Microwave pre-treatment is considered as a promising technique for alleviating cutter wear. This paper introduces a high-power microwave-induced fracturing system for hard rock. The test system consists of a high-powe...Microwave pre-treatment is considered as a promising technique for alleviating cutter wear. This paper introduces a high-power microwave-induced fracturing system for hard rock. The test system consists of a high-power microwave subsystem (100 kW), a true triaxial testing machine, a dynamic monitoring subsystem, and an electromagnetic shielding subsystem. It can realize rapid microwave-induced fracturing, intelligent tuning of impedance, dynamic feedback under strong microwave fields, and active control of microwave parameters by addressing the following issues: the instability and insecurity of the system, the discharge breakdown between coaxial lines during high-power microwave output, and a lack of feedback of rock-microwave response. In this study, microwave-induced surface and borehole fracturing tests under true triaxial stress were carried out. Experimental comparisons imply that high-power microwave irradiation can reduce the fracturing time of hard rock and that the fracture range (160 mm) of a 915-MHz microwave source is about three times that of 2.45 GHz. After microwave-induced borehole fracturing, many tensile cracks occur on the rock surface and in the borehole: the maximum reduction of the P-wave velocity is 12.8%. The test results show that a high-power microwave source of 915 MHz is more conducive to assisting mechanical rock breaking and destressing. The system can promote the development of microwave-assisted rock breaking equipment.展开更多
A two-dimensional model of the silicon NPN monolithic composite transistor is established for the first time by utilizing the semiconductor device simulator, Sentaurus-TCAD. By analyzing the internal distributions of ...A two-dimensional model of the silicon NPN monolithic composite transistor is established for the first time by utilizing the semiconductor device simulator, Sentaurus-TCAD. By analyzing the internal distributions of electric field, current density, and temperature of the device, a detailed investigation on the damage process and mechanism induced by high-power microwaves （HPM） is performed. The results indicate that the temperature elevation occurs in the negative half-period and the temperature drop process is in the positive half-period under the HPM injection from the output port. The damage point is located near the edge of the base-emitter junction of T2, while with the input injection it exists between the base and the emitter of T2. Comparing these two kinds of injection, the input injection is more likely to damage the device than the output injection. The dependences of the damage energy threshold and the damage power threshold causing the device failure on the pulse-width are obtained, and the formulas obtained have the same form as the experimental equations, which demonstrates that more power is required to destroy the device if the pulse-width is shorter. Furthermore, the simulation result in this paper has a good coincidence with the experimental result.展开更多
Research progresses on Cherenkov and transit-time high-power microwave(HPM)sources in National University of Defense Technology(NUDT)of China are presented.The research issues are focused on the following aspects.The ...Research progresses on Cherenkov and transit-time high-power microwave(HPM)sources in National University of Defense Technology(NUDT)of China are presented.The research issues are focused on the following aspects.The pulse-shortening phenomenon in O-type Cerenkov HPM devices is suppressed.The compact coaxial relativistic backward-wave oscillators(RBWOs)at low bands are developed.The power efficiency in M-Type HPM tubes without guiding magnetic field increased.The power capacities and power efficiencies in the triaxial klystron amplifier(TKA)and relativistic transit-time oscillator(TTO)at higher frequencies increased.In experiments,some exciting results were obtained.The X-band source generated 2 GW microwave power with a pulse duration of 110 ns in 30 Hz repetition mode.Both L-and P-band compact RBWOs generated over 2 GW microwave power with a power efficiency of over 30%.There is approximately a 75% decline of the volume compared with that of conventional RBWO under the same power capacity conditions.A 1.755 GHz MILO produced 3.1 GW microwave power with power efficiency of 10.4%.A 9.37 GHz TKA produced the 240 MW microwave power with the gain of 34 dB.A 14.3 GHz TTO produced 1 GW microwave power with power efficiency of 20%.展开更多
High-temperature electromagnetic(EM) protection materials integrated of multiple EM protection mechanisms and functions are regarded as desirable candidates for solving EM interference over a wide temperature range.In...High-temperature electromagnetic(EM) protection materials integrated of multiple EM protection mechanisms and functions are regarded as desirable candidates for solving EM interference over a wide temperature range.In this work,a novel microwave modulator is fabricated by introducing carbonyl iron particles(CIP)/resin into channels of carbonized wood(C-wood).Innovatively,the spaced arrangement of two microwave absorbents not only achieves a synergistic enhancement of magnetic and dielectric losses,but also breaks the translational invariance of EM characteristics in the horizontal direction to obtain multiple phase discontinuities in the frequency range of 8.2-18.0 GHz achieving modulation of reflected wave radiation direction.Accordingly,CIP/C-wood microwave modulator demonstrates the maximum effective bandwidth of 5.2 GHz and the maximum EM protection efficiency over 97% with a thickness of only 1.5 mm in the temperature range 298-673 K.Besides,CIP/C-wood microwave modulator shows stable and low thermal conductivities,as well as monotonic electrical conductivity-temperature characteristics,therefore it can also achieve thermal infrared stealth and working temperature monitoring in wide temperature ranges.This work provides an inspiration for the design of high-temperature EM protection materials with multiple EM protection mechanisms and functions.展开更多
