A positron accumulator for antihydrogen synthesis

A positron accumulator based on the modified Penning-Malmberg design of Surko and co-workers at UCSD has been constructed and undergone testing in preparation for the ATHENA experiment now under way at CERN. This experiment aims to produce and characterize atomic anti- hydrogen. The positron accumulator utilises nitrogen buffer gas to cool and trap a continuous beam of positrons emanating from a /sup 22 /Na radioactive source. A solid neon moderator slows the positrons from the source down to epithermal energies of a few eV before being injected into the trap. It is estimated that around 10/sup 7/ positrons can be trapped and cooled to ambient temperature within a couple of minutes in this scheme using a 6 mCi source. Preliminary tests have so far demonstrated trapping of approximately 3*10/sup 6/ positrons and an efficiency of the Ne moderator of nearly 1%. (8 refs).