Characteristic changes of deuterium retention on tungsten surfaces due to low-energy helium plasma pre-exposure

Deuterium retention in tungsten increases substantially when it is pre-exposed to low-energy He plasma at a high temperature (1600 K), while it decreases when pre-exposed at a low temperature (700 K). The increase of deuterium retention could be attributed to the submicron-sized He bubbles and secondary interstitial defects formed on the tungsten surface. Occupation of trap sites by He atoms during the He pre-exposure at low temperature could decreases the effective number of available trap sites for deuterium atoms, which would decreases the deuterium retention on the tungsten surface. (c) 2004 Elsevier B.V. All rights reserved.