Some electrostrictive ceramics like 0.9 PMN-0.1 PT show large reduction of the apparent Young's modulus (more than 50%) as a function of the electric field. In the literature, this result is always obtained in the direction of the applied electric field. We performed some measurements of the elastic modulus in the direction perpendicular to the electric field and we found an unexpected small variation (less than 6%). This result shows that the apparent mechanical properties are much more dependent of the direction of the electrical field than known previously.

The present study reviews the techniques suitable for twin characterisation in TSMTG-processed ceramics: Conventional Transmission Electron Microscopy, Scanning Electron Microscopy (backscattered electrons images), and X-ray diffraction (pole figures). Optical microscopy can not be used because twin spacing in the studied ceramics are smaller than this technique resolution. A difference between SEM looking like twins average spacing and TEM twins average spacing is pointed out and some explanations are envisaged. Concerning X-ray diffraction, rocking curves can not be used to characterise twins in textured ceramics, but pole figures allow qualitative measurements.

An interesting method based on a variable splitting into two time-scales, the “transient time harmonic method” is proposed allowing to compute transient phasor solutions of problems involving slow, close to quasi-static and fast dynamics simultaneously, yielding stiff properties. The time-step of the dynamic problem can be chosen larger than the fundamental time interval, resulting in an “envelope” model for the problem with the small time constant. The derivation of the FEM matrices is discussed. Examples, including a transformer operating a slow varying load and a transient coupled electromagnetic-thermal problem, are discussed.

In this paper the dependence of the effective secondary emission coefficient-effective electron yield γeff in nitrogen on the reduced field (the ratio of the electric field and the gas density E/N) for various cathode surfaces is determined. Two different methods are applied: swarm measurements (from breakdown voltage) and time delay measurements. In the latter technique, first the breakdown probability is determined as a function of voltage and then γeff is derived from it. The results of applying both methods are in good agreement for the γeffversusE/N dependence. The measurements were made for copper cathode, untreated and treated by gas discharge and also several thousand electrical breakdowns, gold-plated copper and steel cathodes. Secondary electron yield γeff is of the order of a few percent at moderate and high E/N, and slightly increases with increasing E/N up to several kTd. At low E/N, a characteristic peak appears (at about 600 Td for copper). The γeff value increases when copper cathode is treated by gas discharges and becomes stable after several thousand breakdowns, agreeing well with other breakdown results in the literature. The chosen values for the Townsend primary ionization coefficient, obtained from best fits to available experimental data in the literature and the choice of the equilibration distance from the cathode significantly influence determination of γeff. Finally, our results are compared with the results of other authors for different cathode materials and a good agreement is found.

The evolution of initial perturbations in a plasma-filled system with a high current relativistic electron beam is considered. The beam current is assumed to be comparable or higher than the limiting vacuum current. The approach is based on equation for slowly varying amplitude of the induced waveform, which enable us to separate out the most intrinsic peculiarities of the overlimiting electron beam instabilities. An equation for slowly varying amplitude is derived and solved. An analytical expression describing space structure and development dynamics of the fields is obtained and analyzed. The well-known maximal growth rate of beam instability is actually the growth rate in the peak of induced wave train. Results are valid both for instability due to aperiodic modulation of the beam density in medium with negative dielectric constant and for instability due to excitation of beam wave with negative energy. Comparison with the case of a sublimiting beam is carried out.

It is necessary for the optimum design of arc quenching chamber in the molded case circuit breakers to analyze magnetic force acting on the arc in the chamber. The magnetic blowout forces and the distribution of magnetic field induced by arc current depend on the shape, arrangement, and kinds of material of grids in the chamber. The effective method to design V-slotted iron grid in the arc quenching chamber is discussed in this paper. The magnetic blowout force and flux density were obtained by using the 3-D finite element method considering non-linearity of iron grids. The grid model designed optimally was also verified by means of the interruption performances test. It is shown that our design method is a useful tool for design of arc quenching chamber in the circuit breakers.

The generation and the behavior of amorphous hydrogenated carbon particulates in a pure methane rf discharge have been studied for different methane flow rates (2−14 sccm) and different incident rf powers (40−120 W). Laser light scattering provides informations on their localization in the discharge. The 90° laser light scattered is used to determine the appearance times. The higher the incident rf power, the shorter the particulate appearance time: conversely the higher the methane flow rate, the higher the appearance time. The appearance times have been correlated to the inverse of the residence times of CH4 molecules. Good correlations have been observed between the particulate generation and the time evolutions of both laser beam extinction and dc self bias voltage. Whatever our experimental conditions, the influence of the methane flow rate seems lower than the rf power one. An increase of the rf power leads to a more important generation of particulates in the plasma.

Crawford-cells are widespread for carrying out EMC-susceptibility tests. Electric devices are brought inside the test-volume to be illuminated by a TEM-wave in order to find out whether the equipment under test is working properly even under strong environmental conditions. As the Crawford-cell is a resonant cavity, particular consideration on excitation of undesired non-TEM-waves needs to be taken in order to get reasonable test results. In this paper typical magnetic and electric field patterns are calculated and outlined for unwanted waves.

Ion counting with an electron multiplier (EM) is necessary when sputtered ions are used for in situ and precise isotopic abundance measurements (10−4$(1\sigma)$) on small sample volume (about 100 μm3 for pure silicon). Measurements were performed on silicon samples bombarded with Cs+ ions by extracting negative secondary monatomic Si− ions. Pulse-height distributions (PHD) and isotopic ratios were used as diagnostic tools for repeatability studies. Repeatability could be greatly improved by determining the optimal position of the impact area on the conversion dynode and by addressing each isotopic beam properly focused on this area (adaptive optics). A simplified model based on Poisson's laws was developed to fit PHDs and allowed us to calculate quantum detection efficiencies versus thresholds. EM isotopic discriminations were determined with the resulting semiempirical algorithm so as to reconstruct the lost information and get data independent of threshold setting. To reach consistent results, quasi-simultaneous arrivals (QSA) on the conversion dynode had to be assumed and modelled using direct ionisation yields Si−/ Cs+ at different collection efficiencies. The QSA corrected data fitted well on the terrestrial isotopic fractionation line. Dead time uncertainties and possible emission non-linear isotopic fractionation processes were examined. PHDs from other elements and polyatomic ions were also discussed.