D. Wagner, J. Stober,
S. Bäumel, T. Franke, F. Leuterer,
F. Monaco, M. Münich,
D. Schmid-Lorch,
H. Schütz, H Zohm
Max-Plank-Institut für Plasmaphysik,
EURATOM-IPP, Boltzmannstr.2, D-85748 Garching, Germany
1M. Thumm,
2T. Scherer, 2A. Meier, 1G. Gantenbein, 1J. Flamm
Forschungszentrum Karlsruhe, EURATOM-FZK,
1Institut
für Hochleistungsimpuls- und Mikrowellentechnik,
2Institut
für Materialforschung,
PO Box 3640, D-76021 Karlsruhe,
Germany
W. Kasparek,
H. Höhnle, C. Lechte
Institut für Plasmaforschung,
Universität Stuttgart, D-70569 Stuttgart, Germany
A.G. Litvak,
G.G. Denisov, A. Cirkov
Institute of Applied
Physics,
E.M. Tai, L.G. Popov, V.O. Nichiporenko, V.E. Myasnikov,
E.A. Solyanova, SA. Malygin
GYCOM Ltd,
Abstract
A new
ECRH system for the ASDEX Upgrade tokamak is
currently under construction. It will finally consist of 4 depressed collector
gyrotrons, step-tunable in the range 105-140 GHz, with a total output power of 4
MW and a pulse length of 10 s. The transmission is mainly in non-evacuated
corrugated HE11-waveguides with an inner diameter of 87 mm. The
first two-frequency gyrotron (105, 140 GHz) has been in routine operation for
two years. Since 2007 ASDEX Upgrade operates with fully tungsten covered plasma
facing components. Central heating with ECRH plays a key role in suppressing
tungsten accumulation in the plasma center. Several plasma startup scenarios
using both 105 and 140 GHz have been tested successfully. The system is
equipped with fast steerable launchers where the launcher angle can be varied
during the discharge. One of the future tasks will be feedback-controlled
suppression of neoclassical tearing modes.
New
detectors for millimeter wave stray radiation in the tokamak
have been installed. The sniffer
probe antenna is an oversized waveguide (I.D.=27.8mm) with multi-mode reception
within a large solid angle. After successful high-power tests with a prototype
at IPP Greifswald, a compact Fast Directional Switch (FADIS),
compatible with the HE11 corrugated waveguide transmission line of
the ASDEX Upgrade ECRH system, has been constructed. The FADIS allows for
controlled switching of high-power microwaves between two outputs by fine
frequency control as well as for combining of two microwave beams. It is
planned to install the FADIS at ASDEX Upgrade between two
HE11 waveguides as soon as the second two-frequency gyrotron is
operational. A polarisation independent holographic reflector was
mounted on the inner wall of ASDEX Upgrade. It will be used for heating
experiments with high density ITER relevant plasmas in O2-mode with only
partial absorption using a second pass of the non-fully absorbed beam through
the resonant layer.
Possible collaboration:
Polarization control and optimization of ECRH coupling. Stray-radiation
measurements.
(US-EU-JA)