Superfluid Helium in Porous Materials

本文将利用扭转振子技术研究烧结陶瓷氧化铝粉末上的氦膜，以测量超流分数和其他性质。研究了薄膜中涡旋的核心结构与温度、薄膜厚度和氦- 3杂质浓度的关系。第二个实验项目将研究极低孔隙率的陶瓷材料中含氦- 4的第三和第四声传播。预测的发散折射率将在陶瓷孔隙渗流阈值附近进行研究。在低氦浓度情况下，还将研究陶瓷的表面折射率。

Helium films on sintered ceramic alumina powders will be studied using the torsional oscillator technique to measure superfluid fraction and other properties. Core structure of the vortices in thin films will be studied as a function of temperature, film thickness, and helium-three impurity concentration. A second experimental program will study third and fourth sound propagation in helium-four contained in ceramic materials of very low porosity. The predicted divergent index of refraction will be studied near the percolation threshold for pores in the ceramic. The surface index of refraction will also be studied in situations with low helium concentration in the ceramic.