High Resolution Thermal Expansion Measurements of Ice

****技术摘要****本项目涉及大气压力下单晶冰热膨胀的高分辨率测量。这次测量将提供比以前的测量高10000倍的相对分辨率，提供有关热膨胀各向异性的新信息，并首次对115 K下鲜为人知的相变进行结构研究。对冰的热膨胀的进一步了解将影响寒区工程、气候模型、地球极地研究、天体物理学，以及我们对冰中氢原子运动及其在决定其物理性质中的作用的基本理解。该项目产生的新型温度传感器技术将使温度测量的相对分辨率提高100倍；这将改进热膨胀系数的测定，但也可能有其他应用。紧凑的热膨胀电池将由单晶蓝宝石构成，以方便在0.35 K至20 K的范围内进行测量。本科生将负责这个项目的很大一部分。他们将制造实验设备，生长和定向单晶，测试和校准高灵敏度设备，并学习与固体相关的基础物理学。****非技术摘要****水可以说是地球上最重要的物质。它的固体形态，也就是冰，非常复杂。根据压力的不同，它可以呈现出13种不同的晶体结构。地球上最主要的是被称为冰的结构，它存在于大气压下。令人惊讶的是，它在温度变化下的膨胀（热膨胀）从未以非常高的分辨率被测量过。该项目将产生热膨胀数据，其相对分辨率比之前的测量结果高约10,000倍。冰的热膨胀知识的提高将影响寒区工程、气候模型、地球极地研究和天体物理学。它还将提高我们对氢原子的运动和低温冻结的理解，以及它们在决定冰的晶体结构和性质方面的作用。这个项目将在温度测量方面产生重大改进，使相对分辨率提高100倍。在接近绝对零度的温度下测量热膨胀方面也有望取得进展。本科生将负责这项研究的很大一部分。他们将制造实验设备，生长和定向单晶，测试和校准高灵敏度设备，并学习基础物理。

****Technical Abstract****This project is concerned with high-resolution measurements of the thermal expansion of single-crystalline ice at atmospheric pressure. The measurements will provide up to 10,000 times higher relative resolution than previous measurements, yielding new information about the anisotropy of the thermal expansion and the first structural investigation of a poorly understood phase transition at 115 K. Improved knowledge of ice's thermal expansion will impact cold-region engineering, climate modeling, the study of Earth's polar regions, astrophysics, and our basic understanding of the motion of hydrogen atoms in ice and their role in determining its physical properties. New temperature sensor technology resulting from this project will increase the relative resolution of temperature measurements by a factor of 100; this will improve determination of the thermal expansion coefficient, but may have other applications. A compact thermal expansion cell will be constructed of single-crystalline sapphire to facilitate measurements in the range 0.35 K to 20 K. Undergraduates will be responsible for a large portion of this project. They will fabricate experimental equipment, grow and orient single crystals, test and calibrate highly sensitive devices and learn fundamental physics associated with solids.****Non-Technical Abstract****Water is arguably the most important substance on our planet. In its solid form, known as ice, it is highly complex. Depending on the pressure, it can assume thirteen distinct crystal structures. The most predominant on Earth is the structure known as ice Ih, which exists at atmospheric pressure. Surprisingly, its expansion under changes in temperature (thermal expansion) has never been measured to very high resolution. This project will produce thermal expansion data with a relative resolution about 10,000 times better than prior measurements. Improved knowledge of the thermal expansion of ice will impact cold- region engineering, climate modeling, the study of Earth's polar regions, and astrophysics. It will also improve our understanding of the motion and low-temperature freezing of hydrogen atoms, and their role in determining the crystal structure and properties of ice. This project will produce significant improvements in the measurement of temperature, increasing the relative resolution by a factor of 100. Advances in measuring the thermal expansion at temperatures close to absolute zero are also expected. Undergraduate students will be responsible for a large portion of this research. They will fabricate experimental equipment, grow and orient single crystals, test and calibrate highly sensitive devices and learn fundamental physics.