Figure 2: Antihydrogen synthesis.

(a) Illustration of the direct injection scheme, which is used to produce antihydrogen atoms. A positron plasma is confined and compressed at the centre of the nested well (black solid line). The potential is opened (red solid line) when antiprotons with low energy spread are injected into the positron plasma. The antiproton kinetic energy is adjusted to slightly higher than the potential energy of the positron plasma (yellow solid line), which ensures efficient mixing of antiprotons and positrons. To prolong the interaction time during mixing, an rf drive (not shown in the figure) is applied, which drives the axial oscillation of the antiprotons. (b) The number of antihydrogen atoms field-ionized downstream of the nested trap as a function of time. The filled black squares are from an experiment when direct injection was applied. The filled red circles represent results obtained from the rf-assisted direct injection scheme. Error bars show s.d. of the mean. By applying the rf drive the yield of field-ionized antihydrogen atoms was increased by a factor of 3.5.