A Maxwellian electron energy distribution function (EEDF) is often assumed when using the optical emission line-ratio method to determine the electron temperature in low- temperature plasmas. However, in many cases,...A Maxwellian electron energy distribution function (EEDF) is often assumed when using the optical emission line-ratio method to determine the electron temperature in low- temperature plasmas. However, in many cases, non-Maxwellian EEDFs can be formed due to the non-local electron heating or the inelastic-collisional energy loss processes. In this work, with a collisional-radiative model, we propose an approach to obtain the non-Maxwellian EEDF with a 'two-temperature structure' from the emission line-ratios of Paschen 2p levels of argon and kryp- ton atoms. For applications of this approach in reactive gas (CF4, O2, etc) discharges that contain argon and krypton, recommendations of some specific emission line-ratios are provided, according to their sensitivities to the EEDF variation. The kinetic processes of the relevant excited atoms are also discussed in detail.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
This paper proposes a simple collisional-radiative model to characterise capacitively coupled argon plasmas driven by conventional radio frequency in combination with optical emission spectroscopy and Langmuir probe m...This paper proposes a simple collisional-radiative model to characterise capacitively coupled argon plasmas driven by conventional radio frequency in combination with optical emission spectroscopy and Langmuir probe measurements. Two major processes are considered in this model, electron-impact excitation and the spontaneous radiative decay. The diffusion loss term, which is found to be important for the two metastable states (4s[3/2]2, 4s'[1/2]0), is also taken into account. Behaviours of representative metastable and radiative states are discussed. Two emission lines (located at 696.5 nm and 750.4 nm) are selected and intensities are measured to obtain populated densities of the corresponding radiative states in the argon plasma. The calculated results agree well with that measured by Langmuir probe, indicating that the current model combined with optical emission spectroscopy is a candidate tool for electron density and temperature measurement in radio frequency capacitively coupled discharges.展开更多
Non-local thermodynamic equilibrium(NLTE)conditions are universal in laboratory and astrophysical plasmas and,for this reason,the theory of NLTE plasmas is nowadays a very active subject.The populations of atomic leve...Non-local thermodynamic equilibrium(NLTE)conditions are universal in laboratory and astrophysical plasmas and,for this reason,the theory of NLTE plasmas is nowadays a very active subject.The populations of atomic levels and radiative properties are essential magnitudes in the study of these plasmas and the calculation of those properties relies on the so-called collisional-radiative(CR)models.However,the complexity of these models has led to the development of numerous collisionalradiative codes and this is a current research topic in plasmas.In this work is presented a versatile computational package,named ABAKO/RAPCAL,to calculate the populations of atomic levels and radiative properties of optically thin and thick,lowto-high Z,NLTE plasmas.ABAKO/RAPCAL combines a set of analytical approximations which yield substantial savings in computing running time,still comparing well with more elaborated codes and experimental data.In order to show the capabilities of the code and the accuracy of its results,calculations of several relevant plasma magnitudes for various plasma situations are shown and compared.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
In this work, population coefficients of hydrogen's n = 3 excited state from the hydrogen collisional-radiative (CR) model, from the data file of DEGAS 2, are used to calculate the photon emissivity coefficients (...In this work, population coefficients of hydrogen's n = 3 excited state from the hydrogen collisional-radiative (CR) model, from the data file of DEGAS 2, are used to calculate the photon emissivity coefficients (PECs) of hydrogen Balmer-α (n = 3 →n = 2) (Hα). The results are compared with the PECs from Atomic Data and Analysis Structure (ADAS) database, and a good agreement is found. A magnetic surface-averaged neutral density profile of typical double-null (DN) plasma in EAST is obtained by using FRANTIC, the 1.5-D fluid transport code. It is found that the sum of integral Dα and Hα emission intensity calculated via the neutral density agrees with the measured results obtained by using the absolutely calibrated multi-channel poloidal photodiode array systems viewing the lower divertor at the last closed flux surface (LCFS). It is revealed that the typical magnetic surface-averaged neutral density at LCFS is about 3.5×10^16 m^-3 .展开更多
