Total IBA a quantitative tool to study plasma wall interactions

EUROfusion Consortium, JET, Culham Science Centre, OX14 3DB, Abingdon, UK

(1) Instituto de Plasmas e Fusão Nuclear, IST, Universidade de Lisboa, 1049-001 Lisboa, PT
(2) C2TN, IST, Universidade de Lisboa, 1049-001 Lisboa, Portugal
(3) Culham Centre for Fusion Energy,Culham Science Centre, Abingdon, OX14 3DB, UK
(4) University of Helsinki, P.O. Box 64, 00560 Helsinki, Finland
(5) VTT Technical Research Centre of Finland, P.O. Box 1000, FIN-02044 VTT, Finland
(6) Royal Institute of Technology, SE-10044 Stockholm, Sweden

Ion beam techniques, by their nature, are valuable tools to study the effect of energetic particles on the surface region of materials making them very attractive to study plasma wall interactions in fusion devices.  During operation the plasma suffers electric disruptions and large amounts of energy and radiation loads are deposited on wall materials. Also neutrals and high energy particles are allowed to leave the closed plasma surfaces and hit the plasma wall chamber. The interactions cause severe changes on the reactor materials imposing dedicated studies to understand all these phenomena in order to improve and validate the theoretical models allowing a robust design of fusion devices. In this contribution we study the plasma effect on selected tiles of the new ITER like wall (ILW) configuration of JET, combining different ion beam techniques and using the WiNDF code to analyse and   interpret the data.  The sensitivity, depth resolution and elemental analysis characteristics of the techniques are ideal to study the erosion, deposition, mixing and fuel retention on the near surface of the plasma wall materials. The results show areas of strong erosion in the centre of the tiles of the inner wall guard limiter (IWGL) whilst re-deposition occurs at the ends. The deposition zones retain large amounts of Deuterium with values reaching up to 2 orders of magnitude higher compared to the eroded area (from 1x1017 at/cm2 to 5x1019 at/cm2).The tiles at the bottom edges  of the divertor show a narrow and thick zone of deposition along the slope containing mostly beryllium.   

[1] See the Appendix of F. Romanelli et al., Proceedings of the 25th IAEA Fusion Energy Conference 2014, Saint Petersburg, Russia