Studies of In Flight Annihilation of High Energy Channeled Positrons in Single Crystals

这个实验凝聚态物理项目将通过实验探索正电子与晶体物质的基本相互作用。主要的焦点将是通道MeV正电子与晶体价电子的飞行湮灭过程。湮灭产率应该与正电子路径上的电子密度成正比，并且应该对电子的自旋极化非常敏感。该实验有望证明正电子通道可以在原子尺度上发展成为晶体电子和磁性结构的敏感探针。这是一个基础研究项目，但其结果将导致在一系列材料研究领域具有广泛技术应用的新仪器。正电子和电子是反物质和物质的双胞胎，结果是当它们靠得非常近时，它们会湮灭——将它们的能量，质量和动量转化为高能光子，称为伽马射线。最近已经有可能获得具有足够强度的单能量正电子加速束，以发展湮灭相互作用，作为晶体电子和磁性质的敏感原子尺度探针。在这项研究中，高能正电子将被晶体的原子势聚焦（引导）。这些数据将提供有关电子密度的信息，而电子密度决定了材料的原子级电子和磁性能。这是一个基础研究项目，但其结果将导致在一系列材料研究领域具有广泛技术应用的新仪器。**

9623610 Golovchenko This experimental condensed matter physics project will explore experimentally the basic interaction of positrons with crystalline matter. The main focus will be on the process of in-flight annihilation of channeled MeV positrons with crystal valence electrons. The annihilation yields should be proportional to the electron density along the positron path, and should also be very sensitive to the spin polarization of the electrons. The experiments are expected to demonstrate that positron channeling can be developed into a sensitive probe of the electronic and magnetic structures of crystals on the atomic scale. This is a fundamental research project, but the results should lead to new instrumentation having broad technological applications in a range of materials research areas. %%% Positrons and electrons are antimatter-matter twins, with the consequence that when brought very close together, they annihilate - converting their energies, of mass and momentum, into energetic photons called gamma rays. It has recently become possible to obtain accelerated beams of mono- energetic positrons with sufficient intensities to develop the annihilation interaction as a sensitive atomic scale probe of the electronic and magnetic properties of crystals. In this research, energetic positrons will be focused (channeled) by the atomic potential of a crystal. The data will provide information about the density of the electrons that determine the atomic scale electronic and magnetic properties of the materials. This is a fundamental research project, but the results should lead to new instrumentation having broad technological applications in a range of materials research areas. **