Commissioning of inline ECE system within waveguide based ECRH transmission systems on ASDEX upgrade

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

Feasibility of upper port plug tube handling

Central, retractable tubes are proposed in several Upper Port Plugs (UPPs) designs for ITER, to enable fast exchange of specific components of diagnostics housed in these UPPs. This paper investigates into possible designs to enable the efficient handling of tubes. The feasibility of tube handling is analysed by first reviewing the designs drivers. Several concepts for handling of the tube are proposed, exploring the limits described by the design drivers. Suggestions are presented for tube integration into the UPP design, concerning the tube mounting into the UPP, the load takeover and coping with the thermal elongation. It is found that the handling of tubes is feasible but still requires a lot of system level integration. Also, the added value of a tube as a feature in an UPP design to the availability of the subsystem the UPP is a part of, is questionable and needs further assessment on ITER system level. (C) 2011 Elsevier B.V. All rights reserved

Utilization of collinear ECE detection/ECRH heating for active stabilization of plasma instabilities

Experiments on TEXTOR have successfully demonstrated the proof of principle [1] of using Electron Cyclotron Emission (ECE) measured along the Electron Cyclotron Resonance Heating (ECRH) line-of-sight [2] for the control of magnetohydrodynamic (MHD) modes. This work, which was done with a quasi-optical system, motivates the further development and implementation of a similar, but in-waveguide system for detection and control of Neoclassical Tearing Mode (NTM) in larger fusion machines. Progress on the implementation of such a system on ASDEX-Upgrade [3], based on waveguides equipped with a Fast Directional Switch (FADIS), is presented. Since FADIS, will be installed at ASDEX, to switch the gyrotron power between different launchers [4], FADIS can also be employed as a frequency filter serving the purpose of separating a low-power ECE signal from the high power ECRH radiation as required in the co-aligned ECE-ECRH setup [5]. Because additional absorptive filtering is required after the FADIS ECE output in [5] and [6] a non resonant two-beam Mach-Zehnder-type interferometer was chosen. This system has been built and partially tested

Utilization of collinear ECE detection/ECRH heating for active stabilization of plasma instabilities

Experiments on TEXTOR have successfully demonstrated the proof of principle [1] of using Electron Cyclotron Emission (ECE) measured along the Electron Cyclotron Resonance Heating (ECRH) line-of-sight [2] for the control of magnetohydrodynamic (MHD) modes. This work, which was done with a quasi-optical system, motivates the further development and implementation of a similar, but in-waveguide system for detection and control of Neoclassical Tearing Mode (NTM) in larger fusion machines. Progress on the implementation of such a system on ASDEX-Upgrade [3], based on waveguides equipped with a Fast Directional Switch (FADIS), is presented. Since FADIS, will be installed at ASDEX, to switch the gyrotron power between different launchers [4], FADIS can also be employed as a frequency filter serving the purpose of separating a low-power ECE signal from the high power ECRH radiation as required in the co-aligned ECE-ECRH setup [5]. Because additional absorptive filtering is required after the FADIS ECE output in [5] and [6] a non resonant two-beam Mach-Zehnder-type interferometer was chosen. This system has been built and partially tested

A remotely steered millimetre wave launcher for electron cyclotron heating and current drive on ITER

High-power millimetre wave beams employed on ITER for heating and current drive at the 170 GHz electron cyclotron resonance frequency require agile steering and tight focusing of the beams to suppress neoclassical tearing modes. This paper presents experimental validation of the remote steering (RS) concept of the ITER upper port millimetre wave beam launcher. Remote steering at the entrance of the upper port launcher rather than at the plasma side offers advantages in reliability and maintenance of the mechanically vulnerable steering system. A one-to-one scale mock-up consisting of a transmission line, mitre bends, remote steering unit, vacuum window, square corrugated waveguide and front mirror simulates the ITER launcher design configuration. Validation is based on low-power heterodyne measurements of the complex amplitude and phase distribution of the steered Gaussian beam. High-power (400 kW) short pulse (10 ms) operation under vacuum, diagnosed by calorimetry and thermography of the near- and far-field beam patterns, confirms high-power operation, but shows increased power loss attributed to deteriorating input beam quality compared with low-power operation. Polarization measurements show little variation with steering, which is important for effective current drive requiring elliptical polarization for O-mode excitation. Results show that a RS range of up to -12° to +12° can be achieved with acceptable beam quality. These measurements confirm the back-up design of the ITER ECRH&CD launcher with future application for DEMO

Commissioning of inline ECE system within waveguide based ECRH transmission systems on ASDEX upgrade

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