Neutral beam heating on the TCV tokamak

Abstract

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 1MW 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 2.0–2.5keV and toroidal rotation velocities up to 160km/s were promptly attained in the first few L-mode discharges with NB injection. Ion temperatures up to 3.5keV were subsequently achieved in ELMy H-mode. The injector produces a focused deuterium neutral beam with 25keV energy, 1MW neutral power and 2s duration.