Development of an energy-tunable positronium beam apparatus using the photodetachment of the positronium negative ion

We report on the development of an energy-tunable positronium beam apparatus at Tokyo University of Science. The positronium beam is generated using the photodetachment of the positronium negative ion, a bound state of one positron and two electrons. Positronium negative ions are efficiently emitted from a Na- coated tungsten surface by bombardment with a slow positron beam. The intermediate-energy positronium beam produced in this fashion can be used for fundamental studies of antimatter-matter interactions with solid surfaces.