Electroluminescence caused by electron impact

EL properties were investigated in degassed specimens, air absorbed specimens and SF/sub 6/ absorbed specimens. 1). EL starting voltage in the degassed specimen is lower than that in the SF/sub 6/ or the air absorbed specimens. The scattering of EL starting voltage seems small in the degassed specimen compared with the SF/sub 6/ absorbed specimens. 2). It is considered that SF/sub 6/ or O/sub 2/ in polymer free volume captures electrons by attaching and decreases the number of electrons which contribute to EL. 3). In the air absorbed specimen. EL signal was not detected. The air absorbed specimens directly proceeded to tree initiation due to auto-oxidation without EL process.