Speaker
Johan Oosterbeek
(Eindhoven University of Technology)
Description
Diagnostic systems are essential for the development of ITER discharges and to reach the ITER goals. Many of these diagnostics require a line of sight to relay signals from the plasma to the diagnostic, typically located outside the torus shall. Such diagnostics then require vacuum windows that isolate the torus vacuum and crucially ensure tritium containment. While such windows are routine in many fusion experiments, ITER poses new challenges. The vacuum windows are Safety Important Components class 1 that must withstand all ITER loads. As a consequence, in many cases double windows are used. ITER is a long pulse machine with 20 MW microwave heating installed, giving rise to gradual heating of windows due to stray radiation. The particular microwave heating scheme at ITER may also - in case of an erroneous polarization setting - result in a highly focused beam that can be incident on a window and cause thermal shock.
This paper looks at microwave aspects of ITER windows. The microwave response as a function of frequency is calculated for proposed arrangements. This response enables to assess the impact on diagnostic performance, such as the location in frequency space of the minima and maxima in reflection and transmission, as well as the attenuation of signal caused by absorption of the window. In the presence of microwave stray radiation, the absorption may lead to considerable dielectric heating of the window. Mitigation measures, such as reduction of the microwave power incident on the window and the application of coatings, are investigated. Such measures must be verified and qualified and dedicated measurements are discussed such as characterisation of dielectric materials in a low power resonator, directed beam measurements to verify reflection and absorption, high power tests to measure absorption and ITER vacuum qualification tests.
Co-authors
Ageeth A. Bol
(Eindhoven University of Technology, Eindhoven, Netherlands)
Antoine Sirinelli
(ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex, France)
Dmitry Moseev
(Max-Planck-Institut für Plasmaphysik, EURATOM Association, Teilinstitut Greifswald, D-17489 Greifswald, Germany)
George Vayakis
(ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex, France)
Johan Oosterbeek
(Eindhoven University of Technology, Eindhoven, Netherlands)
Karsten Arts
(Eindhoven University of Technology, Eindhoven, Netherlands)
Mike J. Walsh
(ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex, France)
Philippe Maquet
(ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex, France)
Ralf Konig
(Max-Planck-Institut für Plasmaphysik, EURATOM Association, Teilinstitut Greifswald, D-17489 Greifswald, Germany)
Victor S Udintsev
(ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex, France)
Walter Kasparek
(Institut für Grenzflächenverfahrenstechnik und Plasmatechnologie, Universität Stuttgart, Pfaffenwaldring 31, D-70569 Stuttgart, Germany)
