Giant electromagnetic pulses(EMPs) induced by high-power laser irradiating solid targets interfere with various experimental diagnoses and even damage equipment,so unveiling the evolution of EMPs inside the laser cham...Giant electromagnetic pulses(EMPs) induced by high-power laser irradiating solid targets interfere with various experimental diagnoses and even damage equipment,so unveiling the evolution of EMPs inside the laser chamber is crucial for designing effective EMP shielding.In this work,the transmission characteristics of EMPs as a function of distances from the target chamber center(TCC) are studied using B-dot probes.The mean EMP amplitude generated by picosecond laser-target interaction reaches 561 kV m^(-1),357 kV m^(-1),395 kV m^(-1),and 341 kV m^(-1)at 0.32 m,0.53 m,0.76 m,and 1 m from TCC,which decreases dramatically from 0.32 m to 0.53 m.However,it shows a fluctuation from 0.53 m to 1 m.The temporal features of EMPs indicate that time-domain EMP signals near the target chamber wall have a wider full width at half maximum compared to that close to TCC,mainly due to the echo oscillation of electromagnetic waves inside the target chamber based on simulation and experimentation.The conclusions of this study will provide a new approach to mitigate strong electromagnetic pulses by decreasing the echo oscillation of electromagnetic waves inside the target chamber during laser coupling with targets.展开更多
A high-power laser ablating solid targets induces giant electromagnetic pulses(EMPs),which are intimately pertinent to laser parameters,such as energy and pulse width.In this study,we reveal the features of EMPs gener...A high-power laser ablating solid targets induces giant electromagnetic pulses(EMPs),which are intimately pertinent to laser parameters,such as energy and pulse width.In this study,we reveal the features of EMPs generated from a picosecond(ps)laser irradiating solid targets at the SG-Ⅱpicosecond petawatt(PSPW)laser facility.The laser energy and pulse,as well as target material and thickness,show determinative effects on the EMPs’amplitude.More intense EMPs are detected behind targets compared to those at the other three positions,and the EMP amplitude decreases from 90.09 kV/m to 17.8 kV/m with the gold target thickness increasing from 10μm to 20μm,which is suppressed when the laser pulse width is enlarged.The results are expected to provide more insight into EMPs produced by ps lasers coupling with targets and lay the foundation for an effective EMP shielding design in high-power laser infrastructures.展开更多
Ultrashort and powerful laser interactions with a target generate intense wideband electromagnetic pulses(EMPs).In this study,we report EMPs generated by the interactions between petawatt(30 fs,1.4×10^(20) W/cm^(...Ultrashort and powerful laser interactions with a target generate intense wideband electromagnetic pulses(EMPs).In this study,we report EMPs generated by the interactions between petawatt(30 fs,1.4×10^(20) W/cm^(2))femtosecond(fs)lasers with metal flat,plastic flat,and plastic nanowire-array(NWA)targets.Detailed analyses are conducted on the EMPs in terms of their spatial distribution,time and frequency domains,radiation energy,and protection.The results indicate that EMPs from metal targets exhibit larger amplitudes at varying angles than those generated by other types of targets and are enhanced significantly for NWA targets.Using a plastic target holder and increasing the laser focal spot can significantly decrease the radiation energy of the EMPs.Moreover,the composite shielding materials indicate an effective shielding effect against EMPs.The simulation results show that the NWA targets exert a collimating effect on thermal electrons,which directly affects the distribution of EMPs.This study provides guidance for regulating EMPs by controlling the laser focal spot,target parameters,and target rod material and is beneficial for electromagnetic-shielding design.展开更多
The electrostatic discharge(ESD)protection circuit widely exists in the input and output ports of CMOS digital circuits,and fast rising time electromagnetic pulse(FREMP)coupled into the device not only interacts with ...The electrostatic discharge(ESD)protection circuit widely exists in the input and output ports of CMOS digital circuits,and fast rising time electromagnetic pulse(FREMP)coupled into the device not only interacts with the CMOS circuit,but also acts on the protection circuit.This paper establishes a model of on-chip CMOS electrostatic discharge protection circuit and selects square pulse as the FREMP signals.Based on multiple physical parameter models,it depicts the distribution of the lattice temperature,current density,and electric field intensity inside the device.At the same time,this paper explores the changes of the internal devices in the circuit under the injection of fast rising time electromagnetic pulse and describes the relationship between the damage amplitude threshold and the pulse width.The results show that the ESD protection circuit has potential damage risk,and the injection of FREMP leads to irreversible heat loss inside the circuit.In addition,pulse signals with different attributes will change the damage threshold of the circuit.These results provide an important reference for further evaluation of the influence of electromagnetic environment on the chip,which is helpful to carry out the reliability enhancement research of ESD protection circuit.展开更多
The distribution and sources of EMPs produced at Shenguang-Ⅱ(SG-Ⅱ)series laser facilities are systematically investigated.The results indicate that the EMP amplitudes in the SG-Ⅱps PW laser are very strong,one orde...The distribution and sources of EMPs produced at Shenguang-Ⅱ(SG-Ⅱ)series laser facilities are systematically investigated.The results indicate that the EMP amplitudes in the SG-Ⅱps PW laser are very strong,one order higher than those from the SG-Ⅱlaser facility.EMPs outside the target chamber decrease exponentially with the distance from the measuring points to the target chamber center at the two laser facilities.Moreover,EMPs can be remarkably reduced when the picosecond laser together with the nanosecond laser is incident to targets compared to the SG-Ⅱps PW laser alone.The resulting conclusions are expected to offer experimental supports for further effective EMPs shielding design and achievement in high-power laser facilities.展开更多