The latch-up effect induced by high-power microwave（HPM） in complementary metal–oxide–semiconductor（CMOS） inverter is investigated in simulation and theory in this paper. The physical mechanisms of excess carrie...The latch-up effect induced by high-power microwave（HPM） in complementary metal–oxide–semiconductor（CMOS） inverter is investigated in simulation and theory in this paper. The physical mechanisms of excess carrier injection and HPM-induced latch-up are proposed. Analysis on upset characteristic under pulsed wave reveals increasing susceptibility under shorter-width pulsed wave which satisfies experimental data, and the dependence of upset threshold on pulse repetitive frequency（PRF） is believed to be due to the accumulation of excess carriers. Moreover, the trend that HPMinduced latch-up is more likely to happen in shallow-well device is proposed.Finally, the process of self-recovery which is ever-reported in experiment with its correlation with supply voltage and power level is elaborated, and the conclusions are consistent with reported experimental results.展开更多
The argon plasma induced by the L-/C-band high-power microwave(HPM) is investigated theoretically and experimentally. Influences of the microwave power, pulse width, polarization and the plasma electron density on the...The argon plasma induced by the L-/C-band high-power microwave(HPM) is investigated theoretically and experimentally. Influences of the microwave power, pulse width, polarization and the plasma electron density on the protection performance of the plasma array against HPM are studied. The results show that the effect of HPM is caused by energy accumulation, with the gas breakdown emerging only after a short time. The attenuation of the wave by the plasma array with the tubes off can reach approximately 23 dB at 1.3 GHz. It can also be obtained that the protection performance of the plasma array against the TE wave is better than that against the TM one. The plasma array shows better protection performance in the L-band than in the C-band. In addition,the attenuation of 5.6 GHz HPM can reach 30 dB when the tubes are turned on in the experiment.The research shows that the plasma array has protection ability against HPM.展开更多
Plasma filling can dramatically improve the performance of high power microwave devices. The characteristics of high-power microwave propagation along plasma filled waveguides in an axial magnetic field are analyzed i...Plasma filling can dramatically improve the performance of high power microwave devices. The characteristics of high-power microwave propagation along plasma filled waveguides in an axial magnetic field are analyzed in this paper, and the ponderomotive force effect of high power microwave is taken into consideration. Theoretical analysis and preliminary numerical calculations are performed. The analyses show that the ponderomotive effect would change the plasma density, distribution of microwave field intensity, and dispersion of wave propagation. The higher the microwave power, the stronger the ponderomotive effect. In different magnetic fields, the ponderomotive effect is different.展开更多
The fluid model is proposed to investigate the gas breakdown driven by a short-pulse（such as a Gaussian pulse） highpower microwave at high pressures.However,the fluid model requires specification of the electron ene...The fluid model is proposed to investigate the gas breakdown driven by a short-pulse（such as a Gaussian pulse） highpower microwave at high pressures.However,the fluid model requires specification of the electron energy distribution function（EEDF）;the common assumption of a Maxwellian EEDF can result in the inaccurate breakdown prediction when the electrons are not in equilibrium.We confirm that the influence of the incident pulse shape on the EEDF is tiny at high pressures by using the particle-in-cell Monte Carlo collision（PIC-MCC） model.As a result,the EEDF for a rectangular microwave pulse directly derived from the Boltzmann equation solver Bolsig＋ is introduced into the fluid model for predicting the breakdown threshold of the non-rectangular pulse over a wide range of pressures,and the obtained results are very well matched with those of the PIC-MCC simulations.The time evolution of a non-rectangular pulse breakdown in gas,obtained by the fluid model with the EEDF from Bolsig＋,is presented and analyzed at different pressures.In addition,the effect of the incident pulse shape on the gas breakdown is discussed.展开更多
A new LHW antenna will be used in LHCD system on tokanak HT-7U, where a high-power microwave waveguide power divider is a key device. This paper presents the power divider structure whose coupling element is in the co...A new LHW antenna will be used in LHCD system on tokanak HT-7U, where a high-power microwave waveguide power divider is a key device. This paper presents the power divider structure whose coupling element is in the common narrow wall between two identical waveguides, a certain of which is completely excavated. Green's Function Method is used to analyze the electric field distributions of the structure, and consequently the graphs between the scattering matrix and the geometrical dimensions are given. The graphs can be straightly applied to the process of the power divider.展开更多
