2014 In a helium glow discharge, the A. C. Stark shift of the 4 3S1 ~ 2 3P0,1,2 transition (03BB ~ 4 713 Å) induced by nonresonant interaction of the 4 3S and 4 3P levels with a multimode CO2 laser field is measured as a function of laser intensity in the range IL 35 MW/cm2. Departure from the linear intensity dependence given by second order perturbation theory is observed for IL > 2 MW/cm2. A three-level atom model taking into account the interaction with the laser field in a non perturbative way agrees with the experiment. Strong broadening is also detected for IL > 1 MW/cm2. This broadening grows with IL until a quasi-continuum spreading over 50 Å is observed for IL = 33 MW/cm2. This broadening results from amplitude and phase fluctuations of the laser field modes during interaction. For IL = 33 MW/cm2 the recorded 4 713 Å spectral line shape reflects the statistical distribution of the mode amplitudes. J. Physique 43 (1982) 875-881 1 JUIN 1982, ]

This paper is devoted to a detailed presentation of all aspects involved in a demonstration of a novel pulsed electric field (PEF) technique that does not generate neither conduction currents nor Joule effects. Details are given of both the experimental arrangement and the electro-optic Kerr-effect-based diagnostic used in the measurement of the intense PEFs in water. The results show unequivocally that the novel technique is effective in significantly reducing the initial concentration of Escherichia coli bacteria. Finally, a brief comment on the way ahead is provided.

A number of high-power applications require a transportable high-energy, high-current GW generator to drive a pulsed power system at the output. A first prototype, based on exploding wire technology and using an H-bridge circuit configuration, was developed at Loughborough University a few years ago and has been previously reported. The present stage of the work has necessitated the development of a more powerful and energetic source, and this is now based on inductive storage technology. A 400 kJ capacitor bank is connected by a high-Coulomb explosively driven closing switch with an air-cored 0.6 MV transformer, an exploding wire array, and a high-power diode based on a polarity-dependent spark-gap completing the arrangement. The GW generator, including the command and control module, is accommodated in two ISO containers. The various components of the generator are described in this paper, together with results obtained from full-scale tests.

The curing process of a cycloaliphatic epoxy resin was defined using different experimental techniques to obtain a material with optimal mechanical and electrical behaviour and with the ultimate objective of its application in the production of polymer-based insulator for railway transportation. The temperature domain characteristic of the crosslinking was determined by differential scanning calorimetry. However, thermogravimetric analyses of the reactive species supported that a low curing temperature had to be chosen during the initial crosslinking stage. Then, kinetic viscoelastic experiments were performed to identify the time and temperature conditions necessary to observe the gelation and vitrification of the reactive mixture. To fulfil higher requirements of productivity and performances, a two-step thermal cycle was defined and optimized by investigating the influence of different curing schedules on the glass transition temperature of the crosslinked material. The effects of the curing profile on the dielectric strength of the material were also investigated. Good correlations between the different techniques were observed and explained in terms of structure–property relationships.

The lightning station has been installed at the top of the Pic du Midi to observe and record the lightning attachment to an instrumented rod. Direct measurements of the lightning current and atmospheric electric field are recorded. Various video cameras are used to analyse the flash impacts to the rod and also to various parts of its surroundings. Our goal is to instrument mainly one Observatory building protected by means of a rod to record lightning impacts and, if any, notice some possible LPS by-passes, a direct evaluation of the protected zone. New results obtained during summer 2013 lightning season will be presented.

Two essential requirements arise before any proposed and novel non-invasive pulsed electric field (PEF) food processing technique can be implemented in industrially meaningful systems. These are the reliable measurement of the intense fast transient electric fields generated in water close to metallic electrodes and a convincing proof-of-principle demonstration of the non-invasive technique. Recently, both of these milestones have been very successfully achieved in a joint research programme in progress at Loughborough University (UK) and Université de Pau (France). The paper reports on results from preliminary experiments with a non-invasive proof-of-principle treatment chamber, showing the paramount importance of electro-optic measurements. In addition, very successful proof-of-principle non-invasive processing experiments are discussed, in which only extremely small displacement currents flow inside water samples. The electric field in the samples was monitored using the Kerr effect and a 6 log reduction was obtained in the Escherichia coli initially present. The possible future of the novel technology is briefly commented on.

