Speaker
Marek Rubel
(Fusion Plasma Physics)
Description
All optical spectroscopy and imaging diagnostics in next-step fusion devices will be based on metallic mirrors. The performance of mirrors is studied in present-day tokamaks and under laboratory conditions. This work deals with comprehensive tests of mirrors: (i) exposed in JET with the ITER-Like Wall (JET-ILW); (b) irradiation by He and heavy ions to simulate the impact of neutrons under reactor conditions.
First Mirror Test at JET for ITER. Mo mirrors placed in pan-pipe cassettes were exposed to plasma in the main chamber wall and in the divertor inner, outer and base. In the main chamber only mirrors located at the entrance to the cassette lost reflectivity (Be deposition from the eroded limiters), while those in the channels were slightly affected. The performance of mirrors in the JET-ILW divertor was strongly degraded by deposition of beryllium, tungsten and other species. Splashing of metal droplets on mirrors also occurred. It should be stressed, that these solid Mo mirrors were not damaged by arcing.
Radiation damage in mirrors: work towards DEMO. Optically active layer in mirrors is 20-30 nm thick. The conditions for the ion irradiation, He++ (1-2 keV) and 9898Mo++ (30 keV), were based on SRIM simulations. Studies were performed for mirrors irradiated by a single type and by both types of ions. The stepwise irradiation up to 30 dpa by 9898Mo++ caused only small changes in the optical performance. Much stronger effects have been produced by helium because of bubble formation which led to the reflectivity decrease by more than 20%. Helium retention studies revealed that only 9% of the implanted He was retained.
Consequences of various plasma-wall interaction processes on the performance and reliability of plasma diagnostic systems will be discussed.
Co-authors
Alvaro Garcia-Carrasco
(Fusion Plasma Physics, Royal Institute of Technology (KTH), Stockholm, Sweden)
Anders Hallen
(Royal Institute of Technology (KTH), Stockholm, Sweden)
Anna Widdowson
(Culham Science Centre, Culham Centre for Fusion Energy, Abingdon, United Kingdom)
Elzbieta Fortuna-Zalesna
(Department of Materials Science, Warsaw University of Technology, Warsaw, Poland)
Justyna Grzonka
(Department of Materials Science, Warsaw University of Technology, Warsaw, Poland;Institute of Electronic Materials Technology, Warsaw, Poland)
Marek Rubel
(Fusion Plasma Physics, Royal Institute of Technology (KTH), Stockholm, Sweden)
Matias Brix
(Culham Science Centre, Culham Centre for Fusion Energy, Abingdon, United Kingdom)
Per Petersson
(Fusion Plasma Physics, Royal Institute of Technology (KTH), Stockholm, Sweden)
