Preliminary Monte Carlo simulation of beryllium migration during JET ITER-like wall divertor operation M.I. Airila a,b,⇑ , A. Järvinen a,c , M. Groth a,c , P. Belo a,d , S. Wiesen a,e , S. Brezinsek a,e , K. Lawson a,f , D. Borodin a,e , A. Kirschner a,e , J.P. Coad a,b , K. Heinola a,f,g , J. Likonen a,b , M. Rubel a,h , A. Widdowson a,f , JET-EFDA Contributors 1 a JET-EFDA, Culham Science Centre, Abingdon OX14 3DB, UK b VTT Technical Research Centre of Finland, PO Box 1000, 02044 VTT, Finland c Department of Applied Physics, Aalto University, PO Box 14100, 00076 AALTO, Finland d Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Av Rovisco Pais, 1049-001 Lisbon, Portugal e Forschungszentrum Jülich, Institut für Energie- und Klimaforschung Plasmaphysik, 52425 Jülich, Germany f Culham Centre for Fusion Energy, Abingdon OX14 3DB, UK g University of Helsinki, PO Box 43, 00014 University of Helsinki, Finland h Royal Institute of Technology, Fusion Plasma Physics, 10044 Stockholm, Sweden article info Article history: Available online 16 September 2014 abstract Migration of beryllium into the divertor and deposition on tungsten in the final phase of the first ITER-like-wall campaign of JET are modelled with the 3D Monte Carlo impurity transport code ERO. The simulation covers the inner wall and the inner divertor. To generate the plasma background for Monte Carlo tracing of impurity particles, we use the EDGE2D/EIRENE code set. At the relevant regions of the wall, the estimated plasma conditions vary around T e  5 eV and n e  2  10 17 m 3 (far-scrape-off layer; more than 10 cm away from the LCFS). We calculate impurity distributions in the plasma using the main chamber source as a free parameter in modelling and attempt to reproduce inter-ELM spectroscopic Be II line (527 nm) profiles at the divertor. The present model reproduces the level of emission close to the inner wall, but further work is needed to match also the measured emission peak values and ultimately link the modelled poloidal net deposition profiles of beryllium to post mortem data. Ó 2014 EURATOM. Published by Elsevier B.V. All rights reserved. 1. Introduction The ITER first-wall material mix of beryllium and tungsten is being tested at JET to gain understanding on the durability and plasma compatibility of such a metallic environment. The main motivation of discarding carbon completely in plasma-facing components is its tendency to accumulate tritium in co-deposits. Indeed, already the first ITER-like wall (ILW) campaign soon con- firmed a large reduction in impurity release and hydrogen retention rate compared to an all-carbon machine [1,2]. However, further analysis is required for other major differences between JET-C and JET-ILW, related to wall durability and plasma operation in eventually high-performance scenarios. This contribution focuses on changes in wall composition due to beryllium migration from the main wall to the tungsten divertor. After the installation of the ILW, it was anticipated that eroded beryllium from the main wall is transported to the tungsten divertor and form mixed-materials. Indeed, significant changes in the diver- tor composition were already evident from the evolution of spectro- scopic signals and related modelling in the very first phase of the campaign [3]. For a detailed investigation of the resulting deposits and possible mixed materials, the first experimental year with the ILW was concluded with a long series of identical H-mode dis- charges, followed by removal and detailed analysis of selected sam- ples from the first wall [4–7]. The surface analysis methods include IBA, SIMS and mechanical tile profiling at the divertor. Spectro- scopic observations of the Be I line (457 nm) indicate that steady conditions at the divertor were achieved rapidly (about in 1 day) in this experiment, as illustrated in Fig. 1. Such conditions are favourable for modelling, although the plasma-facing components http://dx.doi.org/10.1016/j.jnucmat.2014.09.010 0022-3115/Ó 2014 EURATOM. Published by Elsevier B.V. All rights reserved. ⇑ Corresponding author at: VTT Technical Research Centre of Finland, PO Box 1000, FI-02044 VTT, Finland. E-mail address: markus.airila@vtt.fi (M.I. Airila). 1 See the Appendix of F Romanelli et al., Proc. 24th IAEA Fusion Energy Conference 2012 San Diego, USA. Journal of Nuclear Materials 463 (2015) 800–804 Contents lists available at ScienceDirect Journal of Nuclear Materials journal homepage: www.elsevier.com/locate/jnucmat