EAPSI: Variable Energy Positron Beam for Positronium Diffraction

Gladen Randall W, Fort Worth TX

Investigators

Abstract

This award supports participation of a U.S. graduate student in a cutting edge experiment using the new positronium beam developed by Professor Yasuyuki Nagashima of Tokyo University of Science (TUS). The Nagashima beam consists of positronium particles, which will be diffracted from solid surfaces. In the experiment, positronium particles will be diffracted from solid surfaces, providing a unique neutral-particle spectroscopic method with several advantages over conventional neutral-particle spectroscopy, including particle size and the reduction in damage of the surface of the sample. This experiment will also provide the first observation of the diffraction of positronium from solid surfaces, providing valuable experimental evidence for theoretical quantum mechanics, as well as experimental results that will aid in the development of other spectroscopic methods. Future experiments may include the study of porous and catalytic materials for the development of fuel cells and the production of hydrogen from water using solar energy. This work will also contribute to the collaboration between the Nagashima laboratory at TUS and the Positron Surface Laboratory group at the University of Texas at Arlington (UTA). Professor Yasuyuki Nagashima and his research group, in collaboration with the High Energy Accelerator Research Organization (KEK), successfully constructed an earlier positronium beam using the photo-detachment of electrons from negative positronium ions, with a new positronium beam currently under construction. Using this unique method, this energy-tunable beam surpassed the previous beam energy limit of 400 eV, with measured minimum and maximum energies of 300 eV and 1.9 keV, respectively, and higher energies possible. The new beam?s properties of high flux, better collimation, and lower energy spread will enable the observation of multiple diffraction beams and the measurement of the energy dependence of the diffraction. Using this new positronium beam, which is expected to be completed by spring 2015, experiments consisting of the observation of high-energy positronium diffraction from solid surfaces, namely Si and LiF, will be performed. This NSF EAPSI award is funded in collaboration with the Japan Society for the Promotion of Science.