High density negative hydrogen ion production in a high power pulsed helicon discharge

Temporospatially resolved measurements of negative hydrogen ion density and related parameters are observed in a 40 ms pulsed high power helicon plasma source with a magnetic mirror configuration. Exceptionally high negative ion densities of 1.2(-0.4)(-0.2) x 10(18) m(-3) are observed on the far side of the magnetic mirror during the early stages of the pulse. It is proposed that the temporal evolution of the negative ion density into the steady-state is primarily associated with neutral dynamics and depletion. This interpretation is further supported by a 2D-axisymmetric model.