Treeing-like Breakdown in Electronic Beam Irradiated LDPE with/without Nano-Powder Doping

The treeing-like breakdown in low density polyethylene (LDPE) samples can be induced by electron beam irradiation without applied field. Pure LDPE samples and LDPE samples doped with inorganic nano-powder (0.5%wt) are used in our experiments. A steel needle electrode is inserted into each sample for about 3mm depth before irradiation. Samples are cut into slices whose surfaces are perpendicular to the inserting direction and perpendicular to the irradiation direction and in parallel with these two directions. The breakdown traces are observed by microscope for slices. The observations show that the configuration of breakdown is very like electric treeing. Characters of treeing-like breakdown in pure LDPE samples and doped LDPE samples are compared, and mechanism of the induction is also discussed in this paper