.3 GHz was designed and simulated. Simulation results show that: the antenna diameter is 96 mm96 mm, with center frequency 9.3 GHz, the gain is 19.51 dB, the axial ratio is 1.05, the reflection coefficient is less than 0.15.
The paper studies an X-band 16-element square helical array antenna. It introduces the background of the rectangular array antenna and the working principle, analyzes coupling characteristics of two kinds of electromagnetic coupling probes in the X-band. A collaborative design of the choke structure and the electromagnetic coupling probe was conducted, the 16-element square helical array antenna with a center frequency of 9.3 GHz was designed and simulated. Simulation results show that: the antenna diameter is 96 mm96 mm, with center frequency 9.3 GHz, the gain is 19.51 dB, the axial ratio is 1.05, the reflection coefficient is less than 0.15.
2014,
26: 063043.
doi: 10.11884/HPLPB201426.063043
Abstract:
In the high gain relativistic klystron amplifier, higher mode self-oscillation seriously degrades klystron performance and causes pulse shortening. The mechanism of higher mode excitation is explored in the PIC simulation, and RF lossy material is introduced to suppress higher mode self-oscillation. The relations of the attenuation characteristics with thickness, electric conductivity and length of the lossy material are studied. The cold test of the lossy material is performed. The attenuation of the lossy material is about 11.25 dB which fulfills the requirement of the suppression of self-oscillation, and can be used in the high gain relativistic klystron amplifier.
In the high gain relativistic klystron amplifier, higher mode self-oscillation seriously degrades klystron performance and causes pulse shortening. The mechanism of higher mode excitation is explored in the PIC simulation, and RF lossy material is introduced to suppress higher mode self-oscillation. The relations of the attenuation characteristics with thickness, electric conductivity and length of the lossy material are studied. The cold test of the lossy material is performed. The attenuation of the lossy material is about 11.25 dB which fulfills the requirement of the suppression of self-oscillation, and can be used in the high gain relativistic klystron amplifier.
2014,
26: 063101.
doi: 10.11884/HPLPB201426.063101
Abstract:
As one kind of terahertz sources, the cross-field backward wave oscillator requires a slow-wave structure (SWS) to transmit electromagnetic waves which is difficult to fabricate. This paper describes the performance of the open rectangular grating wave guide SWS in terahertz and the design of SWSs. By using field-matching method, the dispersion equation and the average coupling impendence expression are obtained and solved. And the length of the period of SWSs is considered to be important because the coupling impedance can be optimized by simply changing it without other adverse effects. The process and results of design of SWSs are summarized and verified by a simulation using PIC method and all the results included different structures with distances between two comb teeth ranging from 0.01 to 0.025 mm，and the frequencies ranging from 300 to 420 GHz.
As one kind of terahertz sources, the cross-field backward wave oscillator requires a slow-wave structure (SWS) to transmit electromagnetic waves which is difficult to fabricate. This paper describes the performance of the open rectangular grating wave guide SWS in terahertz and the design of SWSs. By using field-matching method, the dispersion equation and the average coupling impendence expression are obtained and solved. And the length of the period of SWSs is considered to be important because the coupling impedance can be optimized by simply changing it without other adverse effects. The process and results of design of SWSs are summarized and verified by a simulation using PIC method and all the results included different structures with distances between two comb teeth ranging from 0.01 to 0.025 mm，and the frequencies ranging from 300 to 420 GHz.
2014,
26: 063102.
doi: 10.11884/HPLPB201426.063102
Abstract:
A high power backward-wave oscillator (BWO) with a hot cathode is theoretically studied, which has a long life and good stability. Firstly, a single anode electron gun with a hot cathode is simulated by PIC software. The emission current density and the area of the hot cathode are 20 kA/cm2 and 100 cm2, respectively. The optimal design parameters of the electron gun are obtained. The PIC simulation results of BWO show that the output power of BWO can reach 290 MW with a frequency of 10.5 GHz, and the beam-wave interaction efficiency is 29%.
