MRI: Development of an Advanced Positron Beam System for Annihilation Spectroscopies of Surfaces, Interfaces and Nanostructures

1338130魏斯技术摘要：这项授予德克萨斯大学阿灵顿分校的主要研究仪器奖支持开发用于材料研究的新一代高通量可变能量自旋极化正电子束仪器。建成后，该系统将是世界上第一个能够利用自旋极化正电子束进行正电子湮没诱导俄歇电子能谱(PAES)和伽马-伽马能谱的飞行时间系统。由于低能正电子被注入样品的湮灭而发射的俄歇电子和伽马射线的光谱将被用来获得关于材料化学成分和结构的独特信息。该仪器将对表面具有高度的选择性，并对由于正电子在湮灭前捕获而产生的开放体积缺陷具有敏感性。正电子将使用22nA的光源和高效的Ne慢化器系统来获得，该系统旨在保持正电子的极化。这将使自旋相关测量成为可能，并将特别有助于研究与其他非磁性材料相关的不寻常磁性的起源，这些材料表现出与缺陷相关的大磁矩。先进的正电子束系统提供的关于表面和纳米结构的元素含量、缺陷类型和缺陷浓度的独特信息有可能使在纳米磁性、高能产物磁性材料、光催化、纳米粒子光致发光和摩擦学等领域取得突破性发现成为可能。该项目将为本科生、研究生和博士后研究人员提供开发和应用先进材料表征仪器的培训机会。非技术摘要：主要研究仪器项目的这一奖项支持德克萨斯大学阿灵顿分校开发下一代仪器，用于利用低能正电子束(反物质电子)表征材料。建成后，该仪器将是世界上第一个将自旋极化与飞行时间正电子湮没诱导俄歇电子能谱(PAES)和伽马-伽马能谱相结合的仪器。从放射源发射的正电子将被植入地表下选定的深度。对正电子湮没时发射的伽马射线和电子的能量分布的分析将提供关于表面和近表面空洞和缺失原子缺陷的元素含量和物理结构的独特信息。先进的束流系统提供的独特信息将使新的发现成为可能，包括纳米颗粒超磁体的开发，能够吸收光线并促进分解水以制造氢作为燃料的新催化剂的开发，以及亚微观碳烟尘造成的摩擦的研究。该项目将为本科生、研究生和博士后研究人员提供设计、建造和应用先进材料表征仪器的培训机会。

1338130 WeissTechnical Abstract:This Major Research Instrumentation Award to the University of Texas at Arlington supports the development of a next generation high flux variable energy spin-polarized positron beam instrument for materials research. When completed the system will be the first in the world capable of performing time of flight Positron Annihilation induced Auger Electron Spectroscopy (PAES) and gamma-gamma spectroscopy utilizing a spin polarized positron beam. The spectra of Auger electrons and gamma rays emitted as a result of the annihilation of low energy positrons implanted into the sample will be used to obtain unique information about the chemical composition and structure of materials. The instrument will have a high degree of selectivity for surfaces and sensitivity to open volume defects due to the trapping of positrons prior to annihilation. The positrons will be obtained using a 22Na source and a high efficiency Ne moderator system designed to preserve the polarization of the positrons. This will enable spin dependent measurements and will be particularly useful for the study of the origin of the unusual magnetic properties associated with otherwise non-magnetic materials that show large magnetic moments associated with defects. The unique information provided by the advanced positron beam system regarding the elemental content, defect type and defect concentration of surfaces and nano-structures holds the potential to enable breakthrough discoveries in areas including nano-magnetism, high energy product magnetic materials, photo-catalysis, nano-particle photoluminescence, and tribology. This project will provide training opportunities for undergraduate, graduate, and post-doctoral researchers in the development and application of advanced instruments for the characterization of materials. Non-technical Abstract:This award from the Major Research Instrumentation program supports the University of Texas at Arlington with the development of a next generation instrument for the characterization of materials utilizing a beam of low energy positrons (anti-matter electrons). When completed the instrument will be the first in the world to combine spin polarization with a time of flight Positron Annihilation induced Auger Electron Spectroscopy (PAES) and gamma-gamma spectroscopy. Positrons emitted from a radioactive source will be implanted at a selected depth below the surface. An analysis of the distribution of energies of the gamma-rays and electrons emitted when the positrons annihilate will provide unique information regarding the elemental content and physical structure of surfaces and near surface voids and missing atom defects. The unique information provided by the advanced beam system will enable new discoveries in areas including the development of nano-particle based supermagnets, the development of new catalysts that can absorb light and promote the splitting of water to make hydrogen for fuel, and for the study of friction caused by submicroscopic carbon soot. This project will provide training opportunities for undergraduate, graduate, and post-doctoral researchers in the design, construction, and application of advanced instruments for the characterization of materials.