A new type of radiofrequency trap can capture particles with extremely different requirements and could theoretically hold both types of particles at the same time. Researchers in the group of Professor Dr. Dmitry Budker from the PRISMA++ Cluster of Excellence at Johannes Gutenberg University Mainz (JGU) and the Helmholtz Institute Mainz were able to trap calcium ions or electrons in the same apparatus. The team's findings, published in Physical Review A, show the potential of this technology for synthesizing antihydrogen. "Radiofrequency traps, also called Paul traps, have long been used by physicists to trap specific particles," Dr. Hendrik Bekker explained. "However, they are usually limited to a single frequency." This means that only one type of particle can be captured at a time in a typical Paul trap. In order to synthesize antihydrogen, however, two types of particles – antiprotons and positrons – would need to be trapped together at the same time. Due to their low mass, positrons require GHz-frequency fields for stable confinement, while antiprotons are typically trapped with MHz-frequency fields. For their current study, the researchers used electrons and heavy calcium ions (40Ca+) as more readily available stand-ins for antiprotons and positrons. Catching Two Birds in the Same Cage In order to trap the calcium ions and electrons, the dual-frequency Paul-trap, which is being developed in collaboration with Professor Dr. Ferdinand Schmidt-Kaler from JGU as well as the group of Professor Dr. Hartmut Häffner at UC Berkeley, has to generate both GHz and MHz frequency fields. Hendrik Bekker and PhD candidate students Vladimir Mikhailovski and Natalija Rajeshri Sheth generate these fields by layering three printed circuit boards (PCB) and separating them with ceramic spacers. The central board is equipped with what is known as a coplanar waveguide resonator which generates the GHz frequency field to trap electrons.