In recent decades,the potential health hazards of microwave exposure have been attracting increasing attention.Our previous studies have demonstrated that microwave exposure impaired learning and memory in experimenta...In recent decades,the potential health hazards of microwave exposure have been attracting increasing attention.Our previous studies have demonstrated that microwave exposure impaired learning and memory in experimental animal models[1,2].展开更多
Results of experimental investigation of detection (rectification) of high power X-band microwave signal in diodes of various design (semiconductor p-n-junction, point-contact, Schottky, Metal-Isolator-Metal—MIM) are...Results of experimental investigation of detection (rectification) of high power X-band microwave signal in diodes of various design (semiconductor p-n-junction, point-contact, Schottky, Metal-Isolator-Metal—MIM) are reported. The maximum of the detected direct voltage V vs. power P of microwave signal and subsequent polarity reversal, previously found in MIM diodes in the optical and microwave bands, have found to be characteristic of all investigated diodes as well. After the reversal of polarity, this dependence comes linear, and the sign of the voltage corresponds to thermoEMF. In some diodes, the hysteresis on V(P) was observed. All 5 types of V(P) of MIM diodes (have made from different pairs of metals), reported earlier, were reproduced on same p-n-junction diode by variable external DC bias. These results joined with abnormal frequency cutoff forced to suggest that there is an unknown mechanism for direct flow of charge carriers (and for generate direct current) in the high-frequency electrical field, which differs from the conventional rectification.展开更多
Radio frequency/microwave-directed energy sources using wide bandgap SiC photoconductive semiconductors have attracted much attention due to their unique advantages of high-power output and multi-parameter adjustable ...Radio frequency/microwave-directed energy sources using wide bandgap SiC photoconductive semiconductors have attracted much attention due to their unique advantages of high-power output and multi-parameter adjustable ability.Over the past several years,benefitting from the sustainable innovations in laser technology and the significant progress in materials technology,megawatt-class output power electrical pulses with a flexible frequency in the P and L microwave wavebands have been achieved by photoconductive semiconductor devices.Here,we mainly summarize and review the recent progress of the high-power photonic microwave generation based on the SiC photoconductive semiconductor devices in the linear modulation mode,including the mechanism,system architecture,critical technology,and experimental demonstration of the proposed high-power photonic microwave sources.The outlooks and challenges for the future of multi-channel power synthesis development of higher power photonic microwave using wide bandgap photoconductors are also discussed.展开更多
A simple fabrication method of microwave protective mirror is presented. Manufacturing principles, techniques and influence of the materials and film system parameters on the optical characteristics are discussed. Mea...A simple fabrication method of microwave protective mirror is presented. Manufacturing principles, techniques and influence of the materials and film system parameters on the optical characteristics are discussed. Measured spectral transmittance curves of microwave protective mirror are given.展开更多
We conduct a theoretical study of the damage susceptibility trend of a typical bipolar transistor induced by a high-power microwave （HPM） as a function of frequency. The dependences of the burnout time and the damag...We conduct a theoretical study of the damage susceptibility trend of a typical bipolar transistor induced by a high-power microwave （HPM） as a function of frequency. The dependences of the burnout time and the damage power on the signal frequency are obtained. Studies of the internal damage process and the mechanism of the device are carried out from the variation analysis of the distribution of the electric field, current density, and temperature. The investigation shows that the burnout time linearly depends on the signal frequency. The current density and the electric field at the damage position decrease with increasing frequency. Meanwhile, the temperature elevation occurs in the area between the p-n junction and the n n＋ interface due to the increase of the electric field. Adopting the data analysis software, the relationship between the damage power and frequency is obtained. Moreover, the thickness of the substrate has a significant effect on the burnout time.展开更多
