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The development of diplexers for ECRH has been pursued at a number of institutes because of their attractive variety of applications: Power combination, non-mechanical, electrically controlled switching (of combined beams) between launchers with tens of kHz, and discrimination of low-power ECE signals from high-power ECRH is feasible. In a first part, this paper reports on plasma experiments with a ring resonator (Mk IIa) at ASDEX Upgrade. Commissioning experiments on fast switching between two launchers for synchronous stabilization of neoclassical tearing modes, as well as in-line ECE measurements have been performed, and experimental issues and first results are discussed. A clear influence of the switching phase on the amplitude of the 3/2 NTM mode was measured, complete stabilization could, however, not be demonstrated yet mainly due to imperfect resonator control. Concepts for improved tracking of the diplexers to the gyrotron frequency are presented. In a second part, the design of diplexers with ring resonators matched to HE11 fields is briefly discussed; these devices can be connected to corrugated waveguides without any mode converters. A compact version (MQ IV) is under investigation, which is compatible with the ITER ECRH system (170 GHz, 63.5 mm waveguide, vacuum tight casing), with the final goal of high-power tests at the 170 GHz gyrotron facility at JAEA in Naka, Japan. First low-power test results are presented. [ABSTRACT FROM AUTHOR]

Characteristics of ring resonator diplexers for high-power ECRH are briefly reviewed. Commissioning experiments performed on ASDEX Upgrade with the diplexer Mk IIa are presented, which demonstrate slow and fast switching of the power between two launchers, and thus the capability for efficient suppression of neoclassical tearing modes and simultaneous central heating of the plasma. The development of the compact diplexer Mk IIIb is discussed, and test results are presented. Finally, an evacuated design for 170 GHz is shown. [ABSTRACT FROM AUTHOR]

High-power resonant diplexers for millimetre waves have various promising applications in ECRH systems. The round-trip resonator length of a diplexer needs to be accurately tuned to match its prescribed functionality. For this purpose one of the mirrors in the FADIS MkIIa diplexer has been mounted on a motion system, in order to control the mirror to its desired location despite the presence of substantial disturbances. The mechanical properties and control strategy for the mirror motion system have been designed such as to meet the overall system requirements. The performance of the motion system has been experimentally validated in various high power mm-wave tests. [ABSTRACT FROM AUTHOR]

A CW capable inline electron cyclotron emission (ECE) separation system for feedback control, featuring oversized corrugated waveguides, is commissioned on ASDEX upgrade (AUG). The system is based on a combination of a polarization independent, non-resonant, Mach-Zehnder diplexer equipped with dielectric plate beam splitters [2, 3] employed as corrugated oversized waveguide filter, and a resonant Fast Directional Switch, FADIS [4, 5, 6, 7] as ECE/ECCD separation system. This paper presents an overview of the system, the low power characterisation tests and first high power commissioning on AUG. [ABSTRACT FROM AUTHOR]

Electron Cyclotron Resonance Heating (ECRH) systems for next step-fusion devices like W7-X and ITER operate in CW-mode and provide a large flexibility to comply with various physics demands such as plasma start-up, heating and current drive, as well as configuration and MHD control. The request for many different sophisticated applications results in a growing complexity of the systems. This is in conflict with the request for high availability, reliability, and maintainability, which arises from DEMO demands. 'Advanced' ECRH-components must, therefore, comply with both the complex physics demands and operational robustness and reliability. The W7-X ECRH system is the first CW facility of an ITER relevant size and is used as a test bed for such components. Results on improvements of gyrotrons, transmission components and launchers are presented together with proposals for future developments. [ABSTRACT FROM AUTHOR]