Speaker
Description
See full abstract here:
http://ocs.ciemat.es/EPS2019ABS/pdf/P5.1025.pdf
Dust in tokamaks is unlike to be mobilized prior to the beginning of plasma discharges, then dust presence in the vessel during the start-up phase of discharges is not considered an issue. Problems could arise due to the presence of magnetic dust [1,2,3] that are more likely to fly in the vessel volume during stat-up phase [4] and could interfere with the plasma discharge [5]. In fact the presence of dust in the early phase of discharges can induce a shift of the optimal loop-voltage vs. gas pressure curve during breakdown phase (i.e. shift in the Paschen's curve), or perturb the plasma resistivity, through the perturbation of Z_eff, leading to a change of the current rise time and a limitation in the plasma current plateau during start-up. In the perspective of the use of stainless steel for the ITER diagnostic first wall [6] and RAFM steel in future fusion plants [7], the presence of magnetic dust could not be negligible.
In this work we propose a model to describe the start-up phase of plasma discharges in presence of solid metallic particles (dust). Examples on how the presence of dust can interfere with the current rump-up phase for relevant dust densities and dust nature scenarios, being dust generally composed by different materials, is presented.
[1] D. Ivanova, M. Rubel, V. Philipps, et al., Phys. Scripta T138, 014025 (2009).
[2] A.N. Novokhatsky, A.E. Gorodetsky, V.K. Gusev, et al. Proc. 38th EPS Conference on Plasma Physics, 27 June-1 July 2011, Strasbourg, France, Vol. 35G, P5.066.
[3] M. De Angeli, L. Laguardia, G. Maddaluno, et al. Nucl. Fusion 55, 123005 (2015).
[4] M. De Angeli, E. Lazzaro, P. Tolias, S. Ratynskaia, et al., submitted to Nucl. Fusion.
[5] J. Winter, Phys. Plasmas 7, 3862 (2000).
[6] R.A Pitts, B. Bazylev, J. Linke, et al. J. Nucl. Mater. 463, 748 (2015).
[7] K. Sugiyama, K. Schmid, W. Jacob, Nucl. Mater. Energy 8, 1 (2016).
