Micrometer-scale discharge in high-pressure H₂O and Xe environments including supercritical fluid

We generated micrometer-scale discharge in high-pressure H2 O and Xe up to supercritical conditions. In our previous paper, we reported the existence of two peculiar features in the breakdown voltages under high-pressure C O2. The first one was the downward shift at the right-hand side of Paschen's curve above about 2.5 MPa, and the second one was the drastic decrease in the breakdown voltages near the critical point. We have experimentally confirmed that these features are also observed in H2 O and Xe, even though there are some differences among these materials. Our theoretical fitting involving a density fluctuation term FD agrees well with the experimental results, especially for Xe. We suppose that these unique features are brought about by decreases in the electron-to-particle cross section , ionization potential i, and secondary electron coefficient γ′ and changes in the discharge space.