This paper reports the results of spectral measurements and a theoretical analysis of the temporal and spatial evolution of laser-produced Cu plasma in vacuum in the range of 8–14 nm.The time dependence of the extrem...This paper reports the results of spectral measurements and a theoretical analysis of the temporal and spatial evolution of laser-produced Cu plasma in vacuum in the range of 8–14 nm.The time dependence of the extreme ultraviolet band spectrum at different positions near the target surface was obtained and found to be dominated by three broad-band features.The 3p and 3d excitations of Cu5+–Cu9+ions were calculated using the Hartree–Fock theory with configuration interactions.The characteristics of the spectral line distribution for the 3p–nd and 3d–nf transition arrays were analyzed.Based on the steady-state collisional radiation model and the normalized Boltzmann distribution,the complex spectral structure in the band of 13–14 nm is accurately explained through consistency comparisons and benchmarking between the experimental and theoretical simulation spectra,demonstrating that the structure mainly stems from the overlapping contribution of the 3d–4f and 3p–3d transition arrays for the Cu5+–Cu9+ions.These results may help in studying the radiation characteristics of isoelectronic series highly-charged ions involving the 3d excitation process.展开更多
We proposed a theoretical spatio-temporal imaging method,which was based on the thermal model of laser ablation and the two-dimensional axisymmetric multi-species hydrodynamics model.By using the intensity formula,the...We proposed a theoretical spatio-temporal imaging method,which was based on the thermal model of laser ablation and the two-dimensional axisymmetric multi-species hydrodynamics model.By using the intensity formula,the integral intensity of spectral lines could be calculated and the corresponding images of intensity distribution could be drawn.Through further image processing such as normalization,determination of minimum intensity,combination and color filtering,a relatively clear species distribution image in the plasma could be obtained.Using the above method,we simulated the plasma ablated from Al-Mg alloy by different laser energies under 1 atm argon,and obtained the theoretical spatio-temporal distributions of Mg I,Mg II,Al I,Al II and Ar I species,which are almost consistent with the experimental results by differential imaging.Compared with the experimental decay time constants,the consistency is higher at low laser energy,indicating that our theoretical model is more suitable for the plasma dominated by laser-supported combustion wave.展开更多
A non-equilibrium atmospheric pressure argon(Ar)plasma excited by microsecond pulse is studied experimentally by laser scattering and optical emission spectroscopy(OES),and theoretically by collisional-radiative(CR)mo...A non-equilibrium atmospheric pressure argon(Ar)plasma excited by microsecond pulse is studied experimentally by laser scattering and optical emission spectroscopy(OES),and theoretically by collisional-radiative(CR)model.More specifically,the electron temperature and electron density of plasma are obtained directly by the laser Thomson scattering,the gas temperature is measured by laser Raman scattering,the optical emissions of excited Ar states of plasma are measured by OES.The laser scattering results show that the electron temperature is about 1 eV which is similar to that excited by 60 Hz AC power,but the gas temperature is as low as 300 K compared to about 700 K excited by 60 Hz AC power.It is shown that the microsecond pulsed power supply,rather than nanosecond ones,is short enough to reduce the gas temperature of atmospheric pressure plasma to near room temperature.The electron temperature and electron density are also obtained by CR model based on OES,and find that the intensities of the optical emission intensity lines of 727.41,811.73,841.08,842.83,852.44 and 912.86 nm of Ar can be used to characterize the behavior of electron density and electron temperature,it is very useful to quickly estimate the activity of the atmospheric pressure Ar plasma in many applications.展开更多
Extreme ultraviolet emission from laser-produced A1 plasma is experimentally and theoretically investigated. Spatial-evolution emission spectra are measured by using the spatio-temporally resolved laser produced plasm...Extreme ultraviolet emission from laser-produced A1 plasma is experimentally and theoretically investigated. Spatial-evolution emission spectra are measured by using the spatio-temporally resolved laser produced plasma technique. Based on the assumptions of a normalized Boltzmann distribution among the excited states and a steady-state collisional-radiative model, we succeed in reproducing the spectra at different detection positions, which are in good agreement with experiments. The decay curves about the electron temperature and electron density, as well as the fractions of individual A1 ions and average ionization stage with increasing the detection distance are obtained by comparison with the experimental measurements. These parameters are critical points for deeply understanding the expanding and cooling of laser produced plasmas in vacuum.展开更多
