A full relativistic detailed-level-accounting approach has been developed independently to deal with the detailed spectral line effects on the opacity of the third most abundant element in stars: oxygen. The atomic e...A full relativistic detailed-level-accounting approach has been developed independently to deal with the detailed spectral line effects on the opacity of the third most abundant element in stars: oxygen. The atomic energy levels and the oscillator strengths of the radiative transitions between the energy levels are obtained by carrying out the full relativistic one-configuration Dirac-Fock calculations. The photoionization cross sections are obtained via an average atom scheme with a consideration for the splitting of the ionization threshold due to the ionization stages and the term-couplings. As an example, the spectra resolved opacities and the mean opacities of oxygen are calculated to show the importance of the detailed spectral line profiles with the density of the matter.展开更多
Opacity of stellar materials with the composition and relative abundance specified according to sun has been calculated by using an average-atom scheme, which is designed to treat electronic structures of atoms and io...Opacity of stellar materials with the composition and relative abundance specified according to sun has been calculated by using an average-atom scheme, which is designed to treat electronic structures of atoms and ions in a mixture. Different relative abundances of the metallic elements are considered. Oomparisons between the present results and those of OPAL are made for the opacity to show that the difference is less than 10% for mostcases and less than 30% for the largest point with the density of 1.0g/cm^3 and temperatures from 50 to 6000eV. In view of the simplicity of the present approach, it is quite flexible to apply the method to different models of the stellar materials with changes in composition as well as in relative abundance.展开更多
We have used the ShenguangⅡlaser in third harmonic(351 nm)to investigate the emission of L-shell radiation in the 3.3–4.4 ke V range generated using thin foils of Sn coated onto a parylene substrate with irradiation...We have used the ShenguangⅡlaser in third harmonic(351 nm)to investigate the emission of L-shell radiation in the 3.3–4.4 ke V range generated using thin foils of Sn coated onto a parylene substrate with irradiation of order 1015 W cm-2 and nanosecond pulse duration.In our experiment,we have concentrated on assessing the emission on the non-laser irradiated side as this allows an experimental geometry relevant to experiments on photo-ionised plasmas where a secondary target must be placed close to the source,to achieve x-ray fluxes appropriate to astrophysical objects.Overall L-shell conversion efficiencies are estimated to be of order 1%,with little dependence on Sn thickness between 400 and 800 nm.展开更多
A counter-streaming flow system is a test-bed to investigate the astrophysical collisionless shock(CS) formation in the laboratory. Electrostatic/electromagnetic instabilities, competitively growing in the system and ...A counter-streaming flow system is a test-bed to investigate the astrophysical collisionless shock(CS) formation in the laboratory. Electrostatic/electromagnetic instabilities, competitively growing in the system and exciting the CS formation, are sensitive to the flows parameters. One of the most important parameters is the velocity, determining what kind of instability contributes to the shock formation. Here we successfully measure the evolution of the counter-streaming flows within one shot using a multi-pulses imaging diagnostic technique. With the technique, the average velocity of the high-density-part(ne ≥ 8–9 × 10^(19)cm^(-3)) of the flow is directly measured to be of ～ 10~6cm/s between 7 ns and 17 ns.Meanwhile, the average velocity of the low-density-part(ne ≤ 2 × 10^(19)cm^(-3)) can be estimated as ～ 10~7cm/s. The experimental results show that a collisionless shock is formed during the low-density-part of the flow interacting with each other.展开更多
文摘A full relativistic detailed-level-accounting approach has been developed independently to deal with the detailed spectral line effects on the opacity of the third most abundant element in stars: oxygen. The atomic energy levels and the oscillator strengths of the radiative transitions between the energy levels are obtained by carrying out the full relativistic one-configuration Dirac-Fock calculations. The photoionization cross sections are obtained via an average atom scheme with a consideration for the splitting of the ionization threshold due to the ionization stages and the term-couplings. As an example, the spectra resolved opacities and the mean opacities of oxygen are calculated to show the importance of the detailed spectral line profiles with the density of the matter.
文摘Opacity of stellar materials with the composition and relative abundance specified according to sun has been calculated by using an average-atom scheme, which is designed to treat electronic structures of atoms and ions in a mixture. Different relative abundances of the metallic elements are considered. Oomparisons between the present results and those of OPAL are made for the opacity to show that the difference is less than 10% for mostcases and less than 30% for the largest point with the density of 1.0g/cm^3 and temperatures from 50 to 6000eV. In view of the simplicity of the present approach, it is quite flexible to apply the method to different models of the stellar materials with changes in composition as well as in relative abundance.
基金supported by the UK Science and Technology Facilities Council,National Natural Science Foundation of China(No.11573040)Science Challenge Project(No.TZ2016005)The Royal Society International Exchange(No.IE161039).
文摘We have used the ShenguangⅡlaser in third harmonic(351 nm)to investigate the emission of L-shell radiation in the 3.3–4.4 ke V range generated using thin foils of Sn coated onto a parylene substrate with irradiation of order 1015 W cm-2 and nanosecond pulse duration.In our experiment,we have concentrated on assessing the emission on the non-laser irradiated side as this allows an experimental geometry relevant to experiments on photo-ionised plasmas where a secondary target must be placed close to the source,to achieve x-ray fluxes appropriate to astrophysical objects.Overall L-shell conversion efficiencies are estimated to be of order 1%,with little dependence on Sn thickness between 400 and 800 nm.
基金Project supported by the National Basic Research Program of China(Grant No.2013 CBA01501/3)the National Natural Science Foundation of China(Grant Nos.11503041,11135012,11375262,11573040,11574390,and 11220101002)China Postdoctoral Science Foundation(Grant No.2015M571124)
文摘A counter-streaming flow system is a test-bed to investigate the astrophysical collisionless shock(CS) formation in the laboratory. Electrostatic/electromagnetic instabilities, competitively growing in the system and exciting the CS formation, are sensitive to the flows parameters. One of the most important parameters is the velocity, determining what kind of instability contributes to the shock formation. Here we successfully measure the evolution of the counter-streaming flows within one shot using a multi-pulses imaging diagnostic technique. With the technique, the average velocity of the high-density-part(ne ≥ 8–9 × 10^(19)cm^(-3)) of the flow is directly measured to be of ～ 10~6cm/s between 7 ns and 17 ns.Meanwhile, the average velocity of the low-density-part(ne ≤ 2 × 10^(19)cm^(-3)) can be estimated as ～ 10~7cm/s. The experimental results show that a collisionless shock is formed during the low-density-part of the flow interacting with each other.
