Modeling of Space Charge Measurement for Dielectrics with Tip-to-flat Electrode Configuration

Space charge measurement under local electric field concentration is also important because more serious space charge accumulation usually occurs. In this paper, a space charge measurement setup is proposed with tip-to-flat electrode configuration based on the pulsed electroacoustic method. The generation mechanism of the acoustic wave is firstly analyzed, based on which a simulation model is established to study the characteristics of acoustic wave generation and propagation. Compared with the conventional PEA, acoustic waves generating from bulk space charge and the surface charge at the interface of upper electrode and sample are not equal to the convolution of excitation pulse and space charge distribution. Negative overshoot appears in the acoustic wave due to the shape of upper electrode and uneven distribution of the electric field inside the sample. As a result, deconvolution and calibration methods in conventional PEA are not applicable anymore in this situation.