Generation of hydrogen ionic plasma superimposed with positive ion beam

In this study, a hydrogen ionic plasma with relatively low residual fractional electron concentration (ne/n+ ∼ 10−2) is generated using an aluminum plasma grid for the production of negative hydrogen ions and a control grid for negative ion extraction and electron removal. The ionic plasma is composed of negative and positive ions, containing molecular ions. Negative ions are in part produced using positive ions with several electron volts. A positive ion beam with 50 eV or more contributes to increase the density of the ionic plasma. The positive ion beam energy and the control grid bias voltage are tuned in such a way that a high-density ionic plasma is maintained.