Effect of helium irradiation on trapping and thermal release of deuterium implanted in tungsten

Retention and thermal release of D atoms and lattice disorder in W single c rystals pre-irradiated with He were studied by ion beam analysis techniques . The retention of 1 keV D ions implanted in W crystals was strongly enhanc ed by the 10 keV He-4 pre-irradiation to a small dose where a large distort ion was created at room temperature. The total amount of D retained in near surface laver of the W crystal did not vary with a range of He pre-implant ation dose between 10(19) He/m(2) and 10(21) He/m(2). However, the lattice disorder was significantly accumulated in near surface layer above 10(21) H e/m(2) and the thermal release of retained D atoms occurred at higher tempe rature. For a specimen preirradiated at 850 K, the crystal lattice was not heavily damaged, and trapping sites for the D atoms were uniformly distribu ted in the He implanted region probably owing to ordered He bubbles. (C) 20 01 Elsevier Science B.V. All rights reserved.