Material choice for first ITER mirrors under erosion conditions M. Matveeva 1 , A. Litnovsky 1 , L. Marot 2 , B. Eren 2 , E. Meyer 2 , V. Philipps 1 , A. Pospieszczyk 1 , H. Stoschus 1 , D. Matveev 3 and U. Samm 1 1 Institut für Energieforschung - Plasmaphysik, Forschungszentrum Jülich GmbH, Assoziation EURATOM-FZ-Julich, Trilaterales Euregio Cluster, 52428 Jülich, Germany 2 Department of Physics, University of Basel, Klingelbergstr. 82, CH-4056 Basel, Switzerland 3 Department of Applied Physics, Ghent University, Plateaustraat 22, B-9000 Ghent, Belgium Abstract The behaviour of different candidate materials for ITER mirrors under erosion conditions is investigated in TEXTOR tokamak. Results of experiments are presented along with an assessment of applicability of the studied mirror concepts for ITER diagnostics. It is shown that all studied mirror concepts can be applied in ITER under mild erosion conditions (as in equatorial ports) when protective techniques are applied. Molybdenum single crystal mirrors demonstrated the best performance under stronger erosion conditions, corresponding to those expected in the upper diagnostic ports of ITER with gas fueling. Introduction ITER will require accurate and reliable measurements of a wide range of plasma parameters necessary for the machine protection, basic plasma control and research program [1]. For this reason ITER will be equipped with a large set of diagnostics. All optical diagnostics will use metallic mirrors as first plasma-viewing elements which will suffer from such adverse effects as neutron and gamma irradiation, nuclear heating and high particle fluxes. The lifetime of mirrors represents a critical issue [2]. Erosion of the mirror surface and deposition of impurities have the strongest impact on the mirror performance. Surface erosion by charge- exchange atoms with typical flux ranging from (1÷4)×10 19 to 1.7×10 21 atoms/m 2 s [3] with energies up to several keV can significantly change optical properties of mirrors and lead to a shutdown of the respective diagnostics. The reflectivity of mirrors under erosion conditions strongly depends on mirror material [4]. Therefore a proper material and manufacturing technique have to be chosen. To investigate the behaviour of different candidate materials for ITER mirrors under erosion conditions, experiments were performed in TEXTOR tokamak. Mirror manufacturing and characterization Rhodium (Rh) and molybdenum (Mo) coated mirrors on different substrate materials were studied along with single crystal (SC) molybdenum mirrors. Advantages of SC Mo mirrors in comparison with polycrystalline Mo mirrors were investigated earlier [5]. While SC mirrors 37 th EPS Conference on Plasma Physics P2.105