Tungsten behavior under proton flux and high temperature

An experimental study of the physico-chemical behavior of tungsten under severe conditions is presented. High temperatures (1300 <= T <= 2500 K) generated by concentrated solar energy, high vacuum (similar to 10(-6) hPa) and proton flux (1 keV, similar to 10(17) ions m(-2) s(-1)) have been applied on polycrystalline W samples to simulate expected and also unexpected high heat loads that can occur on the ITER divertor (nominal and accidental conditions). During experiment, in situ measurements are performed and the material degradation, the mass loss kinetics, the characterization of the different species coming from the materials under coupled proton flux and high temperatures and the optical properties (reflectivity) are followed. Material characterization using SEM and XRD was investigated before and after treatment to understand the observed behavior. Bidirectional reflectivity measurements were carried out on the tested samples to explain the surface modifications, between the reference sample, the heated sample and the heated and ion irradiated one that can act on the thermo-radiative properties of tungsten. (C) 2009 Elsevier B.V. All rights reserved.