Experimental Investigation of Pure Quantum Turbulence in Superfluid He-4 at Very Low Temperatures

极低温超流He-4纯量子湍流的实验研究

基本信息

批准号：
EP/E016928/1
负责人：
Peter Vaughan Elsmere McClintock
金额：
$ 79.09万
依托单位：
Lancaster University
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2006
资助国家：
英国
起止时间：
2006 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FE016928%2F1
关键词：
Experimental Investigation Pure Quantum Turbulence

项目摘要

Turbulence in classical fluids is important and challenging both for theory and for many practical applications. The research aims to understand how classical turbulence is modified in a superfluid, in which flow is severely restricted by quantum conditions associated with the quantization of angular momentum.At higher temperatures, superfluids exhibit two-fluid behaviour, a normal fluid coexisting with the superfluid component in which the quantum effects are important. There is already strong evidence that at these temperatures turbulent structures on large length scales can be very similar to their classical counterparts, although dissipative processes acting on small scales are very different. It is suspected that a similar situation exists at very low temperatures, where the normal fluid is absent, and where simple mechanisms for the decay of the turbulence have disappeared. Our programme seeks to provide experimental evidence relating to these low temperatures, at which the fundamental behaviour of very pure forms of quantum turbulence ought to be observable. Quantum turbulence is of great intrinsic interest, and its study could lead to a better understanding of classical turbulence.The turbulence - comprised of a seemingly random tangle of quantized vortex lines - will be generated in the superfluid either by a steadily moving grid or by an oscillating grid. The mechanical behaviour of the oscillating grid will provide evidence about the production of turbulence. Calorimetric observations and/or the detection of ion trapping will measure the turbulent decay, which reflects not only dissipation on small scales but also the overall turbulent structure. The quantitative application of the ion trapping detection technique is dependent on measurements of the trapping cross-section, currently in progress at the University of Manchester. Although the oscillating grid provides a proven technique for creating quantum turbulence in the mK temperature range, the turbulence is not well-characterised and nor is its spatial distribution known. In these senses, although technically far more demanding, the steadily moving grid is to be preferred because it will create quantum turbulence that is both well-characterised and spatially homogeneous. Some promising new, more sensitive, detection methods are appearing on the horizon, possibly including the spectroscopy of neutral excitations, and preliminary studies will be made to confirm that the excitations can indeed be trapped on quantized vortex lines.Success of the proposed experiments is dependent on the close interactive collaboration between Florida, Birmingham and Lancaster, and liaison with Newcastle and Osaka where theoretical studies and digital simulations are in progress.. The Lancaster experimental group and the Birmingham Co-Investigator are currently funded by EPSRC (GR/R94848/01) for this work up to the end of June 2006. Their collaboration with the Florida group has been initiated by an EPSRC Visiting Fellowship (EP/D007739/1) for Professor Ihas to visit Lancaster during October 2005 - May 2006. The Florida group proposes to develop the work with the support of NSF Materials World Network funding (DMR-0602778, which has recently been recommended for funding). The Lancaster/Birmingham group has already requested travel/subsistence (WMN-linked proposal EP/D067758/1) to support their collaboration with the Florida group during the period of their NSF MWN grant.The present proposal is for the funding needed to support the UK experimental part of this international collaborative research programme.

经典流体的湍流对于理论和许多实际应用都很重要，而且具有挑战性。该研究的目的是了解如何在超流体中改变经典的湍流，其中流动受到与角动量量化相关的量子条件的严重限制。在较高的温度下，超流体表现出两流体的行为，一种正常的流体与量子效应的超级氟化成分共存。已经有强有力的证据表明，在这些温度下，大长度尺度上的湍流结构可能与它们的经典同行非常相似，尽管作用在小尺度上的耗散过程大不相同。怀疑在不存在正常液体的温度下存在类似情况，而湍流衰减的简单机制消失了。我们的计划旨在提供与这些低温有关的实验证据，在这种证据上应该可以观察到非常纯粹的量子湍流形式的基本行为。量子湍流具有很大的内在兴趣，其研究可能会导致对经典湍流的更好理解。湍流 - 由量化的涡流线组成的湍流 - 将通过稳定移动的网格或通过振荡电网而在超级流体中产生。振荡网格的机械行为将提供有关湍流产生的证据。量热观测和/或离子捕获的检测将测量湍流衰减，这不仅反映了小尺度上的耗散，还反映了整体湍流结构。离子捕获检测技术的定量应用取决于目前在曼彻斯特大学正在进行的捕获横截面的测量值。尽管振荡网格为在MK温度范围内产生量子湍流提供了一种验证的技术，但湍流不是很好的特征，并且其空间分布也不知道。从这些意义上讲，尽管从技术上讲越来越苛刻，但要稳定移动的网格是首选的，因为它会产生量子湍流，既符合特征且在空间上均匀均匀。某些有希望的新，更敏感的检测方法正在范围内出现，可能包括中性兴奋的光谱法，并将进行初步研究，以确认兴奋确实可以被量化的涡旋线上被困在量化的涡流中。拟议的实验的核对依赖于Florida和Florida，New Digition，Birmingham和Lancsaster，Birmingham和Lancsaster之间的近距离互动研究，模拟正在进行中。兰开斯特实验组和伯明翰共同投资者目前由EPSRC（gr/r94848/01）资助，直到2006年6月底，这项工作。他们与佛罗里达集团的合作已由EPSRC访问eps/d007739/1006供佛罗里达州的合作启动。建议在NSF材料世界网络资金（DMR-0602778）的支持下开发工作，最近推荐用于资助）。兰开斯特/伯明翰集团已经要求在NSF MWN Grant期间与他们与佛罗里达集团的合作进行旅行/维持生计（WMN链接提案EP/D067758/1）。目前的建议是为支持这项国际协作研究计划的英国实验部分所需的资金。