Analysis of pressure-wave methods for the nondestructive determination of spatial charge or field distributions in dielectrics

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Abstract
A pressure wave propagating through a charged dielectric produces an electric signal at the sample electrodes. This signal reveals information on the spatial charge or field distribution in the sample. In the present study, the mathematical relations between the signal response and the desired distribution are derived from first principles. For the derivation, the pressure dependence of the relative permittivity must be known; therefore this dependence was calculated for nonpolar as well as for polar dielectrics with the use of the Clausius-Mossotti equation. The resulting response equations are applicable to pressure-pulse, pressure-step, and arbitrary pressure-profile experiments on one- and two-sided metallized samples in open-circuit and in short-circuit configuration. The common features and the differences between the present analysis and existing theoretical descriptions are discussed in detail.