摘要:
ICF内爆物理研究中,示踪元素X射线谱诊断方法是推测内爆压缩温度、 密度以及燃料混合状态的有效方法.针对其中的非平衡物理过程, 研制了非局域热动平衡（non-LTE）下一维谱线输运程序Alpha.程序以辐射流体计算给出的温度、 密度等量为输入条件,求解细致组态（DCA）模型下的原子动力学方程和辐射输运方程, 自洽给出谱线不透明度,和成像面上的X射线谱分布.利用该程序,模拟了神光Ⅱ装置上的掺Ar靶丸内爆示踪元素X射线谱诊断实验, 研究结果表明,谱线的自吸收效应影响发射的X射线谱的强度和形状, 谱线的宽度对自吸收效应的强弱也有影响.因此,在对X射线谱的数值模拟中应该考虑自吸收效应. 另外,与LTE近似下的发射谱的比较表明, LTE近似下,等离子体电离度大～1, 发射谱的形状与non-LTE的结果不同,且LTE近似下,谱线的强度比non-LTE的谱线强度大5-10倍, 采用LTE近似是不合适的.
Abstract:
X-ray spectrum of tracer in ICF implosion target is usually used to infer electron temperature, density and mix of fuel. As the plasma in fuel is in non-local thermodynamic equilibrium （non-LTE）, a line transfer code Alpha is developed. Taking the electron temperature and density provided by radiation hydrodynamic as input condition, atomic kinetics and radiation transfer equation are self-consistently solved with the detailed configuration atom （DCA） model. The opacity for specified frequency intervals is obtained, and X-ray spectrum in the image plane is also presented.As application of Alpha program, the spectrum of doped Ar in implosion target on SG Ⅱ laser facility is simulated. The effect of self-absorption of K α line is studied. And it is shown that self-absorption of K α line affects both the intensity and shape of the spectrum, and it should be considered in simulating X-ray spectrum of Ar. And as the spectrum of local thermodynamic equilibrium （LTE） simulation gives large intensity and different shapes compared with the non-LTE results, non-LTE simulation is necessary in such a simulation.
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