Low density polyethylene 500 mu m thick samples have been submitted to a 15
MV m(-1) rms ac 50 Hz field. No charge accumulation in the samples has bee
n observed after a few hours of polarization. This has been attributed to t
he recombination of the majority of electrons and holes alternately injecte
d each half cycle. To confirm this assumption, a space charge has been inje
cted in the sample by using a de electrical stress. Coupled measurements of
space charge and electroluminescence have been made under a single and a d
ouble alternation ac 50 Hz field. Results have shown that the decrease of t
he installed charge at the interfaces is partially due to the recombination
with injected carriers.