Detailed Configuration Accounting Model Research Articles

Study on laser-irradiated Au plasmas by detailed configuration accounting atomic physics

We coupled the one-dimensional multi-group radiation hydrodynamic code RDMG with the MBDCA atomic physics package, which uses the Matrix-Block Method to solve the coupled rate equations of the Detailed Configuration Accounting (DCA) non-LTE model, and applied the coupled code RDMG-MBDCA with different flux limiters fe to simulate a laser-irradiated CH-tamped Au disk experiment at the SGII laser facility. From our simulations, we found that a higher fe leads to faster laser ablation, earlier x-ray breakout time with a higher maximum x-ray flux, and an x-ray spectrum with a higher intensity. However, for the same fe, the simulation from RDMG with the DCA model shows a slower electron thermal conduction between the laser absorption region and the electron thermal conduction than that with the average-atom model. From our investigation, we can say that it is the lower ionization from DCA in the electron thermal conduction region which causes the slower electron thermal conduction between the two regions. The electron thermal conduction from DCA can be increased remarkably when the atomic processes of dielectronic capture and auto-ionization are turned off in simulation. This indicates that the atomic transition rate coefficients are important in determining the heat conduction and the plasma status for laser generated plasmas.

Dynamic properties of the energy loss of multi-MeV charged particles traveling in two-component warm dense plasmas.

The energy loss of multi-MeV charged particles moving in two-component warm dense plasmas (WDPs) is studied theoretically beyond the random-phase approximation. The short-range correlations between particles are taken into account via dynamic local field corrections (DLFC) in a Mermin dielectric function for two-component plasmas. The mean ionization states are obtained by employing the detailed configuration accounting model. The Yukawa-type effective potential is used to derive the DLFC. Numerically, the DLFC are obtained via self-consistent iterative operations. We find that the DLFC are significant around the maximum of the stopping power. Furthermore, by using the two-component extended Mermin dielectric function model including the DLFC, the energy loss of a proton with an initial energy of ∼15MeV passing through a WDP of beryllium with an electronic density around the solid value n_{e}≈3×10^{23}cm^{-3} and with temperature around ∼40 eV is estimated numerically. The numerical result is reasonably consistent with the experimental observations [A. B. Zylsta etal., Phys. Rev. Lett. 111, 215002 (2013)PRLTAO0031-900710.1103/PhysRevLett.111.215002]. Our results show that the partial ionization and the dynamic properties should be of importance for the stopping of charged particles moving in the WDP.

Numerical demonstration of high-Z doping scheme on ignition-relevant scale implosion

Although it has been demonstrated that high-Z doped plastic can suppress the Rayleigh–Taylor instability, its usability in direct-drive implosion design on mega-joule class reactors is still controversial. In this study, the radiation hydrodynamics code was validated by a planar target experiment of a brominated plastic target, since the result including high-Z strongly depends on the opacity model. Opacity for bromine ion based on the detailed configuration accounting model has better agreement with the experimental results compared to that of the average-ion model. Two-dimensional implosion simulations assuming a mega-joule driver were also conducted to estimate whether a brominated plastic ablator can suppress the hydrodynamic instability. It was revealed that a brominated plastic, which has an appropriate fraction of doping, can assist the generation of a high-density core by suppression of the hydrodynamic instability. A high-Z doped target can suppress the Rayleigh–Taylor instability at the foot-dri...

X-ray conversion efficiency in vacuum hohlraum experiments at the National Ignition Facility

X-ray fluxes measured in the first 96 and 192 beam vacuum hohlraum experiments at the National Ignition Facility (NIF) were significantly higher than predicted by computational simulations employing XSN average atom atomic physics and highly flux-limited electron heat conduction. For agreement with experimental data, it was found that the coronal plasma emissivity must be simulated with a detailed configuration accounting model that accounts for x-ray emission involving all of the significant ionization states. It was also found that an electron heat conduction flux limit of f = 0.05 is too restrictive, and that a flux limit of f = 0.15 results in a much better match with the NIF vacuum hohlraum experimental data. The combination of increased plasma emissivity and increased electron heat conduction in this new high flux hohlraum model results in a reduction in coronal plasma energy and, hence, an explanation for the high (∼85%-90%) x-ray conversion efficiencies observed in the 235 < Tr < 345 eV NIF vacuum hohlraum experiments.

