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Investigations of microwave and THz radiation losses in CVD diamond and chemically modified diamond

Published online by Cambridge University Press:  09 March 2011

T. A. Scherer
Affiliation:
Karlsruhe Institute of Technology KIT, Herrmann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany, theo.scherer@kit.edu (corresponding author); a: IMF-1, b: ANKA
D. Strauss
Affiliation:
Karlsruhe Institute of Technology KIT, Herrmann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany, theo.scherer@kit.edu (corresponding author); a: IMF-1, b: ANKA
A. Meier
Affiliation:
Karlsruhe Institute of Technology KIT, Herrmann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany, theo.scherer@kit.edu (corresponding author); a: IMF-1, b: ANKA
Y.-L. Mathis
Affiliation:
Karlsruhe Institute of Technology KIT, Herrmann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany, theo.scherer@kit.edu (corresponding author); a: IMF-1, b: ANKA
V. Judin
Affiliation:
Karlsruhe Institute of Technology KIT, Herrmann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany, theo.scherer@kit.edu (corresponding author); a: IMF-1, b: ANKA
W. Müller-Sebert
Affiliation:
Fraunhofer-Institut für Angewandte Festkörperphysik (IAF); D-79108 Freiburg, Germany
W. Smirnov
Affiliation:
Fraunhofer-Institut für Angewandte Festkörperphysik (IAF); D-79108 Freiburg, Germany
C. Nebel
Affiliation:
Fraunhofer-Institut für Angewandte Festkörperphysik (IAF); D-79108 Freiburg, Germany
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Abstract

To counteract plasma instabilities like Neoclassical Tearing Modes (NTM-modes) in nuclear fusion reactors (JET, ITER, DEMO) high power microwaves are used for the Electron Cyclotron Resonance Heating (ECRH) and for the plasma current drive (CD). The foreseen power level for ITER (Cadarache, France) is Ptot = 24 MW at f = 170 GHz. Each transmission line is designed for a maximum of 2 MW power. The vacuum and tritium barrier to the ITER vacuum vessel is realized by a CVD diamond disk window assembly. Diamond has an extremely high thermal conductivity of about k = 2100 W/Km and a very low loss tangent of tan δ < 10-5 for this frequency and shows therefore a very small microwave absorption. The normalized absorbed power A=Pabs/P0 can be calculated as A = (f/c) • π • (1+εr‘) • tan δ • t (with the rule of thumb estimate: (f/c)=0.5 mm-1; π • (1+εr‘) = 20; tan δ =10-5; A=10-4 • t [mm]); i.e. each t = 1 mm thickness of diamond absorbs Pabs = 100 W of Po = 1 MW microwave power transmitted through the CVD diamond window with an effective tanδ of 10-5.

Type
Research Article
Copyright
Copyright © Materials Research Society 2011

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References

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