The ratios of intensities of the spectral bands of molecular nitrogen corresponding to transitions N + 2 (B 2 + g , v = 0) → N + 2 (X 2 + g , v = 0), N 2 (C 3 u , v = 0) → N 2 (B 3 g , v = 0) and N 2 (C 3 u , v = 2) → N 2 (B 3 g , v = 5) as a function of the applied electric field strength were measured for air in the pressure range of 300 to 10 5 Pa. The non-self-sustaining dc discharge in a parallel-plane gap was used for excitation of gas molecules. The reduced field strength was varied in the range of (150-5000) × 10 −21 V m 2. The measured ratio of intensities as a function of electric field strength is compared with the theoretical estimates made by other authors. The obtained intensity ratio versus field strength curves can be used for field strength estimation in plasmas if the nitrogen molecules are excited dominantly from the ground state directly by the electron impact.

Analysis and understanding of wall erosion, material transport and fuel retention are among the most important tasks for ITER and future devices, since these questions determine largely the lifetime and availability of the fusion reactor. These data are also of extreme value to improve the understanding and validate the models of the in vessel build-up of the T inventory in ITER and future D-T devices. So far, research in these areas is largely supported by post-mortem analysis of wall tiles. However, access to samples will be very much restricted in the next-generation devices (such as ITER, JT-60SA, W7-X, etc) with actively cooled plasma-facing components (PFC) and increasing duty cycle.This has motivated the development of methods to measure the deposition of material and retention of plasma fuel on the walls of fusion devices in situ, without removal of PFC samples. For this purpose, laser-based methods are the most promising candidates. Their feasibility has been assessed in a cooperative undertaking in various European associations under EFDA coordination. Different laser techniques have been explored both under laboratory and tokamak conditions with the emphasis to develop a conceptual design for a laser-based wall diagnostic which is integrated into an ITER port plug, aiming to characterize in situ relevant parts of the inner wall, the upper region of the inner divertor, part of the dome and the upper X-point region.

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.

This paper presents an experimental investigation of the effect of the electric field strength on the collisional quenching rate of nitrogen states N 2 (C 3 Π u , v = 0) and N 2 + (B 2 Σ + g , v = 0) by nitrogen and oxygen molecules. In experiments, the pulses of non-self-sustained electrical discharge excite gas molecules. The range of reduced electric field strength is from 240 to 4000 Td at pressure range from 70 to 4300 Pa. The experiments show that the field strength has no effect on the quenching rate. The paper discusses the probable reasons for discrepancy of results obtained by different authors and proposes the preferable values for rate coefficients. These coefficients can be used for electric field determination in low temperature gas discharge plasmas via nitrogen emission spectrum, and are of interest to atmospheric air fluorescence investigations.

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)