Studies with Liquid Helium Films

液氦薄膜研究

• 批准号: 9729805
• 负责人: Robert Hallock
• 金额: $ 5万
• 依托单位: University of Massachusetts Amherst
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-06-15 至 1999-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9729805&HistoricalAwards=false
• 关键词: Studies; Liquid; Helium; Films

9729805 Hallock This proposal will support a component of the experimental low temperature physics program at the University of Massachusetts/Amherst. The objectives are: (1) to study new aspects of the He-3-He-4 mixture film system, (2) to study in more detail capillary condensation and avalanche phenomena with helium in porous materials, (3) to conduct studies with helium films on patterned substrates in one and two dimensions, with a focus on two dimensional localization, and (4) to bring to a conclusion our study of helium in the context of C60 substrates. Experimental methods include quartz crystal resonance, third sound, and heat capacity studies of the thermal properties of He- 3/He-4 mixture films; and high resolution capacitance measurements of capillary condensation and avalanche events in porous materials. The work will lead to an improved understanding of helium on hydrogen, including "two transitions" in the case of mixture films; a test of the appropriateness of recent theoretical work concerning avalanche events in magnetic systems for the description of similar events seen in hysteretic capillary condensation, and an improved understanding of a method for determining pore distributions and draining phenomena in porous materials. In addition to contributing to progress in understanding the behavior of helium films themselves, the work will have relevance to the wider community in the areas of Fermi systems, avalanche phenomena, capillary condensation, and non- linear phenomena. The project provides excellent training for graduate students in a number of important techniques that are used in technical fields as well as fundamental research projects. %%% Helium is a remarkable substance with special liquid properties when cooled near the absolute zero of temperature. This proposed grant will study various problems in condensed m atter physics using the unique properties of liquid helium, particularly liquid helium films, as the vehicle to facilitate the study. In some cases the helium itself will be the subject of the study, in others, helium will serve as a convenient fluid to explore the phenomena of interest. In particular, the grant will allow study He-4 and He-3/He-4 mixture films and thereby enhance our understanding of phase transitions on two dimensional surfaces and on weak binding substrates such as hydrogen. Capillary condensation phenomena and avalanche events in porous materials will be studied to gain a deeper understanding of how porous materials drain, an understanding that cannot be reached using ordinary liquids. Finally, studies of helium on C60 substrates will be concluded. The project provides excellent training for graduate students in a number of important techniques that are used in technical fields as well as fundamental research projects. ***

该提案将支持马萨诸塞大学/阿默斯特分校实验低温物理项目的一个组成部分。目的：(1)研究He-3-He-4混合膜体系的新方面；(2)更详细地研究氦在多孔材料中的毛细凝聚和雪崩现象；(3)在图案衬底上进行氦膜的一维和二维研究，重点是二维定位；(4)总结我们在C60衬底下对氦的研究。实验方法包括石英晶体共振、三声和热容研究He- 3/He-4混合膜的热性能；以及多孔材料中毛细管凝结和雪崩事件的高分辨率电容测量。这项工作将导致对氦对氢的更好理解，包括在混合膜的情况下的“两次转变”；对最近关于磁系统中雪崩事件的理论工作的适用性进行了测试，以描述在滞后毛细凝结中看到的类似事件，并改进了对确定多孔材料中孔隙分布和排水现象的方法的理解。除了有助于理解氦膜本身的行为外，这项工作还将与费米系统、雪崩现象、毛细凝聚和非线性现象等领域的更广泛的社区相关。该项目为研究生提供了许多用于技术领域和基础研究项目的重要技术方面的优秀培训。氦是一种非凡的物质，当冷却到接近绝对零度时，它具有特殊的液体性质。这项拟议拨款将研究凝聚态物理中的各种问题，利用液氦的独特性质，特别是液氦膜，作为促进研究的载体。在某些情况下，氦本身将成为研究的主题，在其他情况下，氦将作为一种方便的流体来探索感兴趣的现象。特别是，这笔拨款将允许研究He-4和He-3/He-4混合薄膜，从而增强我们对二维表面和弱结合底物（如氢）上的相变的理解。将研究多孔材料中的毛细凝结现象和雪崩事件，以更深入地了解多孔材料如何排水，这是使用普通液体无法达到的理解。最后对氦在C60底物上的研究进行总结。该项目为研究生提供了许多用于技术领域和基础研究项目的重要技术方面的优秀培训。＊＊＊