Plasma state transition originating from local production of massive negative ions

A dynamic evolution of plasma structures and its associated state transition due to local production of massive negative ions are investigated by the particle-in-cell simulation which is based on an experimental configuration of an open plasma system (Q machine). Two different states, a stationary state and a dynamic state, are achieved depending on the production rate of massive negative ions. The plasma is stationary for a low production rate, while solitary pulses and fluctuations are spontaneously excited and the plasma state is unstable for a high production rate. Phenomena of a two-stream instability and a double layer formation induced by the local production are closely concerned with the excitation of the solitary pulse. The solitary pulses play a role in the rapid ejection of massive negative ions from the system. A staying time distribution of charged particles is analogically introduced for the special convenience of explanation, which corresponds with a so-called population pyramid. The staying time distribution can clearly express the feature of the state since all the phenomena occurring in the system directly reflect the distribution.