A generator of the gliding arc jet (GAJ), which is driven by a transverse magnetic field, is developed to produce non-equilibrium plasma at atmospheric pressure. The gas temperature is estimated using the spectrum o...A generator of the gliding arc jet (GAJ), which is driven by a transverse magnetic field, is developed to produce non-equilibrium plasma at atmospheric pressure. The gas temperature is estimated using the spectrum of OH radicals to be about 2400±400 K. The determinations of electron temperature and electron density by using a line-ratio method are elaborated for the gliding arc jet plasma. This line-ratio method is based on a collisional-radiative model. The experiment results show that electron temperature is about 1.0 eV and electron density is about 6.9×1014 cm-3 . Obviously, the plasma of GAJ is in a non-equilibrium state.展开更多
Plasma radiative properties play a pivotal role both in nuclear fusion and astrophysics.They are essential to analyze and explain experiments or observations and also in radiative-hydrodynamics simulations.Their compu...Plasma radiative properties play a pivotal role both in nuclear fusion and astrophysics.They are essential to analyze and explain experiments or observations and also in radiative-hydrodynamics simulations.Their computation requires the generation of large atomic databases and the calculation,by solving a set of rate equations,of a huge number of atomic level populations in wide ranges of plasma conditions.These facts make that,for example,radiative-hydrodynamics in-line simulations be almost infeasible.This has lead to develop analytical expressions based on the parametrization of radiative properties.However,most of them are accurate only for coronal or local thermodynamic equilibrium.In this work we present a code for the parametrization of plasma radiative properties of mono-component plasmas,in terms of plasma density and temperature,such as radiative power loss,the Planck and Rosseland mean opacities and the average ionization,which is valid for steady-state optically thin plasmas in wide ranges of plasma densities and temperatures.Furthermore,we also present some applications of this parametrization such as the analysis of the optical depth and radiative character of plasmas,the use to perform diagnostics of the electron temperature,the determination of mean radiative properties for multicomponent plasmas and the analysis of radiative cooling instabilities in some kind of experiments on high-energy density laboratory astrophysics.Finally,to ease the use of the code for the parametrization,this one has been integrated in a user interface and brief comments about it are presented.展开更多
基金supported by National Natural Science Foundation of China (Nos. 11075093 and 10935006) and the China Postdoctoral Science Foundation (No. 20100480327)
文摘A Maxwellian electron energy distribution function (EEDF) is often assumed when using the optical emission line-ratio method to determine the electron temperature in low- temperature plasmas. However, in many cases, non-Maxwellian EEDFs can be formed due to the non-local electron heating or the inelastic-collisional energy loss processes. In this work, with a collisional-radiative model, we propose an approach to obtain the non-Maxwellian EEDF with a 'two-temperature structure' from the emission line-ratios of Paschen 2p levels of argon and kryp- ton atoms. For applications of this approach in reactive gas (CF4, O2, etc) discharges that contain argon and krypton, recommendations of some specific emission line-ratios are provided, according to their sensitivities to the EEDF variation. The kinetic processes of the relevant excited atoms are also discussed in detail.
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.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10635010 and 10775103)
文摘This paper proposes a simple collisional-radiative model to characterise capacitively coupled argon plasmas driven by conventional radio frequency in combination with optical emission spectroscopy and Langmuir probe measurements. Two major processes are considered in this model, electron-impact excitation and the spontaneous radiative decay. The diffusion loss term, which is found to be important for the two metastable states (4s[3/2]2, 4s'[1/2]0), is also taken into account. Behaviours of representative metastable and radiative states are discussed. Two emission lines (located at 696.5 nm and 750.4 nm) are selected and intensities are measured to obtain populated densities of the corresponding radiative states in the argon plasma. The calculated results agree well with that measured by Langmuir probe, indicating that the current model combined with optical emission spectroscopy is a candidate tool for electron density and temperature measurement in radio frequency capacitively coupled discharges.
基金supported by the Research Project of the Spanish Government(ENE2008-06668-C02-02/FTN)by the Keep in touch Project of the European Union.
