Retention and surface blistering of helium irradiated tungsten as a first wall material S.B. Gilliam a, * , S.M. Gidcumb a , N.R. Parikh a , D.G. Forsythe a , B.K. Patnaik a , J.D. Hunn b , L.L. Snead b , G.P. Lamaze c a Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Phillips Hall, CB #3255, Chapel Hill, NC 27599-3255, USA b Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6136, USA c National Institute of Standards and Technology, Gaithersburg, MD 20899-3460, USA Abstract The first wall of an inertial fusion energy reactor may suffer from surface blistering and exfoliation due to helium ion irradiation and extreme temperatures. Tungsten is a candidate for the first wall material. A study of helium retention and surface blistering with regard to helium dose, temperature, pulsed implantation, and tungsten microstructure was conducted to better understand what may occur at the first wall of the reactor. Single crystal and polycrystalline tungsten samples were implanted with 1.3 MeV 3 He in doses ranging from 10 19 m 2 to 10 22 m 2 . Implanted samples were analyzed by 3 He(d,p) 4 He nuclear reaction analysis and 3 He(n,p)T neutron depth profiling techniques. Surface blistering was observed for doses greater than 10 21 He/m 2 . For He fluences of 5 · 10 20 He/m 2 , similar retention levels in both microstruc- tures resulted without blistering. Implantation and flash heating in cycles indicated that helium retention was mitigated with decreasing He dose per cycle. Ó 2005 Elsevier B.V. All rights reserved. PACS: 24.30.v; 52.40.Hf; 61.72.Ss; 61.82.Bg 1. Introduction A proposed inertial fusion energy reactor oper- ates at 10 Hz. Each cycle begins with the injection of a pellet with a deuterium–tritium (DT) core. Next, multiple high intensity laser beams are focused on this pellet, which leads to implosion and fusion in the core. Immediately following the fusion event, the chamber wall is subjected to intense radiation. X-rays arrive first, then reflected laser light, followed by high-energy neutrons, and finally fast and slow ion debris [1]. Most of the wall heating results from the energy deposition from X- rays and ion fluxes. Simulations of the thermal evo- lution at the first wall indicate that the maximum 0022-3115/$ - see front matter Ó 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.jnucmat.2005.08.017 * Corresponding author. Tel.: +1 919 962 7160; fax: +1 919 962 0480. E-mail address: sgilliam@physics.unc.edu (S.B. Gilliam). Journal of Nuclear Materials 347 (2005) 289–297 www.elsevier.com/locate/jnucmat