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Methods for measurement of heterogeneous materials with laser-induced breakdown spectroscopy (LIBS).

机译：激光诱导击穿光谱法（LIBS）测量异质材料的方法。

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Laser-Induced Breakdown Spectroscopy (LIBS) is an analytical tool that can be used in a wide range of applications. By focusing a laser pulse onto a small area, material is ionized and heated to 10,000 to 20,000 K. As the plasma cools, atoms emit light. The light contains atomic information about the sample and is analyzed by a spectrometer. In this work, a fundamental study will examine the relationship between ablation and LIBS enhancement in dual-pulse LIBS. Also, an application of LIBS to identify trace metals in molten salt will be presented.;The first experiment will look closely at how spectral enhancement of zinc and copper in brass is influenced by plasma temperature and ablation particles from a dual-pulse laser induced breakdown spectroscopy (DP-LIBS) compared with single-pulse LIBS. The work presented will look at a dual-pulse scheme using two pulsed Nd:YAG laser operating at a fundamental wavelength of 1064 nm. First, a pulse was focused parallel and above the surface forming a pre-ablative plasma in air. A second pulse is then fired to form an ablative (analytical) plasma on a surface while intersecting the volume of the pre-ablative plasma. Two parameters were studied in the DP-LIBS experiments, the inter-pulse delay and the pre-ablative flunce. Both these parameters have an effect on the emission intensity of zinc and copper and the ablation volume. Single-pulse experiments were also conducted by varying the fluence, which also has an effect on the emission intensity of zinc and copper and the ablation volume.;In experiments varying the inter-pulse delay, a 90 mJ pre-ablative laser pulse followed by a 30 mJ ablative (analytical) laser pulse were used. Using this scheme with an inter-pulse delay of 20 mus resulted in a 5 fold increase in intensity for Cu at 521 nm and a 7 fold increase in intensity for Zn at 481 nm compared to single-pulse LIBS. A thirty fold increase in ablation was observed in this DP-LIBS scheme compared to single-pulse LIBS at an inter-pulse delay of 20 mus. With a constant inter-pulse delay there is a mild increase in emission intensity for both zinc and copper with increasing pre-ablation fluence, however, a decrease in ablation volume is also observed with increasing fluence. The single-pulse experiments involved the use of only the ablative analytical pulse. Emission intensity increased with increasing fluence for both Cu and Zn; however, there was a sharp decrease in ablation volume with increasing fluence. The electron temperature was calculated for all experiments using the Boltzmann plot. It was found that emission intensities of Cu and Zn correlated well with the electron temperature; however, considering ablation particle volume along with the electron temperature improved this correlation. The results of this experiment suggest that both particle volume and electron temperature play a significant role on the emission intensity.;The second project involves the use of LIBS to analytically detect trace elements in a molten salt environment. Here an apparatus was built to simulate an electrorefiner and its enclosure. Electrorefiners are used to reprocess nuclear fuel for recycle through electrolysis in a molten salt bath. This is an important application that demonstrates ability of LIBS to analytically detect elements in hostile environments and on liquid surfaces. Chromium, cobalt, and manganese where measured in a eutectic potassium-lithium-chlorine molten salt mixture. Calibration curves were successfully constructed for cobalt (CoCl3) and manganese (MnCl3), while chromium (CrCl3) was used to demonstrate the resolution of the spectrometer. Theoretical detection limits were determined to be 0.04, 0.5 and 0.3 percent mass for CrCl3, CoCl3 and MnCl3, respectively.
机译：激光诱导击穿光谱法（LIBS）是一种分析工具，可广泛用于各种应用中。通过将激光脉冲聚焦到较小的区域，材料被离子化并加热到10,000至20,000K。随着等离子体的冷却，原子发射光。该光包含有关样品的原子信息，并由光谱仪进行分析。在这项工作中，一项基础研究将研究双脉冲LIBS中消融与LIBS增强之间的关系。此外，还将介绍LIBS在鉴定熔融盐中痕量金属中的应用。；第一个实验将仔细研究等离子体温度和双脉冲激光诱导击穿引起的烧蚀颗粒如何影响黄铜中锌和铜的光谱增强光谱法（DP-LIBS）与单脉冲LIBS的比较。提出的工作将研究使用两个脉冲Nd：YAG激光器的双脉冲方案，该激光器工作在1064 nm的基本波长上。首先，将脉冲平行并聚焦在表面上方，在空气中形成预烧蚀等离子体。然后发射第二个脉冲以在表面上形成烧蚀（分析性）等离子体，同时与烧蚀前等离子体的体积相交。在DP-LIBS实验中研究了两个参数：脉冲间延迟和烧蚀前通量。这两个参数都对锌和铜的发射强度以及烧蚀量有影响。还通过改变能量密度来进行单脉冲实验，这也影响锌和铜的发射强度以及消融量。在改变脉冲间延迟的实验中，先使用90 mJ的预烧蚀激光脉冲，然后再进行使用了30 mJ的烧蚀（分析）激光脉冲。与单脉冲LIBS相比，使用此方案的脉冲间延迟为20 mus，导致在521 nm处Cu的强度增加了5倍，而在481 nm处Zn的强度增加了7倍。与单脉冲LIBS相比，该DP-LIBS方案在20 mus的脉冲间延迟下观察到的消融增加了三十倍。在恒定的脉冲间延迟下，随着预烧蚀通量的增加，锌和铜的发射强度都会有所增加，但是，随着通量的增加，烧蚀量也会减少。单脉冲实验仅涉及烧蚀分析脉冲的使用。铜和锌的发射强度随通量的增加而增加；但是，随着通量的增加，消融量急剧减少。对于所有实验，使用玻耳兹曼图计算电子温度。发现铜和锌的发射强度与电子温度有很好的相关性。然而，考虑到烧蚀颗粒体积以及电子温度，这种相关性得到了改善。实验结果表明，粒子体积和电子温度都对发射强度起着重要作用。第二个项目涉及使用LIBS分析检测熔融盐环境中的痕量元素。在这里，建立了一种设备来模拟电精炼机及其外壳。电精炼机用于对核燃料进行再处理，以通过在熔融盐浴中进行电解进行再循环。这是一个重要的应用程序，展示了LIBS在敌对环境和液体表面上分析检测元素的能力。铬，钴和锰含量在共晶的钾-锂-氯熔盐混合物中测得。成功建立了钴（CoCl3）和锰（MnCl3）的校准曲线，而铬（CrCl3）用于证明光谱仪的分辨率。 CrCl3，CoCl3和MnCl3的理论检出限分别为0.04、0.5和0.3％。

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