An electromagnetic pulse（EMP）-induced damage model based on the internal damage mechanism of the Ga As pseudomorphic high electron mobility transistor（PHEMT） is established in this paper. With this model, the rela...An electromagnetic pulse（EMP）-induced damage model based on the internal damage mechanism of the Ga As pseudomorphic high electron mobility transistor（PHEMT） is established in this paper. With this model, the relationships among the damage power, damage energy, pulse width and signal amplitude are investigated. Simulation results show that the pulse width index from the damage power formula obtained here is higher than that from the empirical formula due to the hotspot transferring in the damage process of the device. It is observed that the damage energy is not a constant, which decreases with the signal amplitude increasing, and then changes little when the signal amplitude reaches up to a certain level.展开更多
Significant electromagnetic pulses （EMP） can be generated by the intensive laser irradiating solid targets in inertial confinement fusion （ICF）. To evaluate the EMP intensity and distribution in and outside the la...Significant electromagnetic pulses （EMP） can be generated by the intensive laser irradiating solid targets in inertial confinement fusion （ICF）. To evaluate the EMP intensity and distribution in and outside the laser chamber, we designed and fabricated a discone antenna with ultra-wide bands of over 10 GHz. The return loss （Sn parameter） of this antenna was below -10 dB and could even achieve under -30 dB at 3.1 GHz. The EMP intensity in this study at 80 cm and 40 cm away from the target chamber center （TCC） reached 400 kV/m and 2000 kV/m. The current results are expected to offer preliminary information to study physics regarding laser plasma interactions and will also lay experimental foundation for EMI shielding design to protect various diagnostics.展开更多
With the development of laser technologies,nuclear reactions can happen in high-temperature plasma environments induced by lasers and have attracted a lot of attention from different physical disciplines.However,studi...With the development of laser technologies,nuclear reactions can happen in high-temperature plasma environments induced by lasers and have attracted a lot of attention from different physical disciplines.However,studies on nuclear reactions in plasma are still limited by detecting technologies.This is mainly due to the fact that extremely high electromagnetic pulses(EMPs)can also be induced when high-intensity lasers hit targets to induce plasma,and then cause dysfunction of many types of traditional detectors.Therefore,new particle detecting technologies are highly needed.In this paper,we report a recently developed gated fiber detector which can be used in harsh EMP environments.In this prototype detector,scintillating photons are coupled by fiber and then transferred to a gated photomultiplier tube which is located far away from the EMP source and shielded well.With those measures,the EMPs can be avoided which may result that the device has the capability to identify a single event of nuclear reaction products generated in laser-induced plasma from noise EMP backgrounds.This new type of detector can be widely used as a time-of-flight(TOF)detector in high-intensity laser nuclear physics experiments for detecting neutrons,photons,and other charged particles.展开更多
The damage effect and mechanism of the electromagnetic pulse （EMP） on the GaAs pseudomorphic high electron mobility transistor （PHEMT） are investigated in this paper. By using the device simulation software, the d...The damage effect and mechanism of the electromagnetic pulse （EMP） on the GaAs pseudomorphic high electron mobility transistor （PHEMT） are investigated in this paper. By using the device simulation software, the distributions and variations of the electric field, the current density and the temperature are analyzed. The simulation results show that there are three physical effects, i.e., the forward-biased effect of the gate Schottky junction, the avalanche breakdown, and the thermal breakdown of the barrier layer, which influence the device current in the damage process. It is found that the damage position of the device changes with the amplitude of the step voltage pulse. The damage appears under the gate near the drain when the amplitude of the pulse is low, and it also occurs under the gate near the source when the amplitude is sufficiently high, which is consistent with the experimental results.展开更多
The electromagnetic concentrative coils are indispensable in the functional magnetic stimulation and have potential applications in nondestructive testing. In this paper, we propose a figure-8-shaped coil being compos...The electromagnetic concentrative coils are indispensable in the functional magnetic stimulation and have potential applications in nondestructive testing. In this paper, we propose a figure-8-shaped coil being composed of two arbitrary oblique elliptical coils, which can change the electromagnetic concentrative region and the magnitude of eddy current density by changing the elliptical shape and/or spread angle between two elliptical coils. Pulsed current is usually the excitation source in the functional magnetic stimulation, so in this paper we derive the analytical solutions of transient pulsed eddy current field in the time domain due to the elliptical concentrative coil placed in an arbitrary position over a half-infinite plane conductor by making use of the scale-transformation, the Laplace transform and the Fourier transform are used in our derivation. Calculation results of field distributions produced by the figure-8-shaped elliptical coil show some behaviours as follows： 1） the eddy currents are focused on the conductor under the geometric symmetric centre of figure-8-shaped coil; 2） the greater the scale factor of ellipse is, the higher the eddy current density is and the wider the concentrative area of eddy current along y axis is; 3） the maximum magnitude of eddy current density increases with the increase of spread angle. When spread angle is 180°, there are two additional reverse concentrative areas on both sides of x axis.展开更多
