Speaker
Mr
Andrey Litnovsky
(Germany)
Description
In ITER, mirrors will be used as plasma-viewing elements in all optical and laser diagnostics. In the harsh environment mirror performance will degrade hampering the operation of respective diagnostics. The most adverse effect on mirrors is caused by the deposition of impurities and it is expected that the most challenging situation will occur in the divertor. With envisaged changes to all-metal plasma-facing components (PFCs) in ITER, an assessment of mirror performance in the existing divertor tokamak with all-metal PFCs is urgently needed. Such an experiment was made in the ASDEX Upgrade with all-tungsten PFCs as proposed by the International Tokamak Physics Activity (ITPA) Topical Group on Diagnostics, supported by the Specialists Working Group on First Mirrors and carried out in the frame of collaboration between Forschungszentrum Jülich and IPP Garching.
Four molybdenum and four copper mirrors were mounted at the inner wall, in the dome facing the inner and outer divertor targets and in the pump-duct and exposed for seven months in ASDEX Upgrade. After exposure, degradation of the reflectivity was detected on all mirrors. The mirrors in the pump duct almost preserved their reflectivity unlike the mirrors in the dome facing the outer divertor which suffered from highest deposition and the strongest reflectivity degradation. Remarkably, only on the mirror facing the inner divertor and having very thin deposition layer of 15 nm, the carbon fraction was about 50 at.%. On all other mirrors this fraction did not exceed 20 at.%.
The exposure of diagnostic mirrors in the tokamak with all-metal PFCs demonstrated a positive trend to a reduction of net deposition and minor changes in the reflectivity of mirrors located in the pump-duct far away from divertor plasmas. However, the degradation of all exposed mirrors underlines the necessity of an active mirror recovery. Urgent R&D is needed to address the lifetime issues of mirrors in ITER divertor.
Collaboration (if applicable, e.g., International Tokamak Physics Activities)
International Tokamak Physics Activities
Country or International Organization of Primary Author
Germany
Primary author
Mr
Andrey Litnovsky
(Germany)
Co-authors
Dr
Alan E. Costley
(ITER Organization, Route de Vinon sur Verdon, 13115 St. Paul Lez Durance, France)
Dr
Albrecht Herrmann
(Max-Planck-Institut für Plasmaphysik, D-85748, Garching, Germany)
Ms
Buzi Luxherta
(Department of Applied Physics, Ghent University, B-9000 Ghent, Belgium)
Dr
George Vayakis
(ITER Organization, Route de Vinon sur Verdon, 13115 St. Paul Lez Durance, France)
Dr
Greg De Temmerman
(Dutch Institute For Fundamental Energy Research, 3430BE, Nieuwegein, The Netherlands)
Mrs
Maria Matveeva
(Forschungszentrum Jülich, D-52425, Jülich, Germany)
Dr
Peter Wienhold
(Forschungszentrum Jülich, D-52425, Jülich, Germany)
Dr
Silvia Richter
(Central Facility for Electron Microscopy, RWTH Aachen, D-52056, Aachen, Germany)
Mr
Sören Möller
(Forschungszentrum Jülich, D-52425, Jülich, Germany)
Prof.
Ulrich Samm
(Forschungszentrum Jülich, D-52425, Jülich, Germany)
Dr
Uwe Breuer
(Central Division of Analytical Chemistry, Forschungszentrum Jülich, D-52425 Jülich, Germany)
Dr
Volker Philipps
(Forschungszentrum Jülich, D-52425, Jülich, Germany)
Dr
Volker Rohde
(Max-Planck-Institut für Plasmaphysik, D-85748, Garching, Germany)
Prof.
Volodymir Voitsenya
(IPP, NSC Kharkov Institute of Physics and Technology, Kharkov 61108, Ukraine)
