Fast Ion Generation and Confinement during Reconnection Events in the MST Reversed Field Pinch

Measurements of neutron flux from deuterium plasmas in the MST reversed field pinch used in conjunction with ion temperature measurements indicate the presence of a fast ion population generated at magnetic reconnection events. During a typical event, T$_{i}$ on-axis approximately doubles, from $\sim $ 0.5 keV to $\sim $ 1 keV, in less than 200 $\mu $s. These events often produce neutron fluxes up to ten times higher than from thermal fusion alone. This flux is consistent with, for example, a small (1{\%}), non-thermal population at $\sim $ 15 keV. After an event, the neutron flux decays with a time constant of 1 - 3 ms. However, if an event is followed by a period of reduced magnetic fluctuations (achieved either actively, by inductively driving a parallel current in the edge, or spontaneously), the neutron flux decays at a much slower rate, $\sim $ 20 ms, which indicates improved fast ion confinement.