Intensive electromagnetic pulses （EMPs） can be generated when a high-power laser strikes a target. The transient electromagnetic field can have an intensity of up to several hundred kV m- 1 with a broad frequency of...Intensive electromagnetic pulses （EMPs） can be generated when a high-power laser strikes a target. The transient electromagnetic field can have an intensity of up to several hundred kV m- 1 with a broad frequency of up to several gigahertz, which may affect diagnostics and interfere with, or even damage, electronic equipment. In this paper, the process in which hot electrons produced by the laser-target interaction radiate EMPs is studied and simulated. The physical process is divided into three stages which are： the production of hot electrons; the escape of hot electrons; and the generation of EMPs. Instead of using a general finite difference time domain （FDTD） method to solve the Maxwell equations, a particle-in-cell method together with a time- biased FDTD method is applied in EMP simulation to restrain high-frequency noise. The results show that EMPs are stronger with higher laser intensity and larger target size.展开更多
Electromagnetic pulses(EMPs)produced by the interaction of a TW femtosecond laser with solid targets at the Compact Laser Plasma Accelerator(CLAPA)are measured and interpreted.The statistical results confirm that the ...Electromagnetic pulses(EMPs)produced by the interaction of a TW femtosecond laser with solid targets at the Compact Laser Plasma Accelerator(CLAPA)are measured and interpreted.The statistical results confirm that the intensities of the EMPs are closely related to both target material and thickness.The signal of the titanium target is more abundant than that of the copper target with the same thickness,and the intensity of EMP is positively correlated with the target thickness for aluminium foil.With the boosted EMP radiations,the energy of accelerated protons is also simultaneously enhanced.In addition,EMPs emitted from the front of the target exceed those from the rear,which are also pertinent to the specific target position.The resonant waveforms in the target chamber are analyzed using the fast Fourier transform,and the local resonance and the attenuation lead to changes of the frequency spectra of EMPs with variation of detecting positions,which is well supported by the modeling results.The findings are beneficial to gaining insight into the mechanism of EMP propagation in a typical target chamber and providing more information for EMP shielding design.展开更多
The modern landmine＇s electronic fuse is susceptible to strong interference or can even be damaged by the ultra-wide band electromagnetic pulse（UWB-EMP）. The finite-difference time-domain（FDTD） method in lossy me...The modern landmine＇s electronic fuse is susceptible to strong interference or can even be damaged by the ultra-wide band electromagnetic pulse（UWB-EMP）. The finite-difference time-domain（FDTD） method in lossy media with cylindrical coordinates is used to study the interactions of the UWB-EMP with the landmine. First, the coupling of UWB-EMP into the landmine shielding shell through an aperture is numerically simulated. Second, the coupled electromagnetic field of mine shells made of different shielding materials and with apertures of different sizes is plotted. Third, the aperture coupling laws of UWB-EMP into shells are analyzed and categorized. Such an algorithm is capable of effectively preventing ladder similar errors, and consequently improving the calculation precision, and in addition to adopting the message passing interface（MPI） parallel method to divide the total calculating range into more sub-ranges, the overall calculating efficiency is greatly increased. These calculations are surely a constructive reference for modern landmine design against electromagnetic damage.展开更多
In this study, we explore the far-zero behaviors of a scattered partially polarized spatially and spectrally partially coherent electromagnetic pulsed beam irradiating on a deterministic medium. The analytical formula...In this study, we explore the far-zero behaviors of a scattered partially polarized spatially and spectrally partially coherent electromagnetic pulsed beam irradiating on a deterministic medium. The analytical formula for the cross-spectral density matrix elements of this beam in the spherical coordinate system is derived. Within the framework of the first-order Born approximation, the effects of the scattering angle θ, the source parameters (i.e., the pulse duration T0 and the temporal coherence length Tcxx), and the scatterer parameter (i.e., the effective width of the medium σR) on the spectral density, the spectral shift, the spectral degree of polarization, and the degree of spectral coherence of the scattered source in the far-zero field are studied numerically and comparatively. Our work improves the scattering theory of stochastic electromagnetic beams and it may be useful for the applications involving the interaction between incident light waves and scattering media.展开更多
An electromagnetic coupling mathematical model is established by finite element method and is verified by the contrastive experiments of copper matrix Ni-TiN cylindrical coating electrode,copper electrode and Cu50 W e...An electromagnetic coupling mathematical model is established by finite element method and is verified by the contrastive experiments of copper matrix Ni-TiN cylindrical coating electrode,copper electrode and Cu50 W electrode.The wear mechanism of Ni-TiN/Cu composite electrode in the case of high-frequency pulse current is studied,and the influence of the fluctuation frequency of discharge current on electrode wear in micro-EDM is found out.Compared with the electrode made from homogeneous material,the high frequency electromagnetic properties of Ni-TiN composite layer can be used effectively to inhibit the effect of high frequency pulse on the electrode and improve the distribution trend of current density.展开更多
