Visualization study of vortex-line dynamics in a magnetically levitated helium-4 superfluid drop

磁悬浮氦 4 超流体液滴涡线动力学的可视化研究

• 批准号: 1507386
• 负责人: Wei Guo
• 金额: $ 30.24万
• 依托单位: Florida State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-05-01 至 2018-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1507386&HistoricalAwards=false
• 关键词: Visualization; study; vortex; line; dynamics

Nontechnical AbstractQuantum vortices, which are like little tornados governed by the laws of quantum mechanics, are important in understanding the behavior of systems such as superfluid helium, superconductors, liquid crystals, neutrons stars and perhaps even cosmic strings in the early universe. This project explores the behavior of quantum vortices in small (~1cm) droplets of superfluid liquid helium. Magnetic levitation, which is the same technique being explored for high speed trains and elevators that can move in all 3 dimensions, is used to float the droplet and eliminate the influence of the walls and the motion of the vortices is imaged using tracer molecules which fluoresce when illuminated with laser light. These studies will help us better understand the behavior of this strange form of quantum matter and will benefit studies of advanced materials such as superconductors and liquid crystals. This project will also train a new generation of scientists in technologically important fields such as low-temperature physics, fluid dynamics and advanced laser technologies. The research team plans to conduct demonstrations involving magnetic levitation and superfluid helium in various educational and outreach programs at the National High Magnetic Field Laboratory to introduce these scientific concepts to the general public.Technical AbstractThis project addresses intriguing fundamental problems relevant to the dynamics of quantized vortex lines. The objectives include a thorough investigation on how the appearance of vortices can affect the stability of a rotating superfluid drop and an in-depth study of the evolution of a vortex tangle in a wall-free environment. In superfluid helium-4, vortex lines can be directly visualized by imaging tracer particles trapped on the lines. However, producing tracers in helium at low temperatures and imaging the trapped tracers remains challenging, and the container walls can often affect the vortex-line motion. This project employs a levitated helium-4 drop as the working system, in which the vortices can be produced via fast evaporative cooling and controllable drop rotation. These vortices can be decorated with metastable He2 molecular tracers which can be imaged using a laser-induced fluorescence technique. The study of the vortex configuration in a rotating helium-4 drop helps explain the observed drop morphology and allows the derivation of the stability diagram of rotating superfluid drops. Since a levitated helium drop may serve as a model for other superfluid drop systems, such as neutron stars, the results obtained in this study may generate broad interest. Visualizing the evolution of a vortex tangle in a helium drop can facilitate the study of central questions in quantum turbulence research, such as the existence of polarized vortex bundles and the generation of Kelvin waves on vortices; these studies can directly advance our knowledge about the characteristics of quantum turbulence.

非技术抽象的涡流，就像量子力学定律所支配的小龙卷风一样，对于理解诸如超氟氦，超导体，液晶，中子，中子恒星甚至早期宇宙等系统的行为很重要。 该项目探讨了量子涡旋在超氟液氦的小（〜1cm）液滴中的行为。 对于可以在所有3个维度中移动的高速火车和电梯的磁性悬浮，这是相同的技术，用于漂浮并消除壁的影响，并使用用激光照明的示踪剂分子成像涡旋分子成像。 这些研究将有助于我们更好地了解这种奇怪的量子物质形式的行为，并有益于高级材料（例如超导体和液晶）的研究。该项目还将在技术上重要的领域培训新一代科学家，例如低温物理，流体动力学和先进的激光技术。研究小组计划在国家高磁场实验室的各种教育和外展计划中进行涉及磁性悬浮和超级流体氦气的演示，以向公众介绍这些科学概念。技术抽象摘要该项目解决了与量化涡流线动态有关的有趣的基本问题。这些目标包括对涡旋的外观如何影响旋转超流体下降的稳定性以及对无壁环境中涡流缠结的演变的深入研究。在超流体氦4中，可以通过对捕获在线上的示踪剂颗粒进行成像，可以直接观察涡流线。然而，在低温下氦气中产生示踪剂并成像被困的示踪剂仍然具有挑战性，并且容器壁通常会影响涡旋线运动。该项目采用悬浮的氦气4滴作为工作系统，在该系统中可以通过快速蒸发冷却和可控制的下降旋转产生涡流。这些涡旋可以用亚稳态的HE2分子示踪剂装饰，可以使用激光诱导的荧光技术成像。在旋转氦4滴中对涡旋构型的研究有助于解释观察到的下降形态，并允许衍生旋转的超氟滴的稳定性图。由于悬浮的氦下降可以作为其他超氟滴系统（例如中子星）的模型，因此本研究中获得的结果可能会引起广泛的兴趣。可视化涡旋下降中涡流缠结的演变可以促进量子湍流研究中的中心问题的研究，例如存在偏振涡流束和涡流上开尔文波的产生。这些研究可以直接提高我们对量子湍流特征的了解。