In the present paper we study the influences of the bias voltage and the external components on the damage progress of a bipolar transistor induced by high-power microwaves. The mechanism is presented by analyzing the...In the present paper we study the influences of the bias voltage and the external components on the damage progress of a bipolar transistor induced by high-power microwaves. The mechanism is presented by analyzing the variation in the internal distribution of the temperature in the device. The findings show that the device becomes less vulnerable to damage with an increase in bias voltage. Both the series diode at the base and the relatively low series resistance at the emitter, Re, can obviously prolong the burnout time of the device. However, Re will aid damage to the device when the value is sufficiently high due to the fact that the highest hot spot shifts from the base-emitter junction to the base region. Moreover, the series resistance at the base Rb will weaken the capability of the device to withstand microwave damage.展开更多
The structure and propagation of the plasma in air breakdown driven by high-power microwave have attracted great interest.This paper focuses on the microwave amplitude and frequency dependence of plasma formation at a...The structure and propagation of the plasma in air breakdown driven by high-power microwave have attracted great interest.This paper focuses on the microwave amplitude and frequency dependence of plasma formation at atmospheric pressure using one two-dimensional model,which is based on Maxwell’s equations coupled with plasma fluid equations.In this model,we adopt the effective electron diffusion coefficient,which can describe well the change from free diffusion in a plasma front to ambipolar diffusion in the bulk plasma.The filamentary plasma arrays observed in experiments are well reproduced in the simulations.The density and propagation speed of the plasma from the simulations are also close to the corresponding experimental data.The size of plasma filament parallel to the electric field decreases with increasing frequency,and it increases with the electric field amplitude.The distance between adjacent plasma filaments is close to one-quarter wavelength under different frequencies and amplitudes.The plasma propagation speed shows little change with the frequency,and it increases with the amplitude.The variations of plasma structure and propagation with the amplitude and frequency are due to the change in the distribution of the electric field.展开更多
Carbonyl iron(CI)particles as magnetic microwave absorption material often suffer from serious corrosion under corrosive environment which leads to performance deterioration.In this study,fluorin-containing acrylate t...Carbonyl iron(CI)particles as magnetic microwave absorption material often suffer from serious corrosion under corrosive environment which leads to performance deterioration.In this study,fluorin-containing acrylate type polymer network layers with thickness ranging from tens of nanometers to around one hundred nanometers were formed continuously around CI.The crosslinked coating layer(named FT)effectively increases CI’s thermal decomposition temperature by at least 34%.The FT-coated CI(named CI-FT)was able to resist both inorganic and organic corrosive media attacking efficiently compared with bare CI.The surface polymer network could also help CI withstand organic medium dissolution which proved the firmness of coating.Cyclic voltammetry(CV)test revealed that the coating layer could significantly reduce maximum oxidation current density of CI by more than 45 times.Tafel polarization study during CV tests also confirmed that thicker FT coating layer could help CI sample stabilize corrosion current density.Meanwhile,the surface coating also enhanced the impedance matching properties of CI as microwave absorber and the CI-FT samples demonstrated improved microwave absorption properties which degenerated little after corrosive medium soaking compared with that of CI.展开更多
High-power microwave damage to enhanced-mode Ga N high electron mobility transistors(HEMT)is studied considering the mechanical-electrical synergy effect due to the strong piezoelectric properties of Ga N,which has a ...High-power microwave damage to enhanced-mode Ga N high electron mobility transistors(HEMT)is studied considering the mechanical-electrical synergy effect due to the strong piezoelectric properties of Ga N,which has a wurtzite crystal structure.Based on the piezoelectric constitutive equation,the mechanical and electrical energies were equivalently coupled,and the effective numerical model was built in the simulation software.The results indicated that a part of the electrical energy was stored in the device as a form of elastic energy,causing the burnout time of Ga N HEMT to be extended.The effects of different injection voltages and frequencies were analyzed,and the results revealed that elastic energy plays a different role during the process of device damage.These results are of great significance for the design of Ga N HEMTs with better reliability in harsh electromagnetic environments and for improving their protection design.展开更多
A simple theoretical model based on plasma physics is presented to analyze the microwave plasma effects on the electronic circuits.Results show that under certain parameter conditions the threshold for damaging the el...A simple theoretical model based on plasma physics is presented to analyze the microwave plasma effects on the electronic circuits.Results show that under certain parameter conditions the threshold for damaging the electronic circuits decreases with the decrease of the frequency of the high-power microwave.In addition,the oscillation amplitudes of the plasma electrons increase dramatically when the plasma frequency is near the high-power microwave frequency, which can easily damage the electronic circuits.展开更多
基金support from the Na-tional Natural Science Foundation of China(Grant No.41827806)the liaoning Revitalization Talent Program of China(Grant No.XLYCYSZX1902).
