Flashover triggered by charge detrapping at dielectric-vacuum interface

The first part of the work will show that recent progress in the understanding of the flashover mechanism allows: (1) to explain technical observations made during breakdown: time lag, particle emissions, cathode and anode initiated phenomena, mechanical fracture, etc.; (2) to know what material parameters are deterministic of the breakdown strength: static permittivity, trap energy, variation of the internal energy as function of the polarization, energy density required for damaging the sample, etc.; (3) to explain the importance of technologies on the breakdown strength: insulator technology (machining, surface treatments), vacuum device technology (design of the triple junction, soldering, sealing, conditioning, etc.). In the second part, the attention will be focused on the secondary electron emission. The yield depends on the nature of the material (crystal structure, defect distribution) and, in most cases, electron irradiation produces the trapping of both types of charges. Positive charges are trapped in the outermost layers and negative charges are trapped in the deepest layers. Therefore, the yield is dependent on the space charge field. Moreover, secondary electrons can be produced during electron-solid interactions and during dielectric processes. In the third part, the method that has been developed for measuring the permittivity and the detrapping space charge field will be recalled. These two parameters are linked with the secondary electron yield