Speaker
Description
P. Dwivedi$^{1}$, A. Fraile$^{2}$, G. Bonny$^{3}$, T. Polcar$^{1}$
$^{1}$Department of Control Engineering, Faculty of Electrical Engineering, Czech Technical
University in Prague, Karlovo náměstí 13, 121 35, Czech Republic
$^{2}$Nuclear Futures Institute, Bangor University, Gwynedd, LL57 2DG, United Kingdom
$^{3}$Nuclear Materials Science Institute, SCK CEN, Boeretang 200, B-2400 Mol, Belgium
It has been recognized that the production and dynamics of dust in the vacuum chamber of tokamaks are important problems in the framework of the safety and tokamak performance [1]. It is expected that during plasma discharges most of the dust particles concentrate in the scrape-off layer close to the chamber walls [2]. For almost all materials the hypervelocity regime (when the speed of an impact exceeds the speed of the compression waves both in the target and in the projectile) is reached when the impact speed exceeds a few km/s; it is therefore common to consider velocities above 2–3 km/s as hypervelocity impacts [3]. In studies related with plasma facing materials (PFMs) for future nuclear fusion technology, high velocity impacts have been reported, with velocities being around 500 m/s and up to a few km/s [4,5].
In this study we focus on understanding the fundamental characteristics of the mechanisms
underlying the crater formation caused by nanoparticles impacts on PFMs. From molecular
dynamics involving very large samples (up to 40 million atoms). We have determined the detailed atomistic and thermodynamic aspects of crater formation mechanism. Different stages of the penetration process are identified, and a model is being developed to understand the damage produced by hypervelocity impact in terms of geometrically necessary dislocations, much like in classic indentation theory, will be discussed.
References:
[1] Federici G. et al 2001 Nucl. Fusion 41 1967.
[2] Tsytovich V.N. and Winter J. 1998 Phys.—Usp. 41 815.
[3] Burchell M.J., Cole M.J., McDonnel J.A.M. and Zarnecki J.C. 1999 Meas. Sci. Technol. 10 41.
[4] Castaldo C, et al. 2007 Nucl. Fusion 47 L5-L9.
[5] Ratynskaia S, , et al. 2008 Nucl. Fusion 48 015006.