Radiation from laser-produced plasmas was examined as a potential wavelength calibration source for spectrographs in the extreme ultraviolet(EUV) region.Specifically, the EUV emission of chromium(Cr) plasmas was acqui...Radiation from laser-produced plasmas was examined as a potential wavelength calibration source for spectrographs in the extreme ultraviolet(EUV) region.Specifically, the EUV emission of chromium(Cr) plasmas was acquired via spatiotemporally resolved emission spectroscopy.With the aid of Cowan and flexible atomic code(FAC) structure calculations,and a comparative analysis with the simulated spectra, emission peaks in the 6.5–15.0 nm range were identified as 3 p–4 d, 5 d and 3 p–4 s transition lines from Cr5+–Cr10+ions.A normalized Boltzmann distribution among the excited states and a steady-state collisional-radiative model were assumed for the spectral simulations, and used to estimate the electron temperature and density in the plasma.The results indicate that several relatively isolated emission lines of highly charged ions would be useful for EUV wavelength calibration.展开更多
The temporal evolution of extreme ultraviolet(EUV)emission spectra of laser-produced antimony(Sb)plasmas has been measured in the 7-16 nm wavelength region using spatio?temporally resolved lase-produced plasma spectro...The temporal evolution of extreme ultraviolet(EUV)emission spectra of laser-produced antimony(Sb)plasmas has been measured in the 7-16 nm wavelength region using spatio?temporally resolved lase-produced plasma spectroscopy technique.The spectral profiles involve an intense quasi-continuous band with superimposed intense characteristic radiation and are different with the increase of delay time.The spectral structures were also analyzed according to Hartree-Fock calculations with configuration interaction effects and contributed from 4d^4/;4d-4p,and 4d-5f unresolved transition arrays of Sb7*-Sb131.A steady-state collisionalradiative model was used to estimate the electron temperature and density range of Sb plasmas.This work would enrich the spectral data of highly-charged ions and provided a possible selection for developing EUV light sources.展开更多
Laser-induced plasma is often produced in the presence of background gas,which causes some new physical processes.In this work,a two-dimensional axisymmetric radiation fluid dynamics model is used to numerically simul...Laser-induced plasma is often produced in the presence of background gas,which causes some new physical processes.In this work,a two-dimensional axisymmetric radiation fluid dynamics model is used to numerically simulate the expansion process of plasma under different pressures and gases,in which the multiple interaction processes of diffusion,viscosity and heat conduction between the laser ablated target vapor and the background gas are further considered,and the spatio-temporal evolutions of plasma parameters(species number density,expansion velocity,size and electron temperature)as well as the emission spectra are obtained.The consistency between the actual and simulated spectra of aluminum plasma in 1 atm argon verifies the correctness of the model and the numerical simulation,thus providing a refinement analysis method for the basic research of plasma expansion in gases and the application of laser-induced breakdown spectroscopy.展开更多
A state diagnosis of laser-produced plasma in air generated by a 1064 nm pulse laser was investigated by the Thomson scattering(TS)method.The evolutions of the electron temperature and electron density were obtained a...A state diagnosis of laser-produced plasma in air generated by a 1064 nm pulse laser was investigated by the Thomson scattering(TS)method.The evolutions of the electron temperature and electron density were obtained as a function of the time delay which ranged from 300-3200 ns.The heating effect produced by the 532 nm probe beam with different energies on the air plasma at different interaction times was further studied using a time-resolved optical emission spectroscopy technique.The influence of the probe beam on the electron density was found to be negligible,whereas its influence on electron temperature is evident.In addition,the heating effect of the probe beam on the plasma strongly depends on the energy of the probe beam,and gradually weakens with increasing time delay.Our results are helpful for further understanding the TS method and its application in plasma diagnostics.展开更多
