A scheme to produce the antihydrogen ion (H)over-bar(+) for gravity measurements

We propose to use the charge exchange reaction of antiprotons with positronium atoms in order to produce antihydrogen atoms, (H) over bar, and (H) over bar (+) ions. The ions can be cooled down to mu K temperatures and then ionized to recover an ultra slow neutral (H) over bar atom. Its acceleration is then measured by time of flight. Results on the conversion of slow positrons into positronium are presented. This is a first step towards the creation of a dense cloud of positronium atoms to be used as a target for the antiprotons. The source of positrons is based on a 6 MeV industrial electron linac with 0.2 mA average current to be installed in CEA-Saclay. Equipped with a tungsten target and a moderator, it is aimed at producing rates of order 10(8) s(-1) slow positions.