The first part of the work will show that recent progress in theunderstanding of the flashover mechanism allows: (1) to explaintechnical observations made during breakdown: time lag, particleemissions, cathode and anode initiated phenomena, mechanical fracture,etc.; (2) to know what material parameters are deterministic of thebreakdown strength: static permittivity, trap energy, variation of theinternal energy as function of the polarization, energy density requiredfor damaging the sample, etc.; (3) to explain the importance oftechnologies on the breakdown strength: insulator technology (machining,surface treatments), vacuum device technology (design of the triplejunction, soldering, sealing, conditioning, etc.). In the second part,the attention will be focused on the secondary electron emission. Theyield depends on the nature of the material (crystal structure, defectdistribution) and, in most cases, electron irradiation produces thetrapping of both types of charges. Positive charges are trapped in theoutermost 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 interactionsand during dielectric processes. In the third part, the method that hasbeen developed for measuring the permittivity and the detrapping spacecharge field will be recalled. These two parameters are linked with thesecondary electron yield
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