Low- and high-power measurements on a remote steering upper port launcher mockup for ITER
FOM Institute for Plasma Physics “Rijnhuizen”,
Association EURATOM-FOM, Edisonbaan
14, P.O. Box 1207, 3430 BE Nieuwegein, The Netherlands.1CIEMAT,
Madrid, Spain.2IFP,Consiglio Nazionale delle Ricerche Milano,
Association EURATOM-CNR, Italy. 3IHMa,
IMFb, Forschungszentrum Karlsruhe, Association
EURATOM-FZK and 4IPF,
Universität Stuttgart, Germany.
e-mail: bongers@rijnh.nl, website: www.rijnh.nl/ITERECRH
Abstract
The Euratom association FOM-Rijnhuizen is developing a plug-in 170 GHz ECW launcher system for use in the upper-ports of ITER, based on the remote steering (RS) principle, designed to stabilise the Neoclassical Tearing Modes (NTM) at the q=3/2 and q=2/1 surfaces by inducing off-axis current drive. The launching system enables up to eight mm-wave beams per port plug to be directed from the feeding waveguides through corrugated square waveguides (≈ 44x44 mm2) inside the port plug to the plasma. A mock-up system has been manufactured, capable of vacuum & high-power short-pulse operation.
The transmission line consists of a taper, to launch an HE11 mode in 63.5 mm circular corrugated waveguide. (The taper will be replaced by a gyrotron source in high power testing). The circular waveguide is used as input for the steering mechanism, housed in a vacuum vessel, which directs the beam under an angle between -12˚ and 12˚ through the CVD diamond window [1] into the copper square corrugated waveguide.
Antenna patterns
from the exit aperture of the square waveguide are scanned using a 3-axis
scanner. Low-power measurements, see also [2,3], were a preparatory phase for
high-power tests, which were done in FZK. In the High-power measurements,
waveguide performance will also be inferred from antenna pattern measurements. Good results were obtained using absorbing
heat patterns, viewed by an IR-camera, on a target, made of a thin PVC foil,
and placed at a certain distance after the waveguide. From these measurements
it was shown that a usable range for remote steering is about -12˚ to
12˚ degrees.
In the FOM design, see for example [4] for the upper port launchers for ITER, at this time the square corrugated waveguide (SCW) is 4321 mm in length and has a 44*44 mm2 aperture (optimized for 10.37˚ at 170 GHz). The waveguide under test here was supplied by General Atomics (GA), and is vacuum-tight, so that only the inner part of the waveguide need be evacuated for high power operation. Additionally, this enables easy access to the waveguide outer surface with thermocouples and the infrared camera. For ITER, this vacuum tightness of the waveguide itself is not a requirement. One of the middle sections could be replaced by a Dutch cooled version manufactured by Heeze mechanics.
In the presentation I will present the latest results of the low-and high power measurements on the remote steering waveguide and its input systems at several stages in the testing procedure.
References
[1] R. Heidinger, et al., “Design and performance tests of a high power torus window for a remotely steered EC launcher”, IRMMW 2005 Virginia.
[2] W. Kasparek, et al, “Performance of a remote steering antenna for ECRH/ECCD applications in ITER using four-wall corrugated square waveguide”, Nucl. Fusion 43 (2003), p. 1505-1512.
[3] K. Takahashi, et al “High power experiments of remote steering launcher for electron cyclotron heating and current drive”, Fusion Engineering and Design, Volume 65, Issue 4, July 2003, p. 589-598
[4] M.F. Graswinkel, et al., “Low power measurements on a remote steering upper port launcher mock-up for ITER”, Third IAEA Technical Meeting on "ECRH Physics and Technology for ITER" Como, Italy.
[5] A.G.A. Verhoeven, et al., “Design and test of a Remote Steering upper port launcher for ITER”, IRMMW 2005 Virginia.