RANGE OF Xe133 AND Ar41 IONS OF KEV ENERGIES IN TUNGSTEN

Abstract

An accurate electrochemical technique for the removal of extremely thin (10–1000 Å) uniform layers of metal from a tungsten target has been developed analogous to that used previously for range studies in aluminum. This technique has been used to obtain the range distributions of Xe133 and Ar41 ions in rolled tungsten foils as a function of energy over the region 2–200 kev approximately. The distributions consist of an asymmetric peak followed by a point of inflection and a very penetrating "tail". Unlike the earlier distributions in aluminum, the "tail" in tungsten is exponential only over a limited region; it eventually decreases in an approximately Gaussian manner. Comparison with theory shows that in tungsten the median range is about a factor of two larger than that predicted by the Lindhard theory.A range distribution has also been obtained for 40-kev Kr85 ions in amorphous WO3. This distribution shows no penetrating "tail", a result which is in accordance with recent computer studies by Robinson and Oen (1963), who suggest that the "tails" observed in crystalline (metallic) targets are due to channeling of the incoming ions by the crystal lattice. Also, in WO3, the median range is in reasonable agreement with theory.