Visualization of quantum turbulence and vortex dynamics in superfluid helium

超流氦中的量子湍流由量子化涡旋线的缠结组成，这些涡旋的动力学在很宽的长度尺度范围内提供了丰富多样的物理学，特别是在零温度的极限下，由于热激发而导致的阻尼不存在。该项目将利用最近开发的光学成像设备，并在旋转稀释冰箱上建造，通过量子涡旋核心上捕获荧光粒子（氦准分子和纳米球）来可视化量子湍流。其目的是提高我们的理解如何动态的涡旋有助于能量转移到较短的长度尺度，导致量子湍流耗散。学生将进一步发展该装置并改进实验技术，以提高空间和时间分辨率，从而可以观察到更大范围的现象，包括涡束、涡重联和自重联、开尔文（螺旋）波、环孤子和涡环。学生也可以调整设备，以允许在稳定旋转期间成像，当平衡状态是直线涡线阵列时。扰动这个涡旋阵列将允许观察和研究惯性波和开尔文波的增长和衰减。学生还将开发软件工具，用于分析从实验中获得的图像和视频，并为研究成果的传播做出贡献。

Quantum turbulence in superfluid helium consists of a tangle of quantized vortex lines and the dynamics of these vortices provides a rich variety of physics across a broad range of length scales, particularly in the limit of zero temperature where the damping due to thermal excitations is absent. This project will utilize optical imaging apparatus that was recently developed and constructed on one of rotating dilution refrigerators to visualize quantum turbulence through the trapping of fluorescent particles (helium excimers and nanospheres) on the cores of quantized vortices. The aim is to enhance our understanding of how the dynamics of vortices contribute to the transfer of energy to shorter length scales leading to the dissipation of quantum turbulence. This will lead to an improved understanding of the general phenomena of turbulence.The student will further develop this apparatus and refine the experimental technique to improve the spatial and temporal resolution allowing a greater range of phenomena to be observed, including vortex bundles, vortex reconnections and self-reconnections, Kelvin (helical) waves, loop solitons and vortex rings. The student may also adapt the apparatus to allow imaging during steady rotation when the equilibrium state is an array of rectilinear vortex lines. Perturbing this vortex array will allow the growth and decay of inertial waves and Kelvin waves to be observed and investigated. The student will also develop software tools for analysis of the images and videos obtained from the experiment and contribute to the dissemination of the research outcomes.