Based on the governing equations which include the heat conduction equation in the target and the fluid equations of the vapor plasma,a two-dimensional axisymmetric model for ns-laser ablation considering the Knudsen ...Based on the governing equations which include the heat conduction equation in the target and the fluid equations of the vapor plasma,a two-dimensional axisymmetric model for ns-laser ablation considering the Knudsen layer and plasma shielding effect is developed.The equations of state of the plasma are described by a real gas approximation,which divides the internal energy into the thermal energy of atoms,ions and electrons,ionization energy and the excitation energy of atoms and ions.The dynamic evolution of the silicon target and plasma during laser ablation is studied by using this model,and the distributions of the temperature,plasma density,Mach number related to the evaporation/condensation of the target surface,laser transmissivity as well as internal energy of the plasma are given.It is found that the evolution of the target surface during laser ablation can be divided into three stages:(1)the target surface temperature increases continuously;(2)the sonic and subsonic evaporation;and(3)the subsonic condensation.The result of the internal energy distribution indicates that the ionization and excitation energy plays an important role in the internal energy of the plasma during laser ablation.This model is suitable for the case that the temperature of the target surface is lower than the critical temperature.展开更多
In order to provide detailed information about Cd structure and gain more insight regarding ionization degrees and types of transition,as well as the understanding of the temporal evolution behavior of laser produced ...In order to provide detailed information about Cd structure and gain more insight regarding ionization degrees and types of transition,as well as the understanding of the temporal evolution behavior of laser produced Cd plasmas,extreme ultraviolet spectra of laser-produced cadmium(Cd)plasmas have been measured in the 8.4-12 nm region using spatiotemporally resolved laser-produced plasma spectroscopy technique.Spectral features were analyzed by the Hartree-Fock(HF)method with relativistic correlations(HFR)using the Cowan code.The results showed that the 4p-5s resonance transition arrays from Cd^9+to Cd^13+merged to form intense lines in this spectral region.A number of new spectral features from Cd^9+and Cd^10+ions are reported in this study.Based on the assumption of a normalized Boltzmann distribution among the excited states associated with a steady-state collisional-radiative model,the plasma parameters were obtained by comparing the experimental and simulated spectra.As a result,we succeeded in reproducing the synthetic spectra for different time delays,which yielded good agreement with the experiments.The temporal evolution behaviors of electron temperature and electron density of plasma were also analyzed.展开更多
Armed with four different steady-state collisional-radiative(CR) models,we investigated the effect of dielectronic recombination(DR) on the charge-state distribution in laser-produced silicon plasma. To assess this ef...Armed with four different steady-state collisional-radiative(CR) models,we investigated the effect of dielectronic recombination(DR) on the charge-state distribution in laser-produced silicon plasma. To assess this effect,we performed a series of temporally resolved spectra of highly charged Si ions in the extreme ultraviolet region.Ab initio calculations of the DR rate coefficients were done for Si^(6+)–Si^(4+) ions. We also analyzed the evolution of the collisional ionization, radiative recombination, three-body recombination, photo-ionization, and DR rate coefficients as a function of electron temperature. The electron temperature and electron density for different delay times were obtained by comparing the normalized experimental and simulated spectra. The ion fraction and average charge state from the four different CR models were also obtained. The results indicate that the DR process has a greater influence in the stage of plasma evolution that cannot be neglected in plasma diagnoses.展开更多
基金supported by National Natural Science Foundation of China(Nos.12064040,11874051,11904293,11864036)the Science and Technology Project of Gansu Province(Nos.21JR7RA122,20JR5RA530)the Funds for Innovative Fundamental Research Group Project of Gansu Province(No.20JR5RA541)。
文摘This paper reports the results of spectral measurements and a theoretical analysis of the temporal and spatial evolution of laser-produced Cu plasma in vacuum in the range of 8–14 nm.The time dependence of the extreme ultraviolet band spectrum at different positions near the target surface was obtained and found to be dominated by three broad-band features.The 3p and 3d excitations of Cu5+–Cu9+ions were calculated using the Hartree–Fock theory with configuration interactions.The characteristics of the spectral line distribution for the 3p–nd and 3d–nf transition arrays were analyzed.Based on the steady-state collisional radiation model and the normalized Boltzmann distribution,the complex spectral structure in the band of 13–14 nm is accurately explained through consistency comparisons and benchmarking between the experimental and theoretical simulation spectra,demonstrating that the structure mainly stems from the overlapping contribution of the 3d–4f and 3p–3d transition arrays for the Cu5+–Cu9+ions.These results may help in studying the radiation characteristics of isoelectronic series highly-charged ions involving the 3d excitation process.
