Producing and imaging a thin line of He2* molecular tracers in helium-4
Producing and imaging a thin line of He2* molecular tracers in helium-4
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DOI：
10.1063/1.4930147
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发表时间：
2015-09-01
影响因子：
1.6
通讯作者：
Vinen, W. F.
中科院分区：
文献类型：
--
作者：
Gao, J.;Marakov, A.;Vinen, W. F.
低温氦-4一直被认为是流体研究中的一种有用材料。氦-4在气相和正常液相中的独特性质允许产生具有极高雷诺数和瑞利数的湍流。在超流体阶段，氦-4表现出双流体流体力学，由于其量子性质而具有迷人的特性。然而，由于缺乏有效的可视化和测速技术，研究氦-4中的流动非常具有挑战性。在本文中，我们讨论了基于亚稳He-2*示踪分子细线的生成和成像的新型氦流可视化仪器的发展。这些分子示踪剂是通过飞秒激光场电离氦原子产生的，可以使用激光诱导荧光技术成像。通过观察氦中示踪线的位移和畸变，可以提取流场的定量信息。我们给出了研究超流氦的热逆流的实验结果，验证了该技术的概念。我们还讨论了这种强大的可视化技术的预期未来发展。(C) 2015 AIP出版有限责任公司
Cryogenic helium-4 has long been recognized as a useful material in fluids research. The unique properties of helium-4 in the gaseous phase and the normal liquid phase allow for the generation of turbulent flows with exceptionally high Reynolds and Rayleigh numbers. In the superfluid phase, helium-4 exhibits two-fluid hydrodynamics and possesses fascinating properties due to its quantum nature. However, studying the flows in helium-4 has been very challenging largely due to the lack of effective visualization and velocimetry techniques. In this article, we discuss the development of novel instrumentation for flow-visualization in helium based on the generation and imaging of thin lines of metastable He-2* tracer molecules. These molecular tracers are created via femtosecond-laser field-ionization of helium atoms and can be imaged using a laser-induced fluorescence technique. By observing the displacement and distortion of the tracer lines in helium, quantitative information about the flow field can be extracted. We present experimental results in the study of thermal counterflow in superfluid helium that validate the concept of this technique. We also discuss anticipated future developments of this powerful visualization technique. (C) 2015 AIP Publishing LLC.