Observations of cold antihydrogen

ATRAP's e(+) cooling of (p) over bar in a nested Penning trap has led to reports of cold H produced during such cooling by the ATHENA and ATRAP collaborations. To observe (H) over bar, ATHENA uses coincident annihilation detection and ATRAP uses field ionization followed by (p) over bar storage. Advantages of ATRAP's field ionization method include the complete absence of any background events, and the first way to measure which (H) over bar states are produced. ATRAP enhances the (H) over bar production rate by driving many cycles of e(+) cooling in the nested trap, with more (H) over bar counted in an hour than the sum of all the other antimatter atoms ever reported. The number of (H) over bar counted per incident high energy (p) over bar is also higher than ever observed. The first measured distribution of (H) over bar states is made using a pre-ionizing electric field between separated production and detection regions. The high rate and the high Rydberg states suggest that the (H) over bar is formed via three-body recombination, as expected. (C) 2003 Elsevier B.V. All rights reserved.