A high power backward-wave oscillator (BWO) with a hot cathode is theoretically studied, which has a long life and good stability. Firstly, a single anode electron gun with a hot cathode is simulated by PIC software. The emission current density and the area of the hot cathode are 20 kA/cm2 and 100 cm2, respectively. The optimal design parameters of the electron gun are obtained. The PIC simulation results of BWO show that the output power of BWO can reach 290 MW with a frequency of 10.5 GHz, and the beam-wave interaction efficiency is 29%.
2014,
26: 063103.
doi: 10.11884/HPLPB201426.063103
Abstract:
In the MEMS fabrication process of 345 GHz micro-electric vacuum folded waveguide traveling wave tube（FWG-TWT）, the surface roughness and the verticality of waveguides sidewall are two major challenges. Through theoretical analysis and numerical simulation, the paper considered the roughness and studied the changes of FWG slow wave structures performance when the vertical angle tolerance increased from 0 to 6. When the surface roughness of the waveguide became bigger, the signals transmission loss of the slow wave structure increased. When the angles tolerance increased, the signals transmission loss rose, and angle tolerance which means structure change caused the devices operating voltage drift, bandwidth reduction, etc. The results in this paper is helpful for the devices experiment and the processing.
In the MEMS fabrication process of 345 GHz micro-electric vacuum folded waveguide traveling wave tube（FWG-TWT）, the surface roughness and the verticality of waveguides sidewall are two major challenges. Through theoretical analysis and numerical simulation, the paper considered the roughness and studied the changes of FWG slow wave structures performance when the vertical angle tolerance increased from 0 to 6. When the surface roughness of the waveguide became bigger, the signals transmission loss of the slow wave structure increased. When the angles tolerance increased, the signals transmission loss rose, and angle tolerance which means structure change caused the devices operating voltage drift, bandwidth reduction, etc. The results in this paper is helpful for the devices experiment and the processing.
2014,
26: 063201.
doi: 10.11884/HPLPB201426.063201
Abstract:
A high voltage repetition pulse output based on the application of the hydrogen thyratron coupling with inductive-adder is proposed and the magnetic distribution with coaxial shielding structure is analyzed. The amplitude of working voltage is 25 kV, the repetitive frequency of pulse waveform is 20 Hz and the trigger delay of grids is 5 ns due to the differences of the devices parameters. The experiment results show that the hydrogen thyratron trigger is stable and reliable, and the application of the inductive-adder output mode based on the coaxial shielding has less impact on the reliability and the rising edge of the output pulse waveform and the amplitude of output pulse is about 50 kV, and the feasibility of inductive-adder technique applied in gas switch is confirmed.
A high voltage repetition pulse output based on the application of the hydrogen thyratron coupling with inductive-adder is proposed and the magnetic distribution with coaxial shielding structure is analyzed. The amplitude of working voltage is 25 kV, the repetitive frequency of pulse waveform is 20 Hz and the trigger delay of grids is 5 ns due to the differences of the devices parameters. The experiment results show that the hydrogen thyratron trigger is stable and reliable, and the application of the inductive-adder output mode based on the coaxial shielding has less impact on the reliability and the rising edge of the output pulse waveform and the amplitude of output pulse is about 50 kV, and the feasibility of inductive-adder technique applied in gas switch is confirmed.
2014,
26: 063202.
doi: 10.11884/HPLPB201426.063202
Abstract:
For EMP effects experiments, a miniature Marx generator based on avalanche transistors is developed. The characteristics of avalanche transistor are analyzed and the principles of the pulse generator are studied. The design method of trigger circuit and pulse circuit is discussed, and the choice of device parameters is presented. A monopole and a dual polarity of 10-stage small-sized pulse generator are designed, which can yield double-exponential pulses with a rise time of several ns and a peak voltage of 1.8 kV, and the experimental results show that the output pulses have the virtue of high stability and high repetition rate.
