JMP  Vol.2 No.3 , March 2011
Electric Field and Hot Spots Formation on Divertor Plates
ABSTRACT
In this paper, we consider the intensive erosion of tungsten brush-type armour structures that face the plasma in divertor fusion reactors. Surface erosion caused by multiple transient events (ELMs, disruption, etc.) could lead to the formation of a corrugated wedge-type shape. Our analysis shows that the augmentation of surface roughness increases the electric field at the vicinity of the wedge-type tips, thus enabling the formation of electric arcs. Specifically, under reactor conditions, the breakdown of the sheath potential may trigger unipolar arcs that will strongly contaminate the plasma with the resulting tungsten ions. We show that the erosion caused by arcs is almost two orders of magnitude larger than that caused by DT ion sputtering and comparable with that caused by self-sputtering.

Cite this paper
nullY. Igitkhanov and B. Bazylev, "Electric Field and Hot Spots Formation on Divertor Plates," Journal of Modern Physics, Vol. 2 No. 3, 2011, pp. 131-135. doi: 10.4236/jmp.2011.23020.
References
[1]   A. Loarte, G. Saibene, R. Sartori, et al., "Transient Heat Loads in Current Fusion Experiments, Extrapolation to Iter and Consequences for its Operation,” Physica Scripta, Vol. 128, 2007, pp. 222-228. doi:10.1088/0031-8949/2007/T128/043

[2]   B. Bazylev, G. Janeschitz, I. Landman et al., “ITER Transient Consequences for Material Damage: Modelling Versus Experiments,” Physica Scripta, Vol. T128, 2007, pp. 229-233. doi:10.1088/0031-8949/2007/T128/044

[3]   A. Zhitlukhin, N. Klimov, I. Landman et al., “Effect of ELMS on ITER Armour Materials,” Journal of Nuclear Materials, Vol. 363-365, 2007, pp. 301-307. doi:10.1016/j.jnucmat.2007.01.027

[4]   B. Bazylev, G. Janeschitz, I. Landman and S. Pestchanyi, “Erosion of Tungsten Armor after Multiple Intense Transient Events in ITER,” Journal of Nuclear Materials, Vol. 337-339, 2005, pp.766-770. doi:10.1016/j.jnucmat.2004.10.070

[5]   L. Olson, G. Georgiou and W. Schultz, “An Efficient Finite Element Method for Treating Singularities in Laplace’s Equation,” Journal of Computational Physics, Vol. 96, No. 2, 1991, pp.391-410. doi:10.1016/0021-9991(91)90242-D

[6]   S. Marchetti and T. Rozzi, “Electric Field Behavior near Metallic Wedges,” IEEE Transactions on Antennas and Propagation, Vol. 38,No. 9, 1990, pp.1333-1339. doi:10.1109/8.56983

[7]   L. Landau, E. Lifshitz and L. Pitaevskii, “Electrodynamics of Continuous Media,” Vol. 8, 1984 (1rst Ed.), Butter-Worth-Heinemann, ISBN 978-0-750-62634-7.

[8]   V. Granovski, “The Electric Current in a Gases,” (in Russian), Nauka, Moscow, 1971.

[9]   J. Wesson, “Tokamaks,” 3rd edition, Oxford, 2004.

[10]   G. Hobs and J. Wesson, “Heat Flow through a Langmuir Sheath in the Presence of Electron Emission,” Plasma Physics, Vol. 9, 1967, pp. 85-87. doi:10.1088/0032-1028/9/1/410

[11]   Yu. Igitkhanov, “On the Mechanism of Stationary Burn of Unipolar Micro-Arcs in the Scrape-Off Tokamak Plasma,” Contribution in Plasma Physics, Vol. 28, No. 4-5, 1988, pp. 421-425. doi:10.1002/ctpp.2150280425

[12]   Yu. Igitkhanov and D Naujoks, “Sheath Potential Drop in the Presence of Impurities,” Contribution in Plasma Physics, Vol. 36 S, 1996, pp. 67-72.

[13]   A. Nedospasov and V. Petrov, “Model of the Unipolar Arc on a Tokamak Wall,” Journal of Nuclear Material, Vol. 76 & 77, 1978, pp. 490-491.

 
 
Top