PRODUCTION OF VACUUM POSITRONIUM ATOMS

Positronium atoms are formed efficiently by slow positron beam hitting a solid target surface in vacuum. The fraction of positrons which formed positroniums is determined by applying the "peak method" to the energy spectra of the positron annihilation radiation measured at different target temperatures and incident positron energies. The fraction is dependent on the target material, temperature and incident positron energy. For germanium, the fraction is as high as 80%.