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
Powerful lasers interacting with solid targets can generate intense electromagnetic pulses(EMPs).In this study,EMPs produced by a pulsed laser(1 ps,100 J)shooting at CH targets doped with different titanium(Ti)content...Powerful lasers interacting with solid targets can generate intense electromagnetic pulses(EMPs).In this study,EMPs produced by a pulsed laser(1 ps,100 J)shooting at CH targets doped with different titanium(Ti)contents at the XG-III laser facility are measured and analyzed.The results demonstrate that the intensity of EMPs first increases with Ti doping content from 1%to 7%and then decreases.The electron spectra show that EMP emission is closely related to the hot electrons ejected from the target surface,which is confirmed by an analysis based on the target–holder–ground equivalent antenna model.The conclusions of this study provide a new approach to achieve tunable EMP radiation by adjusting the metal content of solid targets,and will also help in understanding the mechanism ofEMPgeneration and ejection of hot electrons during laser coupling with targets.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
The discharged capillary plasma channel has been extensively studied as a high-gradient particle acceleration and transmission medium.A novel measurement method of plasma channel density profiles has been employed,whe...The discharged capillary plasma channel has been extensively studied as a high-gradient particle acceleration and transmission medium.A novel measurement method of plasma channel density profiles has been employed,where the role of plasma channels guiding the advantages of lasers has shown strong appeal.Here,we have studied the high-order transverse plasma density profile distribution using a channel-guided laser,and made detailed measurements of its evolution under various parameters.The paraxial wave equation in a plasma channel with high-order density profile components is analyzed,and the approximate propagation process based on the Gaussian profile laser is obtained on this basis,which agrees well with the simulation under phase conditions.In the experiments,by measuring the integrated transverse laser intensities at the outlet of the channels,the radial quartic density profiles of the plasma channels have been obtained.By precisely synchronizing the detection laser pulses and the plasma channels at various moments,the reconstructed density profile shows an evolution from the radial quartic profile to the quasi-parabolic profile,and the high-order component is indicated as an exponential decline tendency over time.Factors affecting the evolution rate were investigated by varying the incentive source and capillary parameters.It can be found that the discharge voltages and currents are positive factors quickening the evolution,while the electron-ion heating,capillary radii and pressures are negative ones.One plausible explanation is that quartic profile contributions may be linked to plasma heating.This work helps one to understand the mechanisms of the formation,the evolutions of the guiding channel electron-density profiles and their dependences on the external controllable parameters.It provides support and reflection for physical research on discharged capillary plasma and optimizing plasma channels in various applications.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We would like to thank the Science and Technology on Plasma Physics Laboratory of the China Academy of Engineering Physics for their kind help with the experiment.This work is supported by the Science Challenge Project(No.TZ2016005).
文摘Powerful lasers interacting with solid targets can generate intense electromagnetic pulses(EMPs).In this study,EMPs produced by a pulsed laser(1 ps,100 J)shooting at CH targets doped with different titanium(Ti)contents at the XG-III laser facility are measured and analyzed.The results demonstrate that the intensity of EMPs first increases with Ti doping content from 1%to 7%and then decreases.The electron spectra show that EMP emission is closely related to the hot electrons ejected from the target surface,which is confirmed by an analysis based on the target–holder–ground equivalent antenna model.The conclusions of this study provide a new approach to achieve tunable EMP radiation by adjusting the metal content of solid targets,and will also help in understanding the mechanism ofEMPgeneration and ejection of hot electrons during laser coupling with targets.
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.
基金supported by the National Natural Science Foundation of China(Nos.11975037,61631001 and 11921006)the National Grand Instrument Project(Nos.2019YFF01014400 and 2019YFF01014404).
文摘The discharged capillary plasma channel has been extensively studied as a high-gradient particle acceleration and transmission medium.A novel measurement method of plasma channel density profiles has been employed,where the role of plasma channels guiding the advantages of lasers has shown strong appeal.Here,we have studied the high-order transverse plasma density profile distribution using a channel-guided laser,and made detailed measurements of its evolution under various parameters.The paraxial wave equation in a plasma channel with high-order density profile components is analyzed,and the approximate propagation process based on the Gaussian profile laser is obtained on this basis,which agrees well with the simulation under phase conditions.In the experiments,by measuring the integrated transverse laser intensities at the outlet of the channels,the radial quartic density profiles of the plasma channels have been obtained.By precisely synchronizing the detection laser pulses and the plasma channels at various moments,the reconstructed density profile shows an evolution from the radial quartic profile to the quasi-parabolic profile,and the high-order component is indicated as an exponential decline tendency over time.Factors affecting the evolution rate were investigated by varying the incentive source and capillary parameters.It can be found that the discharge voltages and currents are positive factors quickening the evolution,while the electron-ion heating,capillary radii and pressures are negative ones.One plausible explanation is that quartic profile contributions may be linked to plasma heating.This work helps one to understand the mechanisms of the formation,the evolutions of the guiding channel electron-density profiles and their dependences on the external controllable parameters.It provides support and reflection for physical research on discharged capillary plasma and optimizing plasma channels in various applications.