Mechanism of droplet ejection from liquid gallium interacting with inductively coupled hydrogen plasma

Abstract

In this study, we observed droplet ejection from liquid gallium interacting with an inductively coupled hydrogen plasma. We observed the formation of a bubble in the liquid gallium, and the droplet ejection was synchronized with the burst of the bubble. We examined droplet ejection frequency by varying the ion flux [(0.2 – 7.1) × 1014 cm-2s-1], the ion energy (15 – 215 eV), and the liquid gallium temperature (370 K – 500 K). As a result, we found that the droplet ejection frequency increased with the ion flux and the liquid gallium temperature, whereas it decreased with the ion energy. We observed that the inside of the bubble in the liquid gallium was occupied by hydrogen. Furthermore, the amount of hydrogen dissolved in the liquid gallium was dependent on the discharge conditions. On the basis of the experimental results, we have proposed a mechanism for bubble formation and droplet ejection. The key in the mechanism is the supersaturated dissolution of hydrogen due to the ion irradiation.