基金supported by National Key R&D Program of China(No.2017YFA0304203)National Energy R&D Center of Petroleum Refining Technology(RIPP,SINOPEC)+4 种基金Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China(No.IRT_17R70)National Natural Science Foundation of China(NSFC)(Nos.61975103,61875108,61775125,11434007)Major Special Science and Technology Projects in Shanxi(No.201804D131036)111 Project(No.D18001)Fund for Shanxi‘1331KSC’。
文摘We proposed a theoretical spatio-temporal imaging method,which was based on the thermal model of laser ablation and the two-dimensional axisymmetric multi-species hydrodynamics model.By using the intensity formula,the integral intensity of spectral lines could be calculated and the corresponding images of intensity distribution could be drawn.Through further image processing such as normalization,determination of minimum intensity,combination and color filtering,a relatively clear species distribution image in the plasma could be obtained.Using the above method,we simulated the plasma ablated from Al-Mg alloy by different laser energies under 1 atm argon,and obtained the theoretical spatio-temporal distributions of Mg I,Mg II,Al I,Al II and Ar I species,which are almost consistent with the experimental results by differential imaging.Compared with the experimental decay time constants,the consistency is higher at low laser energy,indicating that our theoretical model is more suitable for the plasma dominated by laser-supported combustion wave.
基金supported by the National Key Research and Development Program of China(Nos.2017YFA0402300,2017YFA0304900 and 2016YFA0300600)National Natural Science Foundation of China(Nos.11604334,11575099,11474347 and 11874051)+1 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Nos.XDB28000000and XDB07030000)the Open Research Fund Program of the State Key Laboratory of Low-Dimensional Quantum Physics(KF201807)。
文摘A non-equilibrium atmospheric pressure argon(Ar)plasma excited by microsecond pulse is studied experimentally by laser scattering and optical emission spectroscopy(OES),and theoretically by collisional-radiative(CR)model.More specifically,the electron temperature and electron density of plasma are obtained directly by the laser Thomson scattering,the gas temperature is measured by laser Raman scattering,the optical emissions of excited Ar states of plasma are measured by OES.The laser scattering results show that the electron temperature is about 1 eV which is similar to that excited by 60 Hz AC power,but the gas temperature is as low as 300 K compared to about 700 K excited by 60 Hz AC power.It is shown that the microsecond pulsed power supply,rather than nanosecond ones,is short enough to reduce the gas temperature of atmospheric pressure plasma to near room temperature.The electron temperature and electron density are also obtained by CR model based on OES,and find that the intensities of the optical emission intensity lines of 727.41,811.73,841.08,842.83,852.44 and 912.86 nm of Ar can be used to characterize the behavior of electron density and electron temperature,it is very useful to quickly estimate the activity of the atmospheric pressure Ar plasma in many applications.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11064012,11364037 and 11564037the Basic Scientific Foundation of Higher Learning of Gansu Provincethe Natural Science Foundation of Gansu Province under Grant Nos 1308RJZA166 and 1104WCGA186
文摘Extreme ultraviolet emission from laser-produced A1 plasma is experimentally and theoretically investigated. Spatial-evolution emission spectra are measured by using the spatio-temporally resolved laser produced plasma technique. Based on the assumptions of a normalized Boltzmann distribution among the excited states and a steady-state collisional-radiative model, we succeed in reproducing the spectra at different detection positions, which are in good agreement with experiments. The decay curves about the electron temperature and electron density, as well as the fractions of individual A1 ions and average ionization stage with increasing the detection distance are obtained by comparison with the experimental measurements. These parameters are critical points for deeply understanding the expanding and cooling of laser produced plasmas in vacuum.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFA0402300)the National Natural Science Foundation of China(Grant Nos.11874051,11274254,and 11564037)
