A research group led by Prof. Yasuyuki Nagashima (Tokyo University of Science) comprising teams from Tokyo University of Science and High Energy Accelerator Research Organization (KEK) succeeded in generating an energy-tunable beam of positroniums (Ps) in an ultrahigh vacuum environment. A Ps atom is a bound state of an electron and its antiparticle, a positron. It cannot be accelerated by conventional means i.e., an electric field, because it has no net charge. However, the new technique allows the generated beam to be readily accelerated to energies over 1 keV.
Michishio, et al., Applied Physics Letters, 100, 254102 (2012).