The effect of ion damage on deuterium trapping in tungsten

A systematic study investigating the effect of ion-induced damage, due to prior ion implantation, on deuterium retention in tungsten has been performed. Implantations with 1.5 keV D-3(+) ions (500 eV/D+) to 10(23) D/m(2) at 500 K show a factor of 3-4 increase in retention for specimens previously exposed to a fluence of 10(24) D/m(2) and a factor of 6-7 increase for specimens previously exposed to a fluence of 3 x 10(24) D/m(2) over specimens exposed only to an incident fluence of 10(23) D/m(2). However, implantations with 1.5 keV D-3(+) (500 eV/D+) ions to 10(23) D/m(2) at 500 K on specimens previously exposed to a fluence of 10(25) D/m(2) show no increase in retention. Implantations with 3 keV D-3(+) ions (1 keV/D+) at the above conditions give retention results which do not depend on prior implantation treatments; only a slight increase in retention values with cumulative fluence is observed. Possible mechanisms are suggested to explain the observed effects. (C) 1999 Elsevier Science B.V. All rights reserved.