文摘Radiation from laser-produced plasmas was examined as a potential wavelength calibration source for spectrographs in the extreme ultraviolet(EUV) region.Specifically, the EUV emission of chromium(Cr) plasmas was acquired via spatiotemporally resolved emission spectroscopy.With the aid of Cowan and flexible atomic code(FAC) structure calculations,and a comparative analysis with the simulated spectra, emission peaks in the 6.5–15.0 nm range were identified as 3 p–4 d, 5 d and 3 p–4 s transition lines from Cr5+–Cr10+ions.A normalized Boltzmann distribution among the excited states and a steady-state collisional-radiative model were assumed for the spectral simulations, and used to estimate the electron temperature and density in the plasma.The results indicate that several relatively isolated emission lines of highly charged ions would be useful for EUV wavelength calibration.
文摘The temporal evolution of extreme ultraviolet(EUV)emission spectra of laser-produced antimony(Sb)plasmas has been measured in the 7-16 nm wavelength region using spatio?temporally resolved lase-produced plasma spectroscopy technique.The spectral profiles involve an intense quasi-continuous band with superimposed intense characteristic radiation and are different with the increase of delay time.The spectral structures were also analyzed according to Hartree-Fock calculations with configuration interaction effects and contributed from 4d^4/;4d-4p,and 4d-5f unresolved transition arrays of Sb7*-Sb131.A steady-state collisionalradiative model was used to estimate the electron temperature and density range of Sb plasmas.This work would enrich the spectral data of highly-charged ions and provided a possible selection for developing EUV light sources.
基金supported by National Key R&D Program of China(No.2017YFA0304203)National Energy R&D Center of Petroleum Refining Technology(RIPP,SINOPEC)+4 种基金Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China(No.IRT_17R70)National Natural Science Foundation of China(NSFC)(Nos.61975103,61875108,61775125,11434007)Major Special Science and Technology Projects in Shanxi(No.201804D131036)111 project(No.D18001)Fund for Shanxi‘1331KSC’。
文摘Laser-induced plasma is often produced in the presence of background gas,which causes some new physical processes.In this work,a two-dimensional axisymmetric radiation fluid dynamics model is used to numerically simulate the expansion process of plasma under different pressures and gases,in which the multiple interaction processes of diffusion,viscosity and heat conduction between the laser ablated target vapor and the background gas are further considered,and the spatio-temporal evolutions of plasma parameters(species number density,expansion velocity,size and electron temperature)as well as the emission spectra are obtained.The consistency between the actual and simulated spectra of aluminum plasma in 1 atm argon verifies the correctness of the model and the numerical simulation,thus providing a refinement analysis method for the basic research of plasma expansion in gases and the application of laser-induced breakdown spectroscopy.
基金This work is supported by the National Key Research and Development Program of China(No.2017YFA0402300)National Natural Science Foundation of China(Nos.11874051,11564037,61741513,11904293)the Special Fund Project for Guiding Scientific and Technological Inno-vation of Gansu Province(No.2019zx-10).
文摘A state diagnosis of laser-produced plasma in air generated by a 1064 nm pulse laser was investigated by the Thomson scattering(TS)method.The evolutions of the electron temperature and electron density were obtained as a function of the time delay which ranged from 300-3200 ns.The heating effect produced by the 532 nm probe beam with different energies on the air plasma at different interaction times was further studied using a time-resolved optical emission spectroscopy technique.The influence of the probe beam on the electron density was found to be negligible,whereas its influence on electron temperature is evident.In addition,the heating effect of the probe beam on the plasma strongly depends on the energy of the probe beam,and gradually weakens with increasing time delay.Our results are helpful for further understanding the TS method and its application in plasma diagnostics.