For EMP effects experiments, a miniature Marx generator based on avalanche transistors is developed. The characteristics of avalanche transistor are analyzed and the principles of the pulse generator are studied. The design method of trigger circuit and pulse circuit is discussed, and the choice of device parameters is presented. A monopole and a dual polarity of 10-stage small-sized pulse generator are designed, which can yield double-exponential pulses with a rise time of several ns and a peak voltage of 1.8 kV, and the experimental results show that the output pulses have the virtue of high stability and high repetition rate.
2014,
26: 063203.
doi: 10.11884/HPLPB201426.063203
Abstract:
By experiment and Random Coupling Model（RCM）, the statistic characteristics of induced voltages at key points in computer box cavity are studied. The calculating method and application diagram of RCM is given. Scattering coefficients, the statistic characteristics of normalized scattering coefficient and normalized impedance coefficient are researched by experiment and theory. It is shown that the experiment results generally agree with the theoretical results in trend. Application of RCM is preliminarily discussed. Applicability of analysis and forecast on systemic electromagnetic environment effects based on RCM is validated. Especially, the RCM is applicable to investigation on electromagnetic compatibility, effects and assessment for the large scale nonparallel surface electronic systems.
By experiment and Random Coupling Model（RCM）, the statistic characteristics of induced voltages at key points in computer box cavity are studied. The calculating method and application diagram of RCM is given. Scattering coefficients, the statistic characteristics of normalized scattering coefficient and normalized impedance coefficient are researched by experiment and theory. It is shown that the experiment results generally agree with the theoretical results in trend. Application of RCM is preliminarily discussed. Applicability of analysis and forecast on systemic electromagnetic environment effects based on RCM is validated. Especially, the RCM is applicable to investigation on electromagnetic compatibility, effects and assessment for the large scale nonparallel surface electronic systems.
2014,
26: 063204.
doi: 10.11884/HPLPB201426.063204
Abstract:
In order to identify and reduce the numerical errors of semiconductor simulator GSRES, drift-diffusion model used in numerical simulation of semiconductor device is studied. Numerical approximation in semiconductor device HPM effect simulator GSRES is analyzed. To build a full physical semiconductor model, Numerical errors caused by approximation of distribution of temperature field in lattice, approximation of recombination rate and generation rate are studied. Application range of simulator is analyzed according to the numerical errors caused by approximation. Terms of the model that need to be improved and enhanced are given.
In order to identify and reduce the numerical errors of semiconductor simulator GSRES, drift-diffusion model used in numerical simulation of semiconductor device is studied. Numerical approximation in semiconductor device HPM effect simulator GSRES is analyzed. To build a full physical semiconductor model, Numerical errors caused by approximation of distribution of temperature field in lattice, approximation of recombination rate and generation rate are studied. Application range of simulator is analyzed according to the numerical errors caused by approximation. Terms of the model that need to be improved and enhanced are given.
2014,
26: 065001.
doi: 10.11884/HPLPB201426.065001
Abstract:
This paper introduces a magnetic compressor charged by fast risetime transformer. It employs high coupling efficiency transformer and discards the counter protection diode. With this novel design, the magnetic compressor can be quickly charged, which helps to decrease the compression stage and the system volume. The equivalent charging and discharging circuits based on T mode transforming are analyzed. The design principle is presented as followed: (1) the time compression gain should be far beyond 1; (2) the magnetic switch should employ high permeability material. According to the theoretical and simulated results, a magnetic compressor charged by fast risetime transformer is manufactured. The compressor can generate 50 kV, 990 ns risetime pulse on 3 nF capacitor load, with 2 kV pre-pulse and 98% voltage efficiency.
