Contactless processing of metallic materials is of great interest and has been used for the fundamental study of melts such as their thermo-physical properties and their solidification behavior. Among the different ways to produce the free suspension of the material, magnetic fields offer a well-adapted mean for metals and alloys. However, due to stability considerations, development of applications has been seriously limited in the past. We present here a new containerless technique combining magnetic suspension with an electromagnetic induction furnace able to produce stable conditions of sustentation even for paramagnetic substances. Suspension experiments on massive metallic samples involving the superimposition of magnetic and electromagnetic forces will be described and analyzed. Conditions to solidify pure Ti and TiAl alloy samples of 45 g without any contact with a container wall are presented.

Secondary Electron Emission (SEE) yield measurements have been used to investigate the desorption of nitrogen adsorbates from amorphous carbon (a-C) surfaces due to swift heavy ion impact. The fluence dependence of ion induced electron emission obeys an exponential decay law when the coverage rate is in the sub-mono-layer range. This reveals the relative contribution of the both emitting zones, the “clean” one (having the SEE properties of carbon) and the covered one (with a higher SEE coefficient) to the total measured yield. The mechanism for the SEE enhancement effect is connected to the surface termination. Nitrogen adsorbates are believed to provide surface states which generate a downwards energy band bending, which on relative scale pushes up the Fermi level towards the conduction band minimum, reducing the work function and increasing the SEE yield subsequently. A shoulder observed on the rising edge of the peak of the true SE peak is ascribe to the fraction of hydrogenated termination of a-C which exhibits a lower electron affinity.

Dielectric properties of resin/carbon-black nanocomposites were measured and shown to differ from results given by a random sets modeling approach. The origin of the discrepancies was traced back to the presence of sets of carbon planes, detached from the carbon-black particles during the composite preparation. These planes are dispersed in the resin matrix and are nearly invisible, even in HRTEM images. EELS measurements revealed the signature of bonding states typical of graphite-like compounds, in regions of the matrix previously supposed to be free of carbon-black. A new approach to texture characterization of HRTEM images, using Haralick parameters based on pixel intensity co-occurrence matrices, showed strong differences between pure resin and regions of the composite between carbon particles. The nano-scale characterization results explain the values obtained in macroscopic measurements.

We present here a new method to calculate, quite instantaneously, the amplitude and phase transverse distribution of the spontaneous emission (SE) produced in a waveguide. The SE is the radiation produced by an electron beam passing through an undulator. It is involved in the operation of Free Electron Lasers (FEL). Some FELs, working in infrared, use a waveguide in place of the vacuum chamber of the undulator. The numerical process which is described here is quasi analytical. It is based on a standard method for wave propagation using the Fast Fourier Transform, and it is compatible with numerical codes for wave propagation. It is limited to planar undulators. Some numerical codes exist to calculate the SE transverse profile, but they are not suitable for waveguide configuration. In addition, a simplified version of the calculation gives the SE radiation without waveguide, i.e. when propagating in free space. In practice, the process can be included in a general code to calculate the cavity losses at the start-up of the FEL operation. These losses are always larger than those for the steady state regime, and they may be large enough to forbid laser operation.

From analytical solutions of the heat conduction equation in an infinite continuous medium with invariable thermal physical properties, the paper regards a laser-irradiated body as a part of the continuous medium, adopts the weighing function of laser power related to the shape of the body, and then gives a semi-analytical approach. The method can approximately estimate the instantaneous temperature field of laser irradiation on an arbitrary shape surface. Comparison of calculation results with accuracy solutions is presented. Finally, examples applied to estimate phase transformation hardening stripes of laser irradiation on cylinder work-pieces are given.

