Production of antihydrogen via double-charge-exchange

Comparison of the 1s-2s transitions in hydrogen and antihydrogen will provide an accurate test of CPT symmetry. While production of antihydrogen using the three-body-recombination (TBR) scheme is an established technique at CERN's Antiproton Decellerator facility (AD), trapping these atoms for spectroscopy has not yet succeeded. Therefore, the ATRAP collaboration has developed a different scheme to produce much colder anti-atoms more suitable for trapping. Cesium atoms are laser-excited to Rydberg-states and travel through positrons stored in a Penning-trap. A collisional charge exchange reaction produces positronium, which is no longer confined by the Penning-trap fields. It can therefore interact with nearby stored antiprotons, creating antihydrogen. The principle was demonstrated in 2004. Since then, ATRAP has developed a new apparatus providing larger particle numbers and a quadrupole Ioffe-trap for neutral atoms. Furthermore, a new solid state laser-system for Cesium excitation has been developed. During the past AD-beam-run, the excitation of cesium to various high-n-states within the 1 T bias field of the Penning trap has been demonstrated.