laser产生等离子体的实验约束多维模拟及其在UV纳秒烧蚀Se和Te中的应用
Experimentally constrained multidimensional simulation of laser-generated plasmas and its application to UV nanosecond ablation of Se and Te
摘要：
我们进行了模拟过程中产生的激光等离子体紫外纳秒脉冲激光烧蚀硫属元素硒（Se）和碲（Te），并与实验结果进行比较。我们利用一个二维轴对称，自适应笛卡尔网格（ACM）框架，使羽流模拟厘米的距离超过几十微秒。我们的模型和计算技术可以与激光等离子体应用进行比较，其中羽流的长期行为是主要关注的，例如脉冲激光合成和材料改性。在模型中引入了一个有效的等离子体吸收项，使模拟受到实验飞行时间动能分布的约束。我们表明，有效的模拟定性捕捉所观察到的激光等离子体的关键特征，包括激光光斑大小的影响。预测的全尺寸实验约束的硒和碲等离子体为4.0 J/cm $^2$激光能量密度和1.8 mm $^2$圆形激光光斑面积相比，更常见的研究铜（Cu）羽流表现出不同的行为。硫族元素羽流的等离子体密度的空间梯度是陡峭的比那些铜高达三个数量级。它们的空间离子分布有中心凸起，在相反的边缘只有电离的铜。对于探索的照射条件，Se和Te的等离子体温度的范围被预测为高于Cu的0.50 eV以上。
英文摘要：
We carry out simulations of laser plasmas generated during UV nanosecond pulsed laser ablation of the chalcogens selenium (Se) and tellurium (Te), and compare the results to experiments. We take advantage of a 2D-axisymmetric, adaptive Cartesian Mesh (ACM) framework that enables plume simulations out to centimeter distances over tens of microseconds. Our model and computational technique enable comparison to laser-plasma applications where the long-term behavior of the plume is of primary interest, such as pulsed laser synthesis and modification of materials. An effective plasma absorption term is introduced in the model, allowing the simulation to be constrained by experimental time-of-flight kinetic energy distributions. We show that the effective simulation qualitatively captures the key characteristics of the observed laser plasma, including the effect of laser spot size. Predictions of full-scale experimentally-constrained Se and Te plasmas for 4.0 J/cm$^2$ laser fluence and 1.8 mm$^2$ circular laser spot area show distinct behavior compared to more commonly studied copper (Cu) plumes. The chalcogen plumes have spatial gradients of plasma density that are steeper than those for Cu by up to three orders of magnitude. Their spatial ion distributions have central bulges, in contrast to the edge-only ionization of Cu. For the irradiation conditions explored, the range of plasma temperatures for Se and Te is predicted to be higher than for Cu by more than 0.50 eV.
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