文摘Non-local thermodynamic equilibrium(NLTE)conditions are universal in laboratory and astrophysical plasmas and,for this reason,the theory of NLTE plasmas is nowadays a very active subject.The populations of atomic levels and radiative properties are essential magnitudes in the study of these plasmas and the calculation of those properties relies on the so-called collisional-radiative(CR)models.However,the complexity of these models has led to the development of numerous collisionalradiative codes and this is a current research topic in plasmas.In this work is presented a versatile computational package,named ABAKO/RAPCAL,to calculate the populations of atomic levels and radiative properties of optically thin and thick,lowto-high Z,NLTE plasmas.ABAKO/RAPCAL combines a set of analytical approximations which yield substantial savings in computing running time,still comparing well with more elaborated codes and experimental data.In order to show the capabilities of the code and the accuracy of its results,calculations of several relevant plasma magnitudes for various plasma situations are shown and compared.
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 National Natural Science Foundation of China(Nos.11075181,10605028 and 11075180)in part by the JSPS-CAS Core-University program in the field of 'Plasma and Nuclear Fusion'
文摘In this work, population coefficients of hydrogen's n = 3 excited state from the hydrogen collisional-radiative (CR) model, from the data file of DEGAS 2, are used to calculate the photon emissivity coefficients (PECs) of hydrogen Balmer-α (n = 3 →n = 2) (Hα). The results are compared with the PECs from Atomic Data and Analysis Structure (ADAS) database, and a good agreement is found. A magnetic surface-averaged neutral density profile of typical double-null (DN) plasma in EAST is obtained by using FRANTIC, the 1.5-D fluid transport code. It is found that the sum of integral Dα and Hα emission intensity calculated via the neutral density agrees with the measured results obtained by using the absolutely calibrated multi-channel poloidal photodiode array systems viewing the lower divertor at the last closed flux surface (LCFS). It is revealed that the typical magnetic surface-averaged neutral density at LCFS is about 3.5×10^16 m^-3 .
基金supported by National Natural Science Foundation of China(Nos.10975136,11035005)USTC-NSRL Association Funding of China(No.KY2090130001)
文摘A generator of the gliding arc jet (GAJ), which is driven by a transverse magnetic field, is developed to produce non-equilibrium plasma at atmospheric pressure. The gas temperature is estimated using the spectrum of OH radicals to be about 2400±400 K. The determinations of electron temperature and electron density by using a line-ratio method are elaborated for the gliding arc jet plasma. This line-ratio method is based on a collisional-radiative model. The experiment results show that electron temperature is about 1.0 eV and electron density is about 6.9×1014 cm-3 . Obviously, the plasma of GAJ is in a non-equilibrium state.
基金the Research Project of the Spanish Government(ENE2009-11208/FTN)the Keep in touch and ToIFE Projects of the European Union.
文摘Plasma radiative properties play a pivotal role both in nuclear fusion and astrophysics.They are essential to analyze and explain experiments or observations and also in radiative-hydrodynamics simulations.Their computation requires the generation of large atomic databases and the calculation,by solving a set of rate equations,of a huge number of atomic level populations in wide ranges of plasma conditions.These facts make that,for example,radiative-hydrodynamics in-line simulations be almost infeasible.This has lead to develop analytical expressions based on the parametrization of radiative properties.However,most of them are accurate only for coronal or local thermodynamic equilibrium.In this work we present a code for the parametrization of plasma radiative properties of mono-component plasmas,in terms of plasma density and temperature,such as radiative power loss,the Planck and Rosseland mean opacities and the average ionization,which is valid for steady-state optically thin plasmas in wide ranges of plasma densities and temperatures.Furthermore,we also present some applications of this parametrization such as the analysis of the optical depth and radiative character of plasmas,the use to perform diagnostics of the electron temperature,the determination of mean radiative properties for multicomponent plasmas and the analysis of radiative cooling instabilities in some kind of experiments on high-energy density laboratory astrophysics.Finally,to ease the use of the code for the parametrization,this one has been integrated in a user interface and brief comments about it are presented.