LIPP and PEA space-charge measurements on LDPE

Several methods of measuring directly the spatial distribution of space-charge in an insulator have been developed during the last decade, e.g. laser induced pressure pulse (LIPP), piezo-electrically induced pressure step (PIPS), pulsed electroacoustic (PEA), thermal pulse (TP), thermal pulse step (TSP) and laser induced modulation (LIMM). While most ofthe samples investigated have been 25-100 μm thick, the PEA and LIPP methods have yielded credible data for coaxial cable samples with insulation 3 mm and 11 mm thick respectively. PIPS and LIPP data for 100 μm thick PVDF samples, and LIPP and LIMM data for 50-85 μm thick multi-layer PVDF films, were found to be similar. In this paper we compare PEA and LIPP space-charge data for planar low density polyethylene (LDPE) samples, approximately 1 mm thick, with organic semiconductor electrodes