NON DESTRUCTIVE DIELECTRIC CHARACTERIZATION OF THIN FERROELECTRIC FILMS MATERIALS USING COPLANAR LINE STRUCTURE

ABSTRACT

This paper presents a nouvelle and non-destructive Broadband characterization method which uses a coplanar line for the measurement of the complex permittivity of linear dielectric materials and precisely, that of ferroelectric thin films. The method uses the transmission coefficient and the quasi-TEM analysis to find the effective permittivity of the multilayer system, and then the coplanar conformal mapping technique is employed to extract the relative permittivity of the thin layer. Comparing our results to those of cavity resonator method at 12 GHz shows a good agreement. The measurement is done in the microwave frequency band (45 MHz–20 GHz).     

Estimation of the Lyman-α signal of the EFILE diagnostic under static or radiofrequency electric field in vacuum

The electric field induced Lyman-α emission diagnostic aims to provide a non intrusive and precise measurement of the electric field in plasma, using a beam of hydrogen atoms prepared in the metastable 2 s state. The metastable particles are obtained by means of a proton beam extracted from a hydrogen plasma source, and neutralised by interaction with vaporised caesium.When a 2 s atom enters a region where an electric field is present, it undergoes a transition to the2 p state(Stark mixing). It then quickly decays to the ground level, emitting Lyman-α radiation,which is collected by a photomultiplier. The 2 s→2 p transition rate is proportional to the square of the magnitude of the electric field, and depends on the field oscillation frequency(with peaks around 1 GHz). By measuring the intensity of the Lyman-α radiation emitted by the beam it is possible to determine the magnitude of the field in a defined region. In this work, an analysis of the behaviour of the diagnostic under static or radiofrequency electric field is presented. Electric field simulations obtained with a finite element solver of Maxwell equations, combined with theoretical calculations of the Stark mixing transition rate, are used to develop a model for the interpretation of photomultiplier data. This method shows good agreement with experimental results for the static field case, and allows to measure the field magnitude for the oscillating case.     

Advanced digital image analysis method dedicated to the characterization of the morphology of filamentous fungus

Filamentous fungi have a complex morphology that induces fermentation process development issues, as a consequence of viscosity increase and diffusion limitations. In order to better understand the relationship between viscosity changes and fungus morphology during fermentations of Trichoderma reesei, an accurate image analysis method has been developed to provide quantitative and representative data for morphological analysis. This method consisted of a new algorithm called FACE that allowed sharp images to be created at all positions, segmentation of fungus, and morphological analysis using skeleton and topological approaches. It was applied and validated by characterizing samples of an industrial strain of Trichoderma reesei that had or had not been exposed to an extreme shear stress. This method allowed many morphological characteristics to be identified, among which nine relevant criteria were extracted, regarding the impact of shear stress on the fungus and on the viscosity of the fermentation medium.