First mirror test in JET for ITER: Complete overview after three ILW campaigns

JET Contributors, Jan Mlynar, T. Ahlgren, L. Aho-Mantila, M. Airila, C. Björkas, A. Lahtinen, K. Nordlund, E. Safi, S. K. Sipila , O. Asunta, M. Groth, A. Hakola, J. Karhunen, S. Koivuranta, T. Kurki-Suonio, B. Lomanowski, J. Lonnroth, A. Salmi, M. I. K. SantalaJ. Varje, P. Siren, J. Likonen, A. Järvinen, Sunwoo Moon

Research output: Contribution to journalArticleScientificpeer-review

Abstract

The First Mirror Test for ITER has been carried out in JET with mirrors exposed during: (i) the third ILW campaign (ILW-3, 2015-2016, 23.33 h plasma) and (ii) all three campaigns, i.e. ILW-1 to ILW-3: 2011-2016, 63,52 h in total. All mirrors from main chamber wall show no significant changes of the total reflectivity from the initial value and the diffuse reflectivity does not exceed 3% in the spectral range above 500 nm. The modified layer on surface has very small amount of impurities such as D, Be, C, N, O and Ni. All mirrors from the divertor (inner, outer, base under the bulk W tile) lost reflectivity by 20-80% due to the beryllium-rich deposition also containing D, C, N, O, Ni and W. In the inner divertor N reaches 5 x 10(17) cm(-2), W is up to 4.3 x 10(17) cm(-2), while the content of Ni is the greatest in the outer divertor: 3.8 x 10(17) cm(-2). Oxygen-18 used as the tracer in experiments at the end of ILW-3 has been detected at the level of 1.1 x 10(16) cm(-2). The thickness of deposited layer is in the range of 90 nm to 900 nm. The layer growth rate in the base (2.7 pm s(-1)) and inner divertor is proportional to the exposure time when a single campaign and all three are compared. In a few cases, on mirrors located at the cassette mouth, flaking of deposits and erosion occurred.
Original languageEnglish
JournalNuclear Materials and Energy
Volume19
Pages (from-to)59-66
Number of pages8
ISSN2352-1791
DOIs
Publication statusPublished - May 2019
MoE publication typeA1 Journal article-refereed

Fields of Science

  • 114 Physical sciences

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