Characterization of Two–Radio-Frequency–Driven Dual Antenna Negative Hydrogen Ion Sources

The characteristics of a two–radio-frequency (RF)–driven dual antenna inductively coupled hydrogen plasma is investigated for the development of a high efficient RF negative hydrogen ion source driver. The two-RF-driven dual antenna system consists of a 2 MHz–driven solenoidal antenna wound around a cylindrical chamber and a 13.56 MHz–driven planar antenna placed on top of it. Compared to the conventional single frequency antenna inductively coupled plasmas, the two-RF-driven dual antenna inductively coupled plasma reveals two distinctive features, i.e., an increase in the power transfer efficiency and the bi-Maxwellization of the electron energy distribution function due to the collisionless heating. These characteristics allow the two-RF-driven dual antenna inductively coupled plasma to accomplish enhanced generation of negative ions and their precursors with a high RF efficiency.