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International audience; In DEMO and future nuclear fusion reactors to produce economically competitive electricity, neutral beam (NB) systems will be required, delivering up to 150 MW of high neutral particle energy (1 MeV) with high wall-plug efficiency (η > 60%). In the Siphore NB concept [1], one of the promising candidates to meet these challenging requirements, negative ions will be extracted from a long, thin ion source 3 m high and 15 cm wide, accelerated and subsequently photo-neutralized. This requires the development of a new generation of negative ion sources. At the Swiss Plasma Center (SPC), a novel helicon plasma source, based on a resonant network antenna, is currently under study. The source delivers up to 10 kW at 13.56 MHz, and is installed on a linear (1.8 m long, 0.4 m diameter) vacuum vessel, allowing for full plasma characterization. In this work, the principles of operation of resonant antennas as helicon sources will be introduced, and absolute spectroscopic, Langmuir probe and interferometry measurements will be presented to characterize the performance of the source in terms of hydrogen/deuterium dissociation and negative ion production as a function of the input power at low gas pressure (0.3 Pa) and moderate magnetic field (~100 Gauss), as required by Siphore.This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014-2018 under grant agreement No 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission.

International audience; A new generation of Neutral Beam systems will be required in future fusion reactors, suchas DEMO, able to deliver high power (up to 150 MW) with high neutral energy (>1 MeV).Negative ion beams can attain this performance, resulting in a strong research focus on negativeion production from either surface or volumetric plasma sources.A novel helicon plasma source, employing on a resonant birdcage network antenna, is currentlyunder study at the Swiss Plasma Center (SPC), before installation on the Cybele negativeion source [1] at CEA-IRFM. The source delivers up to 10 kW at 13.56 MHz, and was installedon a linear (1.8 m length) Resonant Antenna Ion Device (RAID). Passive spectroscopic measurementsof the Ha, Hb and Hg Balmer lines and of all the diagonal Fulcher-a bands were performedwith a sensitive f/2 spectrometer. Multiple viewing lines setup and an absolute intensitycalibration were used to determine the plasma radiance profile, with a space resolution < 3 mm.A minimum Fisher regularisation algorithm is then applied to calculate the absolute emissivityprofile for each emission line, in cylindrical symmetry as experimentally observed. An errorestimate of the Abel-inverted profiles was performed using a Monte Carlo approach. Finally, anRF-compensated Langmuir probe measured the electron temperature and density profiles. Themeasured absolute line emissivities, electron density and temperature are interpreted using thecollisional-radiative code YACORA [2] which estimates the dissociation degree and the distributionof the different atomic and molecular species, including the density of negative ions. Inthis paper, the results of a power scan up to 5 kW in conditions satisfying DEMO requirements,i.e. p 0:3 Pa and B 150 G, are shown.

One challenge for microcrystalline silicon (mu c-Si:H) deposition is to achieve high deposition rates while maintaining high quality films. In this work, an inductively-coupled plasma (ICP) is used to deposit mu c-Si:H on glass substrates by means of a novel planar resonant antenna at 13.56 MHz. No particle formation occurs in the low pressure (5 Pa) plasma, but the films suffer post-oxidation. By embedding a 5 MHz RF-biased substrate, films deposited simultaneously with and without RF bias are compared. It is shown that large area, low pressure (5 Pa), particle-free ICP deposition at 1 nm/s of mu c-Si:H films can be obtained without post-oxidation by means of a planar resonant antenna, provided that RF substrate bias is included for independent control of the ion energy. (C) 2017 Elsevier Ltd. All rights reserved.

Helicon plasma sources operating with hydrogen or deuterium might be attractive for fusion applications due to their higher power efficiency compared to inductive radiofrequency plasma sources. In recent years, the resonant antenna ion device (RAID) has been investigating the physics of helicon plasmas and the possibility of employing them to produce negative ions for heating neutral beam injectors (HNBs). Herein, we present a fluid Monte Carlo (MC) model that describes plasma species transport in a typical helicon hydrogen plasma discharge. This work is motivated by an interest in better understanding the basic physics of helicon plasma devices operating in hydrogen and, in particular, the volume production of negative ions. This model is based on the synergy between two separate self-consistent approaches: a plasma fluid model that calculates ion transport and an MC model that determines the neutral and rovibrational density profiles of H-2. By introducing the electron density and the temperature profiles measured by Langmuir probes as model constraints, the densities of ion species (H+, H-2(+), H-3(+), H-) are computed in a 1.5D (dimensional) geometry. The estimate of the negative ion density profile represents a useful benchmark that is comparable with dedicated diagnostics, such as cavity ring-down spectroscopy and Langmuir probe laser photodetachment. Neutral gas particles (atoms and molecules) are calculated assuming a fixed plasma background. This gas-plasma decoupling is necessary due to the different timescales of plasma (microseconds) and gas kinetics (milliseconds).