Space charge in PET investigated by joint use of the new system of characterization. Another application of the Thermal Step Method.

TSM (Thermal Step Method) is a nondestructive technique to space charge distribution in thin and thick dielectrics. This space charge is responsible for residual electric field which distorts the applied one and consequently decrease the dielectric rigidity of the dielectric materials. The majority of the methods of study are based on a variation of the loads images being on the two electrodes, of share and others of dielectric. This reversible modification can be obtained by an inhomogeneous disturbance which spread in the sample. We have developed a new measurement technique from a variable thermal excitation. For the determination of the charge distribution we did not use a model of temperature but solved the equation of heat. Finally our treatment mathematical is based on techniques of optimization which Valley makes it possible in the case fine thickness to reduce the error of to the treatment. After a brief description of this new system, we will show results obtained on polyethylene terephthalate films of 23 mum. This principle can allow of another type of characterization. It is used on samples of SiO2.