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This paper reports on the current development of a new Thompson-Lampard calculable capacitor at LNE. The goal is to determine the von Klitzing constant RK at a significant level of uncertainty of about one part in 108. The comparison with other accurate measurements of h/e2 serves as a relevant test of validity of the theory predicting RK = h/e2, a decisive issue within the context of the new SI. Conversely, assuming that this relation is exact, the measurement of RK and thus that of the fine structure constant α can be used for testing quantum electrodynamics theory. The mechanical structure of the new LNE calculable cross capacitor has been designed and a new set of electrodes has been fabricated. The assembling of the calculable capacitor is in progress. Cet article présente le développement au LNE d'un nouvel étalon calculable de capacité de Thompson-Lampard. L'objectif poursuivi est la détermination de la constante de von Klitzing RK à un niveau d'incertitude significatif de l'ordre de 1 × 10-8 en valeur relative. La comparaison avec d'autres mesures précises de h/e2 permet de tester la pertinence de l'égalité RK = h/e2 prédite par la théorie, question décisive dans le contexte du nouveau SI. Inversement, en supposant cette relation exacte, la mesure de RK et ainsi celle de la constante de structure fine α permet de tester la théorie de l'électrodynamique quantique. La structure mécanique du nouveau condensateur calculable du LNE a été conçue et un nouveau jeu d'électrodes est en cours de finition. L'assemblage de l'étalon calculable a débuté. [ABSTRACT FROM AUTHOR]

Presents a study on the prebreakdown and breakdown phenomena under ac voltage in mineral oil of very large oil gaps. Measurement of breakdown voltages with the recording of streamers in rod-plane and sphere-plane electrode systems; Discovery of a breakdown mode specific to ac voltage; Responsibility of positive streamers for breakdown in large gaps.

A set of ultra-low value capacitance standards together with a programmable coaxial multiplexer (mux) have been developed. The mux allows the connection of these capacitances in parallel configuration and they together form the programmable capacitance standard. It is capable of producing decadic standard capacitances from 10 aF to at least 0.1 pF, which are later used to calibrate commercial precision capacitance bridges. This paper describes the realization and the characterization of this standard together with results obtained during the calibration of Andeen-Hagerling AH2700A bridges with a maximum uncertainty of 0.8 aF for all the capacitances generated ranging from 10 aF to 0.1 pF, at 1 kHz. These latter could be then integrated to functionalized AFMs or probe stations for quantitative capacitance measurements. Sources of uncertainties of the programmable capacitance standard, such as parasitic effects due to stray impedances, are evaluated and a method to overcome these hindrances is also discussed. [ABSTRACT FROM AUTHOR]

Abstract: Magnetic-field sensors based on the Faraday effect in a Tb3Ga5O12 crystal are investigated in terms of sensitivity, accuracy and directionality. The possibility of an increased sensitivity due to the application of multipass sensitive elements is considered. Signal-to-noise measurements on a 5mm diameter×20mm long sample yield to a magnetic fields equivalent noise of 300nT/Hz1/2 (τ =1s). The sensor has a sensitivity of 5.457(1)rad/T. Using a spinning quarter waveplate ellipsometer, we can measure magnetic fields up to 1T. The data acquisition rate could be up to 80Hz. This sensor is used to check the homogeneity and the orientation of the field provided by the French watt balance magnetic circuit whose aim is to redefine the SI unit of mass in the near future. [Copyright &y& Elsevier]

This paper describes a new method to damp out balance pan oscillations, even, when the balance is operated in a vacuum. The key is to tune the wavelength of the damping liquid by adjusting the depth. The liquid is sealed in a vacuum-compatible container attached above the pan, and the time that the wave travels from one side of the container to the other can be adjusted for maximum damping at the natural pendulum frequencies of the pan. We are investigating the practical application of this damping approach in our respective watt-balance experiments. It is shown that the channels in the shape of rings filled with liquids to the optimum depth work well. [ABSTRACT FROM AUTHOR]