High Resolution Thermal Expansion Measurements of Ice

Montana State University, Bozeman MT

Investigators

Abstract

****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.