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.
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The TCV tokamak contributes to physics understanding in fusion reactor research by harnessing a wide experimental tool set: in particular flexible shaping and high power electron cyclotron heating. Plasma regimes with high plasma pressure, a wider range of temperature ratios and significant fast-ion population are now attainable with a TCV heating system upgrade. In a first stage, a 1 MW neutral beam was installed (2015) and is reported in this paper. The installation of the NB injector required modifications of the vacuum vessel and considerable work on the machine infrastructure, resulting in a shutdown from late 2013 to mid-2015. TCV is now operating partly as a European Medium-Size Tokamak (MST) facility under the auspices of the EUROfusion consortium. The NBI was intensively operated in the February-July 2016 phase of the MST campaign. Record ion temperatures of 2.0-2.5 keV and toroidal rotation velocities up to 160 km/s were promptly attained in the first few L-mode discharges with NB injection. Ion temperatures up to 3.5 keV were subsequently achieved in ELMy H-mode. The injector produces a focused deuterium neutral beam with 25 keV energy, 1 MW neutral power and 2 s duration. Highlights: • Installation of 1 MW, 25 keV neutral beam, direct ion heating, access to Ti/Te ≥ 1. • Specific low divergence neutral beam injector with tunable power and energy. • Ion temperature of 2.0 keV, toroidal rotation of 160 km/s attained with NB heating.
The ITER Heating and Current Drive Upper Launcher (H&CD EC UL) uses a pneumomechanical steering-mirror assembly (SMA) to steer the RF beams for their deposition in the appropriate location in the plasma to control magnetohydrodynamic activity (neoclassical tearing modes (NTMs) and sawtooth oscillations). For NTM stabilization, the mirror rotation needs to be controlled to an accuracy that is better than 0.1 • . A 10 • · s −1 mirror steering speed is also required. To assess the performance of the two SMA prototypes that have been manufactured, a test stand that reproduces the expected pneumatic configuration of the UL has been built. So far, only the first SMA prototype has been tested, and tests on the second prototype are foreseen in the 2009-2010 period. The steering angle of the mirror will be deduced from the pressure applied to the mechanism since there is no in situ angle measurement at present. An "off-the-shelf" commercial servo valve with a proportional-integral-derivative controller has been used to control the pressure with good results for the switching cycle. These tests show that a more advanced controller will be required to attain the desired accuracy and speed for the modulation cycles.Index Terms-Millimeter-wave antennas, pressure control.
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