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.
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.