To determine the wall thickness, conductivity and permeability of a ferromagnetic plate, an inverse problem is established with measured values and calculated values of time-domain induced voltage in pulsed eddy curre...To determine the wall thickness, conductivity and permeability of a ferromagnetic plate, an inverse problem is established with measured values and calculated values of time-domain induced voltage in pulsed eddy current testing on the plate. From time-domain analytical expressions of the partial derivatives of induced voltage with respect to parameters,it is deduced that the partial derivatives are approximately linearly dependent. Then the constraints of these parameters are obtained by solving a partial linear differential equation. It is indicated that only the product of conductivity and wall thickness, and the product of relative permeability and wall thickness can be determined accurately through the inverse problem with time-domain induced voltage. In the practical testing, supposing the conductivity of the ferromagnetic plate under test is a fixed value, and then the relative variation of wall thickness between two testing points can be calculated via the ratio of the corresponding inversion results of the product of conductivity and wall thickness. Finally, this method for wall thickness measurement is verified by the experiment results of a carbon steel plate.展开更多
We experimentally study the generation and storage of double slow light pulses in a pr^3＋：Y2SiO5 crystal. Under electromagnetically induced transparency, a single signal pulse is stored in the spin coherence of the ...We experimentally study the generation and storage of double slow light pulses in a pr^3＋：Y2SiO5 crystal. Under electromagnetically induced transparency, a single signal pulse is stored in the spin coherence of the crystal. By simultaneously switching on two control fields to recall the stored information, the spin coherence is converted into two slow light pulses with distinct frequencies. Furthermore, the storage and controlled retrieval of double slow light pulses are obtained by manipulating the control fields. This study of double slow light pulses may have practical applications in information processing and all-optical networks.展开更多
Considering the limiting weak nonlinearity, we obtained the solution of the coupled equations describing the interaction of ultraintense laser with cold transparent multicomponent plasma. It was indicated that the ion...Considering the limiting weak nonlinearity, we obtained the solution of the coupled equations describing the interaction of ultraintense laser with cold transparent multicomponent plasma. It was indicated that the ions tend to accumulate at the center of the soliton and have large velocity when we consider the mobile ions in the multicomponent plasma, which shows that the result is different from that of the Berezhiani＇s analysis. The change of proportion of ions in the plasma has effects on the amplitude of vector potential and the maximum velocity of the soliton.展开更多
The electromagnetic pulse excited by the collision between a hypervelocity meteoroid and a spacecraft is studied both numerically and theoretically.It is found that there are two kinds of electromagnetic pulse.The hig...The electromagnetic pulse excited by the collision between a hypervelocity meteoroid and a spacecraft is studied both numerically and theoretically.It is found that there are two kinds of electromagnetic pulse.The high-frequency electromagnetic pulse may be excited by the sum of all the electric dipoles.Each electron can be considered as an electric dipole.The low-frequency electromagnetic pulse is produced by the Langmuir oscillation of electrons.The energy flux density and the duration time of the excited low-frequency electromagnetic pulse by the meteoroid are also studied in the present paper.It is shown that the energy flux density increases as either the impact speed or the mass of the meteoroid increases.It is also shown that the duration time decreases as both the impact speed and the mass of the meteoroid increase.By measuring the strength and the duration time of the electromagnetic pulse excited by the collision between the hypervelocity meteoroid and spacecraft,we can estimate the speed and the mass of the hypervelocity meteoroid,which will be helpful in space flight and space exploration.展开更多
Electromagnetic pulses(EMPs)with high intensity and frequency bandwidth can be generated during the intensive laser irradiating solid targets in inertial confinement fusion(ICF).To shield the EMPs radiation and hence ...Electromagnetic pulses(EMPs)with high intensity and frequency bandwidth can be generated during the intensive laser irradiating solid targets in inertial confinement fusion(ICF).To shield the EMPs radiation and hence protect various diagnostics in and outside the target chamber,we designed a multi-layer structure material to shield the EMFs and demonstrate experimentally and numerically shielding performance of the material structure.The thickness of the multi-layer structure material has a great influence on the EMPs shielding.It is shown that,with the increase of the material thickness,the better shielding performance is obtained,and the material structure with polytetrafluoroethyIene of 0.5 mm,copper of 0.4 mm and lead of 2.4 mm reduces 448 times compared the maximum value of EMPs voltage to that without shielded.The design of multilayer structure material for EMPs shielding provides a promising way to reduce EMPs radiation,which is extremely useful for the diagnostics protection and signal processing in ICF.展开更多
基金supported by National Grand Instrument Project (No.2019YFF01014404)the National Key Program for S & T Research and Development (No. 2022YFA1603202)+1 种基金National Natural Science Foundation of China (Nos.U2241281 and 11975037)the Foundation of Science and Technology on Plasma Physics Laboratory (No.6142A04220108)。