基金supported by the National Key Research and Development Program of China (No. 2017YFA0402300)National Natural Science Foundation of China (Nos.11904293, 12064040 and 11874051)+2 种基金the Science and technology project of Gansu Province (No. 20JR5RA530)the Young Teachers Scientific Research Ability Promotion Plan of Northwest Normal University (No. NWNU-LKQN-18-32)the Funds for Innovative Fundamental Research Group Project of Gansu Province (No. 20JR5RA541).
文摘Based on the governing equations which include the heat conduction equation in the target and the fluid equations of the vapor plasma,a two-dimensional axisymmetric model for ns-laser ablation considering the Knudsen layer and plasma shielding effect is developed.The equations of state of the plasma are described by a real gas approximation,which divides the internal energy into the thermal energy of atoms,ions and electrons,ionization energy and the excitation energy of atoms and ions.The dynamic evolution of the silicon target and plasma during laser ablation is studied by using this model,and the distributions of the temperature,plasma density,Mach number related to the evaporation/condensation of the target surface,laser transmissivity as well as internal energy of the plasma are given.It is found that the evolution of the target surface during laser ablation can be divided into three stages:(1)the target surface temperature increases continuously;(2)the sonic and subsonic evaporation;and(3)the subsonic condensation.The result of the internal energy distribution indicates that the ionization and excitation energy plays an important role in the internal energy of the plasma during laser ablation.This model is suitable for the case that the temperature of the target surface is lower than the critical temperature.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFA0402300)the National Natural Science Foundation of China(Grant Nos.11874051,11904293,and 61965015)the Special Fund Project for Guiding Scientific and Technological Innovation of Gansu Province,China(Grant No.2019zx-10).
文摘In order to provide detailed information about Cd structure and gain more insight regarding ionization degrees and types of transition,as well as the understanding of the temporal evolution behavior of laser produced Cd plasmas,extreme ultraviolet spectra of laser-produced cadmium(Cd)plasmas have been measured in the 8.4-12 nm region using spatiotemporally resolved laser-produced plasma spectroscopy technique.Spectral features were analyzed by the Hartree-Fock(HF)method with relativistic correlations(HFR)using the Cowan code.The results showed that the 4p-5s resonance transition arrays from Cd^9+to Cd^13+merged to form intense lines in this spectral region.A number of new spectral features from Cd^9+and Cd^10+ions are reported in this study.Based on the assumption of a normalized Boltzmann distribution among the excited states associated with a steady-state collisional-radiative model,the plasma parameters were obtained by comparing the experimental and simulated spectra.As a result,we succeeded in reproducing the synthetic spectra for different time delays,which yielded good agreement with the experiments.The temporal evolution behaviors of electron temperature and electron density of plasma were also analyzed.
基金supported by the National Key Research and Development Program of China (Grant No. 2017YFA0402300)National Natural Science Foundation of China (NSFC) (Grant Nos. 11904293, 11874051)。
文摘Armed with four different steady-state collisional-radiative(CR) models,we investigated the effect of dielectronic recombination(DR) on the charge-state distribution in laser-produced silicon plasma. To assess this effect,we performed a series of temporally resolved spectra of highly charged Si ions in the extreme ultraviolet region.Ab initio calculations of the DR rate coefficients were done for Si^(6+)–Si^(4+) ions. We also analyzed the evolution of the collisional ionization, radiative recombination, three-body recombination, photo-ionization, and DR rate coefficients as a function of electron temperature. The electron temperature and electron density for different delay times were obtained by comparing the normalized experimental and simulated spectra. The ion fraction and average charge state from the four different CR models were also obtained. The results indicate that the DR process has a greater influence in the stage of plasma evolution that cannot be neglected in plasma diagnoses.
