Laser-Controlled Antihydrogen Production by Two-Stage Charge Exchange

Our ATRAP collaboration has now demonstrated a second technique for antihydrogen (H-bar) production. Lasers are used for the first time to control the production of H-baratoms in our cryogenic apparatus at CERN. As suggested in ref. [2] and first reported in ref. [1], lasers excite a thermal beam of cesium (Cs) atoms to a Rydberg state. In a first charge exchange collision one of these laser-excited Cs atoms (Cs*) and a cold e+ produces positronium (Ps). Our measurements at Harvard([3]) and at CERN([1]) confirm CTMC simulations([2]) that the laser-selected binding energy in the Cs atom is preserved by the collision and results in Ps with the selected binding energy. A second charge exchange is between one of these Ps atoms and a trapped p-bar. H-baris produced by this second collision and is expected to again have the same binding energy. One advantage of this technique as discussed in ref. [2] is that the H-barproduced is expected to be extremely cold, at the temperature of the trapped p-bar, allowing for possible confinement of the H-baratoms in a magnetic trap