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

1338130 Weiss技术摘要：德克萨斯大学阿灵顿分校获得的这项重大研究仪器奖支持开发下一代高通量可变能量自旋极化正电子束仪器，用于材料研究。 完成后，该系统将成为世界上第一个能够利用自旋极化正电子束进行飞行时间正电子湮没诱导俄歇电子能谱（PAES）和伽马-伽马能谱的系统。由于注入样品的低能正电子的湮灭而发射的俄歇电子和伽马射线的光谱将用于获得关于材料的化学成分和结构的独特信息。该仪器将具有高度的表面选择性和灵敏度的开放体积缺陷，由于正电子的捕获前湮灭。正电子将使用22Na源和设计用于保持正电子极化的高效Ne减速器系统获得。这将使自旋相关的测量，并将是特别有用的研究与其他非磁性材料，显示与缺陷相关的大磁矩相关的不寻常的磁性的起源。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具有在包括纳米磁性、高能产物磁性材料、光催化、纳米颗粒光致发光和摩擦学等领域实现突破性发现的潜力。该项目将为本科生，研究生和博士后研究人员提供培训机会，开发和应用先进的材料表征仪器。 非技术摘要：主要研究仪器计划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。 完成后，该仪器将是世界上第一台将联合收割机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到地表以下的选定深度。 对正电子湮灭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隙和缺失原子缺陷的元素含量和物理结构的独特信息。 先进的光束系统提供的独特信息将使新的发现领域，包括纳米粒子为基础的超磁体的发展，新的催化剂的发展，可以吸收光，促进水的分裂，使氢燃料，并为研究摩擦引起的亚微观碳烟灰。该项目将为本科生，研究生和博士后研究人员提供设计，建造和应用先进仪器表征材料的培训机会。

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.