This paper introduces a magnetic compressor charged by fast risetime transformer. It employs high coupling efficiency transformer and discards the counter protection diode. With this novel design, the magnetic compressor can be quickly charged, which helps to decrease the compression stage and the system volume. The equivalent charging and discharging circuits based on T mode transforming are analyzed. The design principle is presented as followed: (1) the time compression gain should be far beyond 1; (2) the magnetic switch should employ high permeability material. According to the theoretical and simulated results, a magnetic compressor charged by fast risetime transformer is manufactured. The compressor can generate 50 kV, 990 ns risetime pulse on 3 nF capacitor load, with 2 kV pre-pulse and 98% voltage efficiency.
2014,
26: 065002.
doi: 10.11884/HPLPB201426.065002
Abstract:
A Blumlein pulse forming network (PFN) with 20 impedance was designed by using lumped parameter capacitance and inductance. The three-dimensional models of the pulse forming network in two different connecting configurations were established and simulated via finite integration software. The results show that, 98% voltage transfer efficiency of the PFN in linear connecting configuration can be achieved, and the voltage transfer efficiency of the PFN in folded connecting configuration is close to 90%. The high voltage experiments of the PFN in two different connecting configurations were done, and the experiment results were generally consistent with the theoretical simulation results. In the end, the reason for the difference of the voltage and power transfer efficiency was preliminarily analyzed by calculating the coupling parameter of the PFN in two different connecting configurations.
A Blumlein pulse forming network (PFN) with 20 impedance was designed by using lumped parameter capacitance and inductance. The three-dimensional models of the pulse forming network in two different connecting configurations were established and simulated via finite integration software. The results show that, 98% voltage transfer efficiency of the PFN in linear connecting configuration can be achieved, and the voltage transfer efficiency of the PFN in folded connecting configuration is close to 90%. The high voltage experiments of the PFN in two different connecting configurations were done, and the experiment results were generally consistent with the theoretical simulation results. In the end, the reason for the difference of the voltage and power transfer efficiency was preliminarily analyzed by calculating the coupling parameter of the PFN in two different connecting configurations.
2014,
26: 065003.
doi: 10.11884/HPLPB201426.065003
Abstract:
A magnetic switch based high power long pulse generator was developed, consisting of a pulsed transformer, a low impedance pulse forming network, magnetic core type main switches and an inductive voltage adder. Key subsystems were individually investigated and tested. The pulsed transformer was set up based on magnetic cores with a rectangular cross section and a raceway loop. The two stage magnetic compression system was made via hard connection windings, which were convenient for adjustment. The ceramic capacitor based low impedance pulse forming network was Blumlein type of a circumference symmetrical structure and with magnetic core type main switches cooperated. The inductive voltage adder of 4 stages was developed with each cell feeding by one port via azimuthal transmission line. Furthermore, preliminary experimental researches were carried out on the whole system, which verified the design concept.
A magnetic switch based high power long pulse generator was developed, consisting of a pulsed transformer, a low impedance pulse forming network, magnetic core type main switches and an inductive voltage adder. Key subsystems were individually investigated and tested. The pulsed transformer was set up based on magnetic cores with a rectangular cross section and a raceway loop. The two stage magnetic compression system was made via hard connection windings, which were convenient for adjustment. The ceramic capacitor based low impedance pulse forming network was Blumlein type of a circumference symmetrical structure and with magnetic core type main switches cooperated. The inductive voltage adder of 4 stages was developed with each cell feeding by one port via azimuthal transmission line. Furthermore, preliminary experimental researches were carried out on the whole system, which verified the design concept.
2014,
26: 065004.
doi: 10.11884/HPLPB201426.065004
Abstract:
Analysis and experimentally demonstrated results of a solid state pulsed forming network Marx（PFN-Marx） generator are presented. A quasi-square pulse can be got by using the pulsed forming network. The generators charging way, switch structure and device structure are also studied. The generator with 10-stage PFN cells generated an output pulse with voltage of 400 kV and width of 100 ns, and the generator with 20-stage PFN cells achieved an electric pulse with 500 kV voltage, 70 ns pulse width in the experiments.
