Linear and Nonlinear Spin Transport in Random Porous Media

9501171坎德拉核磁共振等技术将用于研究扩散和弥散粒子和波在三种类型体系中的传播。第一类是随机多孔介质中的自旋极化量子流体。例如，用8-10T磁铁极化磁珠和硅气凝胶中的纯3He液体和3He-4He混合物，在10MK以下冷却，研究混合物相图、量子局域效应和自旋波的干涉和局域化。第二个系统是室温下多孔介质中的流体。脉冲场梯度核磁共振将被用来研究孔隙空间的几何结构，并在广泛的Peclet数范围内研究应用流动中的痕迹弥散。最后，我们将在极化量子流体和室温水波实验中研究非线性波，以测试逆谱变换对物理系统的适用性。%本项目的目标是更好地了解粒子和波在具有随机结构的复杂物理系统中的传播。核磁共振将被用来研究分子在填充材料孔隙的流体中的运动，如微粉、硅胶和天然岩石。研究将在非常低的温度下进行，在那里量子效应将占主导地位，也将在室温下进行，在那里可以发现经典行为。低温研究将检验与电子在金属和半导体中传播有关的理论。这项室温工作将为研究多孔材料的结构开辟新的方法，并将检验有关示踪剂通过流体流动分散的理论。非线性波也将在一个面向本科生参与研究的子项目中进行研究。***

9501171 Candela Nuclear magnetic resonance (NMR) and other techniques will be used to study the propagation of diffusing and dispersing particle and waves in three types of system. The first consists of spin-polarized quantum fluids in random porous media. For example, pure 3He liquid and 3He-4He mixtures in the pores of bead packs and silica aerogel will be polarized by an 8 - 10 T magnetic files and cooled below 10 mK to study the mixture phase diagram, quantum localization effect, and interference and localization of spin waves. The second system is fluids in porous media at room temperature. Pulsed-field-gradient NMR will be used to study the geometric structure of the pore space, and to study trace dispersion in an applied flow over a wide range of Peclet numbers. Finally, nonlinear waves will be studied both in polarized quantum fluids and in a room-temperature water-wave experiment to test the applicability of the inverse spectral transform to physical systems. %%% The objective of this project is to better understand the propagation of particles and waves in complex physical systems that have a random structure. Nuclear magnetic resonance (NMR) will be used to study the motions of molecules in fluids filling the pores of materials like fine powders, silica gels, and natural rock. The studies will take place both at very low temperature, where quantum effects will dominate, and at room temperature, where classical behavior is found. The low temperature studies will test theories relevant to the propagation of electrons in metals and semiconductors. The room temperature work will develop new methods for studying the structure of porous materials, and will test theories concerning the dispersion of tracers by fluid flow. Nonlinear waves will also be studied in a sub-project geared toward engaging undergraduate students in resear ch. ***