文摘Microwave pre-treatment is considered as a promising technique for alleviating cutter wear. This paper introduces a high-power microwave-induced fracturing system for hard rock. The test system consists of a high-power microwave subsystem (100 kW), a true triaxial testing machine, a dynamic monitoring subsystem, and an electromagnetic shielding subsystem. It can realize rapid microwave-induced fracturing, intelligent tuning of impedance, dynamic feedback under strong microwave fields, and active control of microwave parameters by addressing the following issues: the instability and insecurity of the system, the discharge breakdown between coaxial lines during high-power microwave output, and a lack of feedback of rock-microwave response. In this study, microwave-induced surface and borehole fracturing tests under true triaxial stress were carried out. Experimental comparisons imply that high-power microwave irradiation can reduce the fracturing time of hard rock and that the fracture range (160 mm) of a 915-MHz microwave source is about three times that of 2.45 GHz. After microwave-induced borehole fracturing, many tensile cracks occur on the rock surface and in the borehole: the maximum reduction of the P-wave velocity is 12.8%. The test results show that a high-power microwave source of 915 MHz is more conducive to assisting mechanical rock breaking and destressing. The system can promote the development of microwave-assisted rock breaking equipment.
文摘A two-dimensional model of the silicon NPN monolithic composite transistor is established for the first time by utilizing the semiconductor device simulator, Sentaurus-TCAD. By analyzing the internal distributions of electric field, current density, and temperature of the device, a detailed investigation on the damage process and mechanism induced by high-power microwaves （HPM） is performed. The results indicate that the temperature elevation occurs in the negative half-period and the temperature drop process is in the positive half-period under the HPM injection from the output port. The damage point is located near the edge of the base-emitter junction of T2, while with the input injection it exists between the base and the emitter of T2. Comparing these two kinds of injection, the input injection is more likely to damage the device than the output injection. The dependences of the damage energy threshold and the damage power threshold causing the device failure on the pulse-width are obtained, and the formulas obtained have the same form as the experimental equations, which demonstrates that more power is required to destroy the device if the pulse-width is shorter. Furthermore, the simulation result in this paper has a good coincidence with the experimental result.
基金supported by the National Natural Science Funds Fund of China under Grant No.11505288Provincial Natural Science Foundation of Hunanscientific effort project of NUDT.
文摘Research progresses on Cherenkov and transit-time high-power microwave(HPM)sources in National University of Defense Technology(NUDT)of China are presented.The research issues are focused on the following aspects.The pulse-shortening phenomenon in O-type Cerenkov HPM devices is suppressed.The compact coaxial relativistic backward-wave oscillators(RBWOs)at low bands are developed.The power efficiency in M-Type HPM tubes without guiding magnetic field increased.The power capacities and power efficiencies in the triaxial klystron amplifier(TKA)and relativistic transit-time oscillator(TTO)at higher frequencies increased.In experiments,some exciting results were obtained.The X-band source generated 2 GW microwave power with a pulse duration of 110 ns in 30 Hz repetition mode.Both L-and P-band compact RBWOs generated over 2 GW microwave power with a power efficiency of over 30%.There is approximately a 75% decline of the volume compared with that of conventional RBWO under the same power capacity conditions.A 1.755 GHz MILO produced 3.1 GW microwave power with power efficiency of 10.4%.A 9.37 GHz TKA produced the 240 MW microwave power with the gain of 34 dB.A 14.3 GHz TTO produced 1 GW microwave power with power efficiency of 20%.
