Controlled Mirror Motion System for Resonant Diplexers in ECRH Applications

Niek Doelman ,G Michel,W Klop,F Monaco,R Van Den Braber,V Erckmann,M Maraschek,F Purps,B Krijger,W Kasparek,F Noke,Frank Hollmann ,Stefan Müller ,Erik Fritz ,J Stöber ,M De Baar ,H Schütz ,Bert Dekker ,W.a Bongers ,D Wágner

doi:10.1051/epjconf/20123204005

Abstract

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. © Owned by the authors, published by EDP Sciences, 2012.

Highlights

High-power diplexers for millimetre waves have been developed and experimentally validated for their potential use in ECRH systems as well as for plasma diagnostics; see [1] for the background and design considerations of these diplexers
The FADIS (FAst DIrectional Switch) diplexer is a quasi-optical ring resonator for millimetre waves that consists of 4 mirrors which are mounted in a rigid aluminum support structure
The leaf spring mechanism has a high stiffness in five degrees of freedom (DoF) of the mirror, whereas it is compliant for motion in the desired direction

Summary

Introduction

High-power diplexers for millimetre waves have been developed and experimentally validated for their potential use in ECRH systems as well as for plasma diagnostics; see [1] for the background and design considerations of these diplexers. Ministry of Economic Affairs, in the ’Fond Economische Structuurversterking’ program High-power, resonant diplexers have a large field of potential applications. These include the adjustable distribution of gyrotron power over the output ports (either by mechanical tuning of a diplexer mirror (slow) or by modulation of the gyrotron voltage (fast)), a mode purification device, a narrow band-pass filter to discriminate between low power ECE signals and high power ECRH in a line-ofsight ECE sensing configuration and a combiner of gyrotron power from two input ports into a single transmission line. Further details of the versatile application field can be found in [1,2,3]

Requirements on the mirror motion system

Mechanical design

Output power feedback

Frequency signal feedforward

Experimental results

Conclusions