NSF World Materials Network: A Collaborative Experimental Investigation of Pure Quantum Turbulence in Superfluid He-4 at Very Low Temperatures

NSF 世界材料网络：极低温下超流体 He-4 纯量子湍流的合作实验研究

基本信息

批准号：
EP/D067758/1
负责人：
Peter Vaughan Elsmere McClintock
金额：
$ 6.2万
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%2FD067758%2F1
关键词：
NSF World Materials Network Collaborative

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 nucleation of turbulence, and calorimetric observations 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 development of close interactive collaboration between Florida, Birmingham and Lancaster. The Lancaster experimental group and the Birmingham Co-Investigator are already funded by EPSRC for this work up to the end of June 2006. Their collaboration with the Florida group is being initiated by an EPSRC Visiting Fellowship 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; the Lancaster/Birmingham group will submit a research grant application for continuation and development of the Lancaster experimental programme early in 2006. In the present proposal they just request travel/subsistence to support their collaboration with the Florida group during the period of the proposed NSF MWN grant.

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。夸张的湍流具有极大的内在兴趣，其研究可能会更好地理解经典的湍流，或者通过量化的湍流或构成量子的构成，或者是量身定量的湍流，或者由量子构成的构成范围，超过量子的构成范围，超过了，超过的vorture consect consect of Quartire consect of Quartire consect of Supperful croment of Supperful consece of Quartire consect of Supperful consece of超过构成的湍流 /振荡网格。振荡网格的机械行为将提供有关湍流成核的证据，量热观测或离子陷阱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，可能包括中性激发的光谱，并将进行初步研究，以确认确实可以将激发捕获在量化的涡旋线上。拟议的实验的核对措施取决于佛罗里达州和Lancaster之间的近距离互动协作的发展。兰开斯特实验小组和伯明翰的共同投资者已经由EPSRC资助，直到2006年6月底为止。兰开斯特/伯明翰集团将在2006年初提交兰开斯特实验计划的延续和开发的研究赠款申请。在本提案中，他们只要求旅行/生存，以支持他们在拟议的NSF MWN赠款期间与佛罗里达集团的合作。