Effect of He-appm/DPA ratio on the damage microstructure of tungsten
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Effect of He-appm/DPA ratio on the damage microstructure of tungsten R.W. Harrison, H. Amari, G. Greaves, J.A. Hinks and S.E. Donnelly MRS Advances / FirstView Article / August 2016, pp 1 - 7 DOI: 10.1557/adv.2016.385, Published online: 23 May 2016
Link to this article: http://journals.cambridge.org/abstract_S2059852116003856 How to cite this article: R.W. Harrison, H. Amari, G. Greaves, J.A. Hinks and S.E. Donnelly Effect of He-appm/DPA ratio on the damage microstructure of tungsten. MRS Advances, Available on CJO 2016 doi:10.1557/adv.2016.385 Request Permissions : Click here
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MRS Advances © 2016 Materials Research Society DOI: 10.1557/adv.2016.385
Effect of He-appm/DPA ratio on the damage microstructure of tungsten R.W. Harrison, H. Amari, G. Greaves, J.A. Hinks and S.E. Donnelly School of Computing and Engineering, University of Huddersfield, Huddersfield, HD1 3DH Abstract In-situ ion irradiation and transmission electron microscopy has been used to examine the effects of the He appm to DPA ratio, temperature and dose on the damage structure of tungsten (W). Irradiations were performed with 15 or 60 keV He+ ions, achieving He-appm/displacements per atom (DPA) ratios of ~40,000 and ~2000, respectively, at temperatures between 500 and 1000°C to a dose of ~3 DPA. A high number of small dislocation loops with sizes around 5–20 nm and a He bubble lattice were observed for both He-appm/DPA ratios at 500°C with a bubble size ~1.5 nm. Using the g.b=0 criterion the loops were characterised as b = ±1/2 type. At 750°C bubbles do not form an ordered array and are larger in size compared to the irradiations at 500°C, with a diameter of ~3 nm. Fewer dislocation loops were observed at this temperature and were also characterised to be b = ±1/2 type. At 1000°C, no dislocation loops were observed and bubbles grew as a function of fluence attributed to vacancy mobility being higher and vacancy clusters becoming mobile. 1 Introduction Tungsten (W) is regarded as the primary candidate for use as a plasma facing material in the divertor of the ITER and DEMO fusion reactors due to its high melting temperature (~3400°C), low sputter yield and high thermal conductivity (~170 W.m-1.K-1 at room temperature)[1]. However, during service, the divertor will be exposed to high heat fluxes, radiation damage from 14.1 MeV neutrons and He injection from the plasma as well as He production from (n,α) reactions. The production of He from (n,α) reactions in W is low, with only around 5 atomic parts per million (appm) He being produced after 2 full power years in the DEMO reactor [2] resulting in a He-appm per displacement per atom (DPA) ratio of ~0.6. However, towards the surface the He-appm/DPA ratio will rise to 1000s from He injection from the plasma. Tanno et al. [3], [4] report the formation of a void lattice in fast neutron irr
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