Chavan, R.

Heidinger, R.

Henderson, M.

Kajiwara, K.

Meier, A.

Sakamoto, K.

Scherer, T.A.

Takahashi, K.

Scherer, T. A.

KITopen

T.A. Scherer1, R. Heidinger1, A. Meier1, K. Sakamoto2, K. Takahashi2, K. Kajiwara2, M. Henderson3, R. Chavan31 Forschungszentrum Karlsruhe, Association EURATOM-FZK, Institut für Materialforschung I, Postfach 3640, D-76021 Karlsruhe, Germany2 Plasma Heating Technology Group, Japan Atomic Energy Agency (JAEA), 801-1 Mukoyama, Naka, Ibaraki 311-0193 JAPAN3 CRPP, Association EURATOM- Conf. Suisse, EPFL, CH-1015 Lausanne, Switzerlandmit der Universität Karlsruhe verbunden inFor the plasma engineering of ITER, EC launchers will be used at the upper port and the equatorial port levels. Part of these studies is to verify the window design and to work out, whether a concept is available for both launchers. To this goal, first experiments with low and high power mm-waves are performed and will be presented. The high power RF behavior of torus window assemblies with corrugated waveguides is being investigated by using IR imaging technique during high power microwave loading with the intention to reach 1 MW at a frequency of 170 GHz at the JAEA gyrotron facility. Short pulse experiments up to 15 seconds pulse duration have been performed to determine the temperature distribution over the whole diamond window area and the efficiency of the indirect cooling by a copper cuff. The occurrence of arcing is being studied as part of evaluation of the assembly design. In a future step also long pulse measurements up to several hundred seconds are planned.Design aspects and RF characterization of ITER-RF-CVD- diamond windowsFig. 1: Dielectric loss mapping of the bare CVD diamond window disk 70DB1 (Manufacturer: ElementSix) measured at a frequency of 100.71 GHz. The diameter of the diamond disk is 75 mm, the thickness 1.114 mm and the dielectric constant 5.67. The length of the resonator was 116.54 mm.INTRODUCTIONCharacterization of CVD diamond window materialSUMMARYThis work, supported by the European Communities, was carried out within the framework of the European Fusion Development Agreement. The views and opinions expressed herein do not necessarily reflect those of the European Commission.Configuration of the ITER torus window assemblyFigure 2 CAD design and photograph of the CVD diamond torus window unit with the CVD diamond disk separating the torus vacuum section from the dedicated transmission line section. The red section is formed by a copper cuff with two symmetric cooling chambers separated from a vacuum segment at the outer diamond edge. The left part is the torus side, the right part the transmission line side.Experimental setup for high power short pulse 170 GHz measurement at JAEATable 1. Vacuum, leak rate and water flow conditions of the CVD diamond window for the high power tests..VacuumTMPVacuumWindowHe leakRateWaterflow1.6 . 10-4 Pa 10-3 Pa 10-10Pam3/s 12.5 l/minFig. 3: Setup for short-pulse CVD diamond window testing at 170 GHz/1MW gyrotron at JAEAa)1.0 s 320 kWb)2.0 s 320 kWc)15.0 s 320 kWd)2.0 s600 kWFig. 4: IR measurements of the temperature of the CVD diamond window at different short pulse time and RF power at 170 GHz. The temperature-time dependence in the left part of the table corresponds to the indicated letters in the infrared picture. IR picture a) has an other color range in comparison to pictures b), c) and d). Short pulse high power RF measurements at 170 GHz have been performed at JAEA gyrotron facility by means of IR thermography. To understand the inhomogeneous temperature distribution over the diamond disk it is to remark, that the beam profile at the end of the waveguide after passing several miter bends is not purely Gaussian. A non radial symmetric temperature distribution was observed and is accompanied by a non radial symmetric distribution of the electrical field and therefore the electrical power. The influence of this deviation of a non-Gaussian field distribution will be subject to additional investigations. The detailed analysis of the temperature evolution as function of the absorbed mm-wave power has to await the quantification of the mode composition. In future experiments also long pulse measurements are planned.

Design aspects and RF characterization of ITER-RF-CVD-diamond windows

https://publikationen.bibliothek.kit.edu/220071317/3815196

Design aspects and RF characterization of ITER-RF-CVD-diamond windows

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