文摘Giant electromagnetic pulses(EMPs) induced by high-power laser irradiating solid targets interfere with various experimental diagnoses and even damage equipment,so unveiling the evolution of EMPs inside the laser chamber is crucial for designing effective EMP shielding.In this work,the transmission characteristics of EMPs as a function of distances from the target chamber center(TCC) are studied using B-dot probes.The mean EMP amplitude generated by picosecond laser-target interaction reaches 561 kV m^(-1),357 kV m^(-1),395 kV m^(-1),and 341 kV m^(-1)at 0.32 m,0.53 m,0.76 m,and 1 m from TCC,which decreases dramatically from 0.32 m to 0.53 m.However,it shows a fluctuation from 0.53 m to 1 m.The temporal features of EMPs indicate that time-domain EMP signals near the target chamber wall have a wider full width at half maximum compared to that close to TCC,mainly due to the echo oscillation of electromagnetic waves inside the target chamber based on simulation and experimentation.The conclusions of this study will provide a new approach to mitigate strong electromagnetic pulses by decreasing the echo oscillation of electromagnetic waves inside the target chamber during laser coupling with targets.
基金Project supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA25020205)the program of Science and Technology on Plasma Physics Laboratory,China Academy of Engineering Physics(Grant No.6142A04220108)。
文摘A high-power laser ablating solid targets induces giant electromagnetic pulses(EMPs),which are intimately pertinent to laser parameters,such as energy and pulse width.In this study,we reveal the features of EMPs generated from a picosecond(ps)laser irradiating solid targets at the SG-Ⅱpicosecond petawatt(PSPW)laser facility.The laser energy and pulse,as well as target material and thickness,show determinative effects on the EMPs’amplitude.More intense EMPs are detected behind targets compared to those at the other three positions,and the EMP amplitude decreases from 90.09 kV/m to 17.8 kV/m with the gold target thickness increasing from 10μm to 20μm,which is suppressed when the laser pulse width is enlarged.The results are expected to provide more insight into EMPs produced by ps lasers coupling with targets and lay the foundation for an effective EMP shielding design in high-power laser infrastructures.
基金This work was supported by the National Natural Science Foundation of China(Nos.12122501,11975037,61631001,and 11921006)the National Grand Instrument Project(Nos.2019YFF01014400,2019YFF01014404)the Foundation of Science and Technology on Plasma Physics Laboratory(No.6142A04220108).
文摘Ultrashort and powerful laser interactions with a target generate intense wideband electromagnetic pulses(EMPs).In this study,we report EMPs generated by the interactions between petawatt(30 fs,1.4×10^(20) W/cm^(2))femtosecond(fs)lasers with metal flat,plastic flat,and plastic nanowire-array(NWA)targets.Detailed analyses are conducted on the EMPs in terms of their spatial distribution,time and frequency domains,radiation energy,and protection.The results indicate that EMPs from metal targets exhibit larger amplitudes at varying angles than those generated by other types of targets and are enhanced significantly for NWA targets.Using a plastic target holder and increasing the laser focal spot can significantly decrease the radiation energy of the EMPs.Moreover,the composite shielding materials indicate an effective shielding effect against EMPs.The simulation results show that the NWA targets exert a collimating effect on thermal electrons,which directly affects the distribution of EMPs.This study provides guidance for regulating EMPs by controlling the laser focal spot,target parameters,and target rod material and is beneficial for electromagnetic-shielding design.
基金National Natural Science Foundation of China(61974116)。
文摘The electrostatic discharge(ESD)protection circuit widely exists in the input and output ports of CMOS digital circuits,and fast rising time electromagnetic pulse(FREMP)coupled into the device not only interacts with the CMOS circuit,but also acts on the protection circuit.This paper establishes a model of on-chip CMOS electrostatic discharge protection circuit and selects square pulse as the FREMP signals.Based on multiple physical parameter models,it depicts the distribution of the lattice temperature,current density,and electric field intensity inside the device.At the same time,this paper explores the changes of the internal devices in the circuit under the injection of fast rising time electromagnetic pulse and describes the relationship between the damage amplitude threshold and the pulse width.The results show that the ESD protection circuit has potential damage risk,and the injection of FREMP leads to irreversible heat loss inside the circuit.In addition,pulse signals with different attributes will change the damage threshold of the circuit.These results provide an important reference for further evaluation of the influence of electromagnetic environment on the chip,which is helpful to carry out the reliability enhancement research of ESD protection circuit.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (No. XDA25020205)Shanghai Science and Technology Development Funds (No. 20692114101)
文摘The distribution and sources of EMPs produced at Shenguang-Ⅱ(SG-Ⅱ)series laser facilities are systematically investigated.The results indicate that the EMP amplitudes in the SG-Ⅱps PW laser are very strong,one order higher than those from the SG-Ⅱlaser facility.EMPs outside the target chamber decrease exponentially with the distance from the measuring points to the target chamber center at the two laser facilities.Moreover,EMPs can be remarkably reduced when the picosecond laser together with the nanosecond laser is incident to targets compared to the SG-Ⅱps PW laser alone.The resulting conclusions are expected to offer experimental supports for further effective EMPs shielding design and achievement in high-power laser facilities.
