In the present study, a single electrode micro-plasma jet working in helium flow was investigated. The aim of our study was to clarify the influence of the tube diameter on the discharge ignition and sustaining voltage, as well as on nitrogen rotational temperature, helium excitation temperature and electron density. The diameter of the micro-tubes was varied in the range of 80–500 µm. A sinusoidal voltage with a frequency of 6 kHz was applied to ignite and sustain the plasma jet. Both the ignition and sustaining voltage monotonically increased with the decreasing diameter of the tube. The gas temperature of the plasma in the capillary tube estimated by the rotational temperature of the N2 second positive system remained below 500 K and depended weakly on tube diameter, while the excitation temperature of He and electron density, n e, increased as the tube diameter decreased.

The provision of a particle and power exhaust solution which is compatible with first-wall components and edge-plasma conditions is a key area of present-day fusion research and mandatory for a successful operation of ITER and DEMO. The work package plasma-facing components (WP PFC) within the European fusion programme complements with laboratory experiments, i.e. in linear plasma devices, electron and ion beam loading facilities, the studies performed in toroidally confined magnetic devices, such as JET, ASDEX Upgrade, WEST etc. The connection of both groups is done via common physics and engineering studies, including the qualification and specification of plasma-facing components, and by modelling codes that simulate edge-plasma conditions and the plasma-material interaction as well as the study of fundamental processes. WP PFC addresses these critical points in order to ensure reliable and efficient use of conventional, solid PFCs in ITER (Be and W) and DEMO (W and steel)

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