Mid Term Review
Negative hydrogen ion production in the MAGPIE helicon device
Negative ions have numerous of applications in fields such as thruster technology, material processing, and neutral beam injection (NBI) systems. Negative hydrogen ions are of particular interest for high energy (> 1 MeV) NBI systems, such as those used for the heating of large scale magnetically confined fusion devices, such as the ITER experimental reactor. While positive ions are typically used in NBI systems, at such high energies the neutralisation of positive ions becomes extremely inefficient, whereas the neutralisation of negative ions remains efficient. It is therefore necessary to develop high throughput negative ion sources capable of meeting the requirements of these NBI systems. Currently, this is achieved using caesiated ICP sources which require very large power supplies.
In this project I investigate the viability of using helicon coupled devices as negative ion sources through the characterisation of negative ion production in the MAGPIE helicon device, both through experimental measurement and theoretical modelling. Experimentally this is achieved through the probe-based laser photodetachment technique and theoretically through a 2D-axisymmetric extension of an existing global model of an electronegative hydrogen discharge.