基金supported by the National Basic Research Program of China(Grant No.2014CB339900)the Open Fund of Key Laboratory of Complex Electromagnetic Environment Science and Technology,China Academy of Engineering Physics(CAEP)(Grant No.2015-0214.XY.K)
文摘An electromagnetic pulse（EMP）-induced damage model based on the internal damage mechanism of the Ga As pseudomorphic high electron mobility transistor（PHEMT） is established in this paper. With this model, the relationships among the damage power, damage energy, pulse width and signal amplitude are investigated. Simulation results show that the pulse width index from the damage power formula obtained here is higher than that from the empirical formula due to the hotspot transferring in the damage process of the device. It is observed that the damage energy is not a constant, which decreases with the signal amplitude increasing, and then changes little when the signal amplitude reaches up to a certain level.
基金supported by the Fundamental Research Funds for the Central Universities of China(No.ZYGX2015J108)National Natural Science Foundation of China(Nos.11575166 and 51581140)
文摘Significant electromagnetic pulses （EMP） can be generated by the intensive laser irradiating solid targets in inertial confinement fusion （ICF）. To evaluate the EMP intensity and distribution in and outside the laser chamber, we designed and fabricated a discone antenna with ultra-wide bands of over 10 GHz. The return loss （Sn parameter） of this antenna was below -10 dB and could even achieve under -30 dB at 3.1 GHz. The EMP intensity in this study at 80 cm and 40 cm away from the target chamber center （TCC） reached 400 kV/m and 2000 kV/m. The current results are expected to offer preliminary information to study physics regarding laser plasma interactions and will also lay experimental foundation for EMI shielding design to protect various diagnostics.
基金supported by the National Nature Science Foundation of China(Nos.11875191,11890714,11925502,11935001,and 11961141003)the Strategic Priority Research Program(No.CAS XDB1602)。
文摘With the development of laser technologies,nuclear reactions can happen in high-temperature plasma environments induced by lasers and have attracted a lot of attention from different physical disciplines.However,studies on nuclear reactions in plasma are still limited by detecting technologies.This is mainly due to the fact that extremely high electromagnetic pulses(EMPs)can also be induced when high-intensity lasers hit targets to induce plasma,and then cause dysfunction of many types of traditional detectors.Therefore,new particle detecting technologies are highly needed.In this paper,we report a recently developed gated fiber detector which can be used in harsh EMP environments.In this prototype detector,scintillating photons are coupled by fiber and then transferred to a gated photomultiplier tube which is located far away from the EMP source and shielded well.With those measures,the EMPs can be avoided which may result that the device has the capability to identify a single event of nuclear reaction products generated in laser-induced plasma from noise EMP backgrounds.This new type of detector can be widely used as a time-of-flight(TOF)detector in high-intensity laser nuclear physics experiments for detecting neutrons,photons,and other charged particles.
基金supported by the National Basic Research Program of China(Grant No.2014CB339900)the Open Fund of Key Laboratory of Complex Electromagnetic Environment Science and Technology,China Academy of Engineering Physics(CAEP)(Grant No.2015-0214.XY.K)
文摘The damage effect and mechanism of the electromagnetic pulse （EMP） on the GaAs pseudomorphic high electron mobility transistor （PHEMT） are investigated in this paper. By using the device simulation software, the distributions and variations of the electric field, the current density and the temperature are analyzed. The simulation results show that there are three physical effects, i.e., the forward-biased effect of the gate Schottky junction, the avalanche breakdown, and the thermal breakdown of the barrier layer, which influence the device current in the damage process. It is found that the damage position of the device changes with the amplitude of the step voltage pulse. The damage appears under the gate near the drain when the amplitude of the pulse is low, and it also occurs under the gate near the source when the amplitude is sufficiently high, which is consistent with the experimental results.
