Low Energy Positron Beam Apparatus for Near-surface Studies and Its Application

A low-energy positron beam apparatus has been designed and constructed. The beam can deliver a current of 4X 10⁴e⁺/s to a target when a 7.3mCi ²²Na source is used. The energy range,available at present is between 25eV and 16keV. We have applied it to study initially on the dynamic process of WSi_x film formation and on the distribution defects produced by N⁺ ion in nickel.