Stories from China

The vacuum breakdown issue severely hinders the performance of vacuum electrical devices, such as vacuum interrupters, X-ray sources, fusion reactors, and particle accelerators [1]–[3]. In general, vacuum breakdown is initiated by thermal instability at the cathode or anode due to the electron emission current, which heats the protrusion itself or transfers kinetic energy to the anode. Then, the initial vapor and ion population could be produced by the atom evaporation due to extreme heating, induced by the field electron emission current. Due to the evaporated atoms, the gap pressure increases and the mean free path of electrons may become less than the gap distance, where avalanche ionization will occur and cause the plasma discharge. Thus, the dynamics of electron emission and the electrode's properties will determine the dielectric strength and insulation performance of the gap.