温稠密铝等离子体物态方程及其电离平衡研究

Investigation on equation of state and ionization equilibrium for aluminum in warm dense matter regime

温稠密物质的物性参数在惯性约束聚变能源、Z箍缩等高能量密度物理领域的实验结果分析和物理过程数值模拟等方面有着重要的应用价值.本文应用部分电离等离子体模型,在理想自由能的基础上考虑了库仑相互作用、排斥体积作用和极化作用等非理想特性,开展了温稠密等离子体物态方程和电离平衡的研究.计算了温稠密铝等离子体的压强等物态方程数据和在密度为1.0×10^-4-3.0 g/cm^3,温度为1.0×10^4-3.0×10^4 K范围内的粒子组分.计算结果显示,铝等离子体的平均电离度在临界密度区域内随着密度的增加而突然增大.根据非理想Saha方程中有效电离能这一关键参数,分析了铝等离子体平均电离度在临界密度区域内随密度迅速增大的现象.

Warm dense matter is widely found in the high-energy-density-physics researches,such as inertial confinement fusion,X-ray source and wire-array Z-pinch.The equation of state and ionization equilibrium of material in warm dense matter regime play a significant role in explaining experimental results and simulations of physical process.In this paper,the Coulomb interaction between charged particles,and the excluded volume effect due to high density and polarization effect between neutral atoms and charged particles are considered in the equation of state for aluminum in warm dense matter regime.A non-ideal Saha equation is used to account for the ionization equilibrium.The data for pressure and concentration of particles of aluminum plasma are derived by iteration between equation of state and ionization equilibrium model.The pressure and average ionization degree of aluminum plasma are consistent with the calculation results from other models and relevant experimental data.The Coulomb interaction,which dominants the non-ideal effects,is insensitive to temperature and increases with density rising especially near the region of critical density.The excluded volume effect peaks at a density of^0.5 g/cm^3.The polarization effect first becomes stronger with density increasing and then decreases at a density of^0.4 g/cm^3.The ionization equilibrium results with density ranging from1.0×10*4 g/cm^3 to 3.0 g/cm^3 and temperature ranging from 1.0×104 K to 3.0×104 K reveal that the average ionization degree increases with density sharply increasing near the critical density.The non-ideal effects,which lead the ionization energy to decline and the effective ionization potential of specific ions in aluminum plasma to decrease substantially,are responsible for the sharp increase of average ionization degree near the region of critical density.When the temperature is lower than 12000 K,first and second stage of ionization occur in aluminum plasma,and the system is mainly composed of Al1+,Al2+and electrons.The average ionization degree can reach 2 at critical density.The third stage of ionization is dominant in the aluminum plasma when plasma temperature is higher than 12000 K.And then,the charged particles in the plasma are composed of Al3+and electrons,allowing the average ionization degree to reach 3 at critical density.