Thermal analysis of an exposed tungsten edge in the JET divertor

• Published in: Journal of nuclear materials Vol. 463; pp. 415 - 419
• Main Authors: Arnoux, G., Coenen, J., Bazylev, B., Corre, Y., Matthews, G.F., Balboa, I., Clever, M., Dejarnac, R., Devaux, S., Eich, T., Gauthier, E., Frassinetti, L., Horacek, J., Jachmich, S., Kinna, D., Marsen, S., Mertens, Ph, Pitts, R.A., Rack, M., Sergienko, G., Sieglin, B., Stamp, M., Thompson, V.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.08.2015; Elsevier
• Subjects: Data processing; Extrapolation; Heat flux; Heat transfer; Melts; Nuclear engineering; Physics; Plasma Physics; Reduction; Tungsten
• ISSN: 0022-3115; 1873-4820; 1873-4820
• DOI: 10.1016/j.jnucmat.2014.11.005

•We provide experimental evidences that melting of the JET tungsten divertor is achieved by transients only.•The measurements show that less than half the parallel heat flux reaches the melted sample.•We propose ideas to investigate to explain the missing heat flux. In the recent melt experiments with the JET tungsten divertor, we observe that the heat flux impacting on a leading edge is 3–10 times lower than a geometrical projection would predict. The surface temperature, tungsten vaporisation rate and melt motion measured during these experiments is consistent with the simulations using the MEMOS code, only if one applies the heat flux reduction. This unexpected observation is the result of our efforts to demonstrate that the tungsten lamella was melted by ELM induced transient heat loads only. This paper describes in details the measurements and data analysis method that led us to this strong conclusion. The reason for the reduced heat flux are yet to be clearly established and we provide some ideas to explore. Explaining the physics of this heat flux reduction would allow to understand whether it can be extrapolated to ITER.