A new iterative scheme coupled with finite element technique is proposed as a numerical tool to solve Poisson's equation in a positive DC wire-to-plane corona using new boundary conditions. We used the model which separates the corona in two distinct regions. The ionisation region radius and the electric field at the ionisation-region/drift-region (IRDR) interface, which corresponds to a zero net ionisation coefficient of the ambient air, are developed by Hartmann in his investigation on the generalisation of the Peek's law. The proposed model allow to take into account the ionisation region thickness and thus avoids the recourse to the first Deutsch assumption, largely used in the literature. The effectiveness of the proposed method has been tested through application to the wire-to-plane geometry where the field has been measured with the linear biased probe. The agreement between the present calculated current density and electric field profiles as compared to the measured values is satisfactory.

The influence of the photoinjector exit hall on the energy loss for an accelerated electron beam is investigated, by calculating the total energy transferred from the electrons to the wakefields, which are driven by the beam. The obtained energy loss is compared to those previously obtained for a ‘pill-box’ cavity [9]. This comparison shows that the influence of this hall, in terms of energy loss, varies over the beam length. It is strongest in the middle of the beam and decreases towards both ends. In consequence of this perturbation, the center of the beam is displaced from its initial position during the first phase (t < 200 ps) where the exit aperture has no effect to a new equilibrium position which takes place at 200 < t < 250 ps.

This paper is devoted to polystyrene thin films treatment under DC pulsed discharges in oxygen-argon mixtures. AFM analysis is used to study the surface modifications in terms of morphology and corrugation. The use of a glow post-discharge enables to disregard the degradation process in relation to the functionalization process. Thus the increase of the polystyrene wettability is mainly due to the formation of polar functions which are of great interest to a better understanding of the treatment aging. Indeed, the reorganization of the macromolecular chains after a plasma treatment enables to obtain an equilibrium state of the surface in relation to the outer environment. Polar functions orient themselves toward the polymer bulk and may interact with another one to form hydrogen bonds, which establish physical linkages within the surface and its stabilization.

A new indirect method of determining the viscosity of a Newtonian fluid flowing in a tube with a geometrical singularity is proposed. Due to this singularity, the shape of the dimensionless velocity profiles is closely correlated with the Reynolds number of the flow. Newtonian fluid flows were simulated numerically with various Reynolds numbers. Based on the results of these calculations, an abacus was plotted showing the relationship between the dimensionless velocity and the dimensionless viscosity. On the other hand, dimensionless velocities were also obtained by measuring velocity profiles on a hydrodynamic bench with an ultrasonic Doppler velocimeter. These experimental values were plotted on the abacus and the viscosity of the actual fluid was thus determined. Comparisons were made with viscometer measurements in order to assess the accuracy of the method and its range of validity. This method is of great potential interest for application to industrial plans when it is necessary to know the viscosity of a fluid undergoing a transformation without interrupting the process by taking fluid samples.

To achieve optimum imaging performance, any camera system has to be thoroughly checked before being used, particular care being given in evaluating the different contributions due to noise. Our work presents a method for characterising the different sources of noise affecting CCD or CMOS cameras, emphasising the too often overlooked pattern noise. This method is an extended and theoretical approach of the well-known photon transfer technique [1]. Experimentation on our high speed CCD imager illustrates this approach.

A new model of incoherent-to-coherent IR image converter based on a GaAs photoconductor (PC) joined to an electro-optic (EO) Bi12SiO20 crystal has been analyzed theoretically and experimentally. The possibility of field transfer from the PC to the EO crystal under the infrared (IR) radiation sufficient for realization of the EO (Pockels) effect in the EO crystal was assessed. Based on the electric field parameters and the parameters of the PC and EO crystal, the threshold sensitivity of the converter was estimated. The experimental PC-EO crystal structure by which IR-radiation (0.9–1.5 μm) was converted into the coherent visible radiation was obtained on the basis of theoretical calculations. The limiting resolution of readout image was about 10 lp/mm. The measured threshold sensitivity of the converter, 5 × 10−4 W/cm2, was found to be in the limits of theoretical estimation. The results indicate that this device has the potential for use in a high-speed, high-contrast optically addressed spatial light modulators.