基金Project supported by the National Natural Science Foundation of China (Grant No. 50807001)
文摘The electromagnetic concentrative coils are indispensable in the functional magnetic stimulation and have potential applications in nondestructive testing. In this paper, we propose a figure-8-shaped coil being composed of two arbitrary oblique elliptical coils, which can change the electromagnetic concentrative region and the magnitude of eddy current density by changing the elliptical shape and/or spread angle between two elliptical coils. Pulsed current is usually the excitation source in the functional magnetic stimulation, so in this paper we derive the analytical solutions of transient pulsed eddy current field in the time domain due to the elliptical concentrative coil placed in an arbitrary position over a half-infinite plane conductor by making use of the scale-transformation, the Laplace transform and the Fourier transform are used in our derivation. Calculation results of field distributions produced by the figure-8-shaped elliptical coil show some behaviours as follows： 1） the eddy currents are focused on the conductor under the geometric symmetric centre of figure-8-shaped coil; 2） the greater the scale factor of ellipse is, the higher the eddy current density is and the wider the concentrative area of eddy current along y axis is; 3） the maximum magnitude of eddy current density increases with the increase of spread angle. When spread angle is 180°, there are two additional reverse concentrative areas on both sides of x axis.
文摘Intensive electromagnetic pulses （EMPs） can be generated when a high-power laser strikes a target. The transient electromagnetic field can have an intensity of up to several hundred kV m- 1 with a broad frequency of up to several gigahertz, which may affect diagnostics and interfere with, or even damage, electronic equipment. In this paper, the process in which hot electrons produced by the laser-target interaction radiate EMPs is studied and simulated. The physical process is divided into three stages which are： the production of hot electrons; the escape of hot electrons; and the generation of EMPs. Instead of using a general finite difference time domain （FDTD） method to solve the Maxwell equations, a particle-in-cell method together with a time- biased FDTD method is applied in EMP simulation to restrain high-frequency noise. The results show that EMPs are stronger with higher laser intensity and larger target size.
基金supported by the National Natural Science Foundation of China(Grant Nos.11975037 and 11921006)the National Grand Instrument Project of China(Grant Nos.2019YFF01014400 and 2019YFF01014404)。
文摘Electromagnetic pulses(EMPs)produced by the interaction of a TW femtosecond laser with solid targets at the Compact Laser Plasma Accelerator(CLAPA)are measured and interpreted.The statistical results confirm that the intensities of the EMPs are closely related to both target material and thickness.The signal of the titanium target is more abundant than that of the copper target with the same thickness,and the intensity of EMP is positively correlated with the target thickness for aluminium foil.With the boosted EMP radiations,the energy of accelerated protons is also simultaneously enhanced.In addition,EMPs emitted from the front of the target exceed those from the rear,which are also pertinent to the specific target position.The resonant waveforms in the target chamber are analyzed using the fast Fourier transform,and the local resonance and the attenuation lead to changes of the frequency spectra of EMPs with variation of detecting positions,which is well supported by the modeling results.The findings are beneficial to gaining insight into the mechanism of EMP propagation in a typical target chamber and providing more information for EMP shielding design.
基金Project supported by the Postdoctoral Science Foundation of China(Grant No.2014M552610)
文摘The modern landmine＇s electronic fuse is susceptible to strong interference or can even be damaged by the ultra-wide band electromagnetic pulse（UWB-EMP）. The finite-difference time-domain（FDTD） method in lossy media with cylindrical coordinates is used to study the interactions of the UWB-EMP with the landmine. First, the coupling of UWB-EMP into the landmine shielding shell through an aperture is numerically simulated. Second, the coupled electromagnetic field of mine shells made of different shielding materials and with apertures of different sizes is plotted. Third, the aperture coupling laws of UWB-EMP into shells are analyzed and categorized. Such an algorithm is capable of effectively preventing ladder similar errors, and consequently improving the calculation precision, and in addition to adopting the message passing interface（MPI） parallel method to divide the total calculating range into more sub-ranges, the overall calculating efficiency is greatly increased. These calculations are surely a constructive reference for modern landmine design against electromagnetic damage.
基金Project supported by the National Natural Science Foundation of China (Grant No. 11504286)the Natural Science Basic Research Program of Shaanxi Province, China (Grant No. 2019JM-470)+1 种基金the Fund from the International Technology Collaborative Center for Advanced Optical Manufacturing and Optoelectronic Measurementthe Science Fund from the Shaanxi Provincial Key Laboratory of Photoelectric Measurement and Instrument Technology.
文摘In this study, we explore the far-zero behaviors of a scattered partially polarized spatially and spectrally partially coherent electromagnetic pulsed beam irradiating on a deterministic medium. The analytical formula for the cross-spectral density matrix elements of this beam in the spherical coordinate system is derived. Within the framework of the first-order Born approximation, the effects of the scattering angle θ, the source parameters (i.e., the pulse duration T0 and the temporal coherence length Tcxx), and the scatterer parameter (i.e., the effective width of the medium σR) on the spectral density, the spectral shift, the spectral degree of polarization, and the degree of spectral coherence of the scattered source in the far-zero field are studied numerically and comparatively. Our work improves the scattering theory of stochastic electromagnetic beams and it may be useful for the applications involving the interaction between incident light waves and scattering media.