基金Supported by Program for the National Natural Science Foundation of China(No.52071053,U1704253)the Fundamental Research Funds for the Central Universities(DUT20GF111)the China Postdoctoral Science Foundation(2020M670748,2020M680946).
文摘High-temperature electromagnetic(EM) protection materials integrated of multiple EM protection mechanisms and functions are regarded as desirable candidates for solving EM interference over a wide temperature range.In this work,a novel microwave modulator is fabricated by introducing carbonyl iron particles(CIP)/resin into channels of carbonized wood(C-wood).Innovatively,the spaced arrangement of two microwave absorbents not only achieves a synergistic enhancement of magnetic and dielectric losses,but also breaks the translational invariance of EM characteristics in the horizontal direction to obtain multiple phase discontinuities in the frequency range of 8.2-18.0 GHz achieving modulation of reflected wave radiation direction.Accordingly,CIP/C-wood microwave modulator demonstrates the maximum effective bandwidth of 5.2 GHz and the maximum EM protection efficiency over 97% with a thickness of only 1.5 mm in the temperature range 298-673 K.Besides,CIP/C-wood microwave modulator shows stable and low thermal conductivities,as well as monotonic electrical conductivity-temperature characteristics,therefore it can also achieve thermal infrared stealth and working temperature monitoring in wide temperature ranges.This work provides an inspiration for the design of high-temperature EM protection materials with multiple EM protection mechanisms and functions.
基金Project supported by the Open Fund of Key Laboratory of Complex Electromagnetic Environment Science and Technology,China Academy of Engineering Physics(Grant No.2015-0214.XY.K)
文摘The latch-up effect induced by high-power microwave（HPM） in complementary metal–oxide–semiconductor（CMOS） inverter is investigated in simulation and theory in this paper. The physical mechanisms of excess carrier injection and HPM-induced latch-up are proposed. Analysis on upset characteristic under pulsed wave reveals increasing susceptibility under shorter-width pulsed wave which satisfies experimental data, and the dependence of upset threshold on pulse repetitive frequency（PRF） is believed to be due to the accumulation of excess carriers. Moreover, the trend that HPMinduced latch-up is more likely to happen in shallow-well device is proposed.Finally, the process of self-recovery which is ever-reported in experiment with its correlation with supply voltage and power level is elaborated, and the conclusions are consistent with reported experimental results.
基金supported by the National High Technology Research and Development Program of China (Grant No. 2015AA0392)
文摘The argon plasma induced by the L-/C-band high-power microwave(HPM) is investigated theoretically and experimentally. Influences of the microwave power, pulse width, polarization and the plasma electron density on the protection performance of the plasma array against HPM are studied. The results show that the effect of HPM is caused by energy accumulation, with the gas breakdown emerging only after a short time. The attenuation of the wave by the plasma array with the tubes off can reach approximately 23 dB at 1.3 GHz. It can also be obtained that the protection performance of the plasma array against the TE wave is better than that against the TM one. The plasma array shows better protection performance in the L-band than in the C-band. In addition,the attenuation of 5.6 GHz HPM can reach 30 dB when the tubes are turned on in the experiment.The research shows that the plasma array has protection ability against HPM.
基金supported by the Fundamental Research Funds for Central Universities of China(No.ZYGX2010J049)
文摘Plasma filling can dramatically improve the performance of high power microwave devices. The characteristics of high-power microwave propagation along plasma filled waveguides in an axial magnetic field are analyzed in this paper, and the ponderomotive force effect of high power microwave is taken into consideration. Theoretical analysis and preliminary numerical calculations are performed. The analyses show that the ponderomotive effect would change the plasma density, distribution of microwave field intensity, and dispersion of wave propagation. The higher the microwave power, the stronger the ponderomotive effect. In different magnetic fields, the ponderomotive effect is different.
