Studies with Liquid Helium Films

液氦薄膜研究

• 批准号: 9819122
• 负责人: Robert Hallock
• 金额: $ 42万
• 依托单位: University of Massachusetts Amherst
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-02-01 至 2003-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9819122&HistoricalAwards=false
• 关键词: Studies; Liquid; Helium; Films

9819122HallockThis low temperature physics project investigates the unique properties of helium films. Of interest are the fundamental behavior of the films and their application in other studies of problems of interest in Condensed Matter Physics. New aspects of the He-3/He-4 mixture film system, including localization, measurements on hydrogen substrates, the determination of two dimensional Fermi liquid parameters, and the search for a new superfluid state in the two dimensional He-3 atop a He-4 film at very low temperatures will be investigated. The work explores capillary condensation and avalanche phenomena with helium in porous materials, and examines the relevance of current theoretical notions to such systems. Experiments are conducted with helium films on patterned substrates in one and two dimensions, with a focus on two dimensional localization. The methods include NMR, quartz crystal microbalance resonance, third sound, and heat capacity studies of the thermal properties of He-4 and He-3/He-4 mixture films, and high resolution capacitance measurements of capillary condensation and avalanche events in porous materials. In addition to contributing to progress in understanding the behavior of helium films themselves, the work has relevance to the wider community in the areas of Fermi systems, localization, two dimensional phase transitions, avalanche phenomena, and capillary condensation. It also provides excellent training for the graduate students and research participation opportunities for the undergraduates who are associated with it.%%%This research investigates the remarkable properties of liquid helium. Such study provides unique insights into nature which are not available by the study of any other substance. Thin films of helium provide information on the behavior of weak binding surfaces such as hydrogen, which aids in the understanding of the general problem of wetting of surfaces. Study of the wave character of such thin films on surfaces which have been deliberately patterned allows an enhanced understanding of how waves can be trapped in novel environments. The study of thin film mixtures of the two naturally occurring forms of helium may result in the discovery of an exciting new kind of superfluid which is predicted but has not yet been observed. Helium in its friction-free superfluid state is utilized to further understand the dramatic avalanche behavior observed when helium drains from spongy substances. These experiments allow a better understanding of the process of fluid removal from porous materials. Students involved in this work are provided with a high quality hands-on research experience using sophisticated instrumentation.

9819122 Hallock这个低温物理项目研究了氦膜的独特性能。感兴趣的是电影的基本行为及其在其他关于凝结物理学感兴趣问题的研究中的应用。 HE-3/HE-4混合膜系统的新方面，包括定位，氢底物的测量，确定二维费米液体参数以及在非常低的温度下在HE-4膜上搜索新的超流体状态的搜索。这项工作探索了用多孔材料中氦气的毛细管凝结和雪崩现象，并研究了当前理论观念与此类系统的相关性。实验是在一个和二维的图案底物上使用氦膜进行的，重点是二维定位。这些方法包括NMR，石英晶体微量平衡，第三个声音以及He-4和He-3/He-4混合膜的热性能研究，以及在多孔材料中的毛细管凝结和雪崩事件的高分辨率电容测量。除了为了解氦膜本身的行为方面做出贡献外，这项工作还与费米系统，定位，二维相变，雪崩现象和毛细血管凝结领域的更广泛社区有关。它还为研究生提供了出色的培训，并为与之相关的本科生的研究机会提供了出色的培训。%% %%此研究调查了液态氦气的显着特性。这样的研究提供了对自然的独特见解，而这些本质无法获得任何其他物质。 氦的薄膜提供了有关弱结合表面（例如氢）行为的信息，例如氢，这有助于理解表面润湿的一般问题。研究此类薄膜在表面上的波动特征的研究，这些薄膜被故意模式化了，可以增强对如何将波浪捕获在新型环境中的理解。对两种天然发生的氦形式的薄膜混合物的研究可能会导致发现一种令人兴奋的新型超氟，但尚未被观察到。氦气中无摩擦的超流体状态的氦气被用来进一步理解当氦气从海绵状物质排出时观察到的急剧雪崩行为。这些实验可以更好地了解从多孔材料中去除液体的过程。参与这项工作的学生提供了使用复杂仪器的高质量动手研究经验。