Analysis and experimentally demonstrated results of a solid state pulsed forming network Marx（PFN-Marx） generator are presented. A quasi-square pulse can be got by using the pulsed forming network. The generators charging way, switch structure and device structure are also studied. The generator with 10-stage PFN cells generated an output pulse with voltage of 400 kV and width of 100 ns, and the generator with 20-stage PFN cells achieved an electric pulse with 500 kV voltage, 70 ns pulse width in the experiments.
2014,
26: 065005.
doi: 10.11884/HPLPB201426.065005
Abstract:
An electrical breakdown experiment for propylene carbonate with microsecond charging was carried out, in which a compact pulsed power generator based on the Tesla transformer was used as the pulsed voltage source, and a container with spherical electrodes was used as the test cell. The experimental results were presented and analyzed. The conclusions are as follows: For propylene carbonate, its breakdown strength is equal to water dielectrics and its actual measurement resistivity is bigger than 10 Mcm. Moreover, its theoretical operation temperature can arrive -55 centigrade and dielectric constant can improve to 80 through adding ethylene carbonate. Using propylene carbonate and ethylene carbonate / propylene carbonate mixture for a pulse forming line, a practical device will not require the additional processing system, that is conducive to the compact size and miniaturization of the apparatus. In a word, propylene carbonate is fit for the application of the compact pulsed power sources and propylene carbonate has a good application prospect.
An electrical breakdown experiment for propylene carbonate with microsecond charging was carried out, in which a compact pulsed power generator based on the Tesla transformer was used as the pulsed voltage source, and a container with spherical electrodes was used as the test cell. The experimental results were presented and analyzed. The conclusions are as follows: For propylene carbonate, its breakdown strength is equal to water dielectrics and its actual measurement resistivity is bigger than 10 Mcm. Moreover, its theoretical operation temperature can arrive -55 centigrade and dielectric constant can improve to 80 through adding ethylene carbonate. Using propylene carbonate and ethylene carbonate / propylene carbonate mixture for a pulse forming line, a practical device will not require the additional processing system, that is conducive to the compact size and miniaturization of the apparatus. In a word, propylene carbonate is fit for the application of the compact pulsed power sources and propylene carbonate has a good application prospect.
2014,
26: 065006.
doi: 10.11884/HPLPB201426.065006
Abstract:
A transmission line transformer(TLT) with mutually coupled windings is described in this paper. All transmission lines of the transformer except the first stage are wound on a common ferrite core. A equivalent circuit method is introduced to analyze this model and an analytic expression of step response is derived. It is shown that TLT with the above-mentioned structure has a significantly slower drop rate than those with conventional structures. A four-stage TLT with this structure whose input and output impedance are 4.2 and 67.7 respectively was developed. A pulsed power source based on the TLT was developed, which generated voltage pulse with pulse width of 120 ns, and rise time of 20 ns. Amplitude of this pulse is four times of that generated by pulse forming network discharging on a load of 4.2 directly, and these two voltage waveforms have almost the same temporal shape.
A transmission line transformer(TLT) with mutually coupled windings is described in this paper. All transmission lines of the transformer except the first stage are wound on a common ferrite core. A equivalent circuit method is introduced to analyze this model and an analytic expression of step response is derived. It is shown that TLT with the above-mentioned structure has a significantly slower drop rate than those with conventional structures. A four-stage TLT with this structure whose input and output impedance are 4.2 and 67.7 respectively was developed. A pulsed power source based on the TLT was developed, which generated voltage pulse with pulse width of 120 ns, and rise time of 20 ns. Amplitude of this pulse is four times of that generated by pulse forming network discharging on a load of 4.2 directly, and these two voltage waveforms have almost the same temporal shape.
2014,
26: 065007.
doi: 10.11884/HPLPB201426.065007
Abstract:
Gas spark switch has been widely used in repetition rate pulsed power technology. Insulation recovery and repetition rate of gas spark switch are affected by many factors. The influences of gas spark switch energy deposition and pressure on the repetition rate were experimentally studied. The relationships between insulation recovery time of gas spark switch, air pressure and switch power were put forward. The relationships between switch power, repetition rate and pressure were preliminarily analyzed on the condition that the gas switch breakdown channels was cooled in natural convection.