The paper describes a simple and compact 0.5 MV high-voltage capacitive probe developed in common by Université de Pau (France) and Loughborough University (UK). Design details are provided, together with a simple and straightforward methodology developed to assess the characteristics of high-voltage probes. The technique uses a 4 kV pulsed arrangement combined with results from a 2D electric field solver and a thorough PSpice circuit analysis. Finally, a practical example of high-voltage measurement performed using such a probe during the development phase of a high power microwave generator is provided.

The temperature dependence of the Kerr constant for water has been determined over the range 19 °C-45 °C at a wavelength of 658 nm.This paper presents the experimental arrangement used for this purpose and the data obtained, for which a polynomial fit is provided.A formula is also suggested to help estimate the variation of the Kerr constant for water with both temperature and wavelength.

When the load is an antenna, the High Pulsed Power (HPP) generators allow generating electromagnetic waves in the form of pulses for wideband or ultra wideband applications. In this case, the HPP generator is usually made up of a primary energy source loading a power-amplification system. A Marx generator or a Tesla transformer is classically used as a power-amplifier. Our structure uses an innovating very compact resonant transformer. This power amplification device is connected to a fast switch which forwards the energy from this source to the antenna. The antenna behavior is directly linked to the performances of the main element of this whole device: an oil peaking switch.The whole device is composed of a battery set, a DC/DC 300V-10kV converter which feeds four primary capacitors with a 1.2A current, four triggered spark gap switches, a resonant transformer with four primaries generating a few hundreds kV pulses, the oil peaking switch and the dipole antenna. The device must transmit waveforms with a wide frequency band.This paper presents first the preliminary studies on an oil switch used in a transmission line setup. Several oils are studied, tested and compared. First experimental tests aimed at determining the electrical breakdown field in oils and the rise-time for conditions close to our application. The switch characteristics (breakdown voltage, breakdown electric field, rise time, etc) are thus studied for various electrodes gap distances. These results and the influence of these previous parameters on the antenna performances (antenna factor, figure-of-merit, radiated field) are predicted by CST Microwave Studio and compared to measurements.

This paper investigates the electric power extractable from an helicopter conical nozzle equipped with thermoelectrical modules. The thermoelectric nozzle is heated by the final exhaust gas from helicopter turbine and cooled by oil. A computer model has been developed to simulate the performance of the thermoelectric system. Results were obtained for various operating conditions showing that the electrical power produced in real operating conditions is significant but currently insufficient if we consider the weight-to-power ratio. The numerical model is also used to optimize the electric power showing a good potential for the future.

Replacing traditional open fire stoves, characterized by low efficiency, with improved ones is an important challenge for developing countries. Adding TE (thermoelectric) generators can provide electricity that permits not only the use of an electric fan increasing the ratio air to fuel to achieve a complete combustion in the stoves but also the satisfaction of basic needs: light, phones and other electronic devices. A review of existing TE generators for stoves is presented. To test the TE modules, an experimental device has been carried out in our laboratory where a gas heater simulates the stove. The generator set-up is described including the switching electric regulator that stabilizes the fluctuating voltage from the modules and stores the energy in a battery. The performance of the generator mostly depends on the heat transfer through the modules and especially on the thermal contact resistances. First experiments show the influence of the pressure on these resistances. Then a study of temperatures and electrical power measurements is compared to a theoretical analysis using TE and heat transfer equations. The very reasonable value of the obtained contact resistances shows that the mechanical design of the generator is almost optimized. The TE generator has produced up to 9.5 W.