基金the National Natural Science Foundation of China for financially supporting this research through project No.51005027
文摘An electromagnetic coupling mathematical model is established by finite element method and is verified by the contrastive experiments of copper matrix Ni-TiN cylindrical coating electrode,copper electrode and Cu50 W electrode.The wear mechanism of Ni-TiN/Cu composite electrode in the case of high-frequency pulse current is studied,and the influence of the fluctuation frequency of discharge current on electrode wear in micro-EDM is found out.Compared with the electrode made from homogeneous material,the high frequency electromagnetic properties of Ni-TiN composite layer can be used effectively to inhibit the effect of high frequency pulse on the electrode and improve the distribution trend of current density.
基金supported by the National Defense Basic Technology Research Program of China(Grant No.Z132013T001)
文摘To determine the wall thickness, conductivity and permeability of a ferromagnetic plate, an inverse problem is established with measured values and calculated values of time-domain induced voltage in pulsed eddy current testing on the plate. From time-domain analytical expressions of the partial derivatives of induced voltage with respect to parameters,it is deduced that the partial derivatives are approximately linearly dependent. Then the constraints of these parameters are obtained by solving a partial linear differential equation. It is indicated that only the product of conductivity and wall thickness, and the product of relative permeability and wall thickness can be determined accurately through the inverse problem with time-domain induced voltage. In the practical testing, supposing the conductivity of the ferromagnetic plate under test is a fixed value, and then the relative variation of wall thickness between two testing points can be calculated via the ratio of the corresponding inversion results of the product of conductivity and wall thickness. Finally, this method for wall thickness measurement is verified by the experiment results of a carbon steel plate.
基金supported by the National Basic Research Program of China (Grant No.2011CB921603)the National Natural Science Foundation of China (Grant Nos.11074097,10904048,10974071,11004079,and 11004080)+1 种基金the Basic Research Program of Jilin Universitythe China Postdoctoral Science Foundation (Grant No.2011M500924)
文摘We experimentally study the generation and storage of double slow light pulses in a pr^3＋：Y2SiO5 crystal. Under electromagnetically induced transparency, a single signal pulse is stored in the spin coherence of the crystal. By simultaneously switching on two control fields to recall the stored information, the spin coherence is converted into two slow light pulses with distinct frequencies. Furthermore, the storage and controlled retrieval of double slow light pulses are obtained by manipulating the control fields. This study of double slow light pulses may have practical applications in information processing and all-optical networks.
文摘Considering the limiting weak nonlinearity, we obtained the solution of the coupled equations describing the interaction of ultraintense laser with cold transparent multicomponent plasma. It was indicated that the ions tend to accumulate at the center of the soliton and have large velocity when we consider the mobile ions in the multicomponent plasma, which shows that the result is different from that of the Berezhiani＇s analysis. The change of proportion of ions in the plasma has effects on the amplitude of vector potential and the maximum velocity of the soliton.
基金supported by National Natural Science Foundation of China(Nos.11965019,42004131 and 42065005).
文摘The electromagnetic pulse excited by the collision between a hypervelocity meteoroid and a spacecraft is studied both numerically and theoretically.It is found that there are two kinds of electromagnetic pulse.The high-frequency electromagnetic pulse may be excited by the sum of all the electric dipoles.Each electron can be considered as an electric dipole.The low-frequency electromagnetic pulse is produced by the Langmuir oscillation of electrons.The energy flux density and the duration time of the excited low-frequency electromagnetic pulse by the meteoroid are also studied in the present paper.It is shown that the energy flux density increases as either the impact speed or the mass of the meteoroid increases.It is also shown that the duration time decreases as both the impact speed and the mass of the meteoroid increase.By measuring the strength and the duration time of the electromagnetic pulse excited by the collision between the hypervelocity meteoroid and spacecraft,we can estimate the speed and the mass of the hypervelocity meteoroid,which will be helpful in space flight and space exploration.
基金National Natural Science Foundation of China(No.61405167)the Fundamental Research Funds for the Central Universities(Nos.2682018GF10 and 2682019LK08)We would like to thank China Academy of Engineering Physics for their assistance in experiments.
文摘Electromagnetic pulses(EMPs)with high intensity and frequency bandwidth can be generated during the intensive laser irradiating solid targets in inertial confinement fusion(ICF).To shield the EMPs radiation and hence protect various diagnostics in and outside the target chamber,we designed a multi-layer structure material to shield the EMFs and demonstrate experimentally and numerically shielding performance of the material structure.The thickness of the multi-layer structure material has a great influence on the EMPs shielding.It is shown that,with the increase of the material thickness,the better shielding performance is obtained,and the material structure with polytetrafluoroethyIene of 0.5 mm,copper of 0.4 mm and lead of 2.4 mm reduces 448 times compared the maximum value of EMPs voltage to that without shielded.The design of multilayer structure material for EMPs shielding provides a promising way to reduce EMPs radiation,which is extremely useful for the diagnostics protection and signal processing in ICF.