Gas spark switch has been widely used in repetition rate pulsed power technology. Insulation recovery and repetition rate of gas spark switch are affected by many factors. The influences of gas spark switch energy deposition and pressure on the repetition rate were experimentally studied. The relationships between insulation recovery time of gas spark switch, air pressure and switch power were put forward. The relationships between switch power, repetition rate and pressure were preliminarily analyzed on the condition that the gas switch breakdown channels was cooled in natural convection.
2014,
26: 065008.
doi: 10.11884/HPLPB201426.065008
Abstract:
Dielectric window is an important component of high power microwave (HPM) generation device. However, breakdown easily occurs on vacuum/dielectric interface with the development of HPM device. Surface breakdown limits the generation and transmission of HPM, and becomes the bottle neck of HPM technology development. For further understanding the breakdown mechanism and improving the threshold, the theoretical and experimental investigation of multipactor suppressed in rectangular grooves simulation model is built in this paper. From the dynamic analysis and PIC simulation, the movement of multipactor electron in grooves is obtained and the physical process of rectangular grooves suppression breakdown is simulated. Breakdown experiments of polytetrafluoroethylene (PTFE) under an S-band (2.86 GHz) HPM are conducted, and the obtained results correspond to the suppression theory.
Dielectric window is an important component of high power microwave (HPM) generation device. However, breakdown easily occurs on vacuum/dielectric interface with the development of HPM device. Surface breakdown limits the generation and transmission of HPM, and becomes the bottle neck of HPM technology development. For further understanding the breakdown mechanism and improving the threshold, the theoretical and experimental investigation of multipactor suppressed in rectangular grooves simulation model is built in this paper. From the dynamic analysis and PIC simulation, the movement of multipactor electron in grooves is obtained and the physical process of rectangular grooves suppression breakdown is simulated. Breakdown experiments of polytetrafluoroethylene (PTFE) under an S-band (2.86 GHz) HPM are conducted, and the obtained results correspond to the suppression theory.
2014,
26: 065009.
doi: 10.11884/HPLPB201426.065009
Abstract:
An electric thermal model of PIN diodes was established with the T-CAD software, the steady-state and transient characteristics of PIN diodes have been numerically investigated. The electric thermal properties of PIN diodes were simulated under pulse and stable signals with forward and reverse voltage biases respectively, and the effects of the thickness of the intrinsic layer on the temperature inside the diode were studied with their steady-state and transient response curves. The simulation results show that, when the thickness of intrinsic layer increases, the peak temperature inside the diode increases slowly and the position of the high-temperature region moves from the junction to the middle of the diode.
An electric thermal model of PIN diodes was established with the T-CAD software, the steady-state and transient characteristics of PIN diodes have been numerically investigated. The electric thermal properties of PIN diodes were simulated under pulse and stable signals with forward and reverse voltage biases respectively, and the effects of the thickness of the intrinsic layer on the temperature inside the diode were studied with their steady-state and transient response curves. The simulation results show that, when the thickness of intrinsic layer increases, the peak temperature inside the diode increases slowly and the position of the high-temperature region moves from the junction to the middle of the diode.
2014,
26: 065010.
doi: 10.11884/HPLPB201426.065010
Abstract:
Cross-link polystyrene insulators was fluoridized at different temperature，and the vacuum flashover properties was tested by impulse voltage with width of 0.5 s. The flashover voltage of cross-link polystyrene insulators was enhanced by 40%-60% after surface fluoridization at 50-60℃. Multilayer high gradient insulator with new structure was processed by incorporating conducting layers into the surface of insulator orderly, and the flashover voltage was enhanced by 40%-50%, compared with general insulator with the same material, while maintaining good mechanical and machining properties.