基金supported by the National Basic Research Program of China(Grant No.2013CB328904)the NSAF of China(Grant No.U1330109)2012 Doctoral Innovation Funds of Southwest Jiaotong University
文摘The fluid model is proposed to investigate the gas breakdown driven by a short-pulse（such as a Gaussian pulse） highpower microwave at high pressures.However,the fluid model requires specification of the electron energy distribution function（EEDF）;the common assumption of a Maxwellian EEDF can result in the inaccurate breakdown prediction when the electrons are not in equilibrium.We confirm that the influence of the incident pulse shape on the EEDF is tiny at high pressures by using the particle-in-cell Monte Carlo collision（PIC-MCC） model.As a result,the EEDF for a rectangular microwave pulse directly derived from the Boltzmann equation solver Bolsig＋ is introduced into the fluid model for predicting the breakdown threshold of the non-rectangular pulse over a wide range of pressures,and the obtained results are very well matched with those of the PIC-MCC simulations.The time evolution of a non-rectangular pulse breakdown in gas,obtained by the fluid model with the EEDF from Bolsig＋,is presented and analyzed at different pressures.In addition,the effect of the incident pulse shape on the gas breakdown is discussed.
基金the National Meg-Science Engineering Project of the Chinese Government.
文摘A new LHW antenna will be used in LHCD system on tokanak HT-7U, where a high-power microwave waveguide power divider is a key device. This paper presents the power divider structure whose coupling element is in the common narrow wall between two identical waveguides, a certain of which is completely excavated. Green's Function Method is used to analyze the electric field distributions of the structure, and consequently the graphs between the scattering matrix and the geometrical dimensions are given. The graphs can be straightly applied to the process of the power divider.
基金supported by National Science Foundation of China[No.81172620]。
文摘In recent decades,the potential health hazards of microwave exposure have been attracting increasing attention.Our previous studies have demonstrated that microwave exposure impaired learning and memory in experimental animal models[1,2].
文摘Results of experimental investigation of detection (rectification) of high power X-band microwave signal in diodes of various design (semiconductor p-n-junction, point-contact, Schottky, Metal-Isolator-Metal—MIM) are reported. The maximum of the detected direct voltage V vs. power P of microwave signal and subsequent polarity reversal, previously found in MIM diodes in the optical and microwave bands, have found to be characteristic of all investigated diodes as well. After the reversal of polarity, this dependence comes linear, and the sign of the voltage corresponds to thermoEMF. In some diodes, the hysteresis on V(P) was observed. All 5 types of V(P) of MIM diodes (have made from different pairs of metals), reported earlier, were reproduced on same p-n-junction diode by variable external DC bias. These results joined with abnormal frequency cutoff forced to suggest that there is an unknown mechanism for direct flow of charge carriers (and for generate direct current) in the high-frequency electrical field, which differs from the conventional rectification.
基金supported in part by the National Natural Science Foundation of China(Nos.62071477 and 62101577)the Natural Science Foundation of Hunan Province(No.2021JJ40660)。
文摘Radio frequency/microwave-directed energy sources using wide bandgap SiC photoconductive semiconductors have attracted much attention due to their unique advantages of high-power output and multi-parameter adjustable ability.Over the past several years,benefitting from the sustainable innovations in laser technology and the significant progress in materials technology,megawatt-class output power electrical pulses with a flexible frequency in the P and L microwave wavebands have been achieved by photoconductive semiconductor devices.Here,we mainly summarize and review the recent progress of the high-power photonic microwave generation based on the SiC photoconductive semiconductor devices in the linear modulation mode,including the mechanism,system architecture,critical technology,and experimental demonstration of the proposed high-power photonic microwave sources.The outlooks and challenges for the future of multi-channel power synthesis development of higher power photonic microwave using wide bandgap photoconductors are also discussed.
文摘A simple fabrication method of microwave protective mirror is presented. Manufacturing principles, techniques and influence of the materials and film system parameters on the optical characteristics are discussed. Measured spectral transmittance curves of microwave protective mirror are given.
基金Project supported by the National Natural Science Foundation of China (Grant No. 60776034)
文摘We conduct a theoretical study of the damage susceptibility trend of a typical bipolar transistor induced by a high-power microwave （HPM） as a function of frequency. The dependences of the burnout time and the damage power on the signal frequency are obtained. Studies of the internal damage process and the mechanism of the device are carried out from the variation analysis of the distribution of the electric field, current density, and temperature. The investigation shows that the burnout time linearly depends on the signal frequency. The current density and the electric field at the damage position decrease with increasing frequency. Meanwhile, the temperature elevation occurs in the area between the p-n junction and the n n＋ interface due to the increase of the electric field. Adopting the data analysis software, the relationship between the damage power and frequency is obtained. Moreover, the thickness of the substrate has a significant effect on the burnout time.