Radiative opacities and configuration interaction effects of hot iron plasma using a detailed term accounting model

We have calculated the radiative opacities of iron plasma in local thermodynamic equilibrium using a detailed term accounting model. The extensive atomic data are obtained by multiconfiguration Hartree-Fock (MCHF) method, with Breit-Pauli relativistic corrections. Extensive configuration interaction (CI) has been included based on LS coupling to obtain energy levels and the bound-bound transition cross sections. A detailed configuration accounting model is applied to evaluate the bound-free absorption cross sections. We simulate two experimental transmission spectra [G. Winhart et al., Phys. Rev. E 53, R1332 (1996); P. T. Springer et al., J. Quant. Spectrosc. Radiat. Transf. 58, 927 (1997)] to verify our calculation model, one is at a temperature of 22 eV and a density of 10(-2) g/cm(3) and the other is at a temperature of 20 eV and a lower density of 10(-4) g/cm(3). It is shown that the strong CI can effectively change the oscillator strengths in contrast to the single configuration HF method. For both of the two simulated transmission spectra good agreement is obtained between the present MCHF results and the experimental data. Spectrally resolved opacities and Planck and Rosseland mean opacities are also calculated. For the isothermal sequence of T=20 eV, when the density decreases from 10(-2) to 10(-5) g/cm(3), the linewidth also decreases so that the iron transition arrays show more discrete line structures and the linewidth becomes very important to the Rosseland mean opacity.

Theoretical investigation of the increase in the Rosseland mean opacity for hot dense mixtures.

Based on a detailed configuration accounting model with the term structures treated by the unresolved transition array model, a large scale calculation has been performed for the opacities of medium- and high-Z materials and mixtures. Agreement between our calculated results and previous theoretical simulations is obtained. By filling in the low-opacity regions of one material with the high-opacity regions of other materials, the Rosseland mean opacity of their combination will be increased. This should be of great interest to hohlraum design in indirect-drive inertial confinement fusion. Based on our studies, many mixtures, such as Au+Nd, or Ho+Sn, can result in a similar (or higher) increase in the Rosseland mean as the previously proposed Au+Gd mixture.

Theoretical Study of the Opacity for Mixture Materials at HighTemperatures

Using a detailed configuration accounting model with term structurestreated by the unresolved transition array model, we have extensively investigatedthe opacities of mixture materials. For plasmas at the temperature of 250 eV anddensity of 1 g/cm3, our calculated Rosseland mean opacities are in good agreementwith other theoretical results. A high increase in the Rosseland mean opacity to2944 cm2/g is achieved for a multi-element mixture compared to the value of1729 cm2/g for pure gold. Various mixtures at other plasma conditions are also studied.

Resonant photoionization for average ions

The authors try to develop a method to calculate the rate of the reverse process of dielectronic recombination that can be used in the rate equations in an average ion model. Based on the detailed configuration accounting (DCA) model, an approximate formula for the above calculation is presented and is tested by the DCA model.

The Non-local Thermodynamical Equilibrium Effects on Opacity**The project supported by the Science and Technology Funds of China Academy of Engineering Physics (990221)

Based on the detailed configuration accounting (DCA) model, a method is developed to include the resonant photoionization and the excitation-autoionization in the non-local thermodynamical equilibrium (NLTE) average atom (AA) model. Using this new model, the mean charge states and the opacity are calculated for NLTE high- plasmas and compared with other results. The agreement with AA model is poor at low electron density. The present results agree well with those of DCA model within 10%. The calculations show that the NLTE effects on opacity are strong.

Effect of excitation-autoionization in non-local thermodynamic equilibrium plasmas

Based on the detailed configuration accounting model, the authros have developed a method to calculate the rate of excitation-autoionization (EA) in the average atom model and used it in the rate equations. The numerical results show that EA effect is signifficant in high temperature low density plasma and can cause an additional ionization up to 15% of an ionization stage.

Effect of Resonant Photoionization in Non-Local Thermodynamical Equilibrium Plasmas

Based on the detailed configuration accounting model (DCA), a method is developed to calculate the rate of the resonant photoionization (RP) in the average atom (AA) model. Using this method, the RP rates are calculated for an average ion and compared with DCA calculation. The comparison shows the reasonableness of the proposed method. The RP process is included in the AA rate equations and the numerical results show that RP can cause an additional ionization up to 10% or so in some cases.