Cross-link polystyrene insulators was fluoridized at different temperature，and the vacuum flashover properties was tested by impulse voltage with width of 0.5 s. The flashover voltage of cross-link polystyrene insulators was enhanced by 40%-60% after surface fluoridization at 50-60℃. Multilayer high gradient insulator with new structure was processed by incorporating conducting layers into the surface of insulator orderly, and the flashover voltage was enhanced by 40%-50%, compared with general insulator with the same material, while maintaining good mechanical and machining properties.
2014,
26: 065011.
doi: 10.11884/HPLPB201426.065011
Abstract:
After the problem of damping effect on the nanotubes and the substrate was settled, Carbon nanotubes (CNT) films with champion emission characteristic would be synthesized by pyrolysis of iron phthalocyanine. If the pulse electrical field was up to 30 MV/m, the emission relativity beam current was 15 kA, the corresponding current density exceeded 1 kA/cm2 and the potential emission mechanism was flashover plasma emission. When the high-current emission repetitive frequency was 10 Hz, the emission threshold electrical field was low, the current waveform was almost synchronized with the voltage waveform, the emission amplitude was equal, the extent of emission stabilization was better than that of graphite cathode. After the emission times were up to 1000 shots, the morphology of CNT was intact, the desorptions from the interface of CNT didnt occur.
After the problem of damping effect on the nanotubes and the substrate was settled, Carbon nanotubes (CNT) films with champion emission characteristic would be synthesized by pyrolysis of iron phthalocyanine. If the pulse electrical field was up to 30 MV/m, the emission relativity beam current was 15 kA, the corresponding current density exceeded 1 kA/cm2 and the potential emission mechanism was flashover plasma emission. When the high-current emission repetitive frequency was 10 Hz, the emission threshold electrical field was low, the current waveform was almost synchronized with the voltage waveform, the emission amplitude was equal, the extent of emission stabilization was better than that of graphite cathode. After the emission times were up to 1000 shots, the morphology of CNT was intact, the desorptions from the interface of CNT didnt occur.
2014,
26: 065101.
doi: 10.11884/HPLPB201426.065101
Abstract:
A C band(5712 MHz) energy doubler (SLED) is successfully developed, which is the first one in China. This paper presents the design, simulation and optimization about the resonant cavity, coupling irises and 3 dB directional coupler using HFSS and CST code. The SLED is tested in low RF power, the measurement results are very well and all the technical parameters are reached or exceeded.
A C band(5712 MHz) energy doubler (SLED) is successfully developed, which is the first one in China. This paper presents the design, simulation and optimization about the resonant cavity, coupling irises and 3 dB directional coupler using HFSS and CST code. The SLED is tested in low RF power, the measurement results are very well and all the technical parameters are reached or exceeded.
2014,
26: 063028.
Abstract:
An overmoded high power millimeter generator with resonant cavity reflector which works under TM035 mode is designed. The reflection coefficient of the resonant cavity reflector to TM01 mode is larger than 0.9 from 58 GHz to 62 GHz. The process of interaction between beam and microwave is analyzed based on particle in cell simulations. By optimizing the length between the resonant cavity reflector and the slow-wave structure for this device, the simulated output power is 1.06 GW at 60.2 GHz frequency with a 570 kV, 6.0 kA electron beam guided by an external magnetic field of 4 T. The corresponding beam-wave conversion efficiency is about 31%, and the starting time is about 3.3 ns.
An overmoded high power millimeter generator with resonant cavity reflector which works under TM035 mode is designed. The reflection coefficient of the resonant cavity reflector to TM01 mode is larger than 0.9 from 58 GHz to 62 GHz. The process of interaction between beam and microwave is analyzed based on particle in cell simulations. By optimizing the length between the resonant cavity reflector and the slow-wave structure for this device, the simulated output power is 1.06 GW at 60.2 GHz frequency with a 570 kV, 6.0 kA electron beam guided by an external magnetic field of 4 T. The corresponding beam-wave conversion efficiency is about 31%, and the starting time is about 3.3 ns.