基金supported by the National Natural Science Foundation of China (Grant No. 60776034)
文摘In the present paper we study the influences of the bias voltage and the external components on the damage progress of a bipolar transistor induced by high-power microwaves. The mechanism is presented by analyzing the variation in the internal distribution of the temperature in the device. The findings show that the device becomes less vulnerable to damage with an increase in bias voltage. Both the series diode at the base and the relatively low series resistance at the emitter, Re, can obviously prolong the burnout time of the device. However, Re will aid damage to the device when the value is sufficiently high due to the fact that the highest hot spot shifts from the base-emitter junction to the base region. Moreover, the series resistance at the base Rb will weaken the capability of the device to withstand microwave damage.
基金supported by China National Natural Science Foundation of Shaanxi Province(No.2020JQ-643)China Postdoctoral Science Foundation funded project(No.2019M653545)the Fundamental Research Funds for the Central Universities,China(No.JB210510)。
文摘The structure and propagation of the plasma in air breakdown driven by high-power microwave have attracted great interest.This paper focuses on the microwave amplitude and frequency dependence of plasma formation at atmospheric pressure using one two-dimensional model,which is based on Maxwell’s equations coupled with plasma fluid equations.In this model,we adopt the effective electron diffusion coefficient,which can describe well the change from free diffusion in a plasma front to ambipolar diffusion in the bulk plasma.The filamentary plasma arrays observed in experiments are well reproduced in the simulations.The density and propagation speed of the plasma from the simulations are also close to the corresponding experimental data.The size of plasma filament parallel to the electric field decreases with increasing frequency,and it increases with the electric field amplitude.The distance between adjacent plasma filaments is close to one-quarter wavelength under different frequencies and amplitudes.The plasma propagation speed shows little change with the frequency,and it increases with the amplitude.The variations of plasma structure and propagation with the amplitude and frequency are due to the change in the distribution of the electric field.
基金financially supported by the National Natural Science Foundation of China(Nos.U19A2096,51903030,52021001)。
文摘Carbonyl iron(CI)particles as magnetic microwave absorption material often suffer from serious corrosion under corrosive environment which leads to performance deterioration.In this study,fluorin-containing acrylate type polymer network layers with thickness ranging from tens of nanometers to around one hundred nanometers were formed continuously around CI.The crosslinked coating layer(named FT)effectively increases CI’s thermal decomposition temperature by at least 34%.The FT-coated CI(named CI-FT)was able to resist both inorganic and organic corrosive media attacking efficiently compared with bare CI.The surface polymer network could also help CI withstand organic medium dissolution which proved the firmness of coating.Cyclic voltammetry(CV)test revealed that the coating layer could significantly reduce maximum oxidation current density of CI by more than 45 times.Tafel polarization study during CV tests also confirmed that thicker FT coating layer could help CI sample stabilize corrosion current density.Meanwhile,the surface coating also enhanced the impedance matching properties of CI as microwave absorber and the CI-FT samples demonstrated improved microwave absorption properties which degenerated little after corrosive medium soaking compared with that of CI.
基金supported by the National Natural Science Foundation of China(Grant No.61974116)the Innovation Fund of Xidian University(Grant No.YJSJ23019)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.ZYTS23029)the China Postdoctoral Science Foundation(Grant No.2019M663927XB)。
文摘High-power microwave damage to enhanced-mode Ga N high electron mobility transistors(HEMT)is studied considering the mechanical-electrical synergy effect due to the strong piezoelectric properties of Ga N,which has a wurtzite crystal structure.Based on the piezoelectric constitutive equation,the mechanical and electrical energies were equivalently coupled,and the effective numerical model was built in the simulation software.The results indicated that a part of the electrical energy was stored in the device as a form of elastic energy,causing the burnout time of Ga N HEMT to be extended.The effects of different injection voltages and frequencies were analyzed,and the results revealed that elastic energy plays a different role during the process of device damage.These results are of great significance for the design of Ga N HEMTs with better reliability in harsh electromagnetic environments and for improving their protection design.
文摘A simple theoretical model based on plasma physics is presented to analyze the microwave plasma effects on the electronic circuits.Results show that under certain parameter conditions the threshold for damaging the electronic circuits decreases with the decrease of the frequency of the high-power microwave.In addition,the oscillation amplitudes of the plasma electrons increase dramatically when the plasma frequency is near the high-power microwave frequency, which can easily damage the electronic circuits.
