Electron-cooled accumulation of 4 × 109 positrons for production and storage of antihydrogen atoms

Four billion positrons (e⁺) are accumulated in a Penning-Ioffe trap apparatus at 1.2 K and <6 × 10^-17 Torr. This is the largest number of positrons ever held in a Penning trap. The e⁺ are cooled by collisions with trapped electrons (e^-) in this first demonstration of using e^- for efficient loading of e⁺ into a Penning trap. The combined low temperature and vacuum pressure provide an environment suitable for antihydrogen (\bar{{{H}}}) production, and long antimatter storage times, sufficient for high-precision tests of antimatter gravity and of CPT.