Overview of the ITER EC upper launcher

Abstract

Abstract. The ITER electron cyclotron (EC) upper port antenna (or launcher) is nearing completion of the detailed design stage and will soon be starting the final build to print design. The main objective of this launcher is to drive current locally to stabilise the NTMs (depositing ECCD inside of the island that forms on either the q=3/2 or 2 rational magnetic flux surfaces) and control the sawtooth instability (deposit ECCD near the q=1 surface). The launcher should be capable of steering the focused beam deposition location to the resonant flux surface over the range in which the q=1, 3/2 and 2 surfaces are expected to be found, for the various plasma equilibria susceptible to the onset of NTMs and sawteeth. The aim of this paper is to provide the design status of the principle components that make up the launcher: port plug, mm-wave system and shield block components. The port plug represents the chamber that provides a rigid support structure that houses the mm-wave and shield blocks. The mm-wave system is comprised of the components used to guide the RF beams through the port plug structure and refocus the beams far into the plasma. The shield block components are used to attenuate the nuclear radiation from the burning plasma, protecting the fragile in-port components and reducing the neutron streaming through the port assembly. The design of these three subsystems is described, in addition, the relevant thermo-mechanical and electro-magnetic analysis are reviewed for the critical design issues.

Preliminary design of the ITER ECH upper launcher

“…Based on the conceptual upper launcher design [13] the analysis of different optical beam paths [14] led to a modification of the optical design from a mitre bend solution towards a quasi-optical system, increasing the steering range and thereby the upper launcher performance. With the new "Extended Physics Launcher" (EPL, [15]) the steering angles of USM and LSM have been decoupled, the goal is to cover a range between ρ T =0.3 to near the plasma edge at ρ T =0.95. With an overlap in the NTM regime; the extended range allows (in addition to NTM and sawtooth stabilization) triggering in the Frequency Interrupted Regime (FIR) and opens the possibility of Edge Localized Modes (ELMs) control.…”

“…The cantilevered front steering mirrors (figure 7) consist of the mirror, rotor and stator, the supply lines for cooling and He for angular steering [15]. The mirror rotates around a frictionless flexure pivot driven by He-pressurized bellows and counteracting springs.…”

Diplexers for Power Combination and Switching in High Power ECRH Systems

“…This is too slow to cope with power switching in the frequency range of 1-10 kHz, which is required for MHD-stabilization in AUG, but fast enough for any application, which requires power switching in response to plasma changes on the energy confinement time scale or the current diffusion time scale. For ITER, this method would be adequate to redistribute the power between the Equatorial [14] and Upper [15] ECRH launchers to act on the power deposition profile (on-off axis heating) or the current profile by Electron Cyclotron Current Drive (ECCD). This could also be interesting for applications, where frequency variation by HV-modulation is not possible or not intended, but where the gyrotron should not be turned off during the switching process (e.g.…”

Design and manufacturing of the ITER ECRH upper launcher mirrors

“…The Quasi-optical design here outlined [2] has replaced the traditional waveguide & mitre bends with free space mirrors, and increases flexibility in optics, reduces astigmatism, system complexity, component costs, volume occupied by beams and improves thermal efficiency by:…”