Positrons outshine electrons

In a process inverse to the photoelectric effect, phosphors and other cathodoluminescent materials emit photons when struck by sufficiently energetic electrons. That process is central to the function of old-style televisions and certain light-emitting diodes, microscopes, and scintillation detectors. But electrons aren’t the only particles that can trigger cathodoluminescence—so can their antimatter counterparts, positrons. Now Eve Stenson at the Max Planck Institute for Plasma Physics in Germany and her colleagues report marked differences in the phosphor luminescence produced by positrons and electrons of the same energy.