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The pulsed electro-acoustic (PEA) method is used for thirty years for measuring space charge distribution in dielectric materials [1]. However, this method was limited to at least 150 μm thick films characterization. For some applications, in spatial industry for example, 50 μm thick outer space dielectric materials must be analyzed. A high resolution optimized measurement system is discussed in this paper in order to expand performances and ranges of this method. To design it, a new pulse generator has been conceived and an optimized acoustic detector, key of the PEA method, has been realized and validated. The optimized High-Resolution PEA apparatus allows to obtain calibration signal with 50 μm thick dielectric materials that can be used to obtain the characteristic transfer function of the PEA system, essential step to use the data processing to find space charge distribution to characterize thinner dielectric materials. [ABSTRACT FROM AUTHOR]

Techniques derived from the near-field microscopies and particularly the Atomic Force Microscopy (AFM) are presented as alternative techniques for space charge measurement compared to classical techniques due to their high sensitivity to the electrostatic force and an improved spatial resolution (few nanometers). One of the AFM derivative methods, which allow obtaining information on the charge state of the dielectric materials, is based on the measurement of Force Distance Curves (FDC) obtained by cycling approach and retraction of the AFM probe to the dielectric surface. In this paper, three-Dimensional (3D) simulation results for the electrostatic force between an AFM tip and the surface of a dielectric are presented for different AFM tip geometries. The first aim is to analyse the effect of tip shape on electrostatic contribution to force-distance curves. The second step consists in extracting cantilever contribution to electrostatic force. Finally, a model merging cantilever and tip shape contributions is developed. Simulation results are shown and compared with experimental data in order to validate our approach. [ABSTRACT FROM AUTHOR]

Dielectric materials are frequently used in satellite structures as thermal blankets. Various aspects of the space environment can cause orbit satellite anomalies. One of these aspects is charge accumulation due to the flux of space charged particles. To get a better control of the discharge, it is necessary to clarify the nature and the time evolution of position and quantity of stored charges space and to understand the dynamics of the charge transport in solid dielectrics used in space. As dielectrics materials for space application are thin, less than 100 ?m, the current pulsed electroacoustic (PEA) method used to recover charges within this kind of material is no longer sufficiently precise, i.e. spatial resolution is on the order of ten ?m. This study aims at improving the spatial resolution of PEA technique in order to reach a resolution of about 1 ?m. To understand physical mechanisms linked to the improvement of space resolution, an electrical model of this technique has been developed using the PSpice software. The acoustic detector is specifically studied in this paper. We highlight the fact that piezoelectric losses and impedance matching between the different materials of PEA cell have a significant influence on the quality of the output voltage of this method. Moreover, an optimization algorithm is presented in order to estimate an optimized set of parameters capable of predicting the output voltage of a PEA cell. [ABSTRACT FROM AUTHOR]

Modeling charge transport and linking charge dynamics with dissipative processes responsible for electrical ageing are a challenging objective for developing a mature approach in insulation design. Such an approach is exemplified here for polyethylene-based materials by introducing two models describing bipolar Space Charge Limited Current in transient and steady states. They rely on two classical descriptions of the distribution function of the energy levels of trap states –single trapping level or exponential distribution. Their predictions are discussed as regards the experimental behavior. They notably highlight the importance of recombination processes in explaining the sigmoidal shape of the steady-state current-voltage characteristic. Also, bipolar charge transport seems to be a necessary factor for the observed features of oscillatory charge packets. The energetic features of charge dynamics is reviewed with particular emphasis on recombination phenomena because the latter promote electronically excited states that are chemically reactive and could be involved in ageing reaction. The relationship between charge recombination and electroluminescence is highlighted through experiments and simulation. The spectral analysis of the emitted light advocates the existence of massive chemical/physical degradation in the electrical regime where recombination is a major factor of the Space Charge Limited Current (SCLC). [ABSTRACT FROM PUBLISHER]