Plasma build-up in stellarators by neutral beams alone

Plasma generation has been achieved in the stellarator W7-AS using neutral beam injection only. Plasma evolution is analysed using a zero-dimensional model. The model gives guidelines for this method to be successful. Both a low neutral gas starting pressure and a small fraction of wall recycling are necessary to get 'ignition' by beams. The predictions of the model are compared to experiments on W7-AS and LHD.