RECENT UPGRADES AND EXTENSIONS OF THE NEW
 MULTI-FREQUENCY ECRH SYSTEM AT ASDEX UPGRADE

 

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, 46 Ulyanov St., Nizhny Novgorod, 603950, Russia

E.M. Tai, L.G. Popov, V.O. Nichiporenko, V.E. Myasnikov, E.A. Solyanova, SA. Malygin

 GYCOM Ltd, 46 Ulyanov St., Nizhny Novgorod, 603155, Russia

 

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)