Atmospheric-pressure gas breakdown from 2 to 100 MHz

We report a detailed study of breakdown voltage of atmospheric-pressure helium gas between two parallel-plate electrodes from 2 to 100 MHz. Experimental data show that the breakdown voltage reduces initially with increasing frequency due to a diminishing contribution of drift-dominated electron wall loss and then begins to increase with increasing frequency. The latter is contrary to the current understanding that relies largely on the electron wall loss mechanism. Particle-in-cell simulation suggests that rapid oscillation of the applied voltage prevents electrons from reaching their maximum achievable kinetic energy, thus compromising the ionization efficiency and increasing the breakdown voltage.