Development of a scanning positron microscope

Maekawa, Masaki; Kawasuso, Atsuo; Hirade, Tetsuya  ; Miwa, Yukio

We developed the scanning positron microscope. By scanning the positron microbeam which diameter is several micrometers, spatial distributions of annihilation rays can be obtained. It becomes possible to acquire the two-dimensional distributions of vacancy-type defects, or to perform the defect observation in the selected area. A small sealed sodium-22 source (effective diameter of 2 mm, 55 MBq) developed by us is used as positron source. Using a objective lens, a positron microbeam of 1.9 micrometer is formed. When the stainless steel which has stress corrosion cracking is observed, we found defective areas far from the tip of crack. Those cannot be detected by conventional optical and electron microscope.