Negative Hydrogen Ion Production in a Helicon Powered Magnetized Plasma Column*

A new generation of neutral beam systems will be required in future fusion reactors, such as DEMO, able to deliver high power (up to 50 MW) with high neutral energy (\textgreater 1 MeV). Negative ions have a higher neutralization fraction (compared to positive ions) in a gas cell at energies greater than 50 keV. They are generated mostly on cesiated metal surfaces inside a magnetized high brightness plasma source but cesium consumption must be limited to a minimum in a fusion power plant to reduce the maintenance of the source. There is hence a strong research focus to optimize the production of negative ions via dissociative attachment of the gas molecule inside the source volume. To achieve this, one must generate a plasma with a hot (\textasciitilde 10 eV) and cold (\textasciitilde 1 eV) electron temperature regions and confine the electrons magnetically. In this work, we will analyse the properties of a hydrogen plasma produced in a thin (20 cm radius and 1.8 m length) magnetized (\textasciitilde 150G) plasma column powered by a helicon discharge [I. Furno et al., EPJ Web of Conferences \textbf{157}, 03014 (2017)]. The numerical simulations are performed with a 2.5D Particle-in-Cell algorithm with Monte-Carlo Collisions (PIC-MCC) [G. Fubiani et al., New J. Phys. \textbf{19}, 015